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Cranking/Starting issue

Old 02-08-2019, 02:34 PM
  #1  
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Cranking/Starting issue

So ...Iím having an issue and was hoping someone could tell me what the problem might be. Iíve got a Ď92 Z28 305 TPI, Manual. The car runs great, starts right up, but after running for a while and shutting it off it doesnít want to start again for an hour or two. Iíve read a few things saying that it might be a problem with the screen/tube on the fuel pump. Iím 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; 02-09-2019 at 07:42 AM.
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Old 02-08-2019, 02:49 PM
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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.
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Old 02-08-2019, 02:59 PM
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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.
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Old 02-08-2019, 03:09 PM
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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?
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Old 02-08-2019, 03:15 PM
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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.
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Old 02-08-2019, 06:12 PM
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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; 02-08-2019 at 06:17 PM.
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Old 02-08-2019, 07:43 PM
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Re: Cranking issue

Thanks for the replies. I double checked the fuel lines and I donít 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?
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Old 02-08-2019, 07:51 PM
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Re: Cranking issue

Originally Posted by SCVFL View Post
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?
Your issue wouldn’t be the ops. The fuel pump relay powers the fuel pump for run and prime. The ops is backup Incase the relay fails.
Your thread title indicates cranking ?
Is this a cranking issue or a no start ?

Last edited by Tuned Performance; 02-08-2019 at 07:55 PM.
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Old 02-08-2019, 08:06 PM
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Re: Cranking issue

Originally Posted by Tuned Performance View Post

Your issue wouldnít be the ops. The fuel pump relay powers the fuel pump for run and prime. The ops is backup Incase the relay fails.
Your thread title indicates cranking ?
Is this a cranking issue or a no start ?
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.
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Old 02-09-2019, 02:15 PM
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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?
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Old 02-09-2019, 02:28 PM
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Re: Cranking/Starting issue

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Old 02-09-2019, 09:02 PM
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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
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Old 02-09-2019, 10:21 PM
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Re: Cranking/Starting issue

https://www.summitracing.com/ga/part...o/submodel/z28

I got these. Work great and fit perfectly
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Old 02-10-2019, 01:11 PM
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Re: Cranking/Starting issue

Originally Posted by Tuned Performance View Post
Delphiís 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
How hard/expensive is it to get tuned?
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Old 02-10-2019, 01:23 PM
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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.
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