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95 K2500 Suburban, 6.5L
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So this is really picking me. It's my sons truck and we have been through it from end to end. I am just looking for suggestions for something I have missed. The truck has had intermittent stalling issues for a while now. Some days it starts and runs like a champ, and other days (more frequent now) it starts, runs for ten minutes and stalls, and then will not run again. It will catch and immediately stall. If we keep trying it will magically run and cause no issues the rest of the day.
We bought the truck this summer cheap with two codes. Optic sensor and stepper motor. We replaced the optic sensor a while ago and the code is gone. It ran fine with and without that code. We also had a stepper motor code. Replaced that and the code did not go away. I pulled the pump and found the piston was actually stuck. (the truck sat for a while before we bought it.) I tapped it and it freed up. I pulled the covers and lubed the heck out of it and it moved easily. Put it all back together and no more stepper motor code. There was a chisel mark to time the pump and I made very sure to put it back in the same spot, but rotating it one to 2 mm either way makes no difference to the stalling anyway. So it runs great when it runs but this stalling thing is a head scratcher. I thought it was air in the fuel but now I am not so sure. To eliminate air leaks and fuel issues I have: dropped the tank. Clean as a whistle and clean sock. New lift pump. Added wires to bypass the FSS and it is verified to work fine and has 7 psi at the pump. Lots of flow at the tee. New fuel filter. replaced all fuel lines. Not a drop of fuel leaking or any wetness anywhere including under the pump. Valley is dry. When I crack the drivers side injectors I have fuel at all four. No bubbles in the fuel. Makes no difference if the fuel cap is on or off. (minor vacuum after running for a while) Along the way we have tried two known good PMD's (one new) with no difference. And when it is not stalling it runs fine on both of them. PMD is on a heat sink out of the valley. When it is stalling and not wanting to start it it makes no difference whether the optic eye is plugged in or not. I have checked every single electrical connection and I have cleaned all the grounds and also added a big heavy new one frame to motor. Truck has 280,000 km on it. What have I missed? Thanks in advance for any suggestions.
How about the crank sensor? Mine was bad (and also gunked up) and never threw a code. Caused all kinds of problems.
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