Fuel problem... help please?

[F3504X496TK]

I have a 1996 F-350 with 378,000 miles on it. Drove it to PA, from MD earlier this week to see my girl in college, and ended up on at a gas station for 4 hours. Truck started choking out, and running very rough. Had almost no power unless the pedal was on the floor and when starting in second gear, it would start out. (1st is a granny gear and I usually don't use it.) Bear in mind the motor didn't have the power to take off in second because of whatever problem I may have. Thought maybe I got bad fuel in Allentown. So, got towed home, changed the fuel filter and fuel/water filter. Also changed the CPS thinking maybe it was going bad. Still nothing. Now, I can't hear my fuel pump when I attempt to turn the truck on and no fuel is making it to the fuel/water bowl. I'm thinking a dead fuel pump? But I'm also confused. Does the truck have an external fuel pump on the frame rail or does it have internal tank pumps? It also may be a bad relay or fuse. But I have no way of testing that. I'm out of ideas and I'm confused as to where to start. I appreciate any help anyone can give me. Thanks.

[bugman]

Your fuel pump is a 2 stage mechanical pump and is located just behind the filter housing and in front of the turbo. So if you are not getting any fuel to the bowl and you have tried both tanks then quite possibly you have a bad pump.

[speeddemon31176]

^ What he said. The only fuel pump on the truck is in the valley of the engine behind the fuel bowl. It sounds like the lift pump side(diaphragm) has ruptured which would not allow it to bring fuel to the bowl.

[F3504X496TK]

I think the guy I bought it from said he installed a electric fuel pump in the rear. I've never worked on diesels before, but I'll be doing all this myself. I know there's a lift pump? From what I've read. But I'm just not sure how it all works.

[Parky66]

I just had to replace mine and followed the Sam Miller how-to guide listed below. It's really not too hard to do... I happen to run into a wiring issue from removing the pump/fuel bowl. The only thing I can add to the how-to is to check all the wiring while the parts are out, take off/replace any old tape and give a good look and clean all the connectors with some good spray electrical cleaner.


"FUEL PUMP REPLACEMENT by Sam Miller

I recommend disconnecting batteries. There is no way to work around the glow plug relay without touching it. Then set up a parts tray, run a good light, throw a pad over the radiator and go for it.

Also, if you have a HPX crossover hose installed, it is easier if you disconnect it from the passenger side oil rail and tie it out of the way. Remove "Y" pipe (compressor manifold) from turbo, taking care not to lose the rubber O-ring inside the fitting (Marmon clamp). If you loosen only the lower clamps on the two silicone hoses the whole assembly can be removed easily and set aside. Cover the openings with rags or plastic wrap and secure with rubber bands.

Draining the fuel filter/water separator canister. You will want to either place a container under the vehicle to catch the diesel (a hose pushed on to the drain tube sure prevents a mess), or pump the canister dry once you get the filter out, in which case you won’t slide the yellow lever to "DRAIN." This is a good occasion to inspect and clean the interior of the canister, so removal of the filter and heater is advised. (Remember, the plastic heater standpipe is LEFT HAND THREADS.) A 7/8" crow’s foot wrench works best, but I have loosened it with a regular open-end wrench. Pull off the heater wire connector with needle-nose pliers. Now you can clean the canister and check for cracks or leaks. You’ll be amazed at the crud in there.

Disconnecting hoses. There are two hoses connected to the top of the pump and one at the bottom. The two top hoses are protected by a removable clip-on heat shield (just yank it off). You can only get to the clamp on the pump side of that bottom hose. And finally, the water drain hose at the front passenger side of the filter housing.

Remove the two bolts attaching the fuel pressure regulator with 10mm and carefully pry it back from the filter housing, taking care not to lose the O-ring. Good time to clean the screen and examine condition of O-ring. There is also a short section of 5/16" hose that may need to be replaced.

Separate the wire harness connector on the passenger side of canister and remove positioning clamp with 8mm. It will NOT slide off the tongue of the clamp as you think it might, since the tongue is barbed. (Remind you of anyone?)

Disconnect wires connected to the canister, two on drivers side, one at bottom rear. (So now you want to know what they are? Aw geez, you’re one of THOSE GUYS: Oh, all right: on the driver’s side, the top connector on the side of the Water Filter/Water Separator Assembly is the fuel heater connection; the connector directly beneath it links to the Water Sensor; and the connector on the bottom rear of the Assembly is for the filter restriction sensor. I believe it is a vacuum switch. Note: In 1996 the fuel filter restriction sensor was moved to the fuel pressure regulator, driver’s side of filter housing. Happy now?)

To continue: Two bolts holding down the filter canister are 13mm. You can lift the whole filter assembly up and forward out of the way with the long blue hose still connected at the bottom.

Getting the pump out is not difficult, using a 1 1/4 inch box end wrench, heated and bent to clear the turbo pedestal, while removing the large banjo bolt. You just have to be patient and content with getting only small incremental turns on it. It takes a while. The two metal ring-gaskets will sometimes remain stuck to the banjo fitting. You can remove them once the pump is out of the way. You do not have to remove or loosen the fuel supply tubes connected to the banjo fitting.

Remove the two 10 mm bolts holding down the pump and carefully remove the pump from the crankcase bore. It will take some twisting and pulling. Be careful here so as not to lose the tappet into the cam crankcase. That would not be good. Examine your new pump to see how the tappet connects. Eventually you'll be able to lift the pump straight up and out of the engine.

Cover or stuff a rag into the pump hole and it's a good time to clean the entire valley. Kind of like being on a treasure hunt, you'll be amazed at what you find down there; valve caps, wire ends, wedding rings, cat hair, baseball gloves, wrenches... It's a lot of fun getting back all your tools.

Check out the exterior of the fuel filter canister. Clean the three wire terminals, check for leaks or cracks and clean everything so if a leak shows up later you'll know exactly where it originates.

Time to put things back together. Remove the two metal banjo gaskets if you haven't already. You might need a knife blade to get them loose. Be sure the interior of the banjo fitting is clean and free of debris.

Hoses: I got 3/8 inch 400 psi fuel hose from NAPA by the foot (by the inch, actually) and simply cut new hoses to match the old ones, three altogether on the pump and a 5/16 inch hose on the regulator. I installed them at this point, along with the clamps. I recommend tightening the clamps just enough so they are "pre-positioned." When the time comes to give them a final set it makes it easier not to have to chase them around with two hands. (One exception: the hose clamp on the bottom of the filter assembly must be tightened completely. You just can’t get to it once everything else is in place.)

If nothing fell into the hole or onto the cam then lower the new pump. I use a little anti-seize on the housing, thinking it might make removal next time a little easier. Grease should already be on the O ring, but if not, I'd grease it. Tighten the bolts carefully and evenly to secure the pump. Make sure the pump does not get in a bind. Just tighten evenly and it should go into the bore ok, regardless of how the cam eccentric is positioned.

The hardest part of the whole operation, for me at least, was getting the banjo bolt restarted. You will quickly come to understand why the shop manual calls for removal of the turbo pedestal for this operation. (Plus, more shop time equals more money. duh!) You will wish you had a Dremel tool and could cut away some of the "webbing" between the legs of the pedestal. It’s a bit of a struggle, figuring out how to position your hands and fingers for the most efficient way to start that large bolt.

Slide one new metal gasket onto the bolt, insert it into the banjo housing and have the second gasket ready to slide into the slot on the interior side of the fitting as you push the bolt in. It may take a couple of attempts to get that second gasket onto the bolt. Just be sure it doesn’t slide on through the fitting and disappear on top of the manifold. Now you just have to carefully turn the bolt with some pressure behind it to "catch" the threads. Once it's started, then it is just a matter of wrenching it in, one tooth at a time. Here's where patience comes in again. Eventually you'll get it in. Then snug it down, recheck the pump hold down bolts for tightness and you're through the worst of it. Time for a congratulatory coffee break. Sometimes even an adult beverage is deservedly appropriate here…

Adjust all the hoses and be sure the clamps are on and positioned for easy access. (Once again, the lower hose will have to be clamped securely to the filter canister at this point since you won’t be able to reach it once the assembly is bolted down.) Lower the filter assembly back onto its pedestal, connecting the lower hose to the fuel pump as you go. Check that the wiring looms and connectors on both sides are positioned correctly. Adjust all three short hoses correctly and tighten the clamps. Remember to "aim" the clamps for easy access later, just in case there is a leak and you need to get to them with a screwdriver or ¼ inch socket. Don’t forget to reconnect the drain hose also. And CLOSE THE YELLOW WATER DRAIN LEVER.

Install the two 13mm bolts securing the filter housing (I use just a touch of anti-seize) and tighten. Plug in the three wire connectors to the canister and join the loom connectors on the passenger side. Reinstall the 8mm hold-down bracket. (or probably like most of us do, just wire-tie the connector to the GP loom).

Re-attach the FPR, being careful to install the O-ring. Tighten the two 10mm bolts evenly so the O-ring sets properly.

Reconnect HPX hose, the "Y" pipe (don’t forget the O-ring) and whatever else you might have removed or disconnected. It is a good time to also re-dry the manifold. Looking for leaks will be a lot easier if everything underneath starts out dry. A long screwdriver and some paper towels work great. Just be sure to get them all back out before you finish.

Check everything twice. Pry back up whatever wires and brackets and connectors and hoses you mashed by laying on them. If it all looks good, reconnect the batteries and you are ready to start.

I leave the heat shield covering the two tops hoses off at this point, just so I can look for leaks once things are up and running. Don’t forget to eventually snap it back on, cause there is a lot of heat back there and the hoses will definitely last longer.



A couple of notes here: If you shimmed the FPR, I would remove the shim at this point and start over with a stock set-up. Once you are up and running again, you can work the pressure back up towards the 70’s, using whatever shims work best.

A NOTE OF CAUTION: The FPR housing is very fragile. It is extremely easy to crack the housing by over tightening the Schrader valve or any fittings you might insert to accommodate a PSI gauge. BE VERY LIGHT ON THE TOUCH WHEN TIGHTENING ANYTHING INTO THE SCHRADER VALVE OPENING.

If everything is working ok, it should fire up within a few cranks. Thereafter, it takes a while to purge the air, usually a couple dozen miles of driving before things begin to settle back in to near normal.

WARNING: You will want to take a good light and look for leaks after the engine is running. BE CAREFUL. The fan and belt can change your nickname to Three-Fingered Jack in a heartbeat.

With any luck at all, you are dry as a bone and ready to roll. Check it again after your test-run.

Good luck,"