I have an 89 f-150 with 300-6 and dual tanks. Starts and runs fine on the rear tank, but when I switch to the front it runs a little while and cuts out. If I switch back to rear it runs fine again. Anyone have any troubleshooting advice as I am still trying to figure out how this system works? Thanks.

 

There's another thread I've been following that talks alot about this. My issue is just the opposite- runs on the front, not on the rear. Check out the other thread for more info.

 

There are two areas to troubleshoot. The first is to check with a volt meter if the fuel tank selector switch is sending power to the low pressure pump in the front tank and the second is to check that the voltage is getting to the pump and if it is working.

A little back ground: there are three fuel pumps in your truck. There is a low pressure pump in each fuel tank and a high pressure pump that draws fuel from the dual function reservoir that is feed by a low pressure pump in the selected tank.

The fuel tank selector switch (FTSW) will have a pink wire with black strip going to it from the fuse box. Place the FTSW in the front position. The red wire leaves the FTSW and goes to the front tank low pressure pump. The brown with white strip wire leaves the FTSW and goes to the rear low pressure pump. With the key in the run position and a wire connected from the PP lead on the self test connector to ground; this grounds the coil of the fuel pump relay, since the EEC will open the ground to the fuel pump relay after one second if the key is not turned to the start position. Leaving the wires connected to the FTSW and using a volt meter, check that there is voltage on the red wire to ground. If there is then the FTSW is providing power to the front tank pump. Change the FTSW to the rear position and check that there is voltage to ground on the brown wire with white stripe. There should be since you said that the truck runs fine on the rear tank.

If there is power to the front tank low pressure pump then you will have to check if the pump is running or if the voltage is getting to the connector on the front fuel tank. If the pump, in the front tank is running, you will have to check that fuel is getting to the dual function reservoir.

I hope this helps.

Keith

 

even easier. select front tank and turn the key on. u should hear the pump come on or not. remember, there is another pump up front, get someone to listen right at the tank if u need too. if u dont hear it, then check for power there.

 

Thanks a bunch. I will try all of this when the weather is a little better. Would you happen to know the name of the thread that was posted about this subject so I can search for it? Also, what would be the most expensive and troublesome thing that could be the problem? I figure with my luck that will be the problem and I may as well check it first and save some time. ha, ha. Merry Christmas.

 

If your are doing the work yourself the most expensive part is a toss up between the front in tank pump which is sold as an assembly that includes the sender and float; $115.00 depending on the size of the tank and if it is metal or plastic, and the dual function reservoir (DFR). I have seen just the pump; $44, for the rear tank, but, not for the front. You have to go to the Ford dealer for the dual function reservoir and I have seen numbers from $77 to $103. IF the dual function reservoir is not functioning. Yours is working for the rear tank, so, the cheap way would be to just run on one tank. I have seen may a post about people that have replaced the DFR and that was not the problem. The important point about the DFR is that it will not work if the fuel pressure from the in tank pump is below the DFR’s switching pressure of approximately 13.8 kPa. Ford has a procedure to test the DFR using air pressure when it is removed and on the bench. That is why I stress just doing the work right the first time and troubleshooting the fuel system methodically step by step. NO SHORT CUTS.

If you are going to have the work done replacement of the low pressure pump in the tank would be the most expensive. You have to remove the tank. The R&R labor would be almost as much as the pump. It takes a little more than an hour so the labor cost could be anywhere from $70 to $100 plus the cost of the part.

Keith

 

I have that selector thing sitting in my garage just taking up space let me know if you end up needing one.

 

I switched to the front tank with the truck running and crawled under it. It sounds like the pump inside the front tank is running. (vibrating noise) After a bit the noise seems to change pitch like it isn't getting fuel or something, then the truck dies. Switch to rear tank and it runs fine. I assume that if it's running it must be the dual function switch thing. How can I be sure? Also, where do I find the "PP" lead on the self test connector?

 

Water in the gas?


Adam J Hendrickson
'94 F150 Red, Reg Cab,Long Box,4.9,E4od,Posi,Overloads,Michelins!

 

Good thought. I didn't think about bad gas. I did put gas in it not long ago, so I'm hoping that's not it. Anyway, after crawling under the truck again, it appears that the vibration noise is the high pressure pump up on the frame rail. So I don't know if the in tank pump is working or not. I am going to try to check the electrical as above. When I find this "PP" lead, will that make my pump run all of the time? If so, couldn't I just pull a fuel line off from the pump and see if it puts out gas?

 

I feel your pain. My problem sounds nearly identical, but it's the rear tank that quits. Last winter I was able to use the rear tank only if it was cold (under 20 degrees) and I'd resorted to only using the front tank. If the outside temp was warmer, it would work for a couple minutes, then stall out.

Now, I suspect trouble with the front tank pump, or the high pressure pump, b/c the whining noise has become louder and she stalled on me twice today.

I tested the switch today and both tanks appear to be getting juice. What is another way to check if the in-tank pump(s) are working besides listening? I'm half-deaf.

 

duback66,
Have you figured anything out yet?