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Old 12-16-2016, 06:05 PM   #1
jhenry72
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2005 GMC Yukon XL Fuel issues......

Hello, I know i have posted this before but this has some additional information that maybe would help someone point me in the right direction...
I have a 2005 GMC Yukon XL that I have just replaced the fuel pump in. After getting the old pump out and installing the new one, reconnecting all the hoses and lines and getting the tank back up in place, I turned the key to the on position about 4-5 times to re pressurize the system. After that the truck started right up. Ran perfect. The wife used to it to run a few errands, and later ran to the store, still no problems.. Next day, I went to run to the gas station and it didn't start right up, I just turned the key to the on position a couple times and it started. As i proceeded to drive down the road, I stepped on the gas pretty good and it like fell flat... wouldn't rev up. I left it run as I ran into the store and on my way back it seemed to slowly rev up more and more... Later that afternoon we went to leave and it took like 15-20 minutes to get started. And every time I would put it in gear it would die. So I left it till the next day and now I cant get it to start, sounds like it wants to but won't. I can still here the fuel pump turn on when I turn the key to the on position but, it sounds like its got air bubbles in it?? Like its pushing air.... I ended up replacing the pressure line because i couldn't get the old fuel line out of the the plastic connector. It took some time but I did end up finally getting the old return line out and was able to use the original plastic connector. I'm just wondering if that old original return connector isn't holding pressure or if I have some other line that isn't seated properly?? Or, do i have a faulty fuel pump or a clogged fuel filter?? Any help would be greatly appreciated! Thank You!!
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Old 12-16-2016, 06:31 PM   #2
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Re: 2005 GMC Yukon XL Fuel issues......

You definitely should replace the fuel filter.
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Old 12-16-2016, 08:04 PM   #3
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Re: 2005 GMC Yukon XL Fuel issues......

Thanks for the quick reply! But my only question is that there is no external fuel filter. Only fuel filter is inside the fuel tank connected to the New fuel pump. Still think that could be the issue? Again, just asking, haven't encountered anything like this before.
Thanks again!!
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Old 12-17-2016, 10:43 AM   #4
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Re: 2005 GMC Yukon XL Fuel issues......

Update! I went and got a fuel pressure tester gauge. When I turn the key to the on position, it takes about 10-15 turns and the pressure reads just under 50psi. I try to start and it starts right up! but he the pressure falls to 0 and it dies... Still think the filter or did I get a faulty pump???
Thanks again
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Old 12-17-2016, 12:44 PM   #5
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Re: 2005 GMC Yukon XL Fuel issues......

I've been doing some reading and searching on other posts and I am now trying to reset the pcm. I've disconnected the negative battery cable and going to leave sit for about an hour. I just don't think I have have a faulty fuel pump. Once I have got the pressure up to just about 50psi, and have not touched it for the passed hour, it has stayed at 45psi. It seems like something trips and the pump cuts out and the pressure drops to 0 when I crank it over. Only thing is is that it starts! But then runs out of fuel and dies...Really frustrating....
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Old 12-17-2016, 01:11 PM   #6
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Re: 2005 GMC Yukon XL Fuel issues......

Fuel pressure should meet the first FSM spec of 55-62 psi, KOEO. The fact that it drops immediately on startup could indicate several things.

I know it not pleasant outside right now, but if you can, jumper the fuel pump relay at the UEC and then try to start. If you still have a gauge connected, monitor pressure.
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Old 12-17-2016, 01:38 PM   #7
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Re: 2005 GMC Yukon XL Fuel issues......

ok, I reconnected the battery cable and turned the key to the on position, fuel pressure jumped to 55psi. i tried to start the engine and same thing happened. Engine started up, fuel pressure dropped to 0 and engine dies. I turned the key to the on position about 10-15 times and the pressure is back up to 55psi. You would think that if the pump pressurizes the system it wouldn't be bad right? I tried changing out the fuel pump relay and still have the same issue. I've seen people talk about a fuel pressure regulator that's mounted on the drivers side of the fuel rail but mine is located on top of the fuel pump itself and came new with the pump. I have the old fuel pump with the old regulator on it. Maybe I'll try to switch it out. The only thing that went wrong with the old fuel pump wa a pin hole on the pressure line on the steel tube that comes out of he pump! Why they did not make those out of plastic amazes me....
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Old 12-17-2016, 02:25 PM   #8
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Re: 2005 GMC Yukon XL Fuel issues......

Instead of exchanging the FP relay with another on, jumper the relay terminals in the UEC. Jumper between contacts 87 and 30. As soon as you do this the fuel pump should run, and continue to run until the jumper is removed. I have several insulated jumpers made from 12 ga. solid copper with flats forged on their ends to connect properly to the relay socket terminals. If you want to drive across the state line I'll gladly give you one. However, anything suitable which does not damage the relay socket contacts will do just fine. Be sure to connect only to the pump power terminals and not the relay coil terminals.

I suggest this so that both the FP relay AND its control are removed from the list of suspects. The anti-theft system can disable both the injectors and the fuel pump if it is not happy. Further, the PCM will not enable the FP relay after its initial 2-second prime cycle if the PCM is not receiving/interpreting the crank reference signals. I suspect that it is, since the injectors and spark plugs are firing, but just in case something may be awry with the PCM jumpering will remove any of that doubt.
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Old 12-17-2016, 02:55 PM   #9
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Re: 2005 GMC Yukon XL Fuel issues......

I really appreciate your help!! I went and jumped the relay, 87 to 30 and ya, the pressure shot right up to about 60psi. I turned the key and the truck started right up but the pressure gauge fell to zero and the truck died. same thing...
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Old 12-17-2016, 03:25 PM   #10
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Re: 2005 GMC Yukon XL Fuel issues......

That sounds like a fuel delivery (volume) problem. The pump can obviously make pressure but cannot maintain that pressure at the required flow. That could be as simple as a clogged filter or restricted fuel line, or could be a poorly performing pump.

Good luck.
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Old 12-17-2016, 03:32 PM   #11
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Re: 2005 GMC Yukon XL Fuel issues......

Thank You! I guess I'll have to drop this tank for the 3rd time... Not till later next week though when it warm up a bit.
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Old 12-17-2016, 03:32 PM   #12
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Re: 2005 GMC Yukon XL Fuel issues......

If the Yukon is Flex Fuel there should be a separate, external filter near the fuel composition sensor along the frame rail. Follow the fuel lines.
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Old 12-17-2016, 03:33 PM   #13
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Re: 2005 GMC Yukon XL Fuel issues......

no, not flex fuel.
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Old 12-17-2016, 03:37 PM   #14
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Re: 2005 GMC Yukon XL Fuel issues......

Then this won't apply:

https://www.youtube.com/watch?v=G3PHPNYnXds



And you may get to lower the tank again. Hopefully the fittings installed correctly and are not not obstructing flow. It might still be worthwhile to inspect the lines for kinking, especially in the hard nylon tubes near the tank and the engine compartment.
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Old 12-17-2016, 03:39 PM   #15
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Re: 2005 GMC Yukon XL Fuel issues......

Ok. Thank you again for your help!
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