Fuel pouring out of front gas cap

[Greg97]

I have a 97 F-250HD 5.8L V8 4X4 with dual fuel tanks. I topped off my front tank last night and at some point on the way back home I decided to switch to the rear fuel tank. With less than a mile to go before I got home I started to smell a very strong odor of gasoline. I decided to pull over and got out to see gas just pouring out of my front filler cap! I immediately switched back to my front fuel switch and eventually this stopped after a bit and after relieving the pressure by unscrewing the cap. I thought it was strange that the fuel was pouring out of the front filler cap after I had switched to the rear tank. I've never experienced anything like this before and I was quite surprised at the amount of fuel which was pouring out! It seemed like it was being fed by the fuel pump because as soon as I switched back to the opposite tank it pretty much stopped. Do I have a bad fuel pump? I've already had my rear fuel tank and pump replaced a while back. I hope I do not need a new front tank.

 

[kenn_chan]

Being new to the forum, and having just bought my truck recently i do not have the experience that many have, Now this is only an guess, but I would think that the system would somehow shut off the fuel pump in the tnak it was not useing when you swapped tanks, so if the system is electronic then look for a relay that is not shutting off, or a burnt contact on the switch itself that would prevent the pump from shutting off. if it is a mechanical system then i would bet it is pressure activated in some fashion and you are looking at a plumbing issue, and I won't hazard a guess there.

 

[dustybumpers]

You really have a gen 8-9 truck. There was a crossover in f 250 and heavier trucks in 97


That being said, the problem is the check valve in your front tank has gone bad.

Some history here so you understand why.

Early model gen 8-9 trucks had a 3 pump system, 2 in tank low pressure pumps, and 1 high pressure pump. The return line to each tank ran through a fuel reserve check valve. It would sence what tank the fuel was being pumped from, and close a flap valve to send the fuel back to the tank it came from.

In 1992, the system was changed to a 2 pump system. A high pressure fuel delivery module ( FDM)

This system uses 1 fuel line, 1 return line. There is a check valve at each FDM, that closes when there is pressure against it from the other tank, keeping the return fuel from filling the wrong tank.

This failed early on, and there was a recall.
The recall placed an external check valve on the fuel pump return line at each tank.

Unfortunatly, the recall has expired, and Ford no longer makes the repair.

Unfortunatly, the external check valve is no longer available


You now need to drop the tank, and replace the FDM with a new unit


You will also need to check your fuel pressure, the cause of the check valve failure was blamed onthe fuel pressure regulator failing, and putting full pressure to the pumps

another thing to look for, is gas in the charcoal can at the battery. If it is over filling the tank, it is filling the charcoal can too

 

[kenn_chan]

DB,

thanks for the back story, as I said, new myself to the newer ford trucks, so most of my ideas are conjecture, based off of experience with other brands, its great to learn something new you can pass on.

kenn

 

[Greg97]

Thanks dustybumpers...you are absolutley correct that the problem is with the check valve which is located off the high pressure fuel line. The problem I have now is the part for this has been discontinued by Ford. The mechanic even tried a junck yard with no success. Any sources you can think of that I could try to locate a replacement check valve ?

 

[dustybumpers]

Sadly, the only thing you can do is replace the FDM. you don't have to replace all of it, you can use your fuel guage assy on the new one, that will save you some money.

Make sure to replace the fuel pressure regulator, that is the culprat of the whole mess.

If you don't have the heart to replace a running fuel pump, just replace the regulator, and always run off the front tank first when you fill up. That way when you run the rear tank, you won't be over filling. Eventually though, the pump will stop pumping, and you'll be forced to make the repair

 

[Greg97]

I am having the mechanic replace the front tank and the fuel pump. Apparently the tank was showing signs of corrosion thanks to the New England weather. I need to find out what the Ford part number is for this check valve so I can do some investigating. Is there not a generic part available to replace this?

 

[dustybumpers]

The check valve is in the FDM. you would have to disassemble it to see the valve. technically, it's a ball that fuel pressure pushes in the return line tube.

If he puts in a new pump, ask him if you can have the old pump to take apart, and explore

 

[Greg97]

Here is the Ford part number I am in search of: F7TZ-9S278-CA I would think somewhere in the U.S. someone has this part that I can purchase.

 

[dustybumpers]

Like I stated earlier, that was the part ford used in the recall. I imagine they were made in a limited supply.
The recall ended 10 years ago, and most of the trucks that got the recall are almost 20 and counting. There are probably some in the junk yards, but that would be like winning the lottery. You would have to pull the tanks first, to see if there was one installed.

If your mechanic is installing a new FDM, you will not have to worry. I have changed the fdm's on my 90, 93, 94, and 95, never to have another problem.

Use an Airtex pump, they carry a lifetime warranty, so if it fails, you get the next one free.

 

[Greg97]

O.K. so I tested both fuel tanks this morning and I flipped the switch to the rear tank. I heard a fairly loud whining noise (Fuel pump) which I previously heard just before the fuel starts overflowing out the front tank filler cap. This noise sounds louder than it should be for a fuel pump I thought. Unfortunately, I was not able to see the immediate overflow result because both tanks now are no longer full. Just before I had the mechanic work on it I siphoned some out of the old front tank which was being fed by the rear. However, by looking at the gas guage I could still see that the rear tank is continuing to feed the new front tank (with new fuel pump) when the switch is set to rear. Interesting observation to note though....if I toggle the tank switch back and forth about 3 times, leaving it on the rear setting after doing this, the loud noise stops and I do not see any indication the rear tank is feeding into the front (Bad switch? Electrical issue?). I ran the truck for a while to see if the rear tank continued to feed the front and all indications were that it was not. When I hear that loud whining noise from the fuel pump though it sounds like it's coming from the area of the front tank (Weird). So I now have a 3 year old tank and fuel pump in the rear and a brand new tank and fuel pump in the front. I feel I've eliminated the bad FDM theory because if I leave the switch on front everything works fine and has been. The issue only occurs when the switch is set to rear and if I hear the loud whining noise. I'm wondering if the tank switch on the dash is possibly bad?