'91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse) - S-10 Forum
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'91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

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Old 08-14-2011, 11:38 PM   #1
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Unhappy '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

Hey guys,

I just acquired a 1991 Chevrolet S-10 Blazer with a 4.3L V6. I Picked it up at an impound lot auction so I really have no clue as to what the history is of this car or what any of the symptoms were before this car stopped starting.

Here are the current symptoms:

-Engine cranks but wont fire
-If starter fluid is sprayed in the TBI then the engine will fire.

Here is what I have deduced from my own troubleshooting and what repairs I have made so far:

-Fuel pressure into the TBI is at about 10psi which seems normal according to the manual
- I replaced the fuel pressure regulator spring and diaphragm (the spring was broken into 3 pieces)
- When I put the TBI back together, the injectors squirted fuel ONCE and then quit.
-I then took it back apart, fiddled with it and put it back together, again when I cranked it, the injector squirted ONCE and then stopped.
- I used the test light deal to check if the injectors were being pulsed and it turns out that the ecm is NOT pulsing the injectors.

I am completely lost at this point and have no Idea where to start if the problem is the ECM.


Thank you for taking time to help!! I hope I have given sufficient information in order for you to have some Ideas of where I can go from here. I am happy to answer any questions which may help you understand the trouble I am experiencing.
Old 08-15-2011, 03:05 AM   #2
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

ign control module

distrib

need signal form these to run injectors

you have ign signal problem

also make sure ecm fuses good
Old 08-15-2011, 03:21 AM   #3
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

Quote: Originally Posted by fast68chevy
ign control module

distrib

need signal form these to run injectors

you have ign signal problem

also make sure ecm fuses good

Well I appreciate your help, however I dont think it can be the ignition system because the engine runs fine if you nurse fuel into the throttle body. I am also skeptical of the distributor because of the same reason, however if you could provide just a little more detail as to what problems there could be with these two systems, that would be a great help, because honestly your 15 word answer really didnt help much. but thanks for summing up my problem
Old 08-24-2011, 09:21 PM   #4
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

Hey!
that was 22 words!!!

i have similar problem and am about to replace PCM.
Here is the game and why people say check ignition stuff for lack of injector pusles...

allegedly, the computer needs to see good, valid ignition pulses before it will send out fuel pulses. I am playing the same game with a 94 'W'

when it runs (getting rare) there are clean pulses (through LED and resistor) at both the fuel injector wire and the ignition signal wire at the PCM (I have it hanging by the wires and am about to put a scope on it). but when it won't run, I see weak pulses on the 'noid' light on both.
I THINK it was making sparks even though it would not run...I checked many times with a plug and wire on the distro....

anyway, that is the theory, I think.
Old 08-25-2011, 01:59 AM   #5
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

Quote: Originally Posted by 0x00
Hey!
that was 22 words!!!

i have similar problem and am about to replace PCM.
Here is the game and why people say check ignition stuff for lack of injector pusles...

allegedly, the computer needs to see good, valid ignition pulses before it will send out fuel pulses. I am playing the same game with a 94 'W'

when it runs (getting rare) there are clean pulses (through LED and resistor) at both the fuel injector wire and the ignition signal wire at the PCM (I have it hanging by the wires and am about to put a scope on it). but when it won't run, I see weak pulses on the 'noid' light on both.
I THINK it was making sparks even though it would not run...I checked many times with a plug and wire on the distro....

anyway, that is the theory, I think.

HEY!! You should check the distributor!! Take off the distributor cap and check to see if anything about the distributor looks old, rusted, broken etc. because that is what was wrong with my blazer! I tried replacing the distributor and the injectors started pulsing right away!!! So before you go spend the money on a PCM, your distributor may be the problem. The distributor serves two functions, One being firing the spark plugs, but the second is pulsing the injectors. the part that fired the spark plugs was working just fine, but the part that fired the injectors was all rusted and falling apart.

anyway, try that FIRST because I doubt that it is your PCM. However if your distributor looks brand new, then you might want to try a new PCM.

Luckily I had an s10 pickup of the same year and with the same engine which I used as a parts truck to test different theories. I eventually ended up swapping the distributor and the injectors immediately started firing, so I have bought a new distributor (but I havent installed it yet :P)
Old 04-01-2013, 12:20 PM   #6
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

This is an old thread but for other people's info I would just like to say that this is MOST LIKELY the ignition module. As an ASE master certified mechanic with 20 years experience, I would say that 90% of the time when the TBI is not pulsing, it is the ignition module. Before you say "but i have spark", it is not uncommon for the injector side of the module to go bad while the ignition side still works. I have seen this over and over. If the pickup coil in the distributor goes out, you lose both. The only other thing that can cause this is a bad ECM and that is rare but possible. If you have fuel pressure, spark and no TBI pulse, the cheapest and most likely thing to go bad is the ignition module.
Old 04-01-2013, 12:25 PM   #7
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

To reply to Kronik, since the ignition module is in the distributor, that is why the problkem was fixed. Buying a NEW distributor will not fix your problem because a new one will not come with a module and your will have to swap them. THE ONLY PART IN A DISTRIBUTOR THAT CAUSE NO INJ PULSE BUT STILL HAVE SPARK IS THE IGNITION MODULE!. Hope this saves you all a lot of Troubleshooting and money.
Old 04-01-2013, 04:16 PM   #8
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

I want to say the pick-up coil in the distributor will cause a no injector pulse condition.
Old 04-07-2013, 06:45 PM   #9
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

Agree... The ICM is the culprit. Replace the ICM. Check the three connectors for corrosion.

The 8-pin ICM uses three plug-in connectors: a 2-pin to the ignition coil, a 4-pin to the ECM, and a 2-pin connector to the pick up coil in the distributor.

Ignition coil connector
Pink.......................12V
White.....................Ignition coil

ECM connector
Black-red stripe........Ground
Tan-black stripe.......ECM reference - 5V
Purple-white stripe...Fuel injector control
White.....................ECM

Pick-up coil connector
Green.
Yellow
Old 04-27-2013, 01:57 PM   #10
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Re: '91 S-10 Blazer Fuel pressure good but injectors wont squirt (no injector pulse)

Quote: Originally Posted by SixPack
Agree... The ICM is the culprit. Replace the ICM. Check the three connectors for corrosion.

The 8-pin ICM uses three plug-in connectors: a 2-pin to the ignition coil, a 4-pin to the ECM, and a 2-pin connector to the pick up coil in the distributor.

Ignition coil connector
Pink.......................12V
White.....................Ignition coil

ECM connector
Black-red stripe........Ground
Tan-black stripe.......ECM reference - 5V
Purple-white stripe...Fuel injector control
White.....................ECM

Pick-up coil connector
Green.
Yellow
I have the same problem with a 90 s-10 blazer. i have replaced the pick up coil and the fuel pump twice and the fuel pump relay. but still no pulse. i have noticed that the fuel pump does not prime every time the ignition is turned on. it primes about once every 8 to 10 turns of the key

Any help would be greatly appreciated
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