Engine cranks, wont start 1990
Thread Starter
6th Gear
Joined: Apr 2015
Posts: 6
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From: Mi
Engine cranks, wont start 1990
Hello, I have a 1990 non ZR1 , last weekend I'd replaced the battery. I started it ran fine for about 30 seconds, then it ran real rough and stalled. I got it to start again the only way I got it to start is press down on the gas pedal, and when it did start it had practically no throttle response, ran rough for about 10 seconds than it stalled again. Not the only way I get it to fire off is spray stating fluid down the TB. I went check the fuel press I had no fuel press at all in the rail. So to eliminate the fuel pump I Jumpered 12 volts to the fuel pump,I got pressure at the rail. I go to start nothing. So im assumming the injectors are not firing. I had tried jumping out the oil pressure switch behind the distributor , got nothing,so I went to check the voltages from the tps, I not only have no voltage coming from it (signal to ECM) I have no voltage (5VDC) going to it. Im going to try retrieve any codes this weekend, BUT im thinking the ECM had died on me. Is there any quick test I can do, to check if this the case before I shell out money for a remag one??
Team Owner
Joined: Jul 2004
Posts: 28,473
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From: Hartford WI
Before you rule that out, take a noid light and hook it to an injector from each bank. See if they light up. You can probably rent one from an Autozone. I did.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Check fuses no voltage possibly fuseable link. Does check engine light work? Do you have FSM or at least a good wiring diagrams. If ecm failed it will have 12v to it and no 5v coming out for sensors.
Thread Starter
6th Gear
Joined: Apr 2015
Posts: 6
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From: Mi
What do you mean "I got pressure at the rail"? How much pressure? How long did it hold? Did you pull out the hose to the fuel pressure regulator and see if there is gas in it? I would let the car sit for a couple of minutes and turn it on to run but don't crank. See if the pressure jumps up. If it does, see how long it stays up. If not, you have a pump issue be it electrical or mechanical.
Before you rule that out, take a noid light and hook it to an injector from each bank. See if they light up. You can probably rent one from an Autozone. I did.
Before you rule that out, take a noid light and hook it to an injector from each bank. See if they light up. You can probably rent one from an Autozone. I did.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
What aklim is getting at is what is your fuel pressure, specifically, in PSI? I don't think that you know., b/c I don't think that you checked it w/a proper gauge. Getting fuel spitting out of the schrader port isn't a pressure test.
Your symptoms,
"ran fine for about 30 seconds, then it ran real rough and stalled. I got it to start again the only way I got it to start is press down on the gas pedal, and when it did start it had practically no throttle response, ran rough for about 10 seconds than it stalled again"
...are very aligned with low fuel pressure. SO...is there a quick test that you can do? YES! Check the fuel pressure w/a proper gauge.
Your symptoms,
"ran fine for about 30 seconds, then it ran real rough and stalled. I got it to start again the only way I got it to start is press down on the gas pedal, and when it did start it had practically no throttle response, ran rough for about 10 seconds than it stalled again"
...are very aligned with low fuel pressure. SO...is there a quick test that you can do? YES! Check the fuel pressure w/a proper gauge.
Team Owner
Joined: Jul 2004
Posts: 28,473
Likes: 3,291
From: Hartford WI
Thanks for the reply, when you first turn the key, the fuel pump should run about 2 seconds or so the pressurize the system. My pump is no doing that, the only way it comes on is when I run 12volts directly to the pump bypassing the relays and fuses, pressure switches. I dont why knowing the pressure would have anything to do with that symptom? What I mean by rail is the the 2 rails running down by the plennum the injectors connect to.
We'll be happy to guess and throw parts at it all day long till we get lucky but your wallet might not like it.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
The OP stated he jumped power to get fuel pump to come on and didn't have 5v going to TPS. There is ECM issue that needs to be resolved first. After ECM is able function correctly then other remaining issues can be dealt with.
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Team Owner
Joined: Aug 2004
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From: Park City Utah
The FIRST thing he should do though, is put a proper gauge on there so he can actually see, WTF is going on with his pressure, rather than guess.
Le Mans Master
Joined: Sep 2013
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From: near the thumb in the mitten
I didn't say ecm failed, but it wasn't working. I believe there is a wiring concern related to battery voltage getting where it needs to be. 12 volts not getting to ECM is still an ECM issue because it not working. If jumping fuel pump would get car to start. Then you would believe ecm and related circuits were ok and focus would be on fuel pump circuit and related components. Maybe OP will post what has been found so far.
Team Owner
Joined: Jul 2004
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From: Hartford WI
I didn't say ecm failed, but it wasn't working. I believe there is a wiring concern related to battery voltage getting where it needs to be. 12 volts not getting to ECM is still an ECM issue because it not working. If jumping fuel pump would get car to start. Then you would believe ecm and related circuits were ok and focus would be on fuel pump circuit and related components. Maybe OP will post what has been found so far.
Thread Starter
6th Gear
Joined: Apr 2015
Posts: 6
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From: Mi
I didn't say ecm failed, but it wasn't working. I believe there is a wiring concern related to battery voltage getting where it needs to be. 12 volts not getting to ECM is still an ECM issue because it not working. If jumping fuel pump would get car to start. Then you would believe ecm and related circuits were ok and focus would be on fuel pump circuit and related components. Maybe OP will post what has been found so far.
Team Owner
Joined: Jul 2004
Posts: 28,473
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From: Hartford WI
Update, I placed my scope on every injector, and I receive no pulses at all. I have no engine light at all when I first turn the key, and I have voltage to the pink and black wire that powers the ecm, and I do have a FSM, Im going to confirm I have a good ground to the ecm, but im really starting to think it is the ecm. Any thoughts??
Le Mans Master
Joined: Sep 2013
Posts: 6,192
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From: near the thumb in the mitten
There are 2 orange wires that should have battery voltage all the time. Terminals D17 and C1 they are powered by a fusible link. Fusible link should be near battery. I would look at that before replacing ecm.
Last edited by Kevova; Jul 7, 2016 at 08:15 AM.
Le Mans Master
Joined: Aug 2000
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From: Australia
Pulling the codes would be a start ; CCM (Comms ) problems can cause no injector signal
Race Director
Joined: Apr 2002
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From: Anaheim CA
It sounds like the fusible link that powers the ECM is blown (or the ECM power connector is disconnected).
This picture shows the fusible link (between the connector and the round black insulator covering the splice between the fusible link and the regular wire (at the bottom of the connector)):
Usually this connector is buried under the brake booster so it can be hard to find.
This picture shows the fusible link (between the connector and the round black insulator covering the splice between the fusible link and the regular wire (at the bottom of the connector)):
Usually this connector is buried under the brake booster so it can be hard to find.
Thread Starter
6th Gear
Joined: Apr 2015
Posts: 6
Likes: 0
From: Mi
It sounds like the fusible link that powers the ECM is blown (or the ECM power connector is disconnected).
This picture shows the fusible link (between the connector and the round black insulator covering the splice between the fusible link and the regular wire (at the bottom of the connector)):
Usually this connector is buried under the brake booster so it can be hard to find.
This picture shows the fusible link (between the connector and the round black insulator covering the splice between the fusible link and the regular wire (at the bottom of the connector)):
Usually this connector is buried under the brake booster so it can be hard to find.