Cranking/Starting issue
Thread Starter
Junior Member
Joined: May 2014
Posts: 10
Likes: 0
From: Aiken, SC
Car: 1992 Z28 Heritage Edition
Engine: 5.0 tpi
Transmission: Manual
Cranking/Starting issue
So ...I’m having an issue and was hoping someone could tell me what the problem might be. I’ve got a ‘92 Z28 305 TPI, Manual. The car runs great, starts right up, but after running for a while and shutting it off it doesn’t want to start again for an hour or two. I’ve read a few things saying that it might be a problem with the screen/tube on the fuel pump. I’m really trying to avoid pulling the tank if at all possible and was hoping someone may have some other ideas of what it might be. Thanks in advance.
Last edited by SCVFL; Feb 9, 2019 at 06:42 AM.
Supreme Member
Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Cranking issue
Do a fuel pressure test when you are having the issue, if good pressure and flow you can probably rule out pulling the tank.
One thing to note the fuel pump is enabled both by oil pressure switch and the ECU. If for some reason the ECU isn't turning on the pump when the car is cold you can normally build enough oil pressure to trigger the fuel pump by spinning the starter a few seconds, but not when the car is warm.
Use a test light or volt meter to see if the pump is turning on during the failure mode, the relay is under the hood driver side firewall.
Report back on findings, the next area to look would be ignition.
One thing to note the fuel pump is enabled both by oil pressure switch and the ECU. If for some reason the ECU isn't turning on the pump when the car is cold you can normally build enough oil pressure to trigger the fuel pump by spinning the starter a few seconds, but not when the car is warm.
Use a test light or volt meter to see if the pump is turning on during the failure mode, the relay is under the hood driver side firewall.
Report back on findings, the next area to look would be ignition.
Supreme Member
Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Cranking issue
Also check your fuel lines, if they are getting hot you could have a vapor lock issue... I've also seen a dozen people in the last month that have had bad fuel injectors. I don't recall which models have it but some of the TBI cars have a cold start injector that primes the intake with fuel for cold starts. This can be enough to get the engine running when cold but the other 8 aren't healthy enough to crank the car when hot.
Thread Starter
Junior Member
Joined: May 2014
Posts: 10
Likes: 0
From: Aiken, SC
Car: 1992 Z28 Heritage Edition
Engine: 5.0 tpi
Transmission: Manual
Re: Cranking issue
I did notice that the fuel lines were hot yesterday and thought it was odd. It was almost instant from the time I started the engine. What would be causing the vapor lock?
Supreme Member
Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Cranking issue
Vapor lock is caused by hot fuel vaporizing in the fuel line this fuel vapor blocks the fuel flow. More than likely your fuel lines are routed too close to something hot. Or your engine could be getting way too hot and your gauge be wrong.
Joined: Dec 2004
Posts: 16,737
Likes: 994
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Cranking issue
There are two other things you might want to look at that heat can effect.
when the no start occurs do you have injector pulse and or spark ?
A bad ignition control module can be the culprit.
89-92 tpi used a grey body injector called multec. These multec injectors often fail when hot. You can ohm them when hot and should see 15.5-16.5 ohms. Lower than that they are shorted and can cause the injector driver to shut down and you would not see injector pulse with a noid light.
Last edited by Tuned Performance; Feb 8, 2019 at 05:17 PM.
Thread Starter
Junior Member
Joined: May 2014
Posts: 10
Likes: 0
From: Aiken, SC
Car: 1992 Z28 Heritage Edition
Engine: 5.0 tpi
Transmission: Manual
Re: Cranking issue
Thanks for the replies. I double checked the fuel lines and I don’t think that is the issue. I am going to test the injectors tomorrow as well as they oil sensor. Which relay is the oil sensor?
Trending Topics
Joined: Dec 2004
Posts: 16,737
Likes: 994
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Cranking issue
Your thread title indicates cranking ?
Is this a cranking issue or a no start ?
Last edited by Tuned Performance; Feb 8, 2019 at 06:55 PM.
Thread Starter
Junior Member
Joined: May 2014
Posts: 10
Likes: 0
From: Aiken, SC
Car: 1992 Z28 Heritage Edition
Engine: 5.0 tpi
Transmission: Manual
Re: Cranking issue
I guess it would be a no start issue. When I turn the key it just spins, but will not start. At least not for an hour or two after running fine.
Thread Starter
Junior Member
Joined: May 2014
Posts: 10
Likes: 0
From: Aiken, SC
Car: 1992 Z28 Heritage Edition
Engine: 5.0 tpi
Transmission: Manual
Re: Cranking/Starting issue
I tested the injectors resistance cold. Here are the results:
1-16.3
2-16.3
3-11.5
4-16.3
5-16.3
6-5.3
7-0
8-12.2
Is there even a reason to test them warm at this point? Can anyone recommend a good set of injectors to order?
1-16.3
2-16.3
3-11.5
4-16.3
5-16.3
6-5.3
7-0
8-12.2
Is there even a reason to test them warm at this point? Can anyone recommend a good set of injectors to order?
Supreme Member
Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Joined: Dec 2004
Posts: 16,737
Likes: 994
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Cranking/Starting issue
Delphi’s should be a direct replacement
https://www.southbayfuelinjectors.co...-1986-1992-851
bosch 3s will work as is but you will run alittle lean without tuning.
https://www.southbayfuelinjectors.co...fuel-injectors
https://www.southbayfuelinjectors.co...-1986-1992-851
bosch 3s will work as is but you will run alittle lean without tuning.
https://www.southbayfuelinjectors.co...fuel-injectors
Member
Joined: Jan 2017
Posts: 124
Likes: 2
From: GA
Car: 1991 rs, 1985 z28
Engine: 3.1 v6, 305 tpi
Transmission: 700r4, 700r4
Axle/Gears: 3.23, 3.23
Re: Cranking/Starting issue
Thread Starter
Junior Member
Joined: May 2014
Posts: 10
Likes: 0
From: Aiken, SC
Car: 1992 Z28 Heritage Edition
Engine: 5.0 tpi
Transmission: Manual
Re: Cranking/Starting issue
Delphi’s should be a direct replacement
https://www.southbayfuelinjectors.co...-1986-1992-851
bosch 3s will work as is but you will run alittle lean without tuning.
https://www.southbayfuelinjectors.co...fuel-injectors
https://www.southbayfuelinjectors.co...-1986-1992-851
bosch 3s will work as is but you will run alittle lean without tuning.
https://www.southbayfuelinjectors.co...fuel-injectors
Joined: Dec 2004
Posts: 16,737
Likes: 994
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Cranking/Starting issue
It’s pretty easy to tune the offsets
https://www.thirdgen.org/forums/diy-...0-voltage.html
you would also need a moates.net g1, burn 2 and a few sst eeproms.
The offsets might not be 100% a fix you might have to correct your volumetric efficiency tables.
For this you will need a aldl to usb cable and tuner pro rt, as well as the $8d definition file.
https://www.thirdgen.org/forums/diy-...0-voltage.html
you would also need a moates.net g1, burn 2 and a few sst eeproms.
The offsets might not be 100% a fix you might have to correct your volumetric efficiency tables.
For this you will need a aldl to usb cable and tuner pro rt, as well as the $8d definition file.
Supreme Member
Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Cranking/Starting issue
SO I just happened by this video, its a vette but its the exact same issue I've seen several people post here lately. Obviously you may not have all the tools this guy does but this is how you diagnose the "no start"
Seems that the 88-92 GM TPI injectors are all dying at the same time based on the corrolation of all the random people having this issue on the internet at the same time
Seems that the 88-92 GM TPI injectors are all dying at the same time based on the corrolation of all the random people having this issue on the internet at the same time
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