engine cranks but will not run
Thread Starter
Drifting
Joined: May 2002
Posts: 1,509
Likes: 3
From: Hazel Park MI
engine cranks but will not run
85 vette. Took my USM HSR off as it has been leaking oil since I got from their welds, in order to fix them. Going thru chart A-3A, got spark and the blinking light at injector. Got fuel pressure, but drops to zero in 5-6 minutes. So I call Holley, they say that's about right for the regulator I have. So on to the next page. Test light to circuit 430 of distrib harness, get injector light. Supposedly a bad ignition module. Got the MSD 8366 less than a year ago from Jeg's. Send it back and get a new one. Right, same condition.
Scanned it on attempted start up. IAC at 144 - never saw that before. Inj. pulse width 12.4 - never scanned on start up before, but it was never even close to that when it was running. When I completed the TPS test on chart A-3B (which I did anyway, even though I had a light telling me faulty ignition module), I got a light following the same circuit 430 test mentioned above. That would mean bad TPS. Yet, I hear my IAC resetting when I shut her down - never did that before. Can anyone shed any light on my situation before I throw parts at it?
TIA, John
Scanned it on attempted start up. IAC at 144 - never saw that before. Inj. pulse width 12.4 - never scanned on start up before, but it was never even close to that when it was running. When I completed the TPS test on chart A-3B (which I did anyway, even though I had a light telling me faulty ignition module), I got a light following the same circuit 430 test mentioned above. That would mean bad TPS. Yet, I hear my IAC resetting when I shut her down - never did that before. Can anyone shed any light on my situation before I throw parts at it?
TIA, John
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
what regulator?
I have to disagree with the Holley folks...dumping off ALL the fuel pressure that quick means that it was never there OR the pump is bad OR the fuel is bleeding off thru the injectors...none of these events would help it run.
You need 40 psi steady to run right....25 psi just to build a fire in the thing...
when pressure falls off that fast that indicates that it does not have ANY chance of keeping up with a runnin g engine. I'd revisit the FP issue and regulator/pump.
I have to disagree with the Holley folks...dumping off ALL the fuel pressure that quick means that it was never there OR the pump is bad OR the fuel is bleeding off thru the injectors...none of these events would help it run.
You need 40 psi steady to run right....25 psi just to build a fire in the thing...
when pressure falls off that fast that indicates that it does not have ANY chance of keeping up with a runnin g engine. I'd revisit the FP issue and regulator/pump.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Did you ever try a little starting fluid or gas just to see if it will start and run for a couple seconds. I would just like to know for sure the spark is strong enough for combustion. If it does run, then you can focus back on the fuel system with a bit more confidence.
Then might want to pull the injector rails to see if it is spraying.
Then might want to pull the injector rails to see if it is spraying.
Thread Starter
Drifting
Joined: May 2002
Posts: 1,509
Likes: 3
From: Hazel Park MI
Thanks guys, I'll head in that direction. I have a rail mounted FP gauge, but haven't had anyone observe it while cranking. I get the pump for 2 secs when key turned and the relay click when shut down, and I do have blue spark. The regulator did not pass the fuel system check in the service manual upon initial diagnosis, and that's why I called holley. But like I mentioned the holley guy told me they are meant to bleed down that quick. So I figure it my not operate the same as the stock reg. under the same test. I'll checks some plugs also.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
what regulator?
I have to disagree with the Holley folks...dumping off ALL the fuel pressure that quick means that it was never there OR the pump is bad OR the fuel is bleeding off thru the injectors...none of these events would help it run.
You need 40 psi steady to run right....25 psi just to build a fire in the thing...
when pressure falls off that fast that indicates that it does not have ANY chance of keeping up with a runnin g engine. I'd revisit the FP issue and regulator/pump.
I have to disagree with the Holley folks...dumping off ALL the fuel pressure that quick means that it was never there OR the pump is bad OR the fuel is bleeding off thru the injectors...none of these events would help it run.
You need 40 psi steady to run right....25 psi just to build a fire in the thing...
when pressure falls off that fast that indicates that it does not have ANY chance of keeping up with a runnin g engine. I'd revisit the FP issue and regulator/pump.
