pressurised tank

[kbob]

Hi everybody first time here but not last its great got a question my 80 CJ7 has a 91 chevy vortec 350 cu. in with tbi on it sometimes when i drive it down the road it just starts to spotter and then dies if i take the gas cap off it blows out like its under pressure it will start then but not stay running if i let it cool down it starts and runs fine temp gets to 200deg. i don't know where to start.

 

[mylittlecj5]

I'd bet your tank vents are plugged. check that and maybe replace your fuel cap?

 

[Old Dog]

I'd get a new vented fuel cap.
As mylittle cj said, the PO probaly did away with the vent lines when they did the 350 swap.

 

[kbob]

thanks guys got vented gas cap but it will still sputter and die only sometimes so i guest it wasn't the gas tank temp is still running around 200deg. but imm move Transmission cooler down so rad. gets more air 3 core rad. so it should cool the 350. not sure what to do with the dieing problem but will keep trying pictures coming soon thanks again

 

[mylittlecj5]

What about vapor lock? If its running that hot, it would cause your symptoms.
Look for the fuel line to be near the exhaust somewhere (probably a steel line most likely) and insulate or relocate it from the heat source.

 

[73jeep]

What about vapor lock? If its running that hot, it would cause your symptoms.
Look for the fuel line to be near the exhaust somewhere (probably a steel line most likely) and insulate or relocate it from the heat source.

Very tough to vapor lock a fuel injection system, But worth a look anyway.

 

[73jeep]

Is the diagnostic plug hooked up in the jeep? Is it throwing any engine codes? Whats the fuel pressure, a lot of guys throw a carb fuel pump in a Tbi system then wonder why it doesn't run right. You need 12-15 PSI.

 

[SoK66]

You may have a variety of problems based upon how the swap was done. Do some basic, common sense checks before you go much further. MAke sure your supply & return fuel lines are flowing freely, no blockages or kinks, etc., and that they are connected properly. If it was originally a V8 CJ, both hard lines from the tank will be on the driver side frame rail. If it was originally a 6 cyl, the supply line is on the passenger side. Make sure you have them connected properly to your FI system, and also be sure they're correct at the tank sending unit. Some guys will reverse them by mistake.

Also, make sure the lines are routed well away from engine heat. Don't run them up over the top of the engine, water pump, etc. I saw one like that a couple weeks ago that stopped dead on a steep mountain trail nearby. I'm not sure what side your EFI's fuel intake line is, but route your line to that cleanly and away from engine heat. If the inlet port is on the left side and your supply hard line is on the right, run the flex line all the way to the front cross member, that is, under the radiator support, then around to the driver side. Do the same with the return.

All that should ensure the lines aren't getting so hot the fuel is boiling. If necessary, insulate the lines with something like foil or glass fiber wrapped in foil, etc.