The Stovebolt Site Forums The Shop Area Engine Shop v6 vaporlock

today while trying to drive to school my truck died, having had this problem in the past, I knew it was the old gremlin Vaporlock. my question is, this hasn't happened to me all summer while driving in 106 degree weather and today it's only 85. the only thing that has changed is my sending unit went bad last week and over the weekend I replaced it, and I got it from my local classic chevy store so it is identical to my old one (outwardly anyway). could this suddenly cause vaporlock somehow and what do I do to fix the situation?


Indy

speaking of my 1969 gmc, sorry

Today was extremely humid here in central Oklahoma, that may have been the problem. Back in the day the easy fix for Vapor Lock was an electric fuel pump.

My experience with vapor lock over the years has been it's a sign of a weak fuel pump. It's likely just coincidence with the sending unit.

Or clothes pins on the fuel line often wrapped in aluminum foil! Ah the good old days.

SimS

The only way clothes pins and aluminum foil would work is you had to wear a tin foil hat to go with them.

Check all flexible lines and connections from tank to pump. An air leak in the suction line will cause vapor lock like symptoms.
Replacing the fuel sender can cause older hoses to crack and leak.

Would you mind explaining how that works?

I'm assuming that the sender is in the tank. Most senders are connected to the hard fuel lines eith flexible hose thei hose has to be removed from the old sender and connected to the new sender. The hose is flexed a lot during this procedure it can crack and break or loosen at the fuel line. Or people like me can forget to tighten the clamp at the sender . All of the above can cause a vacuum leak which will cause the fuel pump to pump air instead of fuel. Viola faux vapor lock. Or as previously stated vapor lock like symptoms. And of course the pump could have crapped out.

Huh? My sender has no hoses attached to it only wiring. I admit I don't have a '69 to look at but my '47, '48 and '53 don't have hoses attached to the sender.

Most later senders are a part of the tank fuel pickup. All this is removed from the tank as an assembly. If sender is separated from pickup tube the tank would (probably) have to be removed to replace it. It is difficult to remove a gas tank or at least lower it without removing or jostling the flexible fuel line. All I'm trying to say is an air leak any where in the suction line will cause poor to none fuel delivery. The only reason I brought this up is when I have sudden onset problem the best place to look is at the last change or repair. Looking at hose connections after replacing a fuel sender seems a logical place to start. (Even for one as stupid as I)

my tank is behind the seat and has no flexible hoses attached until the fuel pump, but I did get my situation fixed. the pump was on it's last leg and my fuel filter was plugged (I did check the pump before replacing it, it was putting out about half of what it should) So thank you all for your input and advice.