92 won't start when engine warm
Thread Starter
Racer
Joined: Aug 2006
Posts: 415
Likes: 0
From: Utah
92 won't start when engine warm
Here is another starting problem. I think this may have been adressed in the forum before, but I don't know how to get to those threads.
My 92 LT1 starts great first thing in the morning or after sitting for a couple of hours. After it has been running at highway speed for a half hour or so, it become hard to start. The starter turns the engine over, but it does not fire up. The only time it has not started after sitting for several hours, was when it had been parked in the sun in Las Vegas and the whole car was blazing hot. I got it started after putting an ice bag on the ECM and waiting for a while. After starting up, the car runs great, idles smooth, and has good power.
My mechanic thinks it is related to the security wiring in the steering column. (bad wire) I went to a parts store to get a new ECM and the store guy said he thought it was more likely to be the fuel pump. I still want to try the ECM but I thought I would try to get some of your opinions first. What would you guys do?
Thanks.
My 92 LT1 starts great first thing in the morning or after sitting for a couple of hours. After it has been running at highway speed for a half hour or so, it become hard to start. The starter turns the engine over, but it does not fire up. The only time it has not started after sitting for several hours, was when it had been parked in the sun in Las Vegas and the whole car was blazing hot. I got it started after putting an ice bag on the ECM and waiting for a while. After starting up, the car runs great, idles smooth, and has good power.
My mechanic thinks it is related to the security wiring in the steering column. (bad wire) I went to a parts store to get a new ECM and the store guy said he thought it was more likely to be the fuel pump. I still want to try the ECM but I thought I would try to get some of your opinions first. What would you guys do?
Thanks.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
When it won't start, that is the time to do some diagnostic testing. First check for stored error codes. Engines require spark (and at the right time), fuel and air (and in the correct ratio) in order to start and run. Check for spark and spark timing with your timing light while someone cranks the engine. Check for weak spark with a wire with clip leads and ground the wire and bring it to within 3/4 inch of a pulled plug wire (3/4" from the metal clip on the inside of the boot), it should jump this gap and make a nice snapping sound. Measure the fuel pressure on the shraeder valve on the end of the fuel rail and see how long it takes to drop with the ign off. If rapid, then you may have a leaky injector making it too rich to start hot. Pull an injector plug and connect a noid light (available at parts store), or a low power 12v lamp like a sidemarker lamp across the injector plug and crank the engine. The lamp should pulse showing that the injectors are being exercised.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
jfb is correct. I will add to this and say to ohm the injectors cold and hot. They should read around 16 ohms and all 8 should be close to the same number. Adding ice to the ECM might be giving you a clue.
Burning Brakes
Joined: Nov 2005
Posts: 1,211
Likes: 2
From: Dumas Arkansas
Mine would do it on cold start up's and bought some engine starter. I sprayed into the air cleaner for 3 seconds according to the directions and she hasn't let me down since. But they say this is only a temp. fix.
Thread Starter
Racer
Joined: Aug 2006
Posts: 415
Likes: 0
From: Utah
Thanks for the ideas. Added info: no codes come up, and the opti and plugs and wires were recently changed along with the water pump. I'm thinking:
1. try fuel pump relay
2. either injectors or ECM
I haven't undertaken the suggested diagnostics yet.
1. try fuel pump relay
2. either injectors or ECM
I haven't undertaken the suggested diagnostics yet.
Race Director
Joined: Apr 2004
Posts: 17,066
Likes: 3
From: Milpitas ca
I bought a used ECM on Ebay when I was getting a "no start when hot" syndrome for 50 bucks two years ago. No problems since. Until then I had to park in shade or under a tree so it would start.
I still contend that GM had an ECM overheating problem that they don't admit.
I still contend that GM had an ECM overheating problem that they don't admit.
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