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4.3: quit, won't start

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Old 06-17-2007, 02:41 AM   #1
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4.3: quit, won't start

Hope someone can help me out here. I am mechanically inclined...

My son has a '98 S Blazer with the 4.3 liter. Last evening he left the house and was back in 10 minutes on the end of a tow rope. He told me he noticed the voltmeter heading toward discharge and before he could get the vehicle home, the engine died. Now, 5 months ago it exhibited the very same symptom, except when it quit the battery was indeed depleted. Turned out the alternator failed, which I diagnosed and replaced with a reman Carquest unit. Since he thought it was the same dilema, he did not try to restart it and had a friend tow him home.

As soon as the vehicle came home last night (it was raining), I hit the key and noticed an approximate indicated 12 volts on the gauge. Further, the engine cranked fine and with good speed. The battery was still up. It cranks very well, but nary a hiccup toward firing at all.

I quit cranking, opened the door, and turned the key to "on". I could hear the fuel pump cycle in the tank. I popped the hood and removed the cap on the Schrader valve on the fuel line, pressed the valve core, and had fuel pressure evident. I definitely have at least some pressure. At that point I figured I had an electrical issue. I removed the underhood fuse panel cover and with my Fluke digital volt/ohm meter checked every fuse. All good. Then I checked every fuse under the panel cover on the left hand dash. All good. I pulled the fuel pump relay and replaced it with another similar in the underhood fuse block (there are several in there, all the same part number....just swapped) Still, no start, cranks fine. With that, since it began to rain hard, I left it until this morning.

Today I pulled the coil high tension lead out of the distributor cap and spark gapped it to a stud ground. While my wife cranked the engine, I had a nice heavy spark jump from the lead to the ground. The coil is putting juice to the distributor. I then removed the cap and rotor. Some buildup was on the cap terminals as well as the rotor lug, so I cleaned all that off. Replaced the cap and rotor and plugged all the wires and coil back in. Hit the key, cranked very well, no sign of firing.

Headscratching. My experience tells me I have fuel and spark and presume the compression is fine (24,000 miles ONLY on the vehicle).

I then think maybe I don't have fuel afterall. I pulled the dipstick and there is no smell of raw gasoline in the crankcase. I pulled the cover over the throttle body and while my son cranked the engine, I squirted raw gas down into the plenum. No firing at all. I most definitely am applying fuel direct to the intake.

I then pulled the most forward lefthand (drivers side) spark plug wire from the plug and put a new plug in the wire, grounded it to the exhaust manifold and had my son crank the engine. I watched a nice blue spark leave the plug electrode each time that lead was told to do so.

Not sure what else to do, I disconnected the battery for a minute and reconnected. I hooked up a battery charger and brought the battery up to a full 13.4 volts surface voltage. I then tried cranking the engine for about 15 seconds. Still, not a single hint of firing.

Here I sit. I am not sure what to do next. I don't have a manual and there is no dealer here in this small Arctic rural town where I live. Sorry for the long post, but I wanted to spell out everything I have tried to do.

I would very much like to hear from you folks and hopefully this is something someone else has experienced and can shed some light on. Anything you can offer would be greatly appreciated.

You may email me direct at home if you wish. I could use some help!

Thanks guys.

Nate
Nome, Alaska
perkins@gci.net
Old 06-18-2007, 01:32 PM   #2
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Re: 4.3: quit, won't start

distributor i had this same problem with mine
Old 06-21-2007, 06:10 PM   #3
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Re: 4.3: quit, won't start

Quote: Originally Posted by airbrushed&bagged
distributor i had this same problem with mine
An update: Still no go. I have changed the Crank Position sensor, the Cam Postion sensor and the Ignition Module. I have taken a GM Tech 2 scanner and read the PCM and have no trouble codes or faults. The fuel pressure is 60 psi. I have tried spraying ether into the intake while cranking, no fire, so it has to be ignition related. I have checked and rechecked every fuse. I have taken out one spark plug and checked compression. The plug has fire when grounded to the exhaust manifold, hence why I decided to change the crank and cam sensors, I thought the timing must be off.

The distributor is fixed, all timing is done though the PCM. The only component in the distributor is the Cam Position sensor, which I have changed.

I can pull the distributor, but what could possibly be wrong with it? I mean all it has on it is the plate on top where the rotor screws to, and it also serves as a reluctor (has a notch in it) as it passes over the Cam sensor. Thats it.

Can you elaborate on what was wrong with your distributor?

I really need help here. The vehicle has been down for 6 days and I am pulling my hair out..
Old 06-21-2007, 06:53 PM   #4
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Re: 4.3: quit, won't start

Your ignition is also based off of the crank sensor not just the cam sensor. Just because you get a spark from the wire doesnt mean it is sparking under pressure. I takes more energy to arc across an electrode under the pressure of the compression stroke. I would also check on the ICM right next to the coil.
Old 06-22-2007, 01:17 PM   #5
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Re: 4.3: quit, won't start

Quote: Originally Posted by 3.4blazerdude
Your ignition is also based off of the crank sensor not just the cam sensor. Just because you get a spark from the wire doesnt mean it is sparking under pressure. I takes more energy to arc across an electrode under the pressure of the compression stroke. I would also check on the ICM right next to the coil.
Thanks for your response. You may have looked over my last post too fast..I have changed the Crank sensor as well. Yesterday I had access to a 2000 blazer with the same engine and I took the ignition module (yes, the one component that bolts to the bracket by the coil) and put it on mine. No start. I then took mine and put it on his. His blazer fired right up. So, my ignition module is fine.

Again, I have changed both the Crank and Cam sensors and have verified the Ignition Module works fine on another rig. I have fire right out of the coil into the distributor cap. I have fire at the #1 spark plug, as I pulled one plug and verified that. A thumb over the plug hole while cranking blows my thumb off, (only 24,000 miles on this rig) I have 60 psi of fuel pressure in the fuel rail. I have shot ether into the TBI unit while the engine was cranked and not a single sign of starting occured. I have been through the underhood fuse panel twice, verified every fuse. I have 12 volts at each of the Crank and Cam sensor feed wires.

I don't see where pulling the distributor will accomplish anything. There is no electrical componet in there except the Cam sensor. The distributor shaft is turning, the cap and rotor are new as well.

Keep the information coming. Its now a week the vehicle is down.

Thanks.
Old 06-22-2007, 03:54 PM   #6
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Re: 4.3: quit, won't start

Assuming you have spark and fuel, the other component is compression. Do a full compression test by removing all the spark plugs and checking it at WOT. You may want to check the injectors with a noid light.

All this cranking may have fouled the plugs?
Old 06-22-2007, 05:19 PM   #7
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Re: 4.3: quit, won't start

The PCM could have also taken a Sh!t too. Here are some other things my GM service manual says EGR valve stuck open, water in fuel system, grounded or intermittently grounded ignition control, bad engine coolant sensor( reading way below real temp).
Old 06-22-2007, 09:03 PM   #8
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Re: 4.3: quit, won't start

Quote: Originally Posted by 3.4blazerdude
The PCM could have also taken a Sh!t too. Here are some other things my GM service manual says EGR valve stuck open, water in fuel system, grounded or intermittently grounded ignition control, bad engine coolant sensor( reading way below real temp).
Have not checked the EGR valve, though past history with them is the engine would still fire and run, but rough and not idle. I ruled out bad gas as I pumped some in a clean can and looked at it. I have not checked the coil itself, but it reliably and visibly throws through a gap when I pulled the lead out of the distributor and placed it near a grounded stud. May be the coolant sensor, but the GM Tech 2 scanner did not reveal this...again, no codes. Even so, a bad coolant sensor would go open loop and still run. But, I'll look at it anway. I am willing to look at ANYTHING right now....the PCM checked with the Tech 2 scanner, as well, so what else to I do to check it, besides unplug it, check the connections and re-plug it in?

Keep the comments coming. I need them.

Thanks

Nate
Old 06-22-2007, 11:26 PM   #9
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Re: 4.3: quit, won't start

Well to check the coil use an ohm meter across the mount of the coil and on of the input pins on the coil it should be infinite resistance. then across the input pin and output pin to the distributor, it should have 5 to 25kohms of resistance. Next measure across both input pins and it should have a measurement of 0.1 ohms. I read your first statement again it definately sound like electrical and if it isnt the coil i am either leaning to a posible problem with the tps maybe, but it seems you might have a PCM problem since it is killing the battery if something is shorting or was shorting, the battery will not take to kindly to that. Oh and if you have the PCM scaned again look at the tempature raw running data not just the problem codes.
Old 06-25-2007, 03:11 AM   #10
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Re: 4.3: quit, won't start

ttt

still looking for some more help/input, guys. Thanks
Old 06-25-2007, 10:24 AM   #11
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Re: 4.3: quit, won't start

You seem to have concluded that the fuel and spark are fine. You have yet to determine timing and fuel injector operation. Timing that is off (jumped chain, distributor adjustment) can be identified with a compression test or a cranking vacuum reading. You can have adequate fuel pressure but if the injectors aren't firing, you can't run the engine.
Old 06-07-2010, 08:13 PM   #12
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Re: 4.3: quit, won't start

I have the EXACT same prob and tried everything to .. so it appears we almost have duplicate post .. have you figured out what has happened to yours yet? .. if I get mine figured out I will let you know what my head ache was...
Old 06-07-2010, 08:13 PM   #13
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Re: 4.3: quit, won't start

ooops your is a 3 yr old post .. gahhh
Old 06-07-2010, 09:40 PM   #14
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Re: 4.3: quit, won't start

lol...try starting it without the maf sensor plugged in...
Old 06-09-2010, 11:26 PM   #15
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Re: 4.3: quit, won't start

Have you had any luck and figured out what is causing your truck not to start? I have the same condition with my 2003 extreme. I have been told if i buy PCM it may start but may not so i was wondering what you figured out with yours? Thanks
Old 06-09-2010, 11:28 PM   #16
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Re: 4.3: quit, won't start

Quote: Originally Posted by Frostbit
ttt

still looking for some more help/input, guys. Thanks

Frostbite did you ever figure out why it wouldn't start i am having the same problem with my 2003 S10?
Old 08-10-2010, 12:14 AM   #17
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Re: 4.3: quit, won't start

i know I am having the exact issue as well, spark, fuel, I think PCM is shot
Old 08-10-2010, 01:49 AM   #18
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Re: 4.3: quit, won't start

if you have spark coming out the #1 cylinder, then test fuel pressure w/ an actual fuel pressure gauge to make sure you have at least 50...if not, then maybe the maf sensor, crank sensor...pcm i guess..? passlock security bullshit i dont know..
Old 08-10-2010, 09:17 PM   #19
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Re: 4.3: quit, won't start

im exactly where you are, cranks but no go, fuel pressure at a solid 60 and got spark, started lookin at timing and found my crank sensor pigtail in bad shape, spliced a new one on, still no go... i was told there may be a relearn procedure for certain years when a new crank sensor is put in, idk what years, still tryin to fix it myself.

Last edited by koeberle04; 08-10-2010 at 09:24 PM.
Old 08-20-2010, 03:18 PM   #20
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Re: 4.3: quit, won't start

I am also in this same boat. Everything in this thread sounds just like my problem and also things I've tried to fix it.

TIME FOR LSX!!!
Old 05-20-2011, 11:18 AM   #21
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Re: 4.3: quit, won't start

mine is doing the same thing. replaced and checked everything. any ideas?
Old 05-20-2011, 01:02 PM   #22
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Re: 4.3: quit, won't start

i got a similar problem . once a day it is cuttin off at 50- 60 mph at part thottleand missing a beat while barly on the gas. i replaced the crank senser last year with a dealer part because it was missin a beat now and then . slight misfirer in all cylinders at random . that time i had a friend with a snapon scanner showed live data while running. no access now though.and no codes light went out last time it shut off .that code then was the vaper emissions code . no reason found.
Old 05-20-2011, 01:03 PM   #23
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Re: 4.3: quit, won't start

it always restarts so far usually on firs time
Old 06-18-2012, 01:23 PM   #24
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Re: 4.3: quit, won't start

I'm also having the same problem. The culprit seems to be the bulkhead connector behind the glove box on the passenger side. The pins come loose and need to be pushed back in. Not a permanent solution but it has been the cause of my intermittent starting problem.
Old 06-19-2012, 05:15 PM   #25
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Re: 4.3: quit, won't start

i forgot about this thred ,my problem inded up being a bad computer .
Old 06-20-2012, 11:03 AM   #26
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Re: 4.3: quit, won't start

Even so, a bad coolant sensor would go open loop and still run...buzzer sounds =wrong
i forgot about this thred ,my problem inded up being a bad computer =right
Old 06-20-2012, 11:40 AM   #27
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Re: 4.3: quit, won't start

I had a similar problem as this. I had fuel pressure and I had spark, but it would not fire. Even when I put gas down the throttle body.
It was my coil. It was throwing spark but not strong enough to ignite the fuel. The coil was weak in the secondary windings.
Old 07-09-2012, 02:25 AM   #28
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Re: 4.3: quit, won't start

I am having a similar problem with my Blazer, is there anyway to test a computer without bringing it into a shop?
Old 07-09-2012, 12:32 PM   #29
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Re: 4.3: quit, won't start

i dought it dealer did look at mine . all they could say was mabe a bad computer , no codes ,it was eracing the codes when the light went back out or when it was shutting down. but i can say i got mad and hit the computer while it was on its not wanting to start . the gauges went back to normal and it cranked. i did this afew times to get it home lol. not the best idea but thats how i narowed it down by area , i done replaced all but the computer and distibutor. by the way the dizzy is plastic and is known for going bad , the rotor gets play in it . summit makes a all metal replacement .
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