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LT1-LT4 Modifications
1993-97 Gen II Small Block V8

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Old 01-19-2009, 10:43 PM   #1
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Default LT1 Extended Crank Hot Start (Heat Soaked)

Hey all,

This one has been pulling my hair out. Cant fiqure this out for the life of me. Car is a 1996 Camaro Z28 LT1. The car always runs perfect. The problem is if you shut the car off, run into the store for 15 minutes, come back out, the car will crank for an extended period of time (longer then normal!) and then start. It runs fine, just takes longer then normal. After the car starts hard starts once, if you shut it off and restart it, its fine.

It only has the problem the first time you start it, after sitting for a few minutes. (heatsoaked)

Notes:

-The car runs fine always
-The car cold starts fine
-It only does it one time after a heat soak. If you shut it off after it messes up and allow it to sit for another 10-15 minutes it will do it again
-Car does not smoke or run rough when it hard starts
-Car just had an optispark (twice), water pump, injectors cleaned (twice) and intake manifold job done. The reason I put twice there is because I thought the problem may lie in one of those areas, but so far nothing.
-Changed the module and coil thinking maybe a heat soaked electronic part. Nothing
-Fuel pressure stays pretty consistent, it does not got to zero once the car is shut off, the system will hold pressure for a couple of hours.

So far everything I have checked and changed has not changed the problem one bit.

Any advice? Tips? Etc? Need more info? Anything would be great. I am at a serious loss here. Thanks in advance!! Dave
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Old 01-20-2009, 12:28 AM   #2
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You seem like you've been checking everything diligently. Seems as if you ruled out fuel and spark as the culprit. Any chance it could be a voltage problem? I know it's a long shot, but I would check the voltage at the starter/battery when the car is acting up.
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Old 01-20-2009, 05:08 PM   #3
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I had something like this goin on with a caprice 9C1 and it seemed like the oil pressure cutout sending unit/relay was not letting the car start until the motor generated oil pressure mechanically high enough to allow the relay to operate the Fuel pump but after changing a bunch of parts etc all that was really wrong was the ground going into the under hood relay/fuse box was bad, made a jumper ground wire and it fired right up every time, cost me a bunch of relays, a fuel pump and full ignition/tuneup stuff but at least I learned something...
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Old 01-20-2009, 05:37 PM   #4
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Is the battery in the front or have you relocated it?
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Old 01-20-2009, 05:41 PM   #5
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Quote:
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Is the battery in the front or have you relocated it?
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Old 01-20-2009, 06:41 PM   #6
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That sometimes (as I have noticed) has an affect on starting when it's warm. I moved my battery to the back and it started having the exact same symptoms he is having -started fine cold, ran fine, just had an extended amount of time to start once it'd been warmed up.
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Old 01-20-2009, 08:18 PM   #7
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Mine sometimes does this too. Fires immediately when cold and sometimes want extended cranking to fire when hot. I want a solution.
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Old 01-20-2009, 11:28 PM   #8
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Battery is in the stock location

I will check out the oil pressure switch related to the fuel. I know it has good pressure while cranking though as far as I remember (ive been screwin with this for 2 months!)

Thanks for all the tips! Any others?
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Old 01-22-2009, 06:47 PM   #9
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TTT!!!

Anything else? Oil pressure switch is working fine. Fuel pump relay works like it should as well. Holds fuel pressure while cranking...
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Old 02-13-2009, 07:04 PM   #10
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Quote:
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TTT!!!

Anything else? Oil pressure switch is working fine. Fuel pump relay works like it should as well. Holds fuel pressure while cranking...
Where is the oil pressure switch?
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Old 02-13-2009, 07:39 PM   #11
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IMO, check the ICM. All electrical components are susceptible to heat, and the ICM is one of the hottest. They are known to fail when hot. Swap it out with a friends car, or just replace it. Then mount it further away from the head.
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Old 02-13-2009, 10:25 PM   #12
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I think he already changed the icm and coil

also if it was icm or coil I believe he'd be having high rpm miss as well

my guess is ignition switch
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Old 02-13-2009, 11:24 PM   #13
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have you tried priming the fuel pump a few times before trying to start it when it is heat soaked?

you do that by cycling the key on and off (listen for the pump to whine for a second or two).

try that
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Old 04-18-2009, 09:38 PM   #14
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TTT!!!

Still have this problem! Put a fuel pump in it just to rule this out.

Im sick of throwing parts at this thing, anyone have any other advice? Thanks!
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Old 04-18-2009, 11:23 PM   #15
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just for ***** and gigs do you have a scanner? That would help out a lot. your ECT could be actin up when the car gets hot *shrug*. Scanner will help you a lot
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Old 04-19-2009, 01:33 AM   #16
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If it has a tune or anything like that (ie fairly modded). You can up the 1st prime pulsewidth for the hot start by 1.6 (min change for this table iirc) or so and it should shorten the cranking time usually. Makes it kind of spunky if thats what it wants and when it lights and it will usually go to 1500rpm for half second or so. I wondered what that table did and one day I just decided to test it out first removing fuel and man crank crank crank then it fired finally. Moved it the same amount the other way yikes fired right up when it was hot just like on a cold morning. If you got spare time to figure it out you can even tweak the initial afr correction to make it even better. All you have to do on my car is look at the key and it starts.
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Old 04-19-2009, 01:39 AM   #17
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well that happens to me but its my starter getting heat soaked and it doesnt have the power to turn the engine over so it takes Alot to get it to start. cold it starts up perfectly fine
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Old 04-19-2009, 02:03 PM   #18
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Quote:
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well that happens to me but its my starter getting heat soaked and it doesnt have the power to turn the engine over so it takes Alot to get it to start. cold it starts up perfectly fine
Ive seen this happen before and it was the same as you - the starter.
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Old 04-19-2009, 02:05 PM   #19
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Ive seen this happen before and it was the same as you - the starter.
yeah im going to wrap my header where it goes past my start to see if itll help prevent that from happening. im afraid to blow my start with my higher compression if i get it to heat soaked again
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Old 04-19-2009, 09:35 PM   #20
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i had this same problem and i did a combination of replacing the battery and the starter and it was fine after that. i agree, i think the starter was getting heat-soaked, and the battery was pretty old so i just changed both and its all good now
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