2.5 not getting gas from the injector - S-10 Forum
S-10 Forum is the resource on GM S-series trucks, Suspension, engine information, Body Modifications, painting tutorials.  Modifications to suit every need, budget and whim

2.5 not getting gas from the injector

Go Back   S-10 Forum > Engine and Drivetrain Tech > 2.5L - 1st gen 4-banging
New User? Register Forgot Password


 
LinkBack Thread Tools
Old 05-16-2010, 09:42 PM   #1
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Unhappy 2.5 not getting gas from the injector

Hi all,


Glad I found this forum.New member from AL.I acquired a 88 2.5 5 sp. from a buddy for $160.It had broken the rings on the back 2 cyls.He bought the rings and gaskets.We pulled it down and replaced the rings.When we put it back together it wouldn't run,no gas from the injector.He got tired of messing with it and sold it to me.

Well I have replaced the ICM,no help.fuel filter and pump sock,no help.I can hear the pump run when I turn the key on.It will run if you pour gas thro the TB.I wound up taking the hall effect switch out and it was broken,dist. fell out of the door and hit driveway while the engine was out.It ran good for about 10 minutes,then I put it in gear and started out the driveway,it started bogging down then quit.Now it won't start back.

Also I have a wire at the back of the engine that the connector is broken,tan wire with white stripe or maybe it's orange w/white stripe.I don't know where this wire goes.Any help is greatly appreciated as I am about ready to put a rag in the gas tank and light it.
Old 05-16-2010, 10:30 PM   #2
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Tan/White would be something to do with the fuel pump circuit. There is also an ECM ground that is Tan/White..... Check out www.autozone.com and set yourself up for free and check out their wiring diagrams for more specifics.... :-) good luck..... P.S. $160 was a good deal....
Old 05-16-2010, 11:05 PM   #3
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by lesterl
Tan/White would be something to do with the fuel pump circuit. There is also an ECM ground that is Tan/White..... Check out www.autozone.com and set yourself up for free and check out their wiring diagrams for more specifics.... :-) good luck..... P.S. $160 was a good deal....

I can't find the wiring diagrams at autozone.com. Thx on the good deal,be a better deal if I can get it running.
Old 05-17-2010, 02:09 AM   #4
Bold as Love
 
Harry Canyon's Avatar
 
Age: 23
Join Date: Jun 2008
Posts: 1,768
Location: Beattyville, KY
User is: OffLine
Re: 2.5 not getting gas from the injector

There is a random tan and white wire that runs to the back from the engine bay that does have something to do with the electric fuel pump, or the relay. I vaguely remember this when I was trying to figure out what was wrong with mine.
Old 05-17-2010, 03:47 PM   #5
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

I have looked at the wiring diagram.I can't figure out where tan/white wire goes,according to the diagram it says fuel pump prime?There is also a tan/white wire with a female conn. that i have been using to test the fuel pump,if i jump it with a hot wire the pump runs.The f/p runs when i turn the key on but I am not getting fuel from the injector.
Old 05-17-2010, 06:14 PM   #6
oly
 
Join Date: Nov 2009
Posts: 12
Location:
User is: OffLine
Re: 2.5 not getting gas from the injector

make sure when you pluged the injector back in you did'nt bend one of the little pins in the connector. also are you getting fuel up to the injector, disconnect the fuel line and see. i know you said you can hear the fuel pump but maybe fuel filter is plugged or a kinked line.
Old 05-17-2010, 07:13 PM   #7
Bold as Love
 
Harry Canyon's Avatar
 
Age: 23
Join Date: Jun 2008
Posts: 1,768
Location: Beattyville, KY
User is: OffLine
Re: 2.5 not getting gas from the injector

I'll second that about the injector pins. Their really easy to bend.
Old 05-17-2010, 07:25 PM   #8
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

www.autozone.com, register your truck, repair info link, vehicle repair guides link, chassis electrical, wiring diagrams, then pick out the diagram that matches your truck.

Do you have 12v on the red wire on the injector with the ignition on? Do you have a 194 lamp out of your side marker that you can put the pins into the connector and crank it over to see if it flashes?
Old 05-17-2010, 09:27 PM   #9
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

There is a wire with a funny looking conn. close to the master cylinder.If I jump it with a hot wire the injector will spray.
Old 05-18-2010, 08:48 PM   #10
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Continual spray (dump gas) or does it actually inject the fuel from the ecms control?
Old 05-18-2010, 10:29 PM   #11
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by lesterl
Continual spray (dump gas) or does it actually inject the fuel from the ecms control?

It's more of a continual spray.
Old 05-18-2010, 10:38 PM   #12
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

What color is the wire?
Old 05-18-2010, 11:00 PM   #13
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by lesterl
What color is the wire?
I'm at work,I'll look in the morning.
Old 05-19-2010, 08:31 AM   #14
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

The wire is white.
Old 05-19-2010, 09:24 PM   #15
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Might snap a pix of the wire and post it, dunno what it would be, the white is the grounding side of the coil/ ICM, there is a grey wire that would feed the fuel pump.
Old 05-22-2010, 09:32 PM   #16
i saw what you did there!
 
fast68chevy's Avatar
 
Age: 36
Join Date: Sep 2002
Posts: 3,571
Location: Lincoln IL
User is: OffLine
Re: 2.5 not getting gas from the injector

tan.brown looking one is the FP hot from the firewall connector to the fuel tank sender connector wire on the 2.5L trucks i just got done doing this on my 88 2.5l dime a couple hours ago my brown wire at the firewall driver side by master sylinder was hot under the hood but nothing at the fuel sender

i had to totally run a new wire along the frame

runs now.

third time ive seen this exact thing happen on these trucks and i have no idea how it happens or why,.,.,., its really crazy.... total wire failure for no reason i dont know how... the second time it happened was on a buddys 99 blazer s10, he also replaced his pump module for no reason. total waste of 300 bucks. i ran new wire and fired right up then. the gm fuel pump hot wire is a total failure 82- late 90s or evne possibly into the 2000s also.

i got the truck for 100 bucks because of this issue he put a brand new pump in it and still had failed wire and he gave up on it and i knew the problem so i gave him a bill for it and hauled it to here,


and at the fuel sender it is gray, starting at the sender wire connector under there at the tank

if the pump runs for a few seconds when you turn ign key to run then all is well with pump and wire

issue is something else

you got spark?
distributor not worn out sloppy shaft?(real common problem somewhere past 100k miles on these)

ign module good?

coil good?

cap and rotor not toasted?

compression 120 on all cyls?

camshaft in time?

the white wire is probably the FP test connector wire

it runs to the FP relay on the fender there, the black little cube shaped one.

unplug it and clean the plug and the relay spades real good with cleaner and then plug it back in.
i should click as soon as you hit run positionj with the key switch and then a few seconds click again

if not then you got issues with the relay or your ign switch or one of the two ECM fuses is toasted inside the truck
check all fuses anyways, especially the ECM ones. one may be burnt anyways

if you have a/c then swap the two relays you have with each other. the a/c one is usually always good. unlike the FP one sometimes and they are the same exact relays.

Last edited by fast68chevy; 05-22-2010 at 09:42 PM.
Old 05-23-2010, 02:43 PM   #17
Bold as Love
 
Harry Canyon's Avatar
 
Age: 23
Join Date: Jun 2008
Posts: 1,768
Location: Beattyville, KY
User is: OffLine
Re: 2.5 not getting gas from the injector

I remember the wire issue with mine now. New fuel pump, relay, etc. and it still wouldn't come on. Started tracing the wires and found that one. Traced it along the frame and it had frayed apart right under the cab. Wired it up and it worked.

Then it quit again, the oil pressure switch went bad and was not allowing the fuel pump to work-thinking that the motor was off. Good failsafe, but a pain in the ass when trying to trouble shoot. I had finnaly had enough, found a wire in the relay that turned the fuel pump on when I ran juice to it. Spliced a wire into it and ran it to a toggle switch, then ran the other side of the switch to the hot battery terminal. Wired a $7 walmart led light bar into the switch as well to tell me when the pump was on. Flick it on when starting, turn it off when you get to your destination.

This was on my '88 S-10 pretty much reskinned as a '54 F-100, S-10 wiring harness, floor, firewall, frame. It was a convertible, so I felt safer having another theft deterrent on the truck as well. Worked for me, but I'd never do it to my daily driver.
Old 05-30-2010, 11:10 PM   #18
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

New question,lol.If the fuel pressure is low will the injector not pulse?
Old 05-30-2010, 11:20 PM   #19
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

If the pressure is low it wont run/ pulse, that being said it would be pretty low I would think tho...
Old 06-09-2010, 09:26 AM   #20
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Sorry so long since I posted,between work and being broke don't get to work on truck much.I tested the fuel pressure it is about 15 psi when you turn the key on,but bleeds back downif you try to crank it or turn the key off.Took ICM(which is new btw) and had it tested Advance and O'Reilly's both say it's good.Got F-I-L out there with his ohmeter,1 injector wire is hot all the time the other is pulsing,still no gas from injector though.I'm about ready to stick a rag in the filler neck light it and walk away.
Old 06-09-2010, 01:13 PM   #21
Cool, Tight, & STRONG....
 
Steady Eddie's Avatar
 
Join Date: Mar 2008
Posts: 1,932
Location: The Great Pacific Northwet
User is: OffLine
Re: 2.5 not getting gas from the injector

SB--

Did it ever set a code or light the service engine soon light??
Old 06-09-2010, 04:47 PM   #22
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by Steady Eddie
SB--

Did it ever set a code or light the service engine soon light??

never set a code
Old 06-09-2010, 05:23 PM   #23
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Will the injector spray if you apply 12v across it (or ground the blue wire with the red wire hot/ ign on?)
Old 06-09-2010, 05:28 PM   #24
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by lesterl
Will the injector spray if you apply 12v across it (or ground the blue wire with the red wire hot/ ign on?)
I gotta work tonite and tomm. nite .I'll try this Friday after I get up.Should the fuel pressure go from 15 psi down to nothing while trying to start the truck?I'm thinking the fuel pump isn't running while cranking.
Old 06-09-2010, 05:43 PM   #25
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Fuel pump only primes for 4 seconds when you first turn the key, it wont run again untill the truck starts or the oil pressure exceeds 4 PSI (all this assuming everything is working correctly.)

If your fuel pressure is dropping from 15PSI to 0PSI, you wont have any fuel pressure in the system to fire from the injector. The system MUST hold pressure for cranking. To test, there should be a little wire on the firewall next to a little splice block with two studs for some red wires. The wire with the female spade connector is the fuel pump prime connector, if you hook it to B+ and try cranking will it start? If you dump some gas in the intake will it start?
Old 06-12-2010, 02:12 AM   #26
86 s10 2.5L 5spd, 4X4
 
isaiahwm's Avatar
 
Age: 26
Join Date: Apr 2010
Posts: 12
Location:
User is: OffLine
Re: 2.5 not getting gas from the injector

I just restored an 86 s10 2.5 5speed 4x4 i had all those problems and more blown clutch fried brakes ... any way, if its not running still, i would check the fuel relay under the hood if thats not it you need to get into the tank, i found it easier to take the bed off than to drop the tank because of the limited space. but you need to get into the tank, there is a fuel filter on the bottom of the pump that would need replacing, and take the pump off the braket clean both ends out dump some rubbing alcohol through it, and use a batery charger to test if it works, then put it back to gether.

If it is running but dumping fuel and runnign at a high RPM the you IAC (idle air control) valve, and or your TPS (throttle position sensor) are probably bad, i had to do all of the above just to get it to run and idle okay. Hope this help!
Old 06-13-2010, 12:57 PM   #27
Registered User
 
Join Date: May 2010
Posts: 29
Location:
User is: OffLine
Re: 2.5 not getting gas from the injector

I'm having a hell of a time with a similar problem. I have changed my Ign Module Ign Coil, fuel pump, injector, distriputor cap and button new plugs, wires and MAP Sensor. I'm not getting any spark either though that's the big issue for me i think, but I am still not getting spray. I tested my injector with 12V across it and it works fine. I can hear the gas getting to the injector it just won't come out the bottom. Are you at least getting it to the injector itself?
Old 06-16-2010, 03:28 AM   #28
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

I saw on another thread that the temp sensor is "critical".That's the 1 behind the valve cover on the driver's side right? Well I noticed the other day that mine has a tang broken off of it,would that keep it from firing the injector?Don't wanna buy anything till I know it could be the problem.
Old 06-16-2010, 10:03 AM   #29
Cool, Tight, & STRONG....
 
Steady Eddie's Avatar
 
Join Date: Mar 2008
Posts: 1,932
Location: The Great Pacific Northwet
User is: OffLine
Lightbulb Re: 2.5 not getting gas from the injector

Quote: Originally Posted by southernboy35611
I saw on another thread that the temp sensor is "critical".That's the 1 behind the valve cover on the driver's side right? Well I noticed the other day that mine has a tang broken off of it,would that keep it from firing the injector?Don't wanna buy anything till I know it could be the problem.
=====================

SB--

IIRC the broken temp sender/sensor that you have is the one for the idiot lamp or temp gauge..the one up next to the t-stat housing is the one that reports directly to the ECU/brainbox..but there is yet another one, in the intake manifold that measures the intake air temperature and it should be there and working right.

These types of sensors can all be checked with a meter, and I agree that you do NOT want to buy a bunch of parts that you do not need.

The very best money that an Owner can spend, is to buy, and use, and study, IS a shop manual, and the second best thing is a volt-ohm meter and knowing HOW to use it.

Last edited by Steady Eddie; 06-16-2010 at 10:07 AM.
Old 06-17-2010, 02:39 AM   #30
Ummmmmm....Does it go?
 
Mystyk_Wynds's Avatar
 
Age: 34
Join Date: May 2010
Posts: 212
Location: Colorado Springs
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by southernboy35611
I saw on another thread that the temp sensor is "critical".That's the 1 behind the valve cover on the driver's side right? Well I noticed the other day that mine has a tang broken off of it,would that keep it from firing the injector?Don't wanna buy anything till I know it could be the problem.
Ok to answer this, that broken tang, thats your OIL PRESSURE SWITCH. Try fixing that first. It might explain why the injector or fuel pump is not staying primed. And also why it the fuel system shut itself down.

Second the tan, black (White) stripe, ummmmmmmm Hook that up also. Thats the computer controlled base timing wire. You unhook that wire, set base timing and then plug it back in. That is the wire the comp uses to advance/retard the timing. its mainly a signal wire for timing.

Also check to make sure your o2 sensor is hooked up.
Old 06-17-2010, 02:48 AM   #31
Ummmmmm....Does it go?
 
Mystyk_Wynds's Avatar
 
Age: 34
Join Date: May 2010
Posts: 212
Location: Colorado Springs
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by BruceSwins
I'm having a hell of a time with a similar problem. I have changed my Ign Module Ign Coil, fuel pump, injector, distriputor cap and button new plugs, wires and MAP Sensor. I'm not getting any spark either though that's the big issue for me i think, but I am still not getting spray. I tested my injector with 12V across it and it works fine. I can hear the gas getting to the injector it just won't come out the bottom. Are you at least getting it to the injector itself?
Try changing the pick up coil. Its inside the distributor, below the advance unit. That will cause no fire on both the injector and the cap. That system is all linked together. The comp reads a signal from the distibutor than tell the coil and the injector to fire.

Oh and you can't hear gas getting into the injector. What you hear is the fuel pump possibly priming.

Read some of my other posts to determine where your problem is... You should be able to pin point the issue within a couple hours.
Old 06-17-2010, 02:50 AM   #32
Ummmmmm....Does it go?
 
Mystyk_Wynds's Avatar
 
Age: 34
Join Date: May 2010
Posts: 212
Location: Colorado Springs
User is: OffLine
Re: 2.5 not getting gas from the injector

Here read my post in this area, it'll tell you how to pin point your injector problem

http://www.s10forum.com/forum/f104/s...-valve-443725/
Old 06-17-2010, 03:29 AM   #33
Ummmmmm....Does it go?
 
Mystyk_Wynds's Avatar
 
Age: 34
Join Date: May 2010
Posts: 212
Location: Colorado Springs
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by Mystyk_Wynds
Here read my post in this area, it'll tell you how to pin point your injector problem

http://www.s10forum.com/forum/f104/s...-valve-443725/

Now let me explain a few things about how your injector and its cuircitry works.

First off a TBI injector is refered to as a 40ppm or continuous flow. What this means is that the injector is capable of roughly 40 cycles per second with the ability to constantly stay open.

Now for how the circuitry works. In simplistic terms, everytime the rotor hits a pin on the cap, there is a reference signal sent to the coil and to the ecm. This signal tell the ignition system when to fire, and tell the computer when to fire the injector.
Also this means the ignition system and the fuel delivery can function independantly. However the injector is its own entity, and is computer controlled. If their is no signal going back to the computer, the injector will NOT function. However the ignition will.
The signal is determined at the distributor. It comprises of the coil, ignition module, pick up coil and all the control wires.

Now for the injector itself. The injector is setup very similiar in the aspects of electricity, very similiar and nearly identical to the tail/signal/brake light systems, only found on S10s'.

There is always two wires for every injector, one that appears as positive (Constant Flow) and one that appears as Negative (Pulsed postive flow).
What you see as a ground, is not actually a ground. Its a wire that is dual purpose.

When you key up, the Positive ALWAYS has positive power. An so long as your not cranking, the negative is negative. Injector is off.
When cranking, the negative actually is used as a pulse wire. The computer will pulse a positive charge down the wire. This causes the circuit to negate itself, and the injector opens. A continuous flow down this wire, holds the injector open.
A positive charged wire that connects to another positive charge wire, actually negates both positive charges, and creates and electron impass. Resulting in zero electical flow. IE It shuts the circuit off.

Hence why when you check the injector, you hit BOTH SIDES with a positive charge. Hence the jumper method.

this is how your tail/signal/brake lights works, also
Old 06-17-2010, 07:41 PM   #34
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by Mystyk_Wynds
Ok to answer this, that broken tang, thats your OIL PRESSURE SWITCH. Try fixing that first. It might explain why the injector or fuel pump is not staying primed. And also why it the fuel system shut itself down.

Second the tan, black (White) stripe, ummmmmmmm Hook that up also. Thats the computer controlled base timing wire. You unhook that wire, set base timing and then plug it back in. That is the wire the comp uses to advance/retard the timing. its mainly a signal wire for timing.

Also check to make sure your o2 sensor is hooked up.
ok,I'm confused.is the sensor at the back of the head the temp sensor or not?The broken tang is on this sensor.I thought the oil pressure switch was on the block under the intake,in front of the dist.
Old 06-17-2010, 11:13 PM   #35
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

The wire on the sensor is green, that is the Dash light/ Guage. The oil pressure switch IS on the passenger side of the block under the intake just forward of the distributor.

The tan wire thing is not on the 2.5l, to bypass the computer timing you jumper the A/B connector with a paperclip. IIRC the 4.3l has the tan wire you unhook to set base time.
Old 06-17-2010, 11:15 PM   #36
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by Mystyk_Wynds
Now let me explain a few things about how your injector and its cuircitry works.

First off a TBI injector is refered to as a 40ppm or continuous flow. What this means is that the injector is capable of roughly 40 cycles per second with the ability to constantly stay open.

Now for how the circuitry works. In simplistic terms, everytime the rotor hits a pin on the cap, there is a reference signal sent to the coil and to the ecm. This signal tell the ignition system when to fire, and tell the computer when to fire the injector.
Also this means the ignition system and the fuel delivery can function independantly. However the injector is its own entity, and is computer controlled. If their is no signal going back to the computer, the injector will NOT function. However the ignition will.
The signal is determined at the distributor. It comprises of the coil, ignition module, pick up coil and all the control wires.

Now for the injector itself. The injector is setup very similiar in the aspects of electricity, very similiar and nearly identical to the tail/signal/brake light systems, only found on S10s'.

There is always two wires for every injector, one that appears as positive (Constant Flow) and one that appears as Negative (Pulsed postive flow).
What you see as a ground, is not actually a ground. Its a wire that is dual purpose.

When you key up, the Positive ALWAYS has positive power. An so long as your not cranking, the negative is negative. Injector is off.
When cranking, the negative actually is used as a pulse wire. The computer will pulse a positive charge down the wire. This causes the circuit to negate itself, and the injector opens. A continuous flow down this wire, holds the injector open.
A positive charged wire that connects to another positive charge wire, actually negates both positive charges, and creates and electron impass. Resulting in zero electical flow. IE It shuts the circuit off.

Hence why when you check the injector, you hit BOTH SIDES with a positive charge. Hence the jumper method.

this is how your tail/signal/brake lights works, also
Have to call BS on that man.....
Old 06-18-2010, 03:51 AM   #37
Ummmmmm....Does it go?
 
Mystyk_Wynds's Avatar
 
Age: 34
Join Date: May 2010
Posts: 212
Location: Colorado Springs
User is: OffLine
Re: 2.5 not getting gas from the injector

Quote: Originally Posted by lesterl
Have to call BS on that man.....
You can call bs on it all you want, that is how all tbi systems function.

If it is BS, than explain how or why you get constant power to an injector, when the key is on, and its not running???

Or rather what part of what I said is BS?

I was GM certified, and specialized in ignition/tbi systems. Multiport threw me for a loop. To many damn variants, to many things to test.
Old 06-18-2010, 11:52 PM   #38
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

Now let me explain a few things about how your injector and its cuircitry works.

First off a TBI injector is refered to as a 40ppm or continuous flow. What this means is that the injector is capable of roughly 40 cycles per second with the ability to constantly stay open.

Now for how the circuitry works. In simplistic terms, everytime the rotor hits a pin on the cap, there is a reference signal sent to the coil and to the ecm. This signal tell the ignition system when to fire, and tell the computer when to fire the injector.
Also this means the ignition system and the fuel delivery can function independantly. However the injector is its own entity, and is computer controlled. If their is no signal going back to the computer, the injector will NOT function. However the ignition will.
The signal is determined at the distributor. It comprises of the coil, ignition module, pick up coil and all the control wires.

The S10 distributor AFAIK uses a Hall Effect switch and a reluctor, the reluctor causes magnetic currents to be induced into the Hall Effect switch which is fed into the Ignition Module. At startup the ICM uses that pulsation to fire the coil and set timing, after the engine starts the ICM hands over timing control to the ECM. This reference signal is also used to help synchronize the firing of the injector.

Now for the injector itself. The injector is setup very similiar in the aspects of electricity, very similiar and nearly identical to the tail/signal/brake light systems, only found on S10s'.

There is always two wires for every injector, one that appears as positive (Constant Flow) and one that appears as Negative (Pulsed postive flow).
What you see as a ground, is not actually a ground. Its a wire that is dual purpose.

When you key up, the Positive ALWAYS has positive power. An so long as your not cranking, the negative is negative. Injector is off.
When cranking, the negative actually is used as a pulse wire. The computer will pulse a positive charge down the wire. This causes the circuit to negate itself, and the injector opens. A continuous flow down this wire, holds the injector open.
A positive charged wire that connects to another positive charge wire, actually negates both positive charges, and creates and electron impass. Resulting in zero electical flow. IE It shuts the circuit off.

Hence why when you check the injector, you hit BOTH SIDES with a positive charge. Hence the jumper method.

If one side is positive and the other is negative/ground the circuit is active.
The TBI injector gets 12vdc feed from switched ignition source. The ECM grounds the other side to produce a magnetic field inside the injector to open it up. It takes about 4 amps of initial startup current to open the injector and much less to hold it (this all happens in less than the blink of an eye). The reason both wires will APPEAR positive when not running is that the injector is a COIL, a piece of wire, of course it will read 12v on both sides without a ground being applied to the other side.

this is how your tail/signal/brake lights works, also
Old 06-19-2010, 11:55 PM   #39
86 s10 2.5L 5spd, 4X4
 
isaiahwm's Avatar
 
Age: 26
Join Date: Apr 2010
Posts: 12
Location:
User is: OffLine
Re: 2.5 not getting gas from the injector

SOUTHERNBOY your right the sensor on the back driver side of the head is the temp switch., it controls the dummy light on the dash.. if your not getting spark, there's something wrong with the ignition, if your injector is working but not gettin fuel try the fuel pump or fuel pump relay,
Old 06-22-2010, 02:06 AM   #40
Ummmmmm....Does it go?
 
Mystyk_Wynds's Avatar
 
Age: 34
Join Date: May 2010
Posts: 212
Location: Colorado Springs
User is: OffLine
Re: 2.5 not getting gas from the injector

Ok so I may have assumed wrong, On a 4.3l that prong would be the Oil pressure switch. On the 2.5 I am mistaken, as it is (a) coolant sensor.
Old 07-14-2010, 05:46 AM   #41
Registered User
 
southernboy35611's Avatar
 
Age: 46
Join Date: May 2010
Posts: 22
Location: Athens,AL
User is: OffLine
Re: 2.5 not getting gas from the injector

Sorry it's been awhile since I posted.After having the ICM tested and told it was good,put it back in truck and now it's not firing.I asked the guy at Autozone for grease to put on the ICM,but he gave me white lithium grease not dielectric grease,wondering if that would keep it from grounding.Or if my pickup coil may be shorting out & blowing the ICM.Being broke most of the time makes it hard to work on the truck.Hopefully I can pull ICM out today and wipe the grease off and try it without any grease just to see if it fires.
Old 07-14-2010, 10:19 PM   #42
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 34
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5 not getting gas from the injector

leave grease on the module, you need dialectric grease tho as it moves the heat better. The hall effect could be bad if the ignition coil isnt firing, also check the 12v line on the coil (pink wire), should be 12v anytime ign is on. Also DOUBLE check the connections to the coil and the ICM.
Old 08-01-2010, 07:35 PM   #43
Registered User
 
vigorpat's Avatar
 
Join Date: May 2010
Posts: 6
Location: va beach
User is: OffLine
Re: 2.5 not getting gas from the injector

im having similar problem with my 89. i replaced tank and fuel pump truck ran fine for 10 minutes then cut off and would not start . pump ran when you turned key but no fuel is getting to injector i am completely confused.
Sponsored Links
Advertisement
 

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the S-10 Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 09:33 PM.

Powered by vBulletin® Copyright ©2000 - 2011, Jelsoft Enterprises Ltd. SEO by vBSEO 3.2.0
SEO by vBSEO
vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.