1994 won't start when hot
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
1994 won't start when hot
Trying to help a friend with his 1994. It starts when cold but once it warms up it starts to run poorly. If you shut it off when the engine is warm it won't start up, sometimes backfires.
We tested the injectors cold and hot. They were fine.
Fuel pressure was 41 and when it warmed up at 39psi.
No codes.
Could the ICM be a problem?
We are checking everything before assuming the opti is the problem.
We tested the injectors cold and hot. They were fine.
Fuel pressure was 41 and when it warmed up at 39psi.
No codes.
Could the ICM be a problem?
We are checking everything before assuming the opti is the problem.
Advanced
Joined: Sep 2013
Posts: 56
Likes: 0
From: Nanticoke PA
Trying to help a friend with his 1994. It starts when cold but once it warms up it starts to run poorly. If you shut it off when the engine is warm it won't start up, sometimes backfires.
We tested the injectors cold and hot. They were fine.
Fuel pressure was 41 and when it warmed up at 39psi.
No codes.
Could the ICM be a problem?
We are checking everything before assuming the opti is the problem.
We tested the injectors cold and hot. They were fine.
Fuel pressure was 41 and when it warmed up at 39psi.
No codes.
Could the ICM be a problem?
We are checking everything before assuming the opti is the problem.
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
Advanced
Joined: Apr 2011
Posts: 58
Likes: 4
From: Fenton MI
Any Resolution?
Any resolution on this issue? Because my '94 did the same thing twice - the last being yesteday.
Engine fully warmed -driven for 30 minutes, coolant at 201, oil temp 190ish. I pulled back into the garage and shut it off. I tried an immediate restart - cranking, but no start. 3-4 more attempts - same.
I pushed the schrader valve on the fuel rail - squirting to the firewall.
I removed #7 plug wire and installed the T125 spark tester - OF COURSE - it had spark then restarted & ran.
Total hot soak time was about 20 minutes. I haven't checked codes, but I suspect none because I never had a CEL. PLUS - it's a GM car. The CEL only goes on for EVAP codes - haha!
What'd ya find? MD
Engine fully warmed -driven for 30 minutes, coolant at 201, oil temp 190ish. I pulled back into the garage and shut it off. I tried an immediate restart - cranking, but no start. 3-4 more attempts - same.
I pushed the schrader valve on the fuel rail - squirting to the firewall.
I removed #7 plug wire and installed the T125 spark tester - OF COURSE - it had spark then restarted & ran.
Total hot soak time was about 20 minutes. I haven't checked codes, but I suspect none because I never had a CEL. PLUS - it's a GM car. The CEL only goes on for EVAP codes - haha!
What'd ya find? MD
Pro
Joined: Mar 2003
Posts: 742
Likes: 5
From: McMurray PA
I'm curious too. My '96 LT4 with 35k miles has a similar issue. It runs perfectly fine, but if you shut it off when hot, the odds are good that it will not restart. It will crank away but won't start. If you let it sit for 20-30 minutes it will start right up and run like nothing ever happened. Until the next time....
Suggestions appreciated.
Terry
Suggestions appreciated.
Terry
Advanced
Joined: Apr 2011
Posts: 58
Likes: 4
From: Fenton MI
An attempt ...
FWIW - I put a new ICM & fuel filter on mine in mid May. Dunno exactly why (see previous post about no codes, etc.). Maybe cost, maybe ease of effort, who knows ... But intuitively, I knew had to do something.
Note: I paid the extra bucks and bought the AC/Delco ICM. I bought it from Rock Auto. That decision proved to be inadequate.The ICM came in the factory box with no heat sink grease! WTF?
Buying that stuff (heat sink grease) is a royal pain. The guys at Autozone & Oreilley's didn't know what I was even talking about. One took me over to the wheel bearing grease aisle! I ended up at Radio Shack paying an extra $14 for a tube of it.
MD
Note: I paid the extra bucks and bought the AC/Delco ICM. I bought it from Rock Auto. That decision proved to be inadequate.The ICM came in the factory box with no heat sink grease! WTF?
Buying that stuff (heat sink grease) is a royal pain. The guys at Autozone & Oreilley's didn't know what I was even talking about. One took me over to the wheel bearing grease aisle! I ended up at Radio Shack paying an extra $14 for a tube of it.
MD
1st Gear
Joined: Nov 2019
Posts: 1
Likes: 0
Will not start when engine is hot
Hello all this it my first time. I am hopeful someone can assist me. I have typed up a quite long message twice and I’m not sure if it’s making its way to the forum, so I’ll type a short one. Mine has the same symptoms, I’ve had GM replace the opti distributor cap and guts, along with the water pump ( unrelated) it didn’t fix it, they then put in new fuel pump and sending unit. Didn’t fix it, I have since taken over, I tested the injectors,two had weak ohm’s cold and worse hot, I replaceed with oem. 24lb 260cc (note: they first sent me 24lb 250 cc) and it ran like crap took weeks for me to figure out their mistake. That change did not fix it. Now thinking about a coil. I’m told the EMC is good. I just lost an entire summer of use. I am now hopeful someone with more knowledge than I can weigh in. Thank you in advance to all reading this post for any assistance that can be provided. Oh yes it has 42 lbs fuel pressure and runs really well, except the throttle response is a bit weak until it’s shut down then no start. It is a 1994 base model 5.7l Un-modified with 80k
Last edited by KGBVETTE; Nov 6, 2019 at 01:11 AM. Reason: Change title
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