So what did you do to your GMC today?
- Thread starter RvRev2
- Start date
Sounds like vapor lock considering both times it happened involved reduced airflow for a period of time.
No idea as far as continuing. Its your comfort factor
No idea as far as continuing. Its your comfort factor
not really. if the engine was hot and the clutch was engaged it would stop faster, but otherwise I think it would coast for a few seconds
A couple of seconds after shutdown for the fan to stop spinning is about right.
This will help with your diagnosis:
Maybe suspect the HEI ignition module. Its inside the distributor at the top rear of the engine where it gets mighty hot. Its a known issue for them to go faulty when hot, then recover when they cool off (thermal intermittent) Make sure you apply heat sink compound to the bottom of the new module before installing.
Finally the time has come to begin installing interior stuff instead of taking everything apart. Woohoo.
This dude started with good bones but with some water damage, ware and tear and 47 years of hanging around it needs some love.
This was the beggining:
Leaks discovered, sealed new wiring scheme being applied and updates to the insulation:
Help from the wood shop and all of the damage has begun to disapear:
This dude started with good bones but with some water damage, ware and tear and 47 years of hanging around it needs some love.
This was the beggining:
Leaks discovered, sealed new wiring scheme being applied and updates to the insulation:
Help from the wood shop and all of the damage has begun to disapear:
Do you have a lift pump plumbed before the selector valve?
If you wire it to the 12v at the valve, when you hit the reserve tank switch it will both switch the valve and power your lift pump, this puts a small pressure on all the lines between the lift pump and the engine mechanical pump. This will eliminate 95% of your vapor lock problems in hot weather.
Thanks for the thumbs up Y'all.
It has been a productive couple of days. The new 12v circuits for lighting and accessories is coming along and some of the new wall panels and trim for the window shades are up. The walls are being finished in heavy canvas and most of the new trim is PVC.
Some of the new lighting now works too. Woohoo.
Howdy all,
Still on my way to the Rally. I had two more incidents today. This morning I installed an auxiliary electric fan to push more air through the radiator. I really thought that worked because it ran great for hours. But, alas, same thing again.
I was able to get online tonight (after 7 pm) and saw some more ideas. I did bring a spare HEI Ignition Module. I'll try changing that out before I set out for the Rally tomorrow. I'm only 3 hours away now, I think.
Still on my way to the Rally. I had two more incidents today. This morning I installed an auxiliary electric fan to push more air through the radiator. I really thought that worked because it ran great for hours. But, alas, same thing again.
I was able to get online tonight (after 7 pm) and saw some more ideas. I did bring a spare HEI Ignition Module. I'll try changing that out before I set out for the Rally tomorrow. I'm only 3 hours away now, I think.
Made it to the Rally. I did change out the HEI Ignition Module this morning. Rig ran fine, but it was a cooler day, shorter drive, and lower speeds, so no idea if this fixed the problem.
Todd, I don't have a lift pump, but I foresee one in the near future wired up just as you said, to the Auxiliary/Reserve Tank toggle switch.
Todd, I don't have a lift pump, but I foresee one in the near future wired up just as you said, to the Auxiliary/Reserve Tank toggle switch.
It's a long pull for the mechanical fuel pump to move the fuel from the tank, and it's by suction which causes the gas to boil at an even lower temperature. It was common on SOB's that they would have a low pressure lift pump, especially on the longer coaches which would push the fuel towards the engine's mechanical fuel pump.
I notice on hot days that even just pausing briefly, the hot pavement will warm up the fuel lines and it will vapor lock and sputter. When that happens I switch the tanks and energize the lift pump the engine will almost immediately start running correctly.
I'm pretty sure it's the blend they sell as gasoline today, it's not what it used to be and boils more easily.
Thats what I think. Modern fuels aren't designed to be sucked by an engine mounted pump, they are meant to by pushed by an in tank fuel pump so vapor lock is no longer a problem
They don't last forever either, I had one go bad virtually right out of the box. It failed in the 'locked up' mode however, so we were still able to continue.
