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Rifleman
Premium
join:2004-02-09
p1a

1985 Ford E350 Dual Fuel Tank Problem

HI. I got the RV out for a test run this weekend and discovered a problem. I bought it and only filled one tank---which is the rear one, and ran off of that until this weekend.
I stopped to fill up and asked to fill the front as well as the rear. It turned out the front tank is already full. If I select the front tank using the dash switch the gas guage drops to dead empty and the engine dies as soon as the fuel in the carb is used up.
From what I can find online there is a separate electric fuel pump in each tank. Then there is a 6 port relay thing somewhere on the frame.
I need some ideas on what to check first? I was leaning toward the fuel pump being the problem but can't understand why the gas guage doesn't read full instead of empty?
Anyone come across this problem or have any ideas?
Here's a link I could find but a diagram would be great. »www.ehow.com/list_7695936_1985-f···ecs.html


BK3

join:2001-04-10
Geneva, IL
Reviews:
·AT&T Yahoo
Always start with the easy stuff first. Check all the fuses, make sure all are good.
I don't know about that particular vehicle, but there may be a separate fuse for each pump / tank. Also, there may be more than one fuse block. Be sure to check them all. If you have the owner's manual, that would be a good place to look for fuse locations and assignments.


Quikee

@rr.com
reply to Rifleman
Just a quick better than nothing answer. I had a 1987 and you could hear the relay "thunk" when you flipped the switch. If it doesn't switch then you won't get a reading.


mattmag
Premium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3
reply to Rifleman


Fairly common failure of the fuel tank switching valve. However as noted, you need to test it, and examine the wiring at and to the valve. It should be mounted on the frame rail near the forward tank. Rusty connections and especially the ground connections to the frame are a good culprit.


Rifleman
Premium
join:2004-02-09
p1a
reply to Rifleman
I'm into a real mess with this now. I removed the dash switch and tested for continuity, One tab showed nothing with the switch in either position, so assumed the switch was the problem.
Turns out that switch is no longer made and a search of junkyards and such was fruitless. I did find one on Ebay but has a different model number and the seller is gone until October 6th.
So I tried repairing the switch I had but it's toast. I then had the bright idea that it's only 4 wires----2 that tested hot and 2 what I assumed are the feed to the valves. So I bought a generic on--off--on switch and wired her up. That promptly blew the fuse--permanently. It was badly corroded in the fuse block and is no longer usable. There is no spare spots.
I found the 6 port valve and it has 4 wires only running to it---so can't understand why the fuse went----unless the valve itself is screwed.
I can't see the valve as the culprit of the original problem as the gas guage is wired separately from the valve--so am assuming the front tank pump and sending unit is the problem as the guage dropped to empty when I switched to the front tank.
There has been rewiring and splices done throughout the wiring so suspect there has been problems before.

I have 2 options as I see it. I am planning to tap into a switched power wire at the fuse block, fuse it and run a new power wire and tap into the power wire for the rear fuel pump. I'll switch it using the switch I bought. That should get me running at least on the rear tank but unsure if the gas guage will function. If not I'll watch the odometer.
I can do the same for the front pump---but may need to drop the tank and install a new pump if it was indeed shot.
I'll then need to power and switch the valve system to change tanks.

OR---I could rip the valve out-----splice the hoses if I can sort them out correctly, and wire 2 inline electric fuel pumps and go without the gas guage.
Trying to track down the wiring through the relays, oil switch etc is next to impossible due to rewiring, splices and finding the damn things.

I am leaning towards the inline fuel pump option and getting rid of the valve system. It's an old RV with new motor and tranny but not worth sinking possibly a grand just to fix this one problem as I'm sure others will pop up as I get mobile. If I get a year out of it I'll be happy.

Any ideas or advice on what my best option is? I'm gonna try powering up the rear pump like I described temporarily tomorrow just to see if it will function.


Rifleman
Premium
join:2004-02-09
p1a
Some pics----it's in good shape----but 25 year old wiring and systems will be maintenance intensive.
»/speak/slidesh···hlci1SVg


mattmag
Premium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3
reply to Rifleman


You'd better get yourself a wiring diagram before you burn something else up for good. The scheme you suggested isn't always the case, as it may be switching a single circuit in a normally-open/normally-closed fashion. And fuel level sender switching is often just switching grounds. You can't just assume on this stuff.


Rifleman
Premium
join:2004-02-09
p1a
I have a diagram--but it's from an 86 truck with dual tank system. It's the only one I could find online. The haynes manual I bought is useless and doesn't get into the dual tank system.
Like you said----the switch requires the identical unit because it controlled the fuel guage as well as the valve unit. It also tied into a start relay and oil pressure relay. Going by the diagram I assumed the switch wires were 2 hot and 2 load wires to the valve unit and wired it that way. But that isn't the case, as well the wiring has been played with before at some point, so I am uncertain of what the setup is at this point.
I am going with new wire properly fused---I'll solder a new extended fuse holder to the bus on the back of the fuse block, run 2 inline fuel pumps from the on-off-on switch and remove the valve altogether. I have read in a few forums of folks having similar problems using this method and seems to work.
At least this way I know it's wired safely and hopefully have both tanks working.
I'm doing the wiring today and will plumb it tomorrow if I can find 2 pumps for a decent price. I'll update on how it went.

rody_44
Premium
join:2004-02-20
Quakertown, PA
Reviews:
·Comcast
reply to Rifleman
Is the valve your talking about mounted on the frame inside the rail. If it is and the truck has fuel injection, thats actually a valve and pump. Each tank has a pump and it also has that pump. In other words its a three pump system. If when switching to the front tank it still runs and just reads empty that means the front tank pump is working as the truck wont run at all on the front pump if the front tank pump is bad. Really depends tho on what motor it has in it as some had fuel injection that year and some didnt. If its carburated rig away. If its fuel injection i strongly suggest any rigging at all as your going to have to deal with fuel return issues also with fuel injection. I think the 302s, and 351ms had injection that year. Im thinking the 460s didnt.


Rifleman
Premium
join:2004-02-09
p1a
reply to Rifleman
Well-----I ended up wiring a new in line pump for the front fuel tank. It runs fine but no guage.
I had plans to do the rear as well but the problem is there is one feed line and one return from the carb. The dual tanks leave me with 2 extra. so the valve switch is necessary.
I found a NOS switch on ebay and ordered it. I'll also buy a new 6 port valve switch. When I hit warm weather in the US I'll get a garage to drop the tanks and install new pumps and reinstall the original setup and hopefully be done with that.
Thanks for the replies.

rody_44
Premium
join:2004-02-20
Quakertown, PA
It returns to the front tank so you should be good for now. thats as long as you dont need the rear tank.

rfnut
Premium
join:2002-04-27
Fisher, IL
kudos:2
reply to Rifleman
If/when you get it switched, you may want to be leary of whats in that tank if you have not run off of it before.


jake

@cox.net
I am currently going through a similar problem. I just bought a 1985 e-350 van with the 460 engine and dual tanks. My front tank has some issue where it does not ventilate and becomes highly pressurized, which I believe in turn destroyed the fuel pump. I added a new in line pump and it worked for a few miles before also dieing. It will also throw gas everywhere every time I open the gas cap. So, I tried to run the rear tank and I get nothing.

So, for now I took the in/out leading to that six port selector and bypassed it with an inline fuel pump that leads directly to the rear tank. Its working for now, but I noticed someone mentioned the return leads to the front tank. Is this true? Ive tried following it but it doesnt seem to. Thanks, Jake

rody_44
Premium
join:2004-02-20
Quakertown, PA
Reviews:
·Comcast

4 edits
I thought the 460 in that year didnt have fuel injection. If its not fuel injection you shouldnt need to worry about the return. If it is than there will be a secondary pump mounted on the inside frame rail under the drivers door. Fuel injected models return there. From there it only returns to the front tank. Im pretty sure only the 351m had fuel injection in that year. Its possible you have a oddball tho. You have to remember you are asking a lot from one electric pump to push and pull the gas that far to the engine. Highly pressurised gas tank sounds to me like your driving a bomb around. Just for shits and grins ide swap the gas caps around. Your problem sounds strange tho. Maybe look around for a plugged line dealing with emissions.

I remember a 87 we had that the front pump went bad and we only ran off the rear tank. Every couple of weeks it would start leaking gas out from the top of the front tank. We just siphoned the gas out of the front tank and used it like that for about 6 months. Since it use to leak from the top there must be some sort of vent up there. Eventually we replaced the front tank pump and the pump on the frame rail. That solved our problem. The pump on the frame rail is more than just a pump tho and is expensive as hell. Keep in mind im going off memories that are at least 20 years old.

Even if it not fuel injection and has a mechanical pump there has to be some valve that tells it what tank to run off of. Ide find and bypass that as test. Probably inside frame on drivers side. I think we payed 350 or so for a rebuilt one 20 years ago. I can only imagine what it costs now


Jake

@cox.net
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Thanks I appreciate it. The 460 I have is carburated, which is why I found it strange that there would be two fuel lines running from the rear tank. There were also two lines running into the valve switch, so I just took the lines from the valve switch and ran them directly to the lines in the rear tank. Seems to be working so far. I just capped off the lines for the front tank until I can get someone to help me drop it and figure out what thats about. Someone put spray foam all around the filler neck and Im thinking it may have clogged a release valve or something in the front tank.

Im trying my best to fix this thing on the cheap. I only paid 500 bucks for it, and the plan was to use it as a mobile storage unit/ occasional camper. I added some photos of my (unhandy) work. Anyone know why this thing would have two fuel lines running into the rear tank? It is not fuel injected.

Also, the inline pump I added is 6-8 psi. Im wondering if I should add a stronger fuel pump as it is working hard.

Thanks again


Rifleman
Premium
join:2004-02-09
p1a
I think there is a return line for each tank-----and if you accidentally hook the rear return line to the front tank or vice versa, your rear tank that you hooked up to the in line pump will slowly fill the front tank through the return line.
My Valve system looked different from yours and had 6 ports for 6 hoses. There was a front and rear feed hose--which are larger diameter than the front and rear return hoses.
So--I had 2 feed ports and one to the carb, 2 return ports and 1 from the carb.
Strangely you mentioned spray foam over the tanks. Mine is the same.
I have since discovered that even with the switch disconnected that the rear and front in tank pumps are energised when the engine is running. I think they are fed from an oil pressure relay and fused with a fusible link. I just ended up looping the lines from the rear tank for now.
I'm running a 6-8 PSI inline as well and it seems to run fine so far.
I plan on getting the system repaired when I hit warm weather the end of november--ifI make it that far. I'll update how things went.
I think the front pump is shot in mine so will need to drop the tanks and get both done.

rody_44
Premium
join:2004-02-20
Quakertown, PA
Reviews:
·Comcast

1 edit
reply to Jake
I think the second line on the rear tank is emission related. Any return on a carburated vehicle i believe should only be fumes and doesnt really need to be worried about. I think you should be good with what you did for now. kind of sux that you have to use only the rear tank as that tank is much smaller than the front tank. Im pretty sure you would have been fine just plugging the return. Looks workable to me. Had it been fuel injected the lines would have been all plastic and a lot harder to rig.

HarryH3
Premium
join:2005-02-21
kudos:3
Reviews:
·Suddenlink
said by rody_44:

I think the second line on the rear tank is emission related. Any return on a carburated vehicle i believe should only be fumes and doesnt really need to be worried about.

Nope. The return lines were added in the 70's, as emission controls elevated underhood temps and created lots of problems with vapor lock. By keeping extra fuel in a circulation loop, it made sure that fuel wasn't sitting in the line in the engine compartment and boiling while idling in traffic.