88 L98 not starting when warm
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Instructor
Joined: Jun 2025
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thank you ctmccloskey
I have not messed with the egr valve but I have not change it either. I don't know if you went back and read all the things I have changed but all of what you wrote. I did have access to the MT2500 that read the OBD1 but at the time we thought we had found the problem. I would purchased one but if I did I would not know how to use it.
I really believe it is somethiing simple but what. I know that the computer is not telling the injectors to fire when warm. but what?
I also have a 40 chevy with a L98 that I've had for 30 years and has not gave me any trouble. I'm a pretty good wrench but I'm not a tech.
I have not messed with the egr valve but I have not change it either. I don't know if you went back and read all the things I have changed but all of what you wrote. I did have access to the MT2500 that read the OBD1 but at the time we thought we had found the problem. I would purchased one but if I did I would not know how to use it.
I really believe it is somethiing simple but what. I know that the computer is not telling the injectors to fire when warm. but what?
I also have a 40 chevy with a L98 that I've had for 30 years and has not gave me any trouble. I'm a pretty good wrench but I'm not a tech.
Thread Starter
Instructor
Joined: Jun 2025
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the way I understand it is the distributor sends pulses to the ECM and the ECM sends pulses to the injectors. If the distributor was bad or a component in the distributor is bad would it post a code
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From: Cotopaxi, Colorado
Supporting Vendor
Joined: Nov 2025
Posts: 277
Likes: 34
From: Cotopaxi, Colorado
If you’re missing injector pulse only a few things can cause it.
engine not cranking 400 rpm or higher. No drp on purple/white wire from icm to ecm or damaged wire. Shorted injectors when warm or power or bad ground for injectors.
engine not cranking 400 rpm or higher. No drp on purple/white wire from icm to ecm or damaged wire. Shorted injectors when warm or power or bad ground for injectors.
Melting Slicks
Joined: Aug 2003
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From: Lakeville MI
Distributor reference pulse (or distributor reference period) depending upon the context.
If you short ALDL pins A & B and turn the ign on, the SES lamp (if you have one) should flash 12. This literally means no distributor reference pulses which would be expected from an engine that is not running with the ign on.
While keeping ALDL pins A & B shorted while cranking (when you have the no start condition present when warm), does it continue to flash 12 the whole time while cranking? or does the ses lamp go off, stay on, or blink steadily at the open loop rate (2.5 hz)?
Note: I've never tried this, but reason would suggest that it will continue to flash 12 during cranking if no reference pulses are detected by the ecm.
If you short ALDL pins A & B and turn the ign on, the SES lamp (if you have one) should flash 12. This literally means no distributor reference pulses which would be expected from an engine that is not running with the ign on.
While keeping ALDL pins A & B shorted while cranking (when you have the no start condition present when warm), does it continue to flash 12 the whole time while cranking? or does the ses lamp go off, stay on, or blink steadily at the open loop rate (2.5 hz)?
Note: I've never tried this, but reason would suggest that it will continue to flash 12 during cranking if no reference pulses are detected by the ecm.
Last edited by tequilaboy; Feb 15, 2026 at 10:02 PM.
Supporting Vendor
Joined: Nov 2025
Posts: 277
Likes: 34
From: Cotopaxi, Colorado
Distributor reference pulse (or distributor reference period) depending upon the context.
If you short ALDL pins A & B and turn the ign on, the SES lamp (if you have one) should flash 12. This literally means no distributor reference pulses which would be expected from an engine that is not running with the ign on.
While keeping ALDL pins A & B shorted while cranking (when you have the no start condition present when warm), does it continue to flash 12 the whole time while cranking? or does the ses lamp go off, stay on, or blink steadily at the open loop rate (2.5 hz)?
Note: I've never tried this, but reason would suggest that it will continue to flash 12 during cranking if no reference pulses are detected by the ecm.
If you short ALDL pins A & B and turn the ign on, the SES lamp (if you have one) should flash 12. This literally means no distributor reference pulses which would be expected from an engine that is not running with the ign on.
While keeping ALDL pins A & B shorted while cranking (when you have the no start condition present when warm), does it continue to flash 12 the whole time while cranking? or does the ses lamp go off, stay on, or blink steadily at the open loop rate (2.5 hz)?
Note: I've never tried this, but reason would suggest that it will continue to flash 12 during cranking if no reference pulses are detected by the ecm.
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From: Cotopaxi, Colorado
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I want to thank everyone for there patience and help. I have never in my life have I had anythng to beat me but this swap has. I have replaced everything that has been suggested. I have checked the ressistance and voltage to everything that I could not replace and still the problem remains that it will not crank when warm, and I do mean warm when run less than a min. I haven't decided if I'm going to buy another truck and sit this project aside or abolish it all together. Again, thank you everone
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Joined: Nov 2025
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From: Cotopaxi, Colorado
I want to thank everyone for there patience and help. I have never in my life have I had anythng to beat me but this swap has. I have replaced everything that has been suggested. I have checked the ressistance and voltage to everything that I could not replace and still the problem remains that it will not crank when warm, and I do mean warm when run less than a min. I haven't decided if I'm going to buy another truck and sit this project aside or abolish it all together. Again, thank you everone
Thread Starter
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Joined: Jun 2025
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I'm sorry just a miss use of words. yes will not star when warm.
I was told yesterday and I don't know where to verify the information. I was told that on corvettes that the ECM was different than the cameros and firebirds.that on the corvette it goes to start mode and after it warms up it goes to run mode and the computer checks for a lot more components and if some are missing then it will not start. the informaton I got was the ECM has to be tuned for a stand alone harness, they said that the cameros and firebirds does not need turning. first does anyone know of a company that does tuning. second, how would I verify if that is true before sending my ECM to someone. and is it the prom or the computer
I was told yesterday and I don't know where to verify the information. I was told that on corvettes that the ECM was different than the cameros and firebirds.that on the corvette it goes to start mode and after it warms up it goes to run mode and the computer checks for a lot more components and if some are missing then it will not start. the informaton I got was the ECM has to be tuned for a stand alone harness, they said that the cameros and firebirds does not need turning. first does anyone know of a company that does tuning. second, how would I verify if that is true before sending my ECM to someone. and is it the prom or the computer
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From: Cotopaxi, Colorado
86-89 tpi used the same 1227175 ecm. Bins are interchangeable but c4 had vats enabled. You might update to $6e w/vats delete but if you have lost injector pulse when warm starting or your fp is bleeding off that’s not the problem. Sounds as if you were misinformed on the camaro/corvette ecms.
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I'm sick of this engine swap. I haven't got it to start when warm as yet. Fuel pressure drops from 45 psi to 0 I immediately when switch is truned off but holds at 40 when running. have just checked my csi and it is spraying proper and no leak as I can see. I hve removed the TPI and raised up the fuel rail enough to see the bottorm of the injectors. switch on I applied 45 psi of fuel pressure without starting and no sigh of leaks. are there any other way to test the injectors.
