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Virtual Wrench (L J)
Virtual Wrench (L J), Chevy Mechanic
Category: Chevy
Satisfied Customers: 13337
Experience:  35 years Master Mechanic
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1992 chevy caprice 305 engine wont start

Customer Question

i am getting spark to my plugs but no fuel to my carborator.after checking fuses for the fuel pump and injectors the car started and ran normal for a few days.then failed to start soon after shutting it off.i had anew fuel filter installed about three months ago.the car has about 160,000 mi. on it and has been maintained with no hint of any hesitation or other problem.it always started prompt and ran great before this problem occurred.i thought reseating the fuses fixed the problem before(all fuses were good).so i checked the fuses again,including the inline fuse to the fuel pump but istill don't get gas whenn cranking the engine.i hope there is some answer other than checking fuel pressure. thanksCustomer
Submitted: 7 years ago.
Category: Chevy
Expert:  Virtual Wrench (L J) replied 7 years ago.

Hello,

First, this vehicle doesnt have a carbutator. It has what is called Throttle Body Injection (TBI) it is fuel injected, and as you know runs on an electric fuel pump in the fuel tank.

I need to ask a few questions:

Will it start now?

If not, can you hear the fuel pump running for a couple of seconds when you turn the key just to the on position?

Do you have a testlight or voltmeter to test for power to the fuel pump?

Customer: replied 7 years ago.
i checked the fuses that feed the fuel pump but iam not sure if there are relays involved in sending the voltage or if that was ever aproblem with a 1992 caprice fuel pump.i don't ever remember hearing the electri fuel pump when my key was on before cranking the engine.should i smell fuel in the chamber near the injectors when i crank the engine if the fuel pump is functiong?i'm not sure which wire goes to the fuel pump that i can access. thanks .the car will run if i pour a little fuel into what i cosidered the carborator but only for a few seconds.but no it will crank but not start.i do have avoltmeter but my manual doesn't give thorough wire diagrams.
Expert:  Virtual Wrench (L J) replied 7 years ago.

Thank you,

This system has a fuel pump relay located in the passenger side firewall area under the hood (see pic below) I have also included the wiring schematic for the relay. First check to see that you have power to the orange wire to the relay with the key in the on position, then make sure power is going through the relay to the grey wire that goes back to the fuel pump.

Keep in mind that with the key only in the on position, the relay will shut off after 1-2 seconds, and is supposed to stay on all the time when cranking the engine.

If all checks out good there, check for power to the grey wire at the fuel pump harness connection, if you have power there,,,,replace the fuel pump.

 

graphic

graphic

 

If you have further questions on this, please feel free to reply.

Thanks for asking!

V W

Virtual Wrench (L J), Chevy Mechanic
Category: Chevy
Satisfied Customers: 13337
Experience: 35 years Master Mechanic
Virtual Wrench (L J) and 3 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
thanks for pinpointing my next step.you were very helpful and i would like to include a ten dollar tip.Customer
Expert:  Virtual Wrench (L J) replied 7 years ago.
Thank you very much!
Customer: replied 7 years ago.
Reply to Virtual Wrench's Post: the information i received is just what i was looking for,but i won't be able to check out the car yet as it is located at my daughters.but now i have what i need when i get there.thanks.
Expert:  Virtual Wrench (L J) replied 7 years ago.

Your welcome!

If you have further questions, just let me know!

Customer: replied 7 years ago.
i was wondering if the oil pressure switch,if defective could inhibit the fuel pump.(i've used rislon in my oil) but about ayear ago my air pump noise misled me to thinking my engine was making a knocking sound.then i used lucas which caused my oil lite to come on.it never affected the cars operation but i see from the diagram that it's labeled "'fuel pump oil press sw."'i appreciate your interest but i won't know anything until i have achance to go to my daughters in a week or so.
Expert:  Virtual Wrench (L J) replied 7 years ago.

The oil pressure switch could be at fault, as soon as it detects around 3psi, it allows the fuel pump to activate, this is a safety fateure for the engine, so if it doesnt have any oil, it wont start and ruin the engine,. You can just unplug it and jumper the connector terminals and see if it starts.

 

Customer: replied 7 years ago.
i guess you've given me enough info to investigate further.when i get a chance to apply them i'll be sure to let you know the results.the only thing i didn't mention was that using a haynes manual my daughter and i checked fuses that were associated with thefuel pump and theinjectors{including the 20 amp inline).right after that the car started and ran for a few days.then my daughter went to a mall and when she tried to stsart the car -it would crank but not start (same problem,car was towed}.later when i visited iwent through the same procedures but the car still wouldn't start.this all took place afew weeks ago.thanks again.
Expert:  Virtual Wrench (L J) replied 7 years ago.

I'm betting that the fuel pump is the culprit here, you will know once you test to see if it is running, if you hear it running, and there is spark to the spark plugs, it will need to be replaced.

Please keep me posted once you get there, and if you need anything else, just holler!

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