Ford Truck

1990 Ford Truck Fuel System   

Ihave a 199o Ford F-800 tanker truck, 35k G.V.W. with a diesel engine. The engine died and would not start so I figured it might not be getting fuel. I changed the 2 fuel filters next to the engine on the passenger side and removed the water seperator filter, which is the filter closest to the fuel tank. With the water seperator off I decided to see if the in tank electric fuel pump is working. I had a friend turn the key to starthe truck and observed no fuel coming out where the water seperator had been. The water seperator is a hose length from the fuel tank. I then removed the electrical contact from the top of the in tank electric fuel and had my friend turn the key to start again while I touched my volt meter to the contacts which had been plugged into the electric fuel pump. I got a burst of power for a second and then as the engine was turned with the key in the start position I had a zero reading on the meter. When the key was then placed into the on position without engaging the starter I got a 10.5 volt reading. My question is, are these voltage readings normal? Should the voltage remain constant while the starter is being engaged or are the readings normal and the electric pump is defective? One more thing: the truck as 3 12volt batteries in parallel.

The readings are a bit low, should be closer to 13.5 volts.If it were mine, I would apply a good source of voltage (jumper cables from car ok) directly to the starter to see if pump is working.If it is, try adding a fuel press. guage back there .As the pump is only a transfer pump. it still should be 10 psi.
The voltage fluctuation you see sometimes when the system is first started if there is already press at the injector pump.I relaced the transfer pump a few times on the diesel Ford towtruck I owned.If the voltage drops when cranking you might have a battery and or an alternator problem.

1990 Ford Truck Fuel System   

I have a 1990 Ford F-800 with a straight 6 diesel engine. The engine won't start and I suspect the fuel pump is faulty. My problem is I am not sure where the fuel pump is. I have determined there is no in tank electric fuel pump. Attached to the outside of the injection pump there is an item that appears to be a fuel pump. The fuel line leaves the tank, goes through the water seperator, goes through an item that has a hose attached heading away from the fuel tank and a hose attached heading back to the fuel tank, the fuel line then enters and leaves the item mentioned above attached on the outside of the injection pump, goes through 2 fuel filters and then enters the injection pump. I am thinking that if this item attached on the side of the injection pump is the priming fuel pump, it must be powered by the injection pump in some way. This mysterious item also has a hand powered priming pump on its top. It is also shaped as if a diaphram is housed inside of it. From my description, can you tell me if this item is the fuel pump? And if not, what is this item and where is the real fuel pump that acts to prime the injection pump?

Hello,

See your other question.

1990 Ford Truck Fuel System   

I sent this question last night,paid, and have gotten no reply. I do not like paying twice. I have a 1990 Ford F-800 with a straight 6 diesel engine. My question is, and was last night, where is the priming fuel pump that feeds the injection pump? I see no sign of an in-tank electric fuel pump. I do see an item that looks like a fuel pump attached to the side of the injection pump. It is labeled 908 and is made by Bosch. The fuel line enters and leaves this Bosch item, goes through 2 fuel filters, and then enters the injection pump. This Bosch item also has a hand pushed primer on top of it. The water seperator is situated between this Bosch device and the fuel tank. I am thinking this Bosch item is mechanically powered by the injection pump. Is this Bosch #908 device a fuel pump, and if not, where is the fuel pump for priming the injection pump? The reason for this question is the vehicle's engine died and will not start.

I see two questions. Contact the site administrator for a refund on the other question. You only have to pay once.

I am not familiar with the F-800, does this have a 7.3 or 7.8L diesel?

The item you described sounds like the lift pump, they can usually be hand primed and tend to be mechanically driven. How much resistance do you feel when you push the primer? If you only feel a little resistance at the end of travel, this indicates the pump is severely worn. If you feel resistance quickly, and feel the plunger effect, over a large percentage of travel the pump the pump is probably okay. Crack the fuel line or nearby bleed port and actuate the primer. Any fuel flow?

Have you taken a fuel sample or tried starting the engine with a starting aid (carburetor cleaner in hot weather OR a small amount of starting fluid in cold). Just enough to see if it'll fire with the aid of fuel.