fieldho

I drive a 87, lariat with the 6 cyl. motor and a 5 speed tranny. Recently I had to replace my fuel vacuum regulator, front fuel tank, fuel sending unit. The MPG was fine on the first tank but on the second tank, the MPG went south quick, from around 20 to about 8. At first I suspected someone was taking gas so I installed a locking gas cap with no change. The truck drives fine with no misses or drag. I can't tell any difference in the operation of the truck except it suddenly started drinking gas like a logger on Saturday night. I can't seem to smell any gas or otherwise detect any leaks. Any guesses on what I might be missing? Could a stuck AC compressor cause such a change? I'm bewildered.

raski

I am suspect of your new fuel pressure regulator. I would pull the vacuum line off and see if raw fuel is present there. Was the old regulator ruptured? Did you put the vacuum line back on?

fieldho

Thanks for your reply. That was the first thing I checked by pulling a vacuum line, off the tree, and looking for raw gas. Before, when the truck would not start, I found raw gas at the vacuum tree so I surmised that that was the final straw that stopped it from running before. After my mechanic changed out the front gas tank, hole in the top, and fuel sending unit from inside the tank, also main fuel pump, filter, and misc., I had to take him by the hand and show him what I was trying to tell him before, no problem as the tank replacement was a safety issue anyway. I like the guy and mechanics are rare in the small town where I live. He was telling me there was no way raw gas could get to the vacuum tree, I don't know what he was thinking. We took a walk around his shop until I found a part of an intake manifold from a similar Ford and I could explain what I was saying. I'm not sure why he was being so hard headed about it unless it was the fact that he just didn't want to tackle the job. On a six cyl. Ford, the fuel feed is stuffed under the intake so it all must be removed to replace the relatively inexpensive part, but with a ruptured diaphragm in the regulator, it ain't going no where until it's fixed. Regarding my problem, I recalled a landscaping job I was doing, here in town, where I spent a couple of hours on the other side of the building, truck was out of site but easy to get to by the local thugs. I suspect someone relieved me of gas, from my truck, while I had my head down. I have replaced the gas cap with a locking Gates cap and the gas gauge is telling me things are normal so far. 25 miles and it's just staring to come down from above the full mark. I'll just have to see how far I get on this next full tank, trip odometer is set. Oh yeah, I'll be more careful about where I park my work vehicle from now on! Nope, it was the dual tank selector pumping gas from the front tank to the "unused" back tank. Nobody was taking my gas, good!

fieldho

Okay, found the problem, stopped the other day and noticed raw gas pouring out of my rear tank filler cap. You guessed it, the ole dual tank valve selector. I realize this generated a recall of this model. Since it's being used as work truck and shelf life of new gas sucks, I saw no need in having dual tanks. The front tank is all new so I dumped the rear tank and installed a single tank reservoir. Now I'm thinking about installing a marine or boat fuel line to the back tank so I can have a filling station for my yard tools without lugging a gas can.

Ford FOTZ-9K044-A Tank Fuel Reserve.

fieldho

One note on the FOTZ-9K044-A. It came without a filter and o-ring was not properly seated. When I first installed it, it leaked a lot. I purchased a filter Wix 33268 that had a new o-ring. Coated the o-ring and the threads on the filter cap with plumber's grease (silicone grease) and made sure all was aligned before reassembling unit. Apply the filter cap hand tight, no tools, and all is well. Since this valve in only made for one tank, there is no diaphragm to go bad so I feel it will last longer than the truck. JUST FIXING MY FORD, ONE LEAK AT A TIME!

Steve83

That's incredibly BAD for the fuel system. Silicone grease is NOT soluble in gasoline, so when little chunks of it break away & move through the fuel system, they stay intact until they block up a filter. In the worst case, it's the filter on an injector, which is one of the few ways to actually ruin one of these injectors. NEVER use silicone grease on a fuel system component. The only approved lubricant is clean motor oil.The diaphragm didn't go bad in the DFR, either. It was the O-rings, and the SFR has O-rings, too. The photos in this album show both reservoirs:


(phone app link)

fieldho

Thanks for the advice about the silicone however I opened the DFR and the diaphragm was perforated and damaged.