'84 E350 460 Fuel problem
 

I have a 1984 E350 motorhome with a 460 and it won't run long enough to move. I can start it, but it will run out of fuel and die before I can move a few feet.
I have checked the fuel delivery at the carb. After cranking a while, a small stream of fuel comes out, very little pressure (I haven't put a gauge on it).
I am very confused about the fuel system on this. I see a mechanical fuel pump listed for this model engine, but there are supposed to be electric fuel pumps in each tank. With the key on, no fuel comes out at the carb with the selector set to either tank. Have the tank pumps packed it in? Does anyone have a part # or source for these tank pumps?

It does not sound like you know what fuel system you have. There are three fuel systems you can have.

One fuel system has one mechanical fuel pump on the engine and a selector solenoid on the frame with no electric fuel pumps in the tanks.

Another system has no mechanical fuel pump and has electric fuel pumps in each tank. This system has a motorized fuel selector on the frame with relays and an oil pressure shut off switch with starter solenoid bypass.

The third is like the second except it has a hot fuel return system on it also.

If I were to guess it sounds like you have a bad oil pressure switch or relays with the electric fuel pumps system.

check the fuel filters.

I think there is a fuel pump in each tank. At the front of the engine near the lower radiator hose there is a blank plate over what looks like where a fuel pump would be. There is a large unit on the frame with hoses coming in from both tanks.
The fuel filter is relatively new.
There seems to be just no pressure coming from the pump. Can a mechanical pump be added to boost pressure? I would need to find replacements for the tank pumps otherwise.
The tank change relay seems to work OK and clicks when the switch is flipped.

As I said above your problem is more than likely a bad oil pressure switch or its fuse may be bad.
It could also be the other relay.
Do you need an electrical diagram of this system?
If it is not the oil switch then it may be the motorized selector valve on the frame.
Does the fuel gauge change tanks when you change the switch on the dash?
You say the engine starts so the in tank fuel pumps must be good.

You can add a mechanical pump if there is an eccentric cam on the cam gear for the mechanical pump but I do not think it would boost the pressure any.
You can change to a different size hot fuel bypass and that may raise the pressure some.

If you put on a mechanical pump you would still want operating pumps in the tanks for the hills in mountainous terrain.

I thought that the electric tank pumps would operate whenever the key was on. I turn the key on and get nothing. Crank the engine for awhile and some gas starts to come out, but the pressure is low (I can stop it with a finger over the hose easily - I think the pressure is supposed to be 6 psi or more). Are you saying that the pumps don't operate until there is oil pressure?
It seems I'm getting gas after cranking long enough to get oil pressure. This would point to deteriorated pumps that put out little pressure or volume. Would these pumps be available from a parts house like NAPA?

No they do not run when you just turn on the key.

That is normal

Unless you know the pumps are running how do you know how much pressure you have?
You would have to put power (jumper power to) on the wire (PK/BK) coming from the starter relay (solenoid) to test the pressure.

No, they will operate when the engine is cranking or if the key is on AND you have oil pressure.

Yes they should be available from a parts house like NAPA.
But it is unlikely that both fuel pumps are bad.

There is a bypass circuit that bypass the oil switch while cranking that is operated by the starter solenoid.

I think these fuel pumps are the same as the fuel pumps used in the 1986-1989 in-tank pumps on the FI trucks and vans. I took a fuel tank from a 1997 FI van and put the tank, pump and all in my 1992 E350 with a 4V Carb. and have been running it that way for 10 years with no problems.
I think they put out between 6-8 PSI as that is what the 4V Carb wants.

Here is a electrical diagram of the fuel system:
http://i54.photobucket.com/albums/g9...83FuelElCT.jpg

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Thanks for the diagram and info - since I am getting some fuel while cranking on the rear tank at least that pump must be running - although not putting out hardly any pressure. I can't tell just yet about the front tank as I think it is empty.

Here is a diagram of your fuel system:
http://i54.photobucket.com/albums/g9...rSeparator.jpg

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my Dad had thie happen to his unit svrl yrs ago and it turned out to be a colasped fuel line from the tank to the carb.. new feul line and prob was gone ...

I put fuel in the front tank and tried it again. If I take the line off the carb and crank, I get a good stream of fuel (like the rear tank did). I can connect the line to the carb, crank and start it (runs maybe 10 seconds and quits). So after it started once I pulled the line off the carb - no fuel flowing at all. So it would seem the oil pressure switch may be bad. Is this on the back of the engine above the bell housing? (Could be a fuse too, which I will look at).

Yes the oil pressure switch is on the back of the engine above the bell housing.

On my '82 E-350, the fuel filter is on the left frame rail about halfway between the front and rear axles. This diagram shows it on the carb itself. Just FYI. My carb is a Carter, and I'm not sure if its OEM.

try your inertia switch. I have an 83 with a 460 ,same system and it did the same thing. I bypassed the switch ,and it ran fine. Mush

Where is the inertia switch? I thought mine was an oil pressure safety scheme (no oil pressure, no fuel pump). I will probably have to bypass the switch in any case as I stopped at a dealer and they didn't have any in stock.