86 Vette not running

[metoo1012]

HELP!!!! Bought a basket case and now am becoming one. Nice vet but, will not run. Starts, runs maybe 3 seconds then dies. I have checked all grounds, replaced ecm,swapped out memcal, coil, pick up coil, fuel pump and filter, spark plugs and wires, tps, est, dist. rotor and cap eliminated the dreaded VATS with bypass unit. Noid light flashes while cranking engine, timing lights flashes while cranking engine 40 psi on fuel rails, new injectors,new starter( lost the first one to abuse) timing is set as close as can be without running.

 

[MBDiagMan]

Have you tried leaving the fuel pressure gauge in place and observing? Make sure it is not losing fuel pressure upon start up. Report results of this test.

 

[metoo1012]

40 lbs, very little variance. Will not run on starting fluid for more than 3 seconds
thanks for the reply

 

[MBDiagMan]

From what you say, the problem seems that it MUST be losing spark. Have you tried closely watching the timing light after it is running and noting if the light stops flashing just before it dies or at the point that the engine comes to a complete stop?

 

[rlg]

my 90 went through the start but would not stay running ordeal, it turned out to be the IAC motor. I don't know if the 86 has one or not.

 

[metoo1012]

its a tie, just plain dies, something is shuting off the elec system, disconnected the bypass from the coil harness and still wants to die

 

[metoo1012]

I will check for an iac motor
thanks

 

[metoo1012]

IAC checks out. ohms and voltage are within specs

 

[rlg]

I am not sure how that test would tell you if the piston is stuck in the extended position. When I pulled mine out it was stuck and wouldn't move. New one fixed the problem. That test may work I just didn't try it.

 

[metoo1012]

vette will start and run 3-5 seconds, shut off, let it set for a few minutes and try again, it will try to start and maybe run 3-5 seconds or not start at all. I still have 40 lbs fuel pressure, the noid light still flashes and I have spark with the timing light on number 1 wire.
Just replaced the ecm, long shot and still have same issue. I will remove the iac and do a visual inspection.
thank you

 

[rlg]

use some Carb cleaner on it, that is supposed to help. I just bought a new one at the local parts store.

 

[metoo1012]

I will buy a new one.

I am trying to run this in bypass mode.

 

[vetteboy86]

Try unplugging the MAF.

 

[redvett]

Sounds like the VAT's theft deterent system. Do you have a security light on?

 

[metoo1012]

maf unplugged, same results

 

[metoo1012]

VATS by passed with bypass module, verified by pulling fuse on vats system, dead. installed bypass module and have fuel, injectors and spark

 

[metoo1012]

IAC motor is new.

HELP!!!!!

 

[rlg]

what about the ignition control module?

 

[vetteboy86]

Pull a plug, put it back into the plug wire boot, and then lay that against a good ground. Use a bracket or something so that the hex part of the plug (where the socket engages the plug) is touching a ground. Have someone turn the car over while you watch the spark. It should be blue if it is strong. If it is orange than the spark is weak. Either way this may not be your problem.

The next thing I would do is disconnect the fuel pump. Turn the the ignition over for at least 10-15 seconds and make sure spark is happening the entire time while cranking the motor over. Next put a timing light on #1 and verify the timing is close while cranking. If that is the one you pulled put it back in now.If the timing is close, than put the plug back in, and plug wire back on. Hook fuel pump back up. Now pull the EST wire that connects to the distributor. This is the electronic spark timing wire. It is brown, and has a brown connector I believe. Start the car again, and verify timing. See if the car runs with this wire unplugged. It will throw a code, not sure what it is off the top of my head.

How does it run for those few seconds while it is running? Does it pop and back fire through intake or exhaust? I am wondering if the spark control isn't correct. Try these things then get back to us.

Craig

 

[The Car Whisperer]

IAC motor is new.

HELP!!!!!

Is the IAC adjusted properly? There is a procedure for this. If you don't adjust it using the prper procedure the engine will not idle properly. Here's a procedure I found online that I have used on my 86 L98 when I installed a new IAC. I hope the author won't mind -