Greetings to all. I have owned my 69 C10 for about 30 years. Engine was rebuilt about 30 years ago, and it only has about 20,000 miles on it since that time: (I uploaded 4 pictures, and hope that they will attach here)
The pictures show the engine and the fuel filter which is about a foot from the carb. The close-up shot shows the filter almost totally empty.
The truck was beginning to show signs that the fuel pump was not delivering enough fuel up to the carb. It still has the original style pump on the lower side of the engine, and a push rod from an engine cam pushs back-n-forth to make the pump work. The truck would idle fine, but when a good load was put on the engine (shifting somewhat agressively from 1st to 2nd and with a desire to "Getty Up"), it would bogg down, and act as if it wasnt getting fuel. Got so bad, that the engine would stall out. I raised the hood and saw that there was very little gas in the see-thru filter.
So, I logically assumed that the fuel pump was bad. I installed a new fuel pump, and at the same time I pulled the tank sending unit and installed a new filter on the tip of the pick-up line, and blew air through the fuel lines to verify that they were not getting clogged up. Lines were not clogged. I started the truck, and I could see that the pump was working......but during a quick test drive, I got the same "bogging down" and then stall out. Raising the hood, I could see that the fuel filter was again almost empty.
I then thought I would try removing the gas line above the fuel filter and try priming it with fuel. When I loosened the clamp and pulled the hose off, there was a "hissing" noise, and the high pressure blew gas in my face (no damage done). So, Im thinking there is something wrong to create so much pressure inside the fuel filter.
To rule out the possibility of a "bad" new fuel pump, I ran the hose into a 2 liter bottle, and started the truck and let run 5 seconds, and shut her off. There was a good 2 inches of gas in the bottle, so Im pretty confident that the pump is fine.
I tried to "prime" the fuel filter with gas, but it just would not work. I put the filter back on, and let it sit overnight. When I looked the next morning, the fuel filter was almost full......so, I guess the pressure of the fuel tank gas was enough to push the gas down, thru the pump, and up into the filter. I started and did another test run, and the same "bogging down" happened.......and an empty fuel filter. Stalled out in my driveway, and I managed to squirt alot of gas on the air filter to get her back in the garage.
So my question to all the experts here:
Is it possible for engine pressure (blow-by pressure) to build up and maybe push its way up through the PCV line and into the carb. From there, could it put an insane amount of pressure back down the fuel line and out-power the fuel pump? I have not yet tried pulling off the large rubber line from the valve cover to the bottom of the carb. I did remove the PCV valve that fits into the top of the valve cover, and cleaned in gas......the metal ball in it was working fine.
And I will toss in some more history that might help: For the past few years the truck has been starting up great when "cold", and running fantastic.....plenty of power, idles great, etc. However, after 10 minutes of running, if I turn the engine off and try to re-start, then I only get a "grunt" from the engine.....has no desire to turn over. If I let the truck sit overnight, then it starts immediately and runs great. But as soon as she warms up, then its almost impossible to start. (And I have replaced almost everything.....battery, battery cables, plugs, wires, points, condensor, rotor, etc.). Someone then mentioned that it might be "vapor lock". So, with this added info., is it possible that the carb. is just old and needs replacing? Is something inside the carb worn out, and allowing too much blow by pressure to go backwards to the filter, and at the same time, allows too much gas/fumes back into the cylinders after running which causes vapor lock?
I have almost pulled out all my hair on this one.........and suggestions would be much appreciated.
