Won't Fire
Thread Starter
Race Director
Joined: Jul 2007
Posts: 15,097
Likes: 279
From: Salt Lake City Utah
2020 C3 of the Year Finalist - Unmodified
2019 C3 of Year Finalist (stock)
Won't Fire
I just picked up my 93 a few weeks ago and am experiencing my FIRST C4 issue. Drove it Thursday night, ran great. Jumped in next morning and it cranks but won't fire. I'm waiting for my service manual to get here and I am a pretty good wrench myself, just need some input on what to look at first. There must be a proper sequence of events that happens when an LT1 fires up. If this were my 81 I would know exactly where to start, not the case on the 93. Is there a breaker or fuse for the fuel pump before I start looking at systems?
Where would you start looking? (kind of looking forward to playing with an LT1, just want to do it right) She's put to bed for the winter now, but I would rather fix it now than wait for Spring.
Thanks!
Where would you start looking? (kind of looking forward to playing with an LT1, just want to do it right) She's put to bed for the winter now, but I would rather fix it now than wait for Spring.
Thanks!
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
As mentioned, I'd hook up a timing light and have somebody crank the car over while I hold the timing gun trigger down. If the light does not flash, it's for sure you don't have spark. If it does flash, then you'll know spark is not your problem. In which case the fuel system should be looked at next.
Thread Starter
Race Director
Joined: Jul 2007
Posts: 15,097
Likes: 279
From: Salt Lake City Utah
2020 C3 of the Year Finalist - Unmodified
2019 C3 of Year Finalist (stock)
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
You can check for spark real easy by arking the coil wire to ground, and then a plug wire. Should be able to pull ½ inch ark. That answers that quickly.
Get a fuel pressure gauge the connects to the schrader valve to check fuel pressure (38-40 lbs). That’s where your heading next and a must to have if you are going to maintain the car.
You also need a node lamp indicator to check the fuel injector pulses. There should by 12 volts on the injector wires and the ECM takes one terminal to ground completing the circuit activating the injector solenoid valve.
Also you should hear the fuel pump run for 2 seconds when you turn the key to the on position. If it doesn’t run, it might start with excessive cranking. The pressure switch activated by oil pressure will eventually start the pump.
To me you don’t have any classic opti symptoms. I wouldn’t go there till I checked the basics first. Hate to say it but the ECMs have been real problems with strange symptoms. Like if you had no injector pulses its not going to start. But just check the basics one by one.
Get a fuel pressure gauge the connects to the schrader valve to check fuel pressure (38-40 lbs). That’s where your heading next and a must to have if you are going to maintain the car.
You also need a node lamp indicator to check the fuel injector pulses. There should by 12 volts on the injector wires and the ECM takes one terminal to ground completing the circuit activating the injector solenoid valve.
Also you should hear the fuel pump run for 2 seconds when you turn the key to the on position. If it doesn’t run, it might start with excessive cranking. The pressure switch activated by oil pressure will eventually start the pump.
To me you don’t have any classic opti symptoms. I wouldn’t go there till I checked the basics first. Hate to say it but the ECMs have been real problems with strange symptoms. Like if you had no injector pulses its not going to start. But just check the basics one by one.
Intermediate
Joined: Sep 2006
Posts: 31
Likes: 0
You can check for spark real easy by arking the coil wire to ground, and then a plug wire. Should be able to pull ½ inch ark. That answers that quickly.
Get a fuel pressure gauge the connects to the schrader valve to check fuel pressure (38-40 lbs). That’s where your heading next and a must to have if you are going to maintain the car.
You also need a node lamp indicator to check the fuel injector pulses. There should by 12 volts on the injector wires and the ECM takes one terminal to ground completing the circuit activating the injector solenoid valve.
Also you should hear the fuel pump run for 2 seconds when you turn the key to the on position. If it doesn’t run, it might start with excessive cranking. The pressure switch activated by oil pressure will eventually start the pump.
To me you don’t have any classic opti symptoms. I wouldn’t go there till I checked the basics first. Hate to say it but the ECMs have been real problems with strange symptoms. Like if you had no injector pulses its not going to start. But just check the basics one by one.
Get a fuel pressure gauge the connects to the schrader valve to check fuel pressure (38-40 lbs). That’s where your heading next and a must to have if you are going to maintain the car.
You also need a node lamp indicator to check the fuel injector pulses. There should by 12 volts on the injector wires and the ECM takes one terminal to ground completing the circuit activating the injector solenoid valve.
Also you should hear the fuel pump run for 2 seconds when you turn the key to the on position. If it doesn’t run, it might start with excessive cranking. The pressure switch activated by oil pressure will eventually start the pump.
To me you don’t have any classic opti symptoms. I wouldn’t go there till I checked the basics first. Hate to say it but the ECMs have been real problems with strange symptoms. Like if you had no injector pulses its not going to start. But just check the basics one by one.
thanks
Don
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
I don't mean to steal this thread but i'm experience lng some of the same issues on my 85. Hard to start after sitting overnight will start after excessive cranking when I turn the key on i don't hear the fuel pump running checked my pressure with guage showed zero. but car finally starts so thought the guage must be broken. pccolt you mentioned about the oil pressure sensor starting up the fuel pump after excessive cranking. if this is indeed my problem and it sounds like it, what do I need to do to fix it?? your help would be greatly appreciated, car seams to run fine once I get it started
thanks
Don
thanks
Don
) I believe you also have a cold start thermo switch ($90) that may be part of the problem (do a search).
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Pro
Joined: Dec 2008
Posts: 658
Likes: 0
From: Lubbock for now, headed for Oklahoma
I don't mean to steal this thread but i'm experience lng some of the same issues on my 85. Hard to start after sitting overnight will start after excessive cranking when I turn the key on i don't hear the fuel pump running checked my pressure with guage showed zero. but car finally starts so thought the guage must be broken. pccolt you mentioned about the oil pressure sensor starting up the fuel pump after excessive cranking. if this is indeed my problem and it sounds like it, what do I need to do to fix it?? your help would be greatly appreciated, car seams to run fine once I get it started
thanks
Don
thanks
Don
this can also be the result of a ruptured fuel pressure regulator. Pull the vacuum line off(plug the manifold end) of it and start the car a few times. Not only will the quick start return but you will probably start getting fuel coming out of the vacuum nipple on the regulator itself. Very common problem.
Leave your fuel pressure gauge connected. After you shut the car off, if the pressure continues to drop to zero you probably have an injector or several that are leaking. The rate that the gauge drops will give you some indication.
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
As stated check for Fuel Pressure if you don't have it turn the radio off and turn key on and listen for the FP it should come on for a couple of seconds. If you don't hear it it is either the FP relay,FP or VATs. Check fuses. Try pushing the key in as you start it the pellet wears down and loses contact some times.