An easier way to change a fuel pump???? Or not?

[TexasTuff]

I have a 1985 Ford E350 with a 460. At times it starts missing and backfiring and goes into a low power mode. It seems this is a common problem with older 460's. Searching the web has turned up several reasons that could be causing the problem. I'm going to tackle these problems one at a time until the fix is found. Number one reason for the problem is starving for fuel. I've already changed the fuel filters. Next, I'm told is Ford has made several different fuel pumps trying to fix the problem and that auto supply pumps are inadequate for the supply needed and you should install a new OEM pump. This I plan to do. The problem now is dropping the tank which is full of fuel. I hate to drain/lose 40 gallons of fuel. What do you think about cutting an access hole in the floor and changing the pump that way? I am replacing the floor anyway. I would then have a permanent entry way to the fuel pump in the future.
I'm not as young as I used to be and I like finding easier ways of doing things.

 

[user 423]

How would you know where to cut the hole? You could easily cut into the tank. Search Ford forums; maybe someone who has done that before made a template for pump location. A slim but possible chance...

BTW: Have you checked the fuel pressure?

 

[TexasTuff]

How would you know where to cut the hole?  You could easily cut into the tank. Search Ford forums; maybe someone who has done that before made a template for pump location. A slim but possible chance...

BTW: Have you checked the fuel pressure?

I know where the pump is located. I can measure to that point. I can drill a hole and set my jig saw to a depth that just cuts through the floor. I've been searching Ford forums for several days for causes of this intermittent problem and the fuel pump gets mentioned most often. Fuel pressure is normal until the problem starts and I haven't had a gauge connected while driving.

 

[closeanuf]

A friend of mine who works at a parts store told me he know of people who have cut holes in the floor.  Shouldn't be too hard if you take your time.  It's not like you're ruining the resale value, might even be an enhancement if you ever do sell it.

 

[highdesertranger]

if it was mine I would cut the hole. however it is was mine I would find the problem before I just started willy nilly replacing parts. that could get expensive, plus a lot of times you are replacing parts of lessor quality. highdesertranger

 

[karl]

That is what I did the last time I had to change out a fuel gauge sending unit/pickup.
some metal strap screwed around the underside of the hole using drill point screws and butyl tape, more tape and screws in the insert and it's sealed and ready for the next time.

 

[TexasTuff]

if it was mine I would cut the hole.  however it is was mine I would find the problem before I just started willy nilly replacing parts.  that could get expensive,  plus a lot of times you are replacing parts of lessor quality.  highdesertranger

To save space I didn't document some of the things a mechanic has already done. A new carburetor has been installed. No help. The mechanic thought there was a vacuum leak at the intake manifold. It was removed and found that it was warped. I found a used intake and it was installed and was no help. At this point, and after having the RV for a very long time he told me to take it. he didn't want to work on anything this old and didn't have any more ideas of what was wrong. 
Some things I will replace, like the carburetor and fuel pump are for later peace of mind. I've ordered a high output, low pressure, fuel pump after finding that fuel pumps have been a long standing problem with older RV's with Ford 460's. Again for future peace of mind. 
I'll also replace the oil and temperature sending units. Both of which can affect performance. There are also a couple of relays that I'll replace as well. All of this information I have gathered from studying several Ford related forums. 
Many of these items are low-cost items and the fuel pump I have chosen is a performance upgrade to the 460.
One other thing I'll try is disconnecting the exhaust to see if there is a restriction in the exhaust system.

 

[highdesertranger]

if you have a carburetor you don't have a fuel pump in the tank. also if you have a carb the sending units will not effect performance because you don't have a computer. what year RV is this? highdesertranger

 

[user 423]

^
Actually it looks like that even though carbed, these have dual tanks with low pressure electric pumps. I would still make sure you have it tuned up well before replacing the pump(s). When you say "new" carb, do you mean a NOS item or a rebuilt? Some of the rebuilts aren't very good at all. Also, is the mechanic who installed the carb (and supposedly adjusted it correctly) the same one who doesn't want to work on an '85?

You might look into getting a vacuum gauge to diagnose exhaust back pressure:

http://www.aa1car.com/library/exhaust_backpressure.htm

 

[jonsun]

yeah they do have feed pumps to the mechanical pumps. Someone on here was talking about this months ago and I had to look it up. supposedly it's due to the long line run...or that was fords reasoning. what I would do before cutting a hole is find the fuel psi specs and rent a gauge. should be able to disconnect at the mechanical and at least see some squirting action.

 

[karl]

if you have a carburetor you don't have a fuel pump in the tank. also if you have a carb the sending units will not effect performance because you don't have a computer. what year RV is this? highdesertranger

I had an 83 460 carbed with dual tanks and in tank pumps......

 

[highdesertranger]

well you learn something new everyday. highdesertranger

 

[TexasTuff]

Update: The MH was manufactured in Feb 1985 but the chassis was manufactured in Oct 1984. After tracing the fuel lines by myself and my son, the fuel pump is indeed in the gas tank. There is no mechanical pump.
I installed another electric pump just outside the gas tank with it spliced into the same wires that run to the internal pump. No change in performance. My next move in the morning will be to run a fused wire with an inline switch from the battery to the fuel pumps which will bypass all the safety wiring to check if this is an electrical problem. Easy and quick check before replacing the fuel pump in the tank.
I know, there are a lot of things it could be, it just seems like the fuel is really leaning out.
slow2day, It is a NEW carb, not rebuilt.

 

[highdesertranger]

adding another pump like you did might help or might not. most electric pumps do not have a bypass so when you try to pump fuel though them there is a big restriction. get a fuel pressure gauge and check before you spend anymore money. hint, when checking the fuel pressure bypass the added pump. highdesertranger

 

[jonyjoe303]

About 2 years ago I had to replace my fuel pump on my astrovan and I promise myself if I ever had to do it again I will cut a hole on the floor. 
Draining the fuel is a several hour long job by itself, your going to get fuel everywhere. I had a friend helping me otherwise I would have never got it done it by myself. The actual change out of the pump is maybe a 10 minute job, but the removing/installing the tank took me all night long. 
There are videos on youtube of people who have cut holes in there vans to replace the pump, so its not an isolated idea.
Myself if I did it, I would get some sort of inspection mirror to see where I would be cutting, it has to be precise to not cut the wires or the straps holding the fuel tank. But no matter what I would be cutting.

 

[jonsun]

this might help

https://www.ford-trucks.com/forums/1063208-460-out-of-a-84-motorhome-no-mechanical-fuel-pump.html

 

[Weight]

There could be a filter with the pump in the fuel tank. If blocked, no amount of added external pumps will help. Have you tried removing a line and seeing how much fuel the pump pushes?

 

[mr_elijah_gardner]

If its a dual tank I've had problems with the diaphragm that exchanges the tanks. You could try bypassing it and running just one tank. Also What year is it? it could be an inline pump. 

If it is running a mechanical pump and you add an inline electric pump be sure to bypass the mechanical pump.

I have cut holes in floors before but it's really not hard to drop a tank unless it's really rusty or nasty. Put a floor jack underneath and unbolt the straps.

I learned the hard way after welding a panel back in place that I cut out be careful of slag. I ended up melting my fuel line in the resulting fire and had to drop the tank anyway. Since then i've put welding blankets over the tank before I started welding.

 

[UptownSport]

get a fuel pressure gauge and check before you spend anymore money

QFT

 

[AquaticsLive]

Hope you figured it out. I have cut outs made for both of my tanks it was done by fleet service people before me. Anyhow pretty handy to check on things saved me from wasting money on new fuel pumps. Essentially if you can access them and test; don't have the urge to replace them without a reason other than I have the tank out already. I had issues with my fuel system when I first got it and ended up being the tank selector valve little plastic plungers inside where worn and not moving all the way so partially blocked off fuel all the time. I drilled out the rivets and repaired it which was a pain but they are expensive.