Injectors won't fire...
Registered User
Joined: Aug 2003
Posts: 564
From: dallas, tx.
Re: Injectors won't fire...
if the fuel pump relay is energizing whenever you crank the engine.....then it seems the PCM is working and it is recieving a signal from the opti. check the TPS output voltage. Your TPS sensor should have 3 wires and they should be like this. PCM GROUND, 5V REFERENCE and OUTPUT VOLTAGE. no particular order. If your output voltage is greater than 2.5V at startup, then the PCM will kill the injector signal. It should be .20V - 1.00V at closed throttle. Check the output voltage with key on, closed throttle.
Thread Starter
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Joined: Jan 2004
Posts: 174
From: ATX
Re: Injectors won't fire...
I haven't tried a noid light, but I have tried using my test light method. It's worked before to tell if the injectors were pulsing. I'm fairly sure that they're not pulsing. When I get home, I'll try using both terminals of the injector connectors at the same time with the test light to test both power and ground.
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Joined: Jan 2003
Posts: 1,362
Re: Injectors won't fire...
Originally Posted by tamatt27
The way I have the fuel pump wired, it's using the relay. The only thing I have done to it different, is that the 'Hot in Run' wire is wired to a 'Hot at all Times'. That only means that the fuel pump will come on when the battery's connected, for 2 seconds, then shut off when the computer doesn't read any RPM's. So whenever I crank it, I hear the fuel pump come on. Also whenever I disconnect some of the PCM connectors, and re connect them, I hear the fuel pump come on for a few seconds.
That tells me that computer's controling the fuel pump relay.
Like I said before, I checked and double checked all the PCM grounds and power sources...they're all as they should be.
Blaze, will the opti have a 5V reference that I can check? Also, is there a way I can check the low res signal coming from the opti, and see if the computer's getting that?
That tells me that computer's controling the fuel pump relay.
Like I said before, I checked and double checked all the PCM grounds and power sources...they're all as they should be.
Blaze, will the opti have a 5V reference that I can check? Also, is there a way I can check the low res signal coming from the opti, and see if the computer's getting that?
Okay, guess my memory is bad, I recalled you having it hot wired to the battery.
Thread Starter
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Joined: Jan 2004
Posts: 174
From: ATX
Re: Injectors won't fire...
Thanks Shoebox, that's what I was looking for.
Well guys, I hooked up the '96 PCM last night, and it cranked and tried to start. It would run, then die a few seconds after it started...like it was doing before I put the MAF on there. I thought the MAF fixed it, I guess it didn't.
Well then, I hooked up the '94 PCM (the one that came with the motor) and it did the same thing. Started then died. It did that a few times, then nothing. After it wouldn't start again, I check spark and injector ground at the same time, I had both, and it still wouldn't start this time! WTF?
Would an ignition switch cause an intermittent no injector ground and frequent dieing? It's a 3rd gen ignition switch BTW.
Welp Pasky, looks like Kitt's gonne miss the March 26 Thirdgen Gathering too! :Mad:
Well guys, I hooked up the '96 PCM last night, and it cranked and tried to start. It would run, then die a few seconds after it started...like it was doing before I put the MAF on there. I thought the MAF fixed it, I guess it didn't.
Well then, I hooked up the '94 PCM (the one that came with the motor) and it did the same thing. Started then died. It did that a few times, then nothing. After it wouldn't start again, I check spark and injector ground at the same time, I had both, and it still wouldn't start this time! WTF?
Would an ignition switch cause an intermittent no injector ground and frequent dieing? It's a 3rd gen ignition switch BTW.
Welp Pasky, looks like Kitt's gonne miss the March 26 Thirdgen Gathering too! :Mad:
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Joined: Dec 1969
Posts: 27,730
From: Little Rock, AR
Re: Injectors won't fire...
I know a MAF engine should run without the MAF working, but the one time I forgot to plug my MAF in after doiing some work on the car, it did just what you are describing-would start, then immediately die.
I never tried to duplicate the scenario (ran fine after I plugged it back in). Just throwing out a bone for chewing.
I never tried to duplicate the scenario (ran fine after I plugged it back in). Just throwing out a bone for chewing.
Thread Starter
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Joined: Jan 2004
Posts: 174
From: ATX
Re: Injectors won't fire...
That's what Pasky and I were thinking. We've got a friend that his LT1 wouldn't run in Speed Density. Once he got a MAF on there, he said it ran like a champ.
Everytime it runs, which is not very long, it sounds like it's got a vacuum leak. Pasky and I tore the damn thing apart looking for one, but we couldn't find one. I have a CAI with cone filter. Is that a normal sound for that filter?
Everytime it runs, which is not very long, it sounds like it's got a vacuum leak. Pasky and I tore the damn thing apart looking for one, but we couldn't find one. I have a CAI with cone filter. Is that a normal sound for that filter?
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Joined: Jan 2003
Posts: 1,362
Re: Injectors won't fire...
Its normal matt. Its definatley not a vacuum leak. I took my air filter housing off and I got that PSSSSSSSH also where the the airfoil is. Are you sure the MAF is getting power? I would try to get your datamaster working to help you diagnose the problem. I remember last time I was there you were saying the injectors weren't firing but I saw the duty cycle and inject calc's working fine. When you hook it up to your laptop, datamaster will have options on which com port to use, try all of them. Your serial connection on your laptop may not be com 1 (default used). Make sure you have the plug that has serial data and pcm ground both hooked up to the ALDl, having just the serial data won't work. Get a datamaster log then post it up here.
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Joined: Sep 2003
Posts: 627
From: Edmonton, AB, Canada
Re: Injectors won't fire...
Originally Posted by tamatt27
Would an ignition switch cause an intermittent no injector ground and frequent dieing? It's a 3rd gen ignition switch BTW.
Welp Pasky, looks like Kitt's gonne miss the March 26 Thirdgen Gathering too! :Mad:
Welp Pasky, looks like Kitt's gonne miss the March 26 Thirdgen Gathering too! :Mad:
Thread Starter
Registered User
Joined: Jan 2004
Posts: 174
From: ATX
Re: Injectors won't fire...
Yeah, Pasky give me a call on my cell phone around 6:30-45 if ya can.
512-971-5064
I work at a dealership, so I'll get a price on an ignition switch. Wonder if that'll fix it.
Also, on Datamaster, I've chosen F-Car M/T. Even though I swapped in a T56 with the LT1, the engine and PCM were mated with an auto originally. Should I choose A/T on Datamaster and see if I can communicate then?
512-971-5064
I work at a dealership, so I'll get a price on an ignition switch. Wonder if that'll fix it.
Also, on Datamaster, I've chosen F-Car M/T. Even though I swapped in a T56 with the LT1, the engine and PCM were mated with an auto originally. Should I choose A/T on Datamaster and see if I can communicate then?
Thread Starter
Registered User
Joined: Jan 2004
Posts: 174
From: ATX
Re: Injectors won't fire...
Ah ko, well that kinda blew my idear outta the water.
I'm pretty sure I hooked up the DLC right.
Since I have access to the 4th gen interior harness, I used the 4th gen DLC. I spent a lot of time color matching wires to use for extensions to it, and I'm fairly sure I have it hooked up right. I'll try tonight to see if you can walk me through Datamaster and getting it working...
I'm pretty sure I hooked up the DLC right.
Since I have access to the 4th gen interior harness, I used the 4th gen DLC. I spent a lot of time color matching wires to use for extensions to it, and I'm fairly sure I have it hooked up right. I'll try tonight to see if you can walk me through Datamaster and getting it working...