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Faint whiff of gas fumes near and inside the truck

Discussion in 'Engine & Drivetrain' started by chilerancher, Jan 20, 2020.

  1. chilerancher

    chilerancher TYF Newbie

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    I did three of them just to make sure the procedure was repeatable. All three came out easily with this process:
    1. Used a small-bladed screwdriver to move the CPA clip up (not off) as shown in the photo below. I inserted the blade in the groove at the bottom of the clip and then gently pushed up. Probably a pick is the better tool? If I pushed up firmly then the clip came all the way off undamaged, but perhaps lost because it could have landed anywhere. I was lucky to find it. For the rest of the clips I kept my other hand over it so it didn't fly off anywhere.
    2. Pressed the top of the CPA clip in. The top of the CPA clip is actually marked "PRESS" as shown in the photo below of the cleaned up part.
    3. While pressing the top of the CPA clip in, pull up gently on the injector connector assembly.
    4. Off!

    CPA = "Connector Position Assurance" as referred to in the GM service manual.

    With hindsight, the procedure in the service manual is consistent with what I did; I was thrown off by the two diagrams not matching what I was seeing. Even now that I know better, I struggle to see how those diagrams are applicable to my installation.

    fuel injectors - CPA clip cleaned up.jpg
     
    Last edited: May 24, 2020
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  2. chilerancher

    chilerancher TYF Newbie

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    Updated observations before starting this project:
    • Yesterday while backing out of the driveway to park in the cul-de-sac to get this project started, there was a very strong gas smell and I could see I was trailing some liquid. Truck was running very rough while backing out. The liquid was clearly gasoline and after parking I could see it streaming underneath from the passenger side back of the engine. It stopped after about 15 seconds. Not sure, but maybe I have a second problem going on? Or could this be related to intake manifold gaskets? The truck had been parked for about 6 days.
    • KOEO fuel pressure confirmed to be 48 psi. After about 10 minutes it drifted down to about 40.

    The intake manifold is now off. It was fairly straight forward and went a little quicker than I expected after @Fless helped with the fuel injector connectors. Current observations:
    • The throttle body doesn't look too bad and should clean up nicely I expect.
    • I'm worried I bunged up the cruise control cable connector to the throttle body.
    • The intake manifold is pretty grimy inside and out.
    • Underneath the manifold ports, surrounding all eight intake ports, was a bunch of leaves and rodent droppings. It was hard to believe how much was there given that this truck has been driven almost every day for the past 18 years. (I was so shocked that I forgot to take a picture and immediately vacuumed most of it up.)
    • The water dams (or whatever they're called) on each end are intact.
    • The flat area with the knock sensors was clean and dry. I don't see any visible signs of corrosion, but haven't pulled the knock sensors to check underneath.
    • The Felpro gasket set I ordered (MS98016T) are different than the parts I pulled off, which apparently are MS96587 that clip in. Even though the the place I ordered them from confirmed they fit my application. Even the Fel-Pro website says it fits my application. Ugh, will try to swap them.
    • All but one of the injectors were clean. One of them looked a little fouled (see attached pic). Is this a concern?

    intake manifold removed.jpg good injector.jpg intake dams.jpg fouled injector.jpg
     
  3. chilerancher

    chilerancher TYF Newbie

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    OK, I'm now questioning my assumption that because the part I ordered didn't look like the part I pulled off that the new part won't work in my application. Fel-Pro pulled up two options for the gasket on this 2002 5.3L Flex fuel (engine code Z):
    https://www.felpro.com/find-my-part...C~Yukon XL 1500&values=2002~GMC~Yukon XL 1500

    One option is what I bought. MS98016T has the metal 'body' and gaskets for other parts like the throttle body and the injectors.
    The other option is what I pulled off. MS96587 looks exactly like what I pulled off the intake manifold. It also explicitly calls out "FLEX" as additional fit criteria.

    Right now I'm inclined to swap for the part that looks like mine and is called out as Flex. Or should I use the one I bought because it also showed up as valid for my application? Just relax and have a homebrew?
     
  4. chilerancher

    chilerancher TYF Newbie

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    Got the exact Fel-Pro part (MS96587) today and I'm going with that.

    Took the knock sensors out and the back one has a lot of corrosion. I had trouble with removing both parts. The plastic hole cover would not slide up the wire and instead bit into it, breaking the connector underneath. Sensors came out real easy. Going to get the ACDelco replacements locally and I already have the Dorman harness. I'll also do the RTV dam around each hole cover.

    original knock sensors.jpg
     
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  5. chilerancher

    chilerancher TYF Newbie

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    Project completed this morning.
    • Installed new ACDelco knock sensors and Dorman cable harness.
    • Built RTV 'dam' around the rear knock sensor only (horseshoe shaped, open end towards rear). Per a GM TSB I stumbled across.
    • Removed the rear intake 'baffle', per GM TSB for knock sensor corrosion.
    • Installed Fel-Pro MS96587 gaskets.
    • Cleaned the throttle body, used new throttle body gasket.
    • Reinstallation of intake manifold was much quicker than the tear-down.
    • Cruise control cable connector seemed to snap back on the throttle body, no issues with the retaining clip being a little bunged up. Cruise control works fine.
    • Cleared all codes.

    First road test was very good. Smooth engine, no gas smell, 50 PSI fuel pressure KOEO. Strong acceleration, short and long-term fuel trims within 0 +/- 10, fuel economy spot check around 14 (OBDII values over 10 miles), up from 11.5.

    That must have been one heck of an intake manifold gasket leak.
     
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