1996 C2500 Fuel Pump Relay Hot

[Opelgt1970]

My 96 c2500 (5.7L) has been having problems with the electrical system for the fuel pump. The fuel pump relay (under black cover, drivers side, Engine Compartment) gets very hot and even melts the plastic and eventually the truck dies (fuel pump can no longer be heard when keys is turned on and it won't start). The fuel pump has been replaced (hoping to solve the problem) and the relay has been changed 4 times with the new fuel pump and the problem is the same.

The pump draws 10 amps when running.


Is it a bad pump?, bad wire, bad ground, short???????

Help please.

Russell

[LanceM]

Just a guess here, 10A sounds like way too much to run a pump and melted plastic would seem to conferm that.

You have replaced the pump already, I would check to see if the hot wire going to the pump is shorted to ground. If you can disconnect it at the pump end then pull the relay and check it from there to ground you should have an open, if you measure any resistance then your hot wire is shorting somewhere.

Lance

[michelq]

sound like burnt relay plug in fuse box.
look me up i am next to you at 9225 manchester i will check it free

[Opelgt1970]

Just replaced the fule pump and it draws the same 10 amps..well 9.8 amps. Check resistance in all the wires and it is low. From the relay fuse box to the last plug at the fuel pump the total resitance is 0.9 ohms. The ground had 0.3 ohms.

The wire coming into the fue box is burnt a little, but good contact is made and i cleaned it just in case.

Now what?

[LanceM]

Reading your post I take it that you measured from the relay socket to the plug on the pump? What you checked there is if the wire is going from the socket to the plug. You just measured the resistance of the wire itself and it should be very low.

What you need to measure is: with the pump disconnected and the plug hanging free, measure from the relay socket to ground like the battery negitive terminal connector or the metal on the altenator, you should measure an open, (don't measure from the input side to ground with your ohm meter you may burn it up! It would probably be best if you disconnect the battery.) if you measure a low resistance then you have a problem with the hot wire rubbed through and shorted somewhere on the frame and will have to either find the short or just run a new wire.

Lance

[Opelgt1970]

Lance,

Great advice, but I did check that, and it was an open circuit, and just for grins sake a ran a 12 gauge wire as the feed wire just to see if there still was a problem.

I talked with the local Chev dealers service center and he said 10-15 amps is normal, but more than 15 is too much. He suggested the connection to the relay could be loose and may need to be retensioned.

I am considering using a different relay on the feed wire to the pump to power it instead of the the one that has the small prongs that Chev uses, but this still does not explain my problem.

I have a friend with the same truck I am going to check the amps his pump draws to confirm.

[LanceM]

Wow 10-15 amps sure seems like a lot to run a fuel pump! Well it sounds like you are going down the right track then.

Good luck!

Lance