All,
I have a 1991 Econoline E250 (Mark III conversion) with a 5.0 L V8,AOD 4 speed Transmission, with a dual tank setup. The mileage is around 75K original miles.

The vin minus the last 4 digits is;

1FDEE14N7MHB3

The vehicle has been a challenge getting back on the road as a everyday driver since the previous owner let it sit for 6 years do to health reasons.

The vehicle is very driveable now and is able to be taken on short trips, which is a considerable improvement from the day I purchased it.

Anyways here is what I have going on;

On a hard accerelation the vehicle will stumble (engine wise) during the accerelation and just after. I checked the fuel pressure and noticed that pressure was below 40lbs just before stumble and immediate after.... reflecting the stumble situation mentioned above. Otherwise the vehicle sits at around 40 lbs.

The vehicle will not quite stall, after the hard accerelation, but gets darn close. During the stumble of course no power is available. Read here "Fuel Starved" as if the hard accerelation ate up the available fuel and the fuel system is having trouble afterwards catching up.

Now I have in the last year since I got the vehicle replaced all three pumps (2 internal and 1 external) with new pumps from Rock Auto/Autozone/Oreilleys (based on availabilty). The tanks,relays, and fuel rail assemblies are all new as well. New Filters (internal to tank/external) and pressure regulator was replaced as well. The multitude of parts were changed due to the condition of the tanks and rails (pump/ascending unit) being severely rusted out and in some cases leaking. The vehicle will be my wifes main vehicle, read kid and toy hauler here, so I am not taking anything to risk here with the vehicle and its reliability.

I have been trying to diagnose if its just a pump issue or maybe the selector valve as I have been troubleshooting the vehicles performance for almost a year on a off. Unfortunately until just recently the front tank could not be filled properly with fuel as a replacement front fuel filler hose (even from dealer) could not be located.

So I am looking for the steps to pinpoint if the selector valve is bad and/or a way to pinpoint whether the issue is the internal or external pumps.

I have located a new selector valve, ford dealer, and pumps are available as well.

I appreciate all the help,
Chris

 

The pressure doesn't sound all that bad, in fact damm good, what was the lowest reading you have seen. When was the last full tuneup

 

All,
The vehicle has had a tuneup , (plugs, wireset, cap, new air filter) in the past year. The oil has been change twice even though I have only put 2000 miles on the vehicle as I figured it might be a good idea to "flush" the engine as it had been sitting for so long.

The pressure at 40 lbs is only during normal running. The pressue will drop considerably during the stumble point and immediately after. I have seen the pressure drop down to 10-15lbs during this stumble situation only to rise right back up to 40 lbs a few seconds later.

The vehicle gives me a "feeling" that there is a "bucket" and the rear internal pump in the tank is filling that bucket. Upon my hard accerelation the vehicle takes off like a "bat out of hell" just a second or two later to stumble as the front external pump sucked the contents from that "bucket" down and the rear internal pump has not been able to keep up.

I am not sure if the Selector valve is that "bucket" or if a series of tests using the front or rear pump selector switch will tell me if the rear or front pump is bad or possibly just the front pump. I have not had the front pump involved until just recently and I have not had a chance to trouble shoot yet.

Thanks for the help,
Chris

 

I would remain open to other possibilities at work, besides the bucket theory which I am not discounting. Distributor fault or wear, exhaust system problems, valve components, coil, leak etc. did you look for codes, do you have a vacuum gauge? that would give you a good internal glimpse of your engine..

 

I don't know if an e-series is different from a pickup, but in 1990 all the pickups had the single in-tank high pressure pump. Are you saying your van has the low-pressure in tank pumps and the single external high pressure pump?

Regardless, the pressure dropping to 10-15 lbs while it's running is not typical behavior for a failing fuel pump. To me, the problem sounds electrical. It seems likely that you're losing power to the fuel pumps momentarily and that's the cause of the stumble. You probably have a wire occasionally grounding out to the frame that's causing this. I would also replace the fuel pump relay and take a close look at the fusible link near the starter solenoid.

 

All,
The vehicle has two low pressure pumps in the tank (one each) and one high pressure external pump.

I was told by a few local ford guys that the manual selector valve/container before the high pressure pump in the system commonly goes bad. The characteristics vary depending on the failure inside the selector (fuel overfilling was one characteristic - not sure really how that would occur). Also some of the selector valves (some years) have replaceable internal filters which if plugged will cause a fuel starving situation.

Does anyone know any other symptoms that are common as well or a way to test the manual selector valve?

If its electrical issue, when I test, I would assume both the front and rear tank selection should act the same correct? Meaning if I do the hard accerelation, regardless of tank selection, I should expect the same result.

I say this as the the electrical diagrams I have seen, show a common ground that both of the in tank pumps share.

At this point I am not ruling anything out.

Again all thanks for the help,
Chris

 

Interesting. Good to know that the vans are different.

Let's say you have half a tank in the front and a full tank in the rear. You're running off the front tank, but the selector valve is returning fuel to the rear tank. Pretty soon you're spilling gas out the rear tank. It's a very common problem on Fords.

True... but intermittently? Seems unlikely.

Seems reasonable.

 

All,
I have no codes reported and I have done a compression test and all cylinders were within 20% of each other. I did this compression test during the tune up process.

I replaced the Ignition module during my work on the vehicle as the ignition module looked extremely corroded (white paste (old heat gel) and aluminum oxide all over). I cleaned up and replaced with a new ignition module and retimed the engine as needed as the rear bolt was not accessible unless the distributor tie down bolt was loose. The stumble existed before and after the module replacement but I hoped that may have been some of the issue.

Again thanks for the help,
Chris

 

No codes too bad...Was the installation of the 3 pumps an effort to cure this very same long term problem. I still think that it may not be the fuel, but maybe see with a flow test the ounces you get in a timed period, I'm not sure what the high pres. should produce but the low pressure pump volume is 6oz min. in 5 second, maybe you have a pinched fuel line???????..... boy..I can't wait till Duck season opens!

 

All,
The pumps were replaced due to the fuel pressure being low initially.

The van initially upon purchase would run for a few seconds and die. Both tank gauges read, If I remember correctly, as empty. This was even after adding 10 gallons of gas to the rear tank. Upon dropping the tanks the vehicle was found to have a completley full front tank and the rear around half tank. The bottom of the one tank had sludge/slurry which looked more like laquer/rust/ink then gasoline.

The fuel rail (ascending unit/pump assembly), especially the rear, was rusted through to the point that just about touching it led to leaks. It was far worse then any other fuel tank I have ever opened. I have have opened at least 20 of my own and friends vehicles. So knowing the vehicle will be used for family outings, my wife's main vehicle, and a toy hauler I just replaced everything.

When I purchase a used vehicle I always replace, belts, hoses, thermostat, plugs, wires, rotor/cap, fuel filter, and replace all fluids as this is the common failure/or reasons for vehicles. Plus I know going forward what needs to be maintained and when.

Thanks for the help,
Chris

 

Found the spec for your bucket theory...volume test on the rail pump, open the hose restrictor, 16 ounces in 20 seconds