A little while back I removed the bed of my 90' with the intention of modifying the fuel tank vents, locating and fixing the full tank fuel leak, and replacing the rear spring bushings. Once I got the bed off the mess I found far exceeded anything I expected which resulted in a significantly larger job than I had originally anticipated. In the end I ended up cleaning and painting the back half of the frame, replacing the spring bushings, replacing both fuel tanks and there corresponding sending units as well as making a few other modifications to get everything working well together.


Throughout this process I ran into a lot of snags, hard to find parts and many situations where I was unsure of what parts would work. As a result of my troubles I thought I would take a few minutes and share what I did, what worked, what didn't work and any other advice that may help others in the future. This is not meant to be a definitive guide on the subject as there are so many small variations between different years of truck, but hopefully the info will help others piece together the own puzzles.

 

Between previous personal experience and what I have read on this forum, I opted to pull the bed for access to both the fuel tanks and the spring bushings. It is certainly possible to do this work with the bed on by dropping the tanks from the bottom, however your life will be a million times easier in the long run with the bed off. If your truck is a rusty, diesel and road grime coated unholy mess like mine was I would definitely recommend pulling the bed.








I do believe you could remove the box with help from a few friends, but the engine hoist was nice because I could take my time while making sure everything was disconnected and free. As a note, all the wiring in the back end have plugs that allow you to disconnect the whole harness so there is no need to go in and remove the tail lights and trailer plug separately. I did opt to pull the rear bumper for better access to the bed bolts. Having said that, I ended up cutting/grinding damn near every bolt I removed on this truck. I would saving yourself lot's of trouble and just a grab a grinder at the start, grind the heads of the bed bolts off, and replace them all later.


And hears the mess I found, 25 year old peeling undercoating, rust, spilled diesel and road grime. At this point I decided I couldn't live with myself If I didn't take the time to clean things up and repaint while I had everything apart.

 

please do elaborate lol, i just had my bed off, thought i fixed a leak and now i still need to drop the tanks and want to replace both with new or one large single rear. i had to do bushings, spring hangers, shackles, all of it.

 

At this point I decided to tackle the spring bushings and frame cleaning outside while the weather co operated, caution, very dirty work. There is no easy way to get these old *******s out. I ended up first cutting the bolts with a zip disc so I could drop the spring out of the hanger, then drilling out as much of the old bushing as possible before spending a considerable amount of time with an air hammer and sledge to remove the old rubber. Once the rubber was out I cut the old metal sleeve out with an air hammer / chisel, cleaned everything up and installed the new bushings.


Old bushing





New bushing





I went with Energy Suspension poly bushings, the same kind I put in the front a while back. Overall I have been happy with there products, although in the case of the bushings someone did drop the ball as the shackle bushing was made the same width as the spring bushings, despite it being a smaller bushing. After much frustration and creative language I ended up trimming one half of the poly bushing which then pressed in okay. I then re installed everything with new hardware.









At this point I went through and cleaned the frame with a combination of an air hammer, scraper and wire wheel on both a grinder and die grinder. Thankfully beneath all the mess the frame itself still appears structurally sound.

 

Now for the fuel tanks, the original reason I went about this whole ordeal. Since I bought the truck both have been a royal pain in the **** to fill, sometimes over half an hour at the pump to get both tanks filled right up. Spending half an hour holding a metal fuel pump with the temperature below freezing and the wind blowing is not fun! Furthermore both tanks, especially the front, had started leaking if filled right full and would continued leaking until the fuel level had dropped down past 3/4 of a tank.


I had originally planned to locate the cause of the leaks and repair as well as modify the vent lines for better filling. However upon removing the tanks I found them to be quite rusted and badly worn in places. I also found that the senders were badly rusted, I had to mangle the lock rings in order to remove them. At this point I opted to replace everything for peace of mind, I did not want to expend all the time and effort only to have problems once it all went back together. Unfortunately this is where the headaches started.

 

I have lots more to put up but I've run out of time for now, I will try to finish the rest soon.

 

In regards to the fuel tanks, it would appear that tanks from different years as well as gas and diesel are interchangeable. I ended up going Spectra tanks as they were the most affordable, available locally and had a good amount of positive feedback. From the research I did it would also appear that the 38 gallon LMC rear tank does also fit, and was something I considered, however for time and budget reasons I opted for two factory sized replacements.


Front tank








Rear tank

 

Before Installing the tanks I went about modifying them for my own vent set up which consists of 5/8" fuel line for that vents externally back up to the top of the filler neck and removing the original vent hose from inside the filler necks. I also added in a 1/4" vent line off each tank filler vent joined into a smaller valve cover breather filter mounted fairly high up inside the box walls. More on all this later.


For now the tank vent connection. Instead of using the factory roll over valve I opted to weld in bungs in their place. (I welded them because I am a welder and have the equipment to do it.) I used cheap cast fittings for most of it, however I would strongly recommend using either a forged steel like you find in a hydraulic fitting or stainless steel for weld ability as the cast fittings were incredibly challenging














The front in the pictures above is a regular 90 degree elbow and I had no real issues with clearance. The rear tank however sits very close to the bottom of the box and even though I sunk the fitting down as low as possible it almost the bed. Since I had to trim the fitting for clearance I welded an appropriate sized washer on the bottom side, to the fitting, then welded the fitting to the tank. As you can see the rear tank was also a forged fitting, so much easier to weld!











After welding in the fittings I sprayed a couple of coats of primer on followed by a nice thick coating of brush on rust paint. I figured I would do everything I can to keep that evil orange plague away for as long as possible.

 

Before mounting everything back in I painted the frame of the truck as well as the skid plates and other components with the same rust paint.





I also had to remove one of the bumper bolts that had sheared off in the frame. I achieved this by welding a nut on the backside of the bolt protruding form the nutcert in the frame and running it out backwards





The bolts on the rear tanks straps were also toast, so modified the straps...





and fabricated my own bolts out of SS hardware

 

With the tanks in place came the biggest headache, the fuel senders. In the LMC catalogue there are literally dozens of part numbers depending on year and engine type. The Diesel senders for brick nose and OBS trucks are incredibly expensive, $449.95 plus extra costs, to be precise. I am willing to put money into my truck to keep it reliable and running well but that is too much!


I spent a ton of time doing research, searching various forums, looking up different parts and suppliers as well as starting a thread on here but I could not come up with a conclusive answer as to what the difference between part numbers was really for. It turns out that the answer, which I found out the hard way, is that different years used different resistance fuel level senders, the tabs the align the sender in the tank are different and the pickup return tubes are oriented differently.


At the end of the day, you should be able to make any sending unit work as long as you are willing to modify the pickup in the tank, rework the connections to the factory plastic fuel lines and re cut the tank so the tabs will line up. The one thing you really want to watch is the fuel gauge resistance, earlier models differ from later models. This site seems to be a good reference to this Fuel Tank Sending Unit Tech - FORDification.com. That being said the date breaks would appear to have deviations.


So here is what I did:


For the front, an LMC 43-4048, made for made for 87 5.8L and 7.5L gas engines. It turns out the fuel tubes were backwards on this one, the resistance was wrong (73-10 ohms), the notches had to be re cut and the pickup had to be modified. I ended up doing my own custom pickup and was able to bend the factory fuel lines around to fit, however I had to install a second aftermarket gauge in the truck since I now had to different resistance sending units.




For the rear, an LMC 43-4180, made for 87-89 diesels. On paper I thought I had this one beat, the right sender for a quarter of the price. In reality it was not a direct fit. Although It had the correct fuel pickup and correct resistance, the fuel tubes were opposite and I was unable to bend the factory lines to fit. I will also note that the sender, although it does work varies from the factory in how it reads on the gauge. Before the truck could be right on the red and still be good, now once that needle hits the line you are done! It also reads above full for over 200km but once the gauge starts to drop it drops real fast. Another point of interest, this should have the wrong for my 90 73-10 resistance but actually had the correct for 90 and newer 16-158, go figure


More details and pictures to come, but for now it is time for some sleep.

 

Keep it up, love the research ur doing. I need to replace both of mine eventually and get the lmc 38 gallon tank. Currently I use just the front. Curious if you could show how to connect both tanks. The po had both disconnected when I bought it with a boat tank in the bed connected. I'll add what I find as well here to keep information in the same post if its OK with you.

 

Front LMC sender as it came, as you can see the pickup is far from what is needed to work with the diesel.





Parts for my custom pickup, scrap stainless pieces I had lying around and a compression to pipe thread fitting. I did my best to take a measurement and did a bunch of math to make things work. The custom end I was making was too long, which worked out, so I trimmed the pickup tube on the sender to make it work. I ended up getting it really close and fine tuned things by bending the pickup tube a little.

 

I don't think I actually took a picture of the rear sender itself, it looked just like the factory one with the exception of the fuel tubes having a different orientation. Since I couldn't get the factory lines to work a got some appropriately sized fuel line and clamps along with some hose barbs and spliced in my own soft lines. The hose barbs were a bit of a challenge to get into the factory plastic lines but they did fit. I sliced some air line and slid it over the rubber lines to keep them from getting rubbed to badly on anything, clearance is limited between the box and frame cross member.

 

By now I should have been almost done, however by un knowingly ordering senders with two different resistances I had a bit of a problem. Since I did not feel like ordering another front sender, reworking it, and hoping that it was the right resistance I opted to add an aftermarket fuel gauge. I dug into the wiring harness at the selector valve, found the sender wire for the back tank and bypassed the valve right to the sender wire for the gauge in the OE dash. Then I bypassed the front tank to a wire I had run to my second gauge.


I thought about it for quite some time but I finally decided the best place to mount the gauge would be where the ash tray resided. I removed the whole ashtray assembly from the dash and broke the parts down, I ended up modifying the factor upper bracket to make an enclosure.




















It also worked out that I could use the power wires that originally fed the cigarette lighter and the small light in the ash tray as well as the ground. The small light was a definite bonus since it is switched with the headlights and perfect for the gauge backlighting. As you can see I used to Equus gauges, one fuel level and I also added a voltmeter that is wired into my own switched power feed and much more accurate than the factory gauge. One point worth noting, the Equus gauges don't have any sort of damping in them so the needle bounces up and down as the fuel sloshed in the tank, I guess you get what you pay for.

 

The only problem with using the ash tray for the gauges is I now had no 12v power in the cab for things like phone chargers. I looked around on line and found some nice looking 12v accesory plugs, I believe the are actually made for marine application, but they work fine. I also found a slick little unit that actually has two usb charging ports in it so you don't even need a phone charger, just the appropriate cable for whatever you want to plug in. I found a spot between the centre cluster and glove box the t was perfect to mount the receptacles so I went about making a small mounting panel and cutting up my dash some more











If I did it again I would centre the hole a little lower as I almost didn't have enough back clearance between the top receptacle and the vent ducting, I definitely got lucky on that one.


I put a switch in the panel too, I had originally planned to have both hooked to constant power through the switch however I have a small solar powered batter tender I plug in and didn't want to have to leave the switch with the light on all time so only the usb plugs are on the switch. (They do cause a slight power drain at all times, even when not plugged in) I tapped into the wiring that I had run into the new gauges to keep things relatively simple.