Pontiac G6 Fuel Pump

**Blksnshn** · 07-14-2011, 03:52 PM

I know this isn't an LSx motor but I figured maybe someone here had run across the same Problem.

I'm working on my cousins 2006 G6 3.5L V6.

Car would crank but not start, couldn't hear the pump, Checked and no power at the pump. Replaced blown fuse and then had 12v on the Gray wire to the pump but it still would not pump.

Put in a used (not my idea) pump and still the pump does not turn on. I can jump both pumps directly to the battery with a couple of jumper wires and both of them turn on.

I've never dealt with this issue before so I would love some advice here.

**Cutlass** · 07-14-2011, 05:39 PM

I would check all the wiring under the car for the fuel pump. Look for road debris damage and corrosion/heat damage on the connector terminals. You might have to drop the tank again to look at all the inline fuel pump connectors. I've had heat damaged fuel pump connectors (from high current flow due to a shorted pump). Since your fuse blew, I'm guessing the fuel pump shorted out and may have melted a connector a little bit before the fuse blew. Sometimes those connectors can still flow a little current to light up a test light or meter, but not enough to run a pump.

**Blksnshn** · 07-14-2011, 05:57 PM

Thanks for the Reply Cutlass.

The tank is out of the car right now. I've inspected the wires, they actually run under the back seat in the G6. I've also checked for burnt connectors at the pump. I know GM had problems with those connectors on their fuel pumps. I've actually been a certified tech for about 8 years now but this one just baffles me. I'm getting a solid 12v all the way back to the pump and a good ground, yet niether pump will work but will work when jumped to a battery.

I know most new pumps come with a redesigned plug and harness pigtail but My cousin doesn't have enough $$$ to buy the new pump/sending unit. Maybe I buy a new pigtail from GM? Maybe there is damage in there I can't see, I don't know.

**JayTA98** · 07-14-2011, 06:37 PM

have you tried to connect the pump directly bypassing the plug? are you getting 12v using the ground at the plug or from ground chassis?

**Blksnshn** · 07-14-2011, 07:24 PM

Originally Posted by JayTA98

have you tried to connect the pump directly bypassing the plug? are you getting 12v using the ground at the plug or from ground chassis?

Yeah, I hooked the pump up directly to the Positive and negative terminal on the battery and it worked.

I'm getting 12V using the ground at the plug. Also have the 5v on the purple wire and good ground on the Blk/Wht wire for the gauge. I have good continuity between the ground in the harness and the chassis.

**JayTA98** · 07-14-2011, 07:28 PM

sounds like a bad plug or harness maybe

**Blksnshn** · 07-14-2011, 07:31 PM

There is nothing visually wrong with the plug but I'm thinking I'm going to try a new pigtail anyway, there isn't anything left that I can think of.

I appretiate the thoughts here guys.

**0rion** · 07-14-2011, 07:37 PM

pump runs....you have voltage back to the plug that goes to the pump......it would almost have to be somewhere between that plug and the pump I would think. These jobs and issues suck because you can't easily just take things apart and test them....royal pain to trouble shoot pumps. Good luck and let us know what you end up finding. Just to rule it out have you tested the fuel pump relay?

**Blksnshn** · 07-14-2011, 07:44 PM

Yeah, I actually changed the Relay.

I have the 12V and ground all the way back to the pump. I tested at the plug that goes into the pump.

It sucks because I'm doing this in my uncles driveway so I don't have most of my tools. One thing I wasn't able to try was testing for power while the pump is plugged in, I didn't have anyway to backprobe the wires. I'll have to do that tomarrow.

I have a feeling I'm going to find something stupid and obvious.

**0rion** · 07-14-2011, 07:56 PM

yeah...having power back there kinda rules out that relay but it's always good to verify it anyhow. I'm not completely sure what the flow chart looks like from the time you turn the key to the time the fuel pump primes. I know it goes through vats and then I'm assuming vats tells the pcm to close the relay and that shoots power back to the pump....that's my rough guess of how it goes. I've made little jumpers in the past to put in connectors so I have a way to test things with the plugs all plugged in. I'll just strip the ends of a wire and put it in the connector and plug the connector back in. I'm sure there are better ways....matter of fact I know there are. That's just the cheap/redneck way.

disclaimer: I would never have bare wires in the tank......I'd take the pump out on the ground and plug it all in. Figure you know but just throwing that out there.

**Blksnshn** · 07-14-2011, 08:41 PM

That's actually a pretty good guess, thats pretty much how the flow of power to the pump.

I've beed tesing everything outside the tank, I'm not a huge fan of uncontrolled fuel fires, lol.

My first week as a tech my old boss was heating up an exhaust bolt on old Taurus right next to the plastic fuel line. It melted through and there was what seemed like an endless stream of flames coming out of the line. I screamed like a girl and ran away.

**Cutlass** · 07-15-2011, 10:10 AM

Originally Posted by Blksnshn

My first week as a tech my old boss was heating up an exhaust bolt on old Taurus right next to the plastic fuel line. It melted through and there was what seemed like an endless stream of flames coming out of the line. I screamed like a girl and ran away.

I did that once. Its a fun time!!

BTW, how are you checking for 12volts and ground back there at the pump. If its with a meter, than that can trick you into thinking everything is ok. It only takes one tiny little fine strand of wire to check for 12 volts with a meter...but one little strand of wire won't carry enough current to run a fuel pump. You need to load test the circuit with a test light or an old sealed beam head light.

**Blksnshn** · 07-15-2011, 10:17 AM

Originally Posted by Cutlass

I did that once. Its a fun time!!

BTW, how are you checking for 12volts and ground back there at the pump. If its with a meter, than that can trick you into thinking everything is ok. It only takes one tiny little fine strand of wire to check for 12 volts with a meter...but one little strand of wire won't carry enough current to run a fuel pump. You need to load test the circuit with a test light or an old sealed beam head light.

I've been using a meter and also checked it with a cheap test light. Maybe I'll have to rig something up with a higher amperage light. I have a couple off off road lights laying around, you think that will do the trick?

Thanks for the suggestion.

**Cutlass** · 07-15-2011, 10:25 AM

yep, an off road light would be perfect!

**Blksnshn** · 07-15-2011, 10:26 AM

Originally Posted by Cutlass

yep, an off road light would be perfect!

Should I fuse the jumper wire or just rely on the fuse in the box to do it's job?

**Blksnshn** · 07-15-2011, 02:23 PM

Well, I just went over with the off road light and the light turned on bright as could be. Also tested continity from the relay in the fuse box back to the connector and that looks good.

I'm about to hack in some new wires.

**vette&ws6** · 07-16-2011, 06:44 AM

Did you check the ground to make sure it is clean and tight. I know you said you have a ground, but, I have chase fuel pump problems around in the past just to find out that the ground is loose. ==Note==a loose ground can still have perfect continuity when checked with a multimeter. Just a thought...

**Blksnshn** · 07-18-2011, 10:06 PM

Well, I got it fixxed today. Turns out I was getting continuity to ground through the B+ wire running from the Relay to the tank. I cut out the old wire and patched in a new one.

I'm still not really sure how I was able to power that 75w off road light on the circuit without blowing the fuse. So I'm not sure how I was getting the readings I was getting. Wiring is not my specialty.

But the car runs good now, so my cousin is happy to have her car back.

**0rion** · 07-19-2011, 04:12 AM

glad you got it fixed......electrical problems in general can drive your ass up the wall. Some of the hardest stuff out there to figure out sometimes because it's not always a case of "work....don't work".

**Blksnshn** · 07-19-2011, 09:56 AM

Wiring drives me insane sometimes, especially when I'm constrained by having few tools to work with. Any time I try to fix a car for someone on the side and it seems like a straight forward operation, I always end up with one of these nitemares.