chev c 10 fuel problem

[kenny]

I have 77 chev c 10 350 cc problem is clear fuel filter running out of liquid gas seems to be vaporizing gas truck runs bad after it gets hot changed fuel pump fuel filter added a clear filter to see gas running out. Dropped tank changed all rubber lines. After you drive truck get It hot very little gas will come into filter. You can turn truck off take line off filter it will blow pressure off then you can crank truck it will run for a while then same thing no liquid gas in bowl just pressure. Changed gas cap. Checked vacuum from line to tank. Can't figure it out.

 

[Quadrajet Power]

Do you have a vented gas cap? Sounds like you are creating a vacuum in your tank and it needs vented.

Those glass filters are scary and I don't recommend using one. They can break easily causing fires. They won't appear full of fuel even when the fuel system is working correctly. The best way to check is to T in a fuel pressure gauge and watch for good, constant pressure to the carburetor.

 

[HotRodPC]

Sounds a bit like a vapor lock issue too.

Running a Quadrajet Carb?

 

[HotRodPC]

77 models don't use the Charcoal Canister Purge do they? I've heard of those going bad and starting to suck charcoal and can clog a vent line too.

 

[MadOgre]

I have 77 chev c 10 350 cc problem is clear fuel filter running out of liquid gas seems to be vaporizing gas truck runs bad after it gets hot changed fuel pump fuel filter added a clear filter to see gas running out. Dropped tank changed all rubber lines. After you drive truck get It hot very little gas will come into filter. You can turn truck off take line off filter it will blow pressure off then you can crank truck it will run for a while then same thing no liquid gas in bowl just pressure. Changed gas cap. Checked vacuum from line to tank. Can't figure it out.

It will BLOW pressure off ? As in fuel/vapor/air is built up on the tank side and blows out of the hose when you disconnect it from the fuel filter ?

 

[wilrab]

I agree with hot rod. Sounds like vapor lock. Was just happening to me. I had the electric fuel pump up in the engine compartment and it would drive great at night then do the same thing you're saying when it was hot out. Moving it under the truck fixed it for me.

 

[PrairieDrifter]

Are your fuel lines routed too close to the exhaust?

 

[pacman1318]

I have 77 chev c 10 350 cc problem is clear fuel filter running out of liquid gas seems to be vaporizing gas truck runs bad after it gets hot changed fuel pump fuel filter added a clear filter to see gas running out. Dropped tank changed all rubber lines. After you drive truck get It hot very little gas will come into filter. You can turn truck off take line off filter it will blow pressure off then you can crank truck it will run for a while then same thing no liquid gas in bowl just pressure. Changed gas cap. Checked vacuum from line to tank. Can't figure it out.

Going through the same thing on my 84 (single tank)
It started about a month ago when it started getting super hot in Bama. new motor is a 60 over 350 edelbrock dual plane performer intake, 600 holley with doug's headers.

It started acting like it was running out of gas after about 10 mins.
This is what I have done in order the last few weeks with no change.
Re-routed the fuel line away from the motor and wrapped it with insulation,new mechanical fuel pump,blew air with a compressor through all the lines (removed the charcoal can when I replaced the motor and put a fuel filter on the end of the line to let it vent),new gas cap, jegs heat plate under the carb,mr gasket electric fuel pump installed in the rear where the lines cross over from the driver side to the passenger side,removed the tank and checked the sock,new hose on all tank connections and screwed sheet metal with insulation to the frame from the fuel pump down to the header collector.
I made a homemade cool can to help rule out fuel boil in the carb but it didn't help.
Tomorrow I am going to install the sheet metal and insulation down the rest of the frame and disconnect the mechanical pump and see if it still does it with just the electric fuel pump.
I still have other things I have to try, Reduce the timing,put a colder thermostat in and install a electric fan on it to help reduce under hood temp. Going nuts here and contemplating taking it somewhere and letting someone look at it.

Let me know if you find a fix.

 

[MadOgre]

Did you guys block off the crossover with the restrictor plates or gaskets ? Are the tanks truly vented ? The fuel pumps should be lubed with moly based lube inside where the spring is and at the end of the push arm where it contacts the push rod. Otherwise they can fail in short order.

 

[pacman1318]

Did you guys block off the crossover with the restrictor plates or gaskets ? Are the tanks truly vented ? The fuel pumps should be lubed with moly based lube inside where the spring is and at the end of the push arm where it contacts the push rod. Otherwise they can fail in short order.

The first thing I did when this all started was swap my fuel pump out (put a new one on it when I installed the new motor and it had less than 1000 miles on it and advanced swapped it for free) checked the vent and even ran it without the cap just to see if it was a vent issue and the performer rpm does not have crossovers.

I think I got mine fixed today, it wasn't a 100 degree day like it has been so Im not sure,
disconnected the mechanical and ran just the electric pump line to the carb and it didn't vapor lock, I went ahead and finished boxing my frame and shielding the pump since I had the time and already bought the metal.
Still going to drop the temp on the thermostat to 160 and bump the timing down some since it runs on when I shut it off.
My personal opinion is the heat of my headers, 60 over 350, 100 degree days , hot thermostat and the ethanol that probably vaporizes at a lower temp caused this event.

 

[MadOgre]

The first thing I did when this all started was swap my fuel pump out (put a new one on it when I installed the new motor and it had less than 1000 miles on it and advanced swapped it for free) checked the vent and even ran it without the cap just to see if it was a vent issue and the performer rpm does not have crossovers.

I think I got mine fixed today, it wasn't a 100 degree day like it has been so Im not sure,
disconnected the mechanical and ran just the electric pump line to the carb and it didn't vapor lock, I went ahead and finished boxing my frame and shielding the pump since I had the time and already bought the metal.
Still going to drop the temp on the thermostat to 160 and bump the timing down some since it runs on when I shut it off.
My personal opinion is the heat of my headers, 60 over 350, 100 degree days , hot thermostat and the ethanol that probably vaporizes at a lower temp caused this event.

Headers wont help for sure. Does your mechanical pump have a return line?

 

[pacman1318]

Headers wont help for sure. Does your mechanical pump have a return line?

It has a 1/4 inch return, when I took the mechanical off I put a small plastic fuel filter on it and turned it down to keep dirt and trash from getting in it and using it for the vent.

 

[MadOgre]

It has a 1/4 inch return, when I took the mechanical off I put a small plastic fuel filter on it and turned it down to keep dirt and trash from getting in it and using it for the vent.

Oh I see. I would pull that fuel sending unit or something, and verify that the return line does not have a check valve or returns below the fuel level. I may be wrong. But I would think that it would have a check valve on it. Maybe just see if you can suck vacuum through your 1/4" rubber line. I would not suggest sucking on it by mouth as that might give you a lung full of vaporized fuel which would be really bad! To ensure that the line is indeed free to vent pressure. I may be completely wrong, Im just guessing but that is one thing that immediately popped to mind

The tanks are supposed to be vented by the third vent line from the fuel sending unit. so unless yours was a diesel it will have a third vent line. At the very least just ensure that the third vent line is venting properly and forget about the jerry rigged return/vent line you made. No offense Jerry lol

 

[pacman1318]

Oh I see. I would pull that fuel sending unit or something, and verify that the return line does not have a check valve or returns below the fuel level. I may be wrong. But I would think that it would have a check valve on it. Maybe just see if you can suck vacuum through your 1/4" rubber line. I would not suggest sucking on it by mouth as that might give you a lung full of vaporized fuel which would be really bad! To ensure that the line is indeed free to vent pressure. I may be completely wrong, Im just guessing but that is one thing that immediately popped to mind

The tanks are supposed to be vented by the third vent line from the fuel sending unit. so unless yours was a diesel it will have a third vent line. At the very least just ensure that the third vent line is venting properly and forget about the jerry rigged return/vent line you made. No offense Jerry lol

I pulled the tank when it started acting up to check the sock filter and the fuel return is a open 1/4 line that dumps into the top of the sending unit and the other line went to the vapor can that I removed so I guess the tank vents through the cap and the sending unit has no vent, 3 line total, fuel pickup,fuel return and the vapor line that went to a vapor can that had a vacuum on it. please take the adult diaper delivery sign off your van LOL

 

[Boone83K10]

Still going to drop the temp on the thermostat to 160 and bump the timing down some since it runs on when I shut it off.

there is half of your problem. your engine is dieseling.

You need to correct this issue. your timing, too hot of spark plug or carb mixture is way off or a combo of all.