c.d.ewen
11-14-2006, 21:31
The twist is that my '98 GMC Suburban (180k miles) has a vegetable oil conversion kit installed, and the engine has stalled while running on veggie. The conversion is one in which an entirely separate fuel system is used for the oil - separate (heated) fuel tank, separate lift pump, separate fuel lines. I'm just about out of ideas about the cause of the problem.
When I had the conversion done, I had a Kennedy Diesel FSD Cooler Package installed, so that should eliminate the hot PMD problem.
A week ago, I drove to a store (on diesel) and parked. Returning 15 minutes later, it started right up, but stalled as soon as I put it into gear. It restarted immediately, but again stalled when I tried to move it. It started immediately again, and revved right up in response to some kicks of the pedal. I then let it idle, and it stalled after about 20 seconds. After that, I cranked and cranked, but it wouldn't start. I switched over to using vegetable oil as the fuel source, and was able to start up.
While running on veggie, I opened the water drain on the diesel fuel filter, and nothing came out, making me suspect the lift pump. It's my understanding that the diesel lift pump operates continuously, even when burning veggie - all of the flow is simple shunted to the return line. I then drove to my local mechanic, a long-time friend, who determined that the pump was getting power but not pumping. He installed a new diesel lift pump.
Everyday since then, however, I've stalled 4-5 times a day on diesel, always at idle. The engine accelerates well, and there is no hesitation or hiccup at highway speeds to indicate an air leak. The first day, I chalked it up to air bubbles coming loose in the fuel line as I made turns, went up/downhill, etc.
I have only had 3 stalls (all at idle) while running on veggie, and two of those were immediately after switching over from diesel. The other was after running an hour on a highway, and coming to a stop-and-go traffic jam.
Just so you know I've done my homework: I've ordered a new Oil Pressure Switch, and no amount of banging on the stearing wheel or ignition switch has causes a stall.
I'll see about hooking up a clear hose on the fuel lines (lots of plumbing to choose from on a converted greaser) and search for air bubbles. In the meantime, if any of you gurus have any suggestions as other places to look, I'd appreciate hearing from you.
Thanks in advance,
Charley
When I had the conversion done, I had a Kennedy Diesel FSD Cooler Package installed, so that should eliminate the hot PMD problem.
A week ago, I drove to a store (on diesel) and parked. Returning 15 minutes later, it started right up, but stalled as soon as I put it into gear. It restarted immediately, but again stalled when I tried to move it. It started immediately again, and revved right up in response to some kicks of the pedal. I then let it idle, and it stalled after about 20 seconds. After that, I cranked and cranked, but it wouldn't start. I switched over to using vegetable oil as the fuel source, and was able to start up.
While running on veggie, I opened the water drain on the diesel fuel filter, and nothing came out, making me suspect the lift pump. It's my understanding that the diesel lift pump operates continuously, even when burning veggie - all of the flow is simple shunted to the return line. I then drove to my local mechanic, a long-time friend, who determined that the pump was getting power but not pumping. He installed a new diesel lift pump.
Everyday since then, however, I've stalled 4-5 times a day on diesel, always at idle. The engine accelerates well, and there is no hesitation or hiccup at highway speeds to indicate an air leak. The first day, I chalked it up to air bubbles coming loose in the fuel line as I made turns, went up/downhill, etc.
I have only had 3 stalls (all at idle) while running on veggie, and two of those were immediately after switching over from diesel. The other was after running an hour on a highway, and coming to a stop-and-go traffic jam.
Just so you know I've done my homework: I've ordered a new Oil Pressure Switch, and no amount of banging on the stearing wheel or ignition switch has causes a stall.
I'll see about hooking up a clear hose on the fuel lines (lots of plumbing to choose from on a converted greaser) and search for air bubbles. In the meantime, if any of you gurus have any suggestions as other places to look, I'd appreciate hearing from you.
Thanks in advance,
Charley