Wiring to fuel pump - JeepForum.com
 
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post #1 of 11 Old 07-29-2020, 12:03 AM Thread Starter
thierry13aix
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Wiring to fuel pump

Hello all, After testing just about everything, I know that there is no power to the fuel pump (WJ 4.7L). everything works up to the relay. If I pull a wire from the relay out to the pump, it works. My deduction is that the wire between the relay and the pump is broken. I tried to follow it from the relay to find out where it is broken but can't find it. My question is: Can I safely pull a new wire between relay and pump or is there another component between the two?

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post #2 of 11 Old 07-29-2020, 12:30 PM
jtec
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you do know the FP will only have 12v for @3seconds if the engine does NOT start?

Makes troubleshooting alone tough ...

Did you check wirinng connectors for a open?
What year is this WJ?
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File Type: pdf 04WJ fuel pump.pdf (113.1 KB, 2 views)

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 11 Old 07-30-2020, 10:27 AM Thread Starter
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Thanks Jtec, it's a 99 V8. I know about the 2/3 seconds thing. I had a helper to test. I can't find any connector between relay and pump except from the one by the gas tank and I know it is fine since I spliced into the wiring harness before it. Is there another connector?
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post #4 of 11 Old 07-30-2020, 12:10 PM
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I see 2 Connectors - C106 and C300

This attachment is from 1999WJ

Do you have an OEM manual? You can look up locations.
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File Type: pdf 99WJ FP.pdf (128.6 KB, 3 views)

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 11 Old 07-30-2020, 08:31 PM
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Quote:
Originally Posted by jtec View Post
you do know the FP will only have 12v for @3seconds if the engine does NOT start?
The OP did not mention whether this function is working or not at enitial key on, if it in fact is working than he may be barking up the wrong tree ?

Also there is no mention if this is a crank no start or a crank start and then quit, you people are not doing proper troubleshooting.
You are not laying out your test procedure, "If I pull a wire from the relay out to the pump, it works" what the heck does that mean ?????
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post #6 of 11 Old 07-31-2020, 07:46 AM
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There is a diagram attached - where is the power 12v missing - shows from fuse to pump - info is all there.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #7 of 11 Old 08-04-2020, 12:53 PM Thread Starter
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Thanks Jtec, I found 300 but not 106 yet. The funny thing is I only need the wire to start. Once started, she runs fine without the wire. In the last few days she started fine without the wire except for a few times when I had to hook it up... I was thinking maybe something to do with the ignition switch behind the key?
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post #8 of 11 Old 08-04-2020, 01:02 PM Thread Starter
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You're right goatboy... it works means it starts... "we" people did follow the proper testing procedure but did not care to write a paperback about it and crowd the text box.
If it was a crank start and quit, I would not incriminate the power to the gas pump because no power to gas tank means no start. I thought you would have understood that but I guess not...
In any case, power to the relay (in and out) for a few seconds after key on but not to connector before fuel pump. Therefore a direct wire does the trick. However, if I remove the extra wire after start up, the car runs fine. I am starting to think more toward the ignition switch.
By the way, if you reply, you need to know that I am not a beginner, just someone who owns a garage and is running into a situation not faced before and looking for advice on the forum, not a lecture. Thanks
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post #9 of 11 Old 08-04-2020, 03:13 PM
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I will add location of C106

I would liked to have known you are a professional, helps knowing what has been done and understood.
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C106.JPG  
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 11 Old 08-04-2020, 03:16 PM
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are you sure PCM is grounding relay cavity 86 with key in start position?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #11 of 11 Old 08-05-2020, 10:48 AM Thread Starter
thierry13aix
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Super cool, thanks a lot
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