Hi folks,

I've got an 87 F150 300ci six with dual fuel (propane and gas). My in tank fuel pump siezed up and hasn't worked for months, so I have been running it off of propane. Just recently the fuel guage for both the propane and the gas has stopped working. When I start the truck with it switched to propane the gas gauge goes all the way over past full but if I switch over to gas the guage goes all the way over on the empty side. I have tried tracing out the fuel guage wire from the propane tank but lost it up by the firewall. My question is could the siezed up in tank fuel pump problem (and likely the float) be related to the propane fuel gauge problem or could it be bad ground or dash guage?


Thanks in advanced
F.O.G.

 

Where is the propane tank? Find it and there should be a wire going to it for the sending unit. I have never worked on a propane system on a truck, but I assume it has a sending unit just like a regular fuel tank.

If it does, take the wire off the sending unit, and with the key in run, ground the wire. The fuel gauge should swing full scale one direction. Then take the wire off ground and let it hang in the air. The fuel gauge should swing full scale the other way. If it passes this test, the wiring and the fuel guage are good.

This test will work for the regular fuel system sending unit too when you switch the fuel tank selector to regular fuel.

 

Thanks, I'll give it a try. As it stands right now the gauge goes all the way over to full so it might be a bad connection or ground. But I'll let you know how I make out.

F.O.G.

 

We'll I undid the sensor wire for the propane guage and grounded it like you said. The guage stayed all the way over to full whether it was grounded or not grounded. I did a continuity test on both the wire and the guage. The wire I got some resistance but the guage didn't read anything. I called an automotive propane repair place and the tech there suspected that the sensor wire was hooped based on what I told him. He suggested replacing the wire. Now I have another question. Since I have dual fuel would the propane sensor wire run to the dual fuel switch and then the guage or would it run directly to the guage? Like I said before any advice or help would be appreciated. BTW as to your question about where the tank is located it's under the box where the spare tire used to be mounted with the wire running up the drivers side frame rail. If gas wasn't so expensive I'd just let it sit and rot but with gas at $1.00 per litre ( 4 liters per gallon) its cheaper to run on propane.

Thanks In Advance
F.O.G.

 

It sounds like you have a factory dual tank system, but instead of a gas tank in the rear you have a propane tank. If we assume this to be true, then yes, both sending unit wires go to the dash switch, and then one wire goes from the switch to the fuel guage.