I have a 78 F250 with a 460 and its got problems. I was told 3 cylinders have no compression, but vehicle still runs fine. Just put a brand new fuel line from pump to carb. and vapor locking still occurs. Any suggestions???

 

I don't know how to handle your question about compression other than to tell you to check your compression and see if those 3 cylinders really do have zero pounds or not. Either you're wrong, the person that told you that is wrong, or you're both wrong. However, with 3 cylinders gone, a 460 probably wouldn't even run. To have zero compression, you've got to burn a valve or a hole in a piston or something catastrophic, and with even one cylinder at zero, you'd definitely notice. I'm sure you don't have 3 cyilnders out but if you want to know what it really is then you have to check, I can't tell you what your compression is.

As for the vapor lock, look for any kinks in the fuel line along the length of the truck. Don't neglect the foot-long length of hose that connects the fuel line to the tank at the back. Look for any obvious exhaust routing issues that would heat the fuel line. How do you know it's vapor lock? Many other no-start issues mask themselves as vapor lock.

 

If you are positive it is vapor lock, check you thermostat. If it is 195 drop down to 180. Should clear up the problem. If it a 180 already, then not sure what to tell you.

 

try running the feul hose as far away from the engine as possible esp. from pump to carb. I had this prob in an old 302 clevo I had on days when the temp was around 113f by keeping it away from the hot engine the feul stopped vapourising. Its a cheap fix to buy a couple feet of feul hose and at least you have some new feul hose feeding the carb. Ofcourse check for kinks and correct thermostat like fmc400 and davepig suggest also. Good luck.

 

make sure you actually used fuel line not just some same size line thats not used for fuel, fuel line is thicker and designed for the draw and won't collapse under pressure and will protect from heat better.(the rubber line) check that something didn't break lose and partially clog the fuel filter also.