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Fuel pump won't fire unless jumpered at ALDL by mr_corean
Started on: 03-11-2014 06:08 PM
Replies: 2 (343 views)
Last post by: mr_corean on 03-12-2014 05:31 PM
mr_corean
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Report this Post03-11-2014 06:08 PM Click Here to See the Profile for mr_coreanSend a Private Message to mr_coreanEdit/Delete MessageReply w/QuoteDirect Link to This Post
So I was having some issues with the car not running correctly and got it figured to a dirty tank. Tank is clean and the car runs good now. While working on this though, at some point, not sure exactly when, the pump quit working under the standard method of does what it is supposed to when it is supposed to. I can make it run at the ALDL connection and have been driving around fine by having it on a switch that I turn off when I get out of the car. Without the fuel jumpered the car will not start at all, even if I crank it unitl I have oil pressure and then continue cranking for a bit. Also, if I take the jumper out of the port while the car is running it will die within a minute. My question is what is causing this?

I know the pump is good since it runs when jumped at the ALDL. I just replaced the relay today as well as tested it with another. I do not know that the old relay is bad, but I do know that the new one is good. I also checked the old fuse and it was good. Replaced it anyway for good measure.

I searched around and got some info on testing the actual wiring to the relay, however I'm not 100% sure I am doing it correctly so here is what I did and the assumptions I made based on the results.
1. I took the relay off and put a voltmeter in the tan wire hole and then the other end to the ALDL port and got resistance so I know there is connectivity between the fuel pump and relay.
2. I tested the ground in the relay port and it was good so I know my ground is good.
3. I turned the key to run and checked for voltage at the orange wire and got none. Don't know what that means but it seemed, based on my research, that no voltage was correct.
4. I turned the key to run and checked for voltage at the green wire and got none. If I'm understanding this correctly then I am not getting a signal from the ECM telling the fuel pump to run and I need to replace the ECM.

Hopefully I am getting this all correct and I am finally learning how to correctly troubleshoot this car. Please let me know if my assumptions above are correct or if I went astray at some point. Thanks!
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Bloozberry
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Report this Post03-11-2014 07:10 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
You should have gotten 12V at the orange wire regardless what position the ignition switch was in. It should be hot at all times with the power coming from the F.Pump Fuse (10 Amp). From the diagram below you can see that the wire is spliced at connector C203 which is the clear connector under the armrest. That may be where the problem is if you've checked that you're getting 12V at the fuse. That's one of the problems.



The other is that you should be getting 12V at the green/white wire for two seconds once the key is turned to RUN, but I'd troubleshoot the orange wire first since that will allow you to start the car with oil pressure.
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mr_corean
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Report this Post03-12-2014 05:31 PM Click Here to See the Profile for mr_coreanSend a Private Message to mr_coreanEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks Blooze, the orange wire was in fact the issue and the car is operating as intended once again. +1 for you
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