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No Start Condition

posted Jun 22, 2016 19:57:04 by Rick Bewick
1995 S10 2.2L Manual Transmission, will run on carbarator cleaner.
(ICM has been replaced)
Have spark and fuel pressure. I get code 54, Low voltage at the fuel pump relay. There is 12V at the relay during prime and cranking when oil pressure is detected.
I do not have any voltage on circuit 120 (PCM terminal B2). Continuity is good from oil pressure switch to PCM and ICM to PCM. It seems I have have a broken connection between the PCM terminal B2 to the tie point into the fuel pump. If you agree with this, do you know where this tie point is located?


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8 replies
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Tyler said Jun 23, 2016 01:42:40
Hey Rick!

I may be misunderstanding you, but are you talking about PCM pin B12, as opposed to B2? B12 would be the PCM's monitor of the fuel pump relay, and the source of your code 54. B2 is a bypass ignition input from the ICM.

If it's B12 that you're talking about, then I'd totally agree that you're looking for some kind of broken wire/high resistance in that circuit. NO idea where that splice is, unfortunately. If there's no obvious harness damage, then I'd be tempted to run a new wire just to make the code go away.

Also, I'm not sure that the code 54 explains the no start. No injection pulse? Just out of curiosity, does the fuel pump relay activate as soon as you start cranking? Or, does it just prime, and it's the oil pressure switch that's supplying power. If there's no injection pulse and no fuel pump relay activation, then I'd wonder about an input problem.
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Chris said Jun 23, 2016 15:43:33
Check for injector pulse. If you dont have it check your IC ref HI at A4 for an on off square wave. If your missing the square wave at that connector its most likely a failed ignition module.

It may be the purple/white wire too. I'm not 100% on which is which but one of the 2 sends the ecm the reference pulse for injection timing. If the input to the ecm isn't there it can still have spark but no fuel injector pulse.

This isn't adressing code 54. I never cared for OBD1 codes. Very rarely do they help it seems.
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Tyler said Jun 24, 2016 01:37:20
This isn't adressing code 54. I never cared for OBD1 codes. Very rarely do they help it seems.


Truth right here. Not saying it was wrong for Rick to pull codes, just can't remember the last time a flash code actually helped my diagnosis, lol.
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Rick Bewick said Jun 24, 2016 22:53:53
Your right, OBD1 is very unrelyable.

I do have power at B12 (fuel pump) at prime and cranking up to oil pressure. I can hear the fuel pump prime.

Upon further testing I discovered I am not getting fuel injector pulse from the ECM. The best I can tell anyway with DC and AC voltage. On to testing the fuel injectors.

[Last edited Jun 26, 2016 21:05:36]
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PaulDanner said Jun 29, 2016 02:29:37
It may be the purple/white wire too. I'm not 100% on which is which but one of the 2 sends the ecm the reference pulse for injection timing.

Yep, purple/white is the distributor reference signal.
With key on, touch a test light to this wire on and off connected to battery positive. Injectors should fire every time.
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Rick Bewick said Jun 29, 2016 19:22:31
I will do that the next chance I get, thanks Paul.

On another note, my manual says injectors should be between 11.6-12.4 ohms. My highest is 15.8 ohms and has fuel in the connector. Second highest is 14.2 ohms. The other two are at the upper limit of 12.4 ohms.

The injectors have about 120,000 miles on them, the engine was replace with a rebuilt long block about 15,000 miles ago.
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Rick Bewick said Jun 30, 2016 19:39:30
Yep, purple/white is the distributor reference signal.
With key on, touch a test light to this wire on and off connected to battery positive. Injectors should fire every time.


With key on there is 12v at the injectors all the time. When I touch a test light PPL/WHT on A4 the fuel rail charges. I can hear a clicking noise I assume is the injector(s) firing.
I also tested the Refrence wire from the ICM on A4 (PPL/WHT) and the PCM is receiving a signal from the ICM.
[Last edited Jul 01, 2016 09:44:47]
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Rick Bewick said Jul 04, 2016 14:08:58
Okay, I have spark, fuel pressure and injection pulse. I must have 2 or more bad injectors, right?
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