dieterschmied

I have a 1989 six cylinder with fuel injection and two tanks. Yesterday, the truck just died on the expressway like it lacked fuel. It sputtered and when I was pulling off the road it came back to life just enough that I felt is was a fluke until I passed the next exit and then it died for real.

I could crank the engine and it wanted to start but it just died when I released the starter switch.

First, I would like to pick up a simple wiring diagram of the fuel supply system so that I might understand how to diagnose the problem. Are there any on line?

It would probably be easier if I had only one tank. I don't need two tanks, so what is the downside to removing or disconnecting, say, the rear one? Is there anything that I should be concerned about?

I stuck a probe into the schraeder valve one the fuel line behind the engine and I got fuel to come out but I can't determine the pressure. I suppose the fuel pump only comes on for a few second is the engine does not start; is my assumption correct? Does that apply to all of the fuel pumps?

farmer12

I wouldnt even bother removing the tank just leave it there and dont use it. Chances are you just have a bad pump. There are three on those trucks, one low pressure pump in each tank and a high pressure pump on the frame rail. The low pressure pumps push fuel up to your dual function selector valve on the frame rail behind the high pressure pump.

Easy way to check it is just listen when you turn the key on for the fuel pump buzz. I bet its your high pressure pump. Get yourself a fuel pressure guage and hook it up on the schrader valve on the fuel rail.

dewman

There are a couple of threads on the board that relate to dual fuel tanks and the pros and cons of removing a tank or only using one tank. Run a search and you will probably find the info you need to make a good decision.

Good luck.

dieterschmied

Thanks!

What it was was the front tank pump and where I put my last gasoline purchase was in the front tank.

The process:
I found the fuel relay and removed it and then jumped the socket terminals ( hot and fuel pump) because I was alone and the relay only turns the pump on for a few seconds. I could then hear the front (high pressure) pump and I could hear the rear tank pump, but when I switched tanks on the dashboard, I could only hear the front (high pressure) pump. I put a gallon of gas in the rear tank and replaced the relay (original) after I removed the jumper and the engine started immediately.

I then put a message on the front tank filler cap to use the rear tank. I will drain the front tank later to save on weight and it gives me a place to stash.

Thanks again for the input.

grilljames

Well if you want to get crafty, LMC Truck offers a rear 38 gallon tank for bout $200. Im kind thinking about removeing my midship tank and replaceing the rear 16 gallon tank with the 38 gallon tank.

Psxmoe

I would love to have a 38 gallon Tank in the back. But if you order it you'll then have to buy a spare tire mount for in the bed.

grilljames

the guy i got my truck from was an older guy and he had his son rip the spare tire mount off being and older guy it woulda been easier to not deal crawling under to get the spare out and i jus got my tire in the bed.

dr_bowtie

Ford put two tanks on there because the gas mileage is so terrible you need both of them to go any distance...LOL

no need to figure it out... if you know one you know both...they are wired in parallel... it is very simple