i just lowered the rear of the tank to access the lines and connector by placing a jack at the rear of the tank and lowering it slowly and then disconnect the lines that way along with the connector for the sending unit from the front of the tank you do have to disconnect the fill hose first to enable the tank to lower to the height required to do this hope his helps
Aft-axle fuel tank access on 85
- Thread starter Sergey
- Start date
wrecked
Full Access Member
I just did the rear tank on my '88. Easier than an astro! But guys are correct it can be done without removing the box fairly easily with a floor jack and blocks. (Safety glasses a must) Remove the harness for the sender from the frame which gives more slack for removing the plug later. Once I had a couple inches gap I used a long slotted screwdriver to twist and pop the fuel line retainer clips back and the lines came off with a firm yoink. (Push line in while twisting) Lowered tank about a foot and disconnected the plug. Out in under an hour. Empty of course.
Detroit80
Full Access Member
I learned a long time ago when living in the midwest - if you're potentially dealing with rusty fasteners...just buy new ones ahead and time and cut the old ones off before making a real mess for yourself.
If you manage to strip out the carriage bolt holes - tack down a carriage bolt washer - https://www.google.com/search?q=carriage+bolt+washer to hold the head in place.
If you manage to strip out the carriage bolt holes - tack down a carriage bolt washer - https://www.google.com/search?q=carriage+bolt+washer to hold the head in place.
Sergey
Registered User
You all are wonderfully skilled and so handy.
I could not have that gap described above on my 1985, since frame cross member blocks access to both fuel line connectors. So I was lowering rear tank with fuel lines connected, severed blue line, repaired it, but apparently damaged something else, hence the frustration and fuel leak. Was under impression that could lower tank a bit and stick hands into gap to disconnect fuel lines, but could not do that properly - unable to work blindly, must see an object.
Another issue was that I could not access filler neck hose clamp screw and had to force pull it, otherwise tank has just hanging on filler hose and not lowering.
Maybe for a skilled handyman it is one hour job, I spend hours tackling damned thing.
wrecked
Full Access Member
I'm sorry if I implied anything untoward. It truly was not my intention. My truck also has a custom service box and I neglected to consider the differences. All the best to you sir.
Fixnstuff
Full Access Member
Sergey: 1) Where are you located in Washington State? In or near what city/town? Reason for asking is that there might be a forum member on one of the IDI forums living nearby who might be willing to offer some help.
2) I am surprised that no one bothered to mention WHAT the problem with your rear tank is. The problem is this: At the bottom of the steel fuel pick-up tube on the sending unit there is a Plastic CONE filter with a stainless steel screen. That cone sticks up from the bottom of the tank about 4 inches where it fits over the end of the steel pick up tube. That plastic one has broken off in is lying in the bottom of the tank, possibly in pieces.
The steel pick-up tube only goes down to about 3-1/2 to 4 inches from the bottom of the tank so when your fuel level gets down to that level the pick-up tube starts sucking air, even though there is 3-1/2 to 4 inches of fuel left in the tank. THAT EQUALS about 3-1/2 to 4-1/2 gallons of fuel that you cant pump to the engine because the cone filter is missing and the pick-up tube doesn't extend far enough down to reach that fuel. In effect you virtually are out of fuel. When you fill that tank up again it will only take 14-1/2 to 15 gallons, when the tank actually holds 19 gallons, which has been your experience.
This is a very common issue and it eventually happens to all of these IDI trucks and vans. Usually at about 20-30 years
It's BEST to replace the entire sending unit with a NEW one, including a new filter cone. (Why the whole unit?) There is a small printed circuit board in the sending unit, it's located in the white plastic part of the unit, near where the float lever mechanism attaches. You can see the edge of it in the photo below, you'll see an ARC that looks like a small protractor where the degree lines would be marked. Instead of degree lines, this circuit board has exposed copper 'fingers' along that arc. They are electrical contacts and I called them 'fingers' for visualization because if you stick your hand out and spread your fingers apart, your fingers would represent the contacts in that arc (except that there are a lot more contacts than you have fingers on one hand.) There is a contact strip, I think it is brass that moves along that arc as the float goes up and down, making contact with separate finger on that circuit board. Each of those contacts provides a different resistance value in circuit that goes to the fuel gauge. Each different resistance contact regulates the voltage to the gauge which controls the position of the needle in the fuel gauge, up or down.
NEXT: YOU MUST ORDER THE CORRECT FUEL SENDER, FRONT OR REAR FROM YOUR YEAR OF TRUCK OR VAN BECAUSE Ford made several changes in the fuel gauge circuitry (resistance values) for diferent model years. If you don't get th correct sender for your truck or van model year, the gauge will NOT work properly. BE SURE to order the CORRECT sending unit.
Here are links to the correct sending units for your rear and front tanks (respectively) and the filter cone. I HIGHLY RECOMMEND ORDERING BOTH UNITS for front and rear tanks because the front one will be failing soon enough and you won't know if the sending units that you need will be available when you need them. I waited 5 years before the correct on for my 1987 Rear Tank became available again. I just bought both of them about 6 weeks ago. I have not installed them yet.
Rear Tank SU:
http://www.trexautoparts.com/products/1985-1986-fordr-fs-pu-19-gal-diesel-rear-tank-su
Fuel Filter Cone:
http://www.trexautoparts.com/products/ford-diesel-in-tank-fuel-filter
Front (Side) Tank SU:
http://www.trexautoparts.com/products/ford-diesel-in-tank-fuel-filter
You will need a new filter cone for the Front (Side) Tank too.
For Full Size Ford Diesel Pickup Sending Units START HERE:
http://www.trexautoparts.com/categories/ford-full-size-pickup-diesel-sending-units
I don't see any sending units listed here for IDI Diesel Vans. I HAVE seen them listed online before. I suggest looking for a company named MTS. They also sell fuel senders for Ford IDI diesels. I don't have a url saved for that site and I can't search for it now. EBAY is another option.
2) I am surprised that no one bothered to mention WHAT the problem with your rear tank is. The problem is this: At the bottom of the steel fuel pick-up tube on the sending unit there is a Plastic CONE filter with a stainless steel screen. That cone sticks up from the bottom of the tank about 4 inches where it fits over the end of the steel pick up tube. That plastic one has broken off in is lying in the bottom of the tank, possibly in pieces.
The steel pick-up tube only goes down to about 3-1/2 to 4 inches from the bottom of the tank so when your fuel level gets down to that level the pick-up tube starts sucking air, even though there is 3-1/2 to 4 inches of fuel left in the tank. THAT EQUALS about 3-1/2 to 4-1/2 gallons of fuel that you cant pump to the engine because the cone filter is missing and the pick-up tube doesn't extend far enough down to reach that fuel. In effect you virtually are out of fuel. When you fill that tank up again it will only take 14-1/2 to 15 gallons, when the tank actually holds 19 gallons, which has been your experience.
This is a very common issue and it eventually happens to all of these IDI trucks and vans. Usually at about 20-30 years
It's BEST to replace the entire sending unit with a NEW one, including a new filter cone. (Why the whole unit?) There is a small printed circuit board in the sending unit, it's located in the white plastic part of the unit, near where the float lever mechanism attaches. You can see the edge of it in the photo below, you'll see an ARC that looks like a small protractor where the degree lines would be marked. Instead of degree lines, this circuit board has exposed copper 'fingers' along that arc. They are electrical contacts and I called them 'fingers' for visualization because if you stick your hand out and spread your fingers apart, your fingers would represent the contacts in that arc (except that there are a lot more contacts than you have fingers on one hand.) There is a contact strip, I think it is brass that moves along that arc as the float goes up and down, making contact with separate finger on that circuit board. Each of those contacts provides a different resistance value in circuit that goes to the fuel gauge. Each different resistance contact regulates the voltage to the gauge which controls the position of the needle in the fuel gauge, up or down.
NEXT: YOU MUST ORDER THE CORRECT FUEL SENDER, FRONT OR REAR FROM YOUR YEAR OF TRUCK OR VAN BECAUSE Ford made several changes in the fuel gauge circuitry (resistance values) for diferent model years. If you don't get th correct sender for your truck or van model year, the gauge will NOT work properly. BE SURE to order the CORRECT sending unit.
Here are links to the correct sending units for your rear and front tanks (respectively) and the filter cone. I HIGHLY RECOMMEND ORDERING BOTH UNITS for front and rear tanks because the front one will be failing soon enough and you won't know if the sending units that you need will be available when you need them. I waited 5 years before the correct on for my 1987 Rear Tank became available again. I just bought both of them about 6 weeks ago. I have not installed them yet.
Rear Tank SU:
http://www.trexautoparts.com/products/1985-1986-fordr-fs-pu-19-gal-diesel-rear-tank-su
Fuel Filter Cone:
http://www.trexautoparts.com/products/ford-diesel-in-tank-fuel-filter
Front (Side) Tank SU:
http://www.trexautoparts.com/products/ford-diesel-in-tank-fuel-filter
You will need a new filter cone for the Front (Side) Tank too.
For Full Size Ford Diesel Pickup Sending Units START HERE:
http://www.trexautoparts.com/categories/ford-full-size-pickup-diesel-sending-units
I don't see any sending units listed here for IDI Diesel Vans. I HAVE seen them listed online before. I suggest looking for a company named MTS. They also sell fuel senders for Ford IDI diesels. I don't have a url saved for that site and I can't search for it now. EBAY is another option.
nelstomlinson
Full Access Member
That's the downside to Ford anything: they couldn't stop fiddling with their designs, so getting parts is always a lot harder than it should be.
Thanks for that post, Fixnstuff, that's good info.
Sergey
Registered User
Thank you kindly. My truck sits in Bellevue, on soil, there is no garage nor shed. It would be brutal to ask for help knowing that work will take place outdoors given the weather.
Due to the latter I do not plan to deal with rear tank till summer. Perhaps then I may seek help.
Thank you for your thoughtful reply about the rear tank issue when it cannot use its entire capacity. Your explanation seems accurate. Ordering correct new sending unit is a good idea. Although I don't know where the rear tank now leaks, maybe the tank itself became damaged and will need to be replaced too.
IDIBRONCO
IDIBRONCO
I've had my current truck (Blue Truck) for 7 1/2 years. When I first got it, I filled both tanks, but decided to only run on the front one (it was already on that tank) just to avoid possible issues on the 180 miles drive home. Later, I switched to the rear tank one time since I was getting lower on fuel. I came out from work that evening and it wouldn't start due to air. After I discovered that, I switched back to the front tank and did manage to get ti started again. It had no bed on it at the time and I replaced the senders in both tanks since neither one worked well. The fuel in the rear tank looked cloudy so I decided to NEVER run on that tank again just to be safe. A few years later, I reached for something on the dash while driving in traffic down the interstate and accidentally hit the FSV switch. I switched it back right away, but that's when it stuck part way and was pulling from the front tank while returning to the rear tank. A couple of months later, I decided to bypass the FSV so that it would fix that issue. Long story short, I've been running my truck on just the front tank since January of 2013. Running yours for a few months won't hurt anything.
