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1990 Chevrolet Blazer Question: What would cause the engine to surge randomly, especially when driving uphill?

 

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lightsaber, 6.2L V8 Diesel, Raton, NM, September 19, 2013, 10:45
 Journeyman

The vehicle is actually a 1983 K-5 full size civilian diesel Blazer with a take-out 1984 military 6.2l J code diesel engine with original military DB-2 injector pump that has a slight fuel leak at the throttle shaft, "new timing chain, and head gaskets installed during engine swap two years ago", 4X4, 700R4 trans. The engine acts like the timing is increasing during the surge with more engine rattle, and speed. The truck has a slight vibration at idle in both park and drive gear, white smoke from passenger side exhaust for 10 seconds after startup but no smoke from drivers side, and #4 cylinder has lower compression (250 psi) than the others(around 300 psi). Other than that, it runs very good for a normally aspirated diesel engine. I cleaned all 8 injectors manually DIY. When I turn the engine over by hand I can hear a clicking sound coming from the passenger side of the engine. Since the injector timing is regulated by the fuel pressure inside the injector pump, the throttle shaft leak might be the cause is my guess. All help is appreciated!

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  • Answer #1

    Greg's Orange Auto (13485 Answers) , Orange, CA - (714) 361-9386
    globalhelper September 20, 2013, 05:57
     Master

    surging could be several things but fuel leak would be where i would start,also ck fuel pressure at lift pump

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    lightsaber, September 20, 2013, 16:48
     Journeyman

    Thank You Global Helper;
    The fuel pressure after the lift pump was around 5 psi a few months ago and this surging has been there since before the pressure check, I did not see any fuel seeping along the supply, or air bubbles in the individual return lines, but the top of the tank had fuel/dirt on top. I dropped the tank to service the fuel sender and cleaned the top of the tank a couple days ago, and will keep an eye on further leaks at the tank. I replaced the temperature sender for the HPCA high idle circuit and didn't notice any more surging so hopefully that was the issue.

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