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  1. #1

    Angry Intermittent starting problem - need help

    Hello all,

    I am new to this forum and I need everyones help.

    I am the proud owner of a 2000 GMC Yukon that I bought new in 2000 and I currently have over 314,000 miles on her. She has been bulletproof up until recently when it itermittently has a starting issue. Here is what happens:

    - The truck will always start first thing in the morning. It will run normally.
    - We will stop somewhere, do something for an hour of 2. When we go back out to the truck to leave, when I turn the key, the engine cranks over normally, but the fuel pump does't prime. The gas gauge will also be stuck on E.
    - After waiting about a half an hour, I will turn the key, the gas gauge will work and the engine will start.

    I have had the truck to 2 GM dealers and a private garage. They have all had problems trying to recreate the problem. But the last garage was able to narrow it down. I know that it is not the fuel pump, because it is only 2 years old and is a Delphi pump. Plus, it always runs fine once it does start. Also. it does'nt make noise like the previous pumps did before they failed and the fuel pressure it normal.

    Like I said, the last garage was able to narrow it down to either the ignition switch or the computer. I had already tried the switch, but that didn't do anything. I did buy a used computer and had it reflashed. That took care of the problem for a month, but now the problem is back.

    Has anyone heard of this problem and what was the cure? Is it a wiring issue or something else. Any help would be appreciated.

    Thanks,

    Jim

  2. #2
    Sr. Engineer
    Join Date
    Oct 2010
    Location
    Indianapolis, In
    Posts
    487

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    I was going to suggest that there may be a ground issue at the new connection at the pump but after looking at the wire diagram it does not seem likely a ground problem. It did come with a new connector and you did use it, Right? Could be the connection but after that the only thing in common is the power train control module. Maybe not the reflash that made it work but the act of removing and replacing the connections.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  3. #3

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    You describe a "hot soak" (high temps under hood after engine turned off) to activate the problem, although 2 hours is long. It never acts up cold in the morning? With the key in "run" the gauge is dead before you try to crank it? Is anything else dead in the dash cluster? I don't see the ign switch reacting to 'hot soak'. An electrical coil or solid state electronics would. Look for other symptoms when this occurs to get some clues.

    The 2000 power distribution wiring diagram shows a primary and secondary fuel pump relay. The primary relay is powered from the 20 amp ECM 'B' fuse. If you lose power there, the ECM is dead but not ECM memory (I believe is the 'A' fuse). There is also a secondary fuel pump relay powered from a 10 amp 'engine 1' fuse that also powers evap, cam sensor and MAF sensor. You'd have other symptoms if those lose power. Two relays failing is a long shot, but it may not have the secondary like the diagram shows.

    Have you replaced/switched the primary (perhaps only) fuel pump relay (for a coil problem)? There are 2 or 3 identical relays in the box under the hood, switch the fuel relay with another of the same type. Replacing the ECU didn't help so I would look elsewhere. ECU connections are very solid and protected. Receiver pin contacts can get loose. Careful visual inspection can see it. It's already been unplugged and plugged in, however you can unplug and plug in the connectors 2 or 3 times to "wipe" the contacts and hopefully get a good connection and see if it helps.

    The Haynes wiring diagram shows a fuel tank pressure sensor feeding a signal to the ECM which may affect it. Otherwise, the fuel level sensor is not electrically related to the fuel pump any way I can see. The fuel level sensor circuit goes from the ECM through the sensor and to ground. Nothing else in the circuit. The ECM drives the gauge.

  4. #4

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    Thanks for the replies guys. Saguaro, in response to your question about the other gauges, they are working, only the gas gauge isn't. I did replace the relay with a different relay with no change. I will check out the fuses that you pointed out. Being that I live in the rust state of Wisconsin, I would not be surprised if corrosion somewhere in the wiring could also be the problem

    Saguaro, by the way, my family and I should be moving back to Arizona in the next few months. I have a company in Gilbert that would like to hire me. We just to need to work out the logistics. We moved to Chandler back in 2007, but in 2008 I lost my mind and thought that it would be a good idea to move back to Wisconsin. It has taken me 4 years to find a job back out in Arizona, but it looks like it will happen.

  5. #5

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    Quote Originally Posted by jimig1990 View Post
    Thanks for the replies guys. Saguaro, in response to your question about the other gauges, they are working, only the gas gauge isn't. I did replace the relay with a different relay with no change. I will check out the fuses that you pointed out. Being that I live in the rust state of Wisconsin, I would not be surprised if corrosion somewhere in the wiring could also be the problem

    Saguaro, by the way, my family and I should be moving back to Arizona in the next few months. I have a company in Gilbert that would like to hire me. We just to need to work out the logistics. We moved to Chandler back in 2007, but in 2008 I lost my mind and thought that it would be a good idea to move back to Wisconsin. It has taken me 4 years to find a job back out in Arizona, but it looks like it will happen.
    Wisconsin? As in salt on winter roads and lots of undercarriage corrosion? OK. And you have a plastic gas tank like all of us. Your symptom cycle may not fit this, but you might try locating the ground wire from the fuel pump/sender module. My grounding diagram says they both combine and ground next to a body mount near the tank. Clean up that connection and make sure it is tight. It's the only common point I can see affecting both fuel pump and sender (therefore the gauge).

    Sorry I haven't had a chance to get back on the forum and just got email of your response.

    Glad to hear your are moving to AZ if your heart is here. It's finally going to drop below 100 soon. We moved from Washington State 2 years ago. What a difference! We bought, rehabbed and are living in a short sale house in Mesa near where the 60 and 202 intersect. It will be up for sale about Feb. "Saguaro" is the name my wife gave our 2005 Silverado for the dk green color. It seems to fit. Take care, Jim.

  6. #6

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    Quote Originally Posted by saguaro View Post
    they both combine and ground next to a body mount near the tank. Clean up that connection and make sure it is tight. It's the only common point I can see affecting both fuel pump and sender (therefore the gauge). Jim.
    I agree with Jim, I believe it is a common ground.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

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