Chevy fuel pump problem? Help on diagnosis please!
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Originally Posted by bosshoss
How about a fuel pump relay sticking? Next time you get ready to start it listen for the fuel pump to pressure up the system then shut off, then crank. If you heare the pump run up then shut off then not start, you need to look at other things. I dont know about the cars, but the trucks with the GM plastic fues box under the hood have caused me many headachs. Good luck.
DP
DP
How do I get to the injector unit? Do I have to take the whole throttle body unit off? Where is the injector located?
Last edited by 76F250HighBoy; Mar 13, 2005 at 08:58 AM.
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Maybe the IAC motor? I'm in the mechanics program at the local community college. One of my instructors told me that he is in the habbit of replacing the fuel pump relay and the IAC motor whenever he changes a fuel pump.
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Originally Posted by maa139
Maybe the IAC motor? I'm in the mechanics program at the local community college. One of my instructors told me that he is in the habbit of replacing the fuel pump relay and the IAC motor whenever he changes a fuel pump.
Ok so it is a car were dealing with here, it's not TBI is MPFI makes things a tad easyer since its a different animal all togather. It should be a 3.1L and have a test port on the fuel rail. Double check and make sure its getting 30-35PSI at the rail. Injectors will not fail all at once and if you hear the pump buzz on with the key the relay is good. It's supposed to turn on with the key then shut down until its started. The 3.1 MPFI system doesent have alot of parts to fail and cause a no start. It is however a DIS system "Distributorless Ignition System". I would make absoulte certain of the fuel pressure before moving on. Forget the injectors move on to spark. There is a CPS "crank posistion sensor" that can go bad and cause irratic spark timing.
If you can verify you have the proper fuel pressure and spark through each of the coil pack/s (TEST each termial for spark seperate) replace the CPS.
Last edited by Torque1st; Mar 13, 2005 at 03:23 PM.
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Originally Posted by SSCX2
ADMIN: Do not by-pass the language filters Ok, you can tell him he's a <!-- dumb @ss --> and thier is a reason he's teaching at a CC. IAC function will not effect fuel in any way shape or form.
Ok so it is a car were dealing with here, it's not TBI is MPFI makes things a tad easyer since its a different animal all togather. It should be a 3.1L and have a test port on the fuel rail. Double check and make sure its getting 30-35PSI at the rail. Injectors will not fail all at once and if you hear the pump buzz on with the key the relay is good. It's supposed to turn on with the key then shut down until its started. The 3.1 MPFI system doesent have alot of parts to fail and cause a no start. It is however a DIS system "Distributorless Ignition System". I would make absoulte certain of the fuel pressure before moving on. Forget the injectors move on to spark. There is a CPS "crank posistion sensor" that can go bad and cause irratic spark timing.
If you can verify you have the proper fuel pressure and spark through each of the coil pack/s (TEST each termial for spark seperate) replace the CPS.
Ok so it is a car were dealing with here, it's not TBI is MPFI makes things a tad easyer since its a different animal all togather. It should be a 3.1L and have a test port on the fuel rail. Double check and make sure its getting 30-35PSI at the rail. Injectors will not fail all at once and if you hear the pump buzz on with the key the relay is good. It's supposed to turn on with the key then shut down until its started. The 3.1 MPFI system doesent have alot of parts to fail and cause a no start. It is however a DIS system "Distributorless Ignition System". I would make absoulte certain of the fuel pressure before moving on. Forget the injectors move on to spark. There is a CPS "crank posistion sensor" that can go bad and cause irratic spark timing.
If you can verify you have the proper fuel pressure and spark through each of the coil pack/s (TEST each termial for spark seperate) replace the CPS.
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From: Omaha
It is in the trottle body it is a little bit smaller then a film canister. It is mounted over the throttle body spraying downwards. It will have the lines and some wires going to it. There are no fuel rails in the Tbi systems just a single injector.
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From: Colorado
I'm actually not too familiar with the injected Iron Dukes, Ive mostly worked on 6's and the quad 4 family. Reguardless it's still a DIS system and most of the post still applies. Have you tried to get it to run off of carb clean? If it runs off of carb clean you do have a restriction in the fuel system. If you test the fuel pressure you will need the special adaptor I mentioned in my first post, the one that replaces the fuel filter while you test. You should have anywhere from 10-18 PSI fuel pressure. If pressure checks out or it doesnt hit off the carb clean you may need that ignition module #DR144. When it comes to GM's especially if they have fuel pressure but dont run a safe bet is the ignition module.
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Is it possible for me to clean the injector out? The car will start right up if I spray starting fluid down the throttle body, and sometimes stay running, sometimes not. I don't want to put any money into it because its just a car I use to get gas mileage.
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Originally Posted by 76F250HighBoy
Is it possible for me to clean the injector out? The car will start right up if I spray starting fluid down the throttle body, and sometimes stay running, sometimes not. I don't want to put any money into it because its just a car I use to get gas mileage.
Rebuilding/cleaning injectors isnt a DIY job. You would be better off just buying new. I still think you may have a fuel pressure problem. It wouldent be the first time a new pump was bad.
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Yeah, but it did the EXACT same thing with the old pump. I took the injector out tonight and then proceeded to pressurize the system by turning the key to the "on" position and fuel went everywhere, so fuel is getting all the way up to the injector. And earlier, I said that it fires right up when you spray starting fluid in it, so it must not be getting enough fuel, which to me, seems like an injector problem.
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Originally Posted by SSCX2
[/b] Ok, you can tell him thier is a reason he's teaching at a CC. IAC function will not effect fuel in any way shape or form.
And you're right. IAC won't affect fuel, but it does affect IDLE. Wasn't one of the original symptoms a problem where it would sometimes start and then idle very poorly? If you zero in on the fuel pump and the fuel pump only, you could be missing other potential causes. I don't know about you, but I don't like to throw parts at a car hoping to guess right.
Also, nobody has mentioned here checking the current that the fuel pump is drawing. I'm not sure what the current draw should be, (a guess would be 1-15 amps) but I'm sure someone on this board would know.
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