Hey guys, got some interesting symptoms was hoping I could get some input on.

1984' Coachmen RV on Ford e350 chassis. Rear fuel pump was bad so I replaced it.

This weekend I did a test run (this coming weekend five day family trip 150 miles away). If I'm going on level surface, or moderate hills, at low speed no problem running on the back tank. But if I'm pulling hard, like on a hill with a good grade to it, or just over 50mph it starts to stumble real bad, definite lack of fuel. I can switch to the front tank and it immediately goes away. If I get up to say 60-65 and set cruise control, I can switch back to rear tank and no problem, it'll run. it just seems to be when it is under extra strain.

What could it be? My fear is a bad fuel pump (I know I have the receipt but can't find it right now) because that is the most involved fix. Are there any other things? I thought maybe a bad hose too? collapsing?

I have another question while we're at this, instead of f&#*ing with a fuel pump again, can't I install external pumps on the frame? then if they ever die again I'm not dropping the tanks?

Thanks very much.

Red

 

Did you replace your fuel filter?

 

yes indeed

 

What brand of pump did you buy? I think Airtex is OEM---they're available from Advanced Auto Parts if you have one nearby?

Along with the filter (which you've already changed) could there be another restriction or partial plugging of the fuel lines?

 

No, you can't install external fuel pumps because the gas in the tank cools the pump. That's how the pump gets fried if you run the tank dry too many times, like I did in my F-series. What you could do is cut an access hole in the floor and put plywood over it, like in a passenger car.

I would do a fuel pressure/volume test first, because it's easy and will usually pinpoint the problem so you don't have to try everything. It takes 15 minutes to do:

Disconnect the TANK side of the fuel filter and let the tube hang into a bottle where you can see it.

Jump the "Fuel Pump Test" pins on the engine computer (google for pictures)

Turn the key on

Watch to see how fast the bottle fills up. A 20 oz soda bottle should fill up in less than 10 seconds.

Then reconnect the line, turn the fuel pump on, then turn the key off and check for residual pressure in the line by pushing in the Scrader valve on the fuel rail.

My guess is that you won't see very much flow from the rear pump. If this is the case and you have 12 volts going to the pump (check as close to pump as possible), you have either a kink in the fuel line or you forgot a wire nut. If you reinstalled the tank with gas in it, since that's hard to do gracefully, my guess is a kinked line. Loosen the tank strap bolts and follow the line with your hand to be sure. Otherwise you'll have to drop the tank again and check the connections, and if they're good bench test the pump. Again, my guess is there's an 80% chance it's a kinked line.

EDIT: I just realized your van is an '84, so you don't have a true engine computer. Use 12v direct from a battery to test the fuel pump. Also, disconnect the fuel line before both the high-pressure pump and reservoir (I forget which is first), NOT at the filter. Flow output should be about the same.

 

732 I gotta disagree with you on a few things..............

You can indeed install an external fuel pump anywhere IF its intended for use externally!! Yes later model vehicles with the higher pressure fuel systems tend to have tank-mounted pumps but that alone wouldn't prevent the external pump.

Cutting a hole in the floor just to avoid dropping the tank is highly ill advised because it invites rust to start growing. Assuming the body is still sound why create a problem for maybe a once in a lifetime part replacement.

I'd also add testing a fuel pump's capacity by filling a 20oz soda bottle is a bit on the crazy side------what prevents a possible mishap and fire during this test? There has to be a better way to accomplish this!!

 

He does not have a high pressure pump on the frame.
Either the electrical fuel selector valve is not opening all the way to the rear tank or the in-tank pump is not putting out what it should.
Maybe low voltage to the rear pump (bad selector switch or wiring and plugs) or the pump is just not very good.

Here is a diagram of his system:


/

 

Hey guys,

Although I didn't test flow rate, I did accidently check flow when I installed this. I just remembered last night when discussing it with my uncle after inspecting the hoses. (they all looked good to me and I found no kinks, breaks or cracks)

When I first put it back in I forgot to hook the rubber hose from the tank to the steel lines on the frame, turned it on and it pumped gas all over the ground, it was a good stream and a lot. now I know that is not an indicator, I'm just saying it at least pumped some.

I'm gonna try and do the rest of the testing tonight. what a PITA.

Bill, in this picture (I'll use yours since it is a bit better than mine, this is exact selector I have) which are the fuel and which are return?


THanks guys!

Red

 

There are two different size of fuel lines.
The supply lines are the larger lines and the smaller ones are the return lines.
The lines on the right go to the engine and the four on the left go to the tanks.

 

When did they stop the dual pump setup? It was my understanding that a single pump wasn't used until 1990.

 

I think you mean started. His is a 1984 460 and they all had one pump in a tank and no frame pump with a Carb. They did not start the frame pump until 1988 on a 460 PU with FI & E-series and ended it in 1991 on the E-series.
You are right if talking about a F-series PU with a 4.9, 5.0 and 5.8L engine.
1989 was the last year for all of the F-series with the pump on the frame.

 

I'm glad I found this thread I actually just installed a fuel pump today in my front tank and am having the same problem as the OP. The only difference is mine starts up and immediately begins to sputter out and die.

I was thinking that I may have kinked a fuel line. By the way I am a total newbie when it comes to fixing vehicles.

 

Hey guys, long time posting what I found out with this. I did every sort of testing possible without removing the tank again. i figured it had to be something with the pump, but didn't get to it until a couple months ago.

turned out it was pump related, but not how you think, but this is a buyer beware. The strainer that came on the pump from autozone had disintegrated and fallen off and there was a large piece in there. I found another one actually I must have missed when I first replaced it from an older pump, more of a thick canvas looking material. between the two pieces of debris in there they'd get sucked up against the intake and I wouldn't get any fuel.

I got everything out of the tank and ran a full tank through it going up into the mountains camping a couple weeks ago, no hickup.

I did by the way get another strainer, this one from napa and completely different material, this one is like a nylon mesh, green, the other was white and felt like paper.

Red

 

Thanks for the follow up----always nice when we get a resolution or possible cure for something like this.

For me I never go the cheap route on any part, always want the best for the job. Of course once I know what brand or type is the best quality I'll search for the best price online or locally. It might cost a few dollars more up front but when the low cost part causes more problems that savings proves to be not such a great deal.