Ok guys, I need some help trying to figure this one out.

A few weeks ago, the fuel pump in my 05 bit the dust, so I swapped it out in my driveway. When it initially died, it was on a cold, rainy day about 20 minutes after a fresh fill up. Fast forward to last Sunday. The wife and I are out running errands so we stop to fill up for fuel and head on. We go into Walmart so I can grab a couple of things, and when we come out the car will not start. "Dead" fuel pump again it seems.

Both times now, relay #55 (fuel pump) has been killed (what exactly would cause this?). Just to see if I could get anything going, I took my old pump (I had not yet discarded it) and hooked it up to a 12v source and it spun away like it never had an issue.

Hopefully my newest pump is OK, but we will see. I just wanted to see if anyone has experienced anything like this?

I think I have a short in one of my harnesses somewhere. It's been cold and rainy for the past couple of days, and I only have a carport to do work in so I havent been able to jumper the fuel pump relay port in the fuse block to test for power, but it is in my plans for tomorrow. Could I have a grounding issue? If not, I guess my only other source for the issue will be the harness that connects the left side pump to the power source of the car (inside the drivers side rear fender).

Wall of text, sorry and thanks in advance!

 

If the relay is cooked, an indication of over current, then you probably do have a short to ground somewhere downstream of the relay. The fuse that feeds the relay should have blown, unless the relay is internally fused. Sounds like a nightmare to locate the short or high draw. Generally speaking , in situations like this, it may be more practical to abandon the questionable circuit, and run a new wire from the relay output to the pump. Not easy either, but it may be quicker than chasing an intermittent short.

 

X2, after you jump it and you rule the relay out etc... try to run a long piece of wire, as said above, straight to the pump and see if it works. Also if it is a wiring issue associated with the problem, make sure to use a decent gauge.. I used 10 gauge. Maybe overkill but it works. I had a simular issue as the pump was not getting a constant continuity from the small factory gauge wiring with my increase in voltage requirements for the pump and power produced.

Bozz

 

Just a few things to check out as well...
The fuel pump assembly has a small harness that goes from the pump itself to the top of the assembly. I don't know how thick these wires are but GM had a problem in the 01-05 GM trucks (maybe others) where the wires were too thin creating a lot of resistance and burning the pumps out. Sometimes if you were lucky it was just the wires that just got fried and a simple modification fixed the problem. Trust me, I've already replaced a few fuel pumps like this. Instead of buying a new assembly ($300) I would just swap out the pump and add my new harness for a total parts cost of $85.

I'm not saying the Vette pumps are the same but it might help to check it out.

 

I went through two fuel pumps in less then 500 miles. DRM and I both thought it was the BAP but now you have me thinking. I hope this one last longer. You will have to let me know what you find.

 

Thanks all, I will certainly look into everything mentioned here. It may be easier to run my own wire vs hunting down a short.

Sparo: Its funny you mention that. When I was trying to test my original "bad" pump, I found that I had an open loop when I checked at the 4 pin connector, but when I went to the leads on the pump itself I found a closed loop.

d.medic: I will certainly update this thread with my findings, however I don't have a BAP so you do indeed still have one more variable than I. I'm going to check for continuity on every wire involved *yay*

I'll know more this weekend. Thanks for the suggestions.

 

Not sure if one of these may help

 

Now that may be substantially easier than fabbing up something myself!

Thanks for that. If it isn't the small harness between the pump and the power feed, I think I will go ahead and do this.

Will this thing be OK if I'm not running a BAP? I'll go search around the FI forum.

 

Yes it works with or without the BAP.

 

I'm a bit confused because I seem to only remember one 4 pin "factory type" connector on my car, is this just an option for dual pump runners?

 

I was using a racetronix harness when my pump went out. I am also still using it without the BAP now

 

You say that the relay is bad, is it the control portion of the relay (Coil itself)? This has nothing to do with the fuel pump itself. The power to energize this relay comes fromt he ECU pin 50 and goes to E7 terminal of the relay socket. Socket pin G6 goes directly to ground. the only resistance in the system is the coil of the relay itself. The only heat generated in the relay will be from the coil (Which is minimal if it has the proper resistance, and the contacts if there is a voltage drop due to a bad connection.
Remove the relay and put a jumper wire on the relay socket pins E6 to G7. Does the fuel pump come on? (ignition on)

Is there any physical damage to the fuse block?

With the relay still removed, try to start the car while monitoring pin E7 with a dc voltmeter. Is the relay getting the full voltage? If it is a little low it will draw more current and create more heat.


DJ

 

I'll check this tomorrow. From just removing the relay, the pins look fine, but I was going to remove the entire top cover of the fuse block tomorrow to take a look. I know the relay itself is no good because if I swap it for one of the other identical relays under the block, the corresponding system does not work (fog lamps, high beams, etc).

In the previous case, the fuel pump did not come on whenever I jumpered the connections. I have not had an opportunity to check this time; it was in my plans for tomorrow to see if I was getting a full 12v at the connector in the fender well, but I will also check pin E7 now that I know for sure.

Also, I have checked for continuity on the pump side of the harness in the fender well and it is an open circuit, which has me pointing my finger at that small harness at this point.

I appreciate all of the advice once again.

 

If it turns out that my issue is on the power side of the harness, hopefully being able to bypass it with this will help me.

Anyone have any idea why it only seems to fail on the next startup right after a fill up? Just a coincidence?

 

Something to do with the fuel level sensor at full range?

BJK

 

So your power from the relay G7 to the pump is open? Three connectors between that relay contact signal to the pump.

If you are to by-pass this, just be sure to use at least a 12 awg wire since it is a 20awg circuit.

You will have an inrush current at the start of any motor which will be greater than the nomial current once at speed. Why after a fill up I am not sure.

DJ

 

This is going off of last time, but then, from G7 to the connector in the back of the car I had power. The open circuit is on the pump side of the harness (the pigtail from the harness to the connector from G7). I'm not sure if the pump is the source of the open circuit, or the harness itself. I'll know that part for sure on Sunday.

I will know tomorrow for certain as to whether or not I'm getting power all the way back.

 

I was thinking this too, but on this most recent occurance, my drivers side fuel level sensor was not operational (my gas gauge didn't work). Could still be related. I was actually going to be going in to replace the fuel level sensor and interior lines this weekend regardless. Instead I get to go hunting for open circuits .


I appreciate all of the help guys.

 

Have you contacted our support dept to gain access to our wide range of technical resources? If not you may want to before spending more money on parts.

 

Sorry about your luck. Keep us posted.