Fuel Pump Relay

[JAFCOJIM]

After about 100 miles on a new fuel pump, the car died; same symptoms as when the fuel pump failed. We found that the cause this time was a failed relay to the pump. This had just been replaced when the fuel pump was replaced.
Any ideas on what's happening? Suggestions for resolution of the problem? I'm getting gun shy about driving more than 100 miles.
jafcojim

 

[97snk]

Is this a stock setup with stock pump?

 

[CWhiteRun]

Get a multi-meter and check the resistance on the ground leg of the relay plug-in.

 

[plumcrazy]

you sure are having a lot of fuel pump issues. you sure its not the guy turning the wrenches issue ?

you might wanna get a call into chuck tator and learn up a bit. 914-763-3136

 

[Phun70]

Get a multi-meter and check the resistance on the ground leg of the relay plug-in.

I respectfully dis-agree. A resistance test is not a valid test of wiring integrity. You must use a voltage drop test to determine the circuits true ability to carry a load. Also, testing with a test light is marginal at best on circuits that carry a high load like a fuel pump. I would strongly recommend using a head lamp as the test light to more closely simulate the load on the circuit. I've only been fixing cars professionally for 20 plus years, so this is just a suggestion LOL. Just google voltage drop testing and you will probably find lots of information including some good illustrations along with acceptable levels of voltage drop across a given run of wiring. It's kind of like testing resistance, but it gives you a true idea of how much load the circuit can carry. A resistance test could show very low resistance even with one strand of copper intact in a stranded wire like what is used in automotive applications, however that one strand of copper would NOT be able to properly carry the load that a fuel pump would pull!!!! ONLY a voltage drop test will tell you if that circuits wiring is up to *****. Hope this helps. ASE L1 CDMAT.

 

[Bandit3]

I agree with Phun70

 

[RTTTTed]

Hopefully your relay was faulty and will be good now.

It's interesting that the relay blew and not the fuse. I would have expected the fuse to go before anything else if there is an electrical problem. I would be tempted to replace the gound wire so I agree that a voltage drop test would be a good idea though.

 

[CWhiteRun]

You disagree that he shouldn't just check to see if there's resistance in the ground leg first? I would....that's the most simple thing to do to start off. If there is then it could be causing the relay to not fully engage, or cycle so rapidly that it kills it all without popping a fuse. My recommended troubleshooting steps would be to Ohm out the ground....if the ground Ohms out 0, then check to make sure you're getting full power to the relay plug. If full power is getting to the plug, THEN do a voltage drop test. I'm not disagreeing with you Phun70, but I don't feel that just doing a voltage drop check will help him solve the problem as he would then have to test power coming in and the ground anyways after failing it.

 

[CWhiteRun]

I hope it's not your ECU causing the issue. I had a jeep do something very similar to this where the ECU would only pull ground long enough to get you away from everything before its resistance increased so much that it would no longer keep the relay held. A temporary fix was to re-route the ground that was running from the relay box to the ecu directly to chassis ground. The permanent fix was an ECU replacement.