Hello, Yesterday, I bought the big, diesel truck I've wanted for years, and got to drive it home. The previous owner informed me that the rear tank was completely empty, and that I should not switch to it. Today, I got to drive it to work, where I noticed a curiously large puddle underneath it. My front fuel-tank appears to have a leak underneath the front strap on it... It seems to be about half-way up the fuel tank, so I'm not in danger of finding it out of gas one morning. No big deal, I'll take the fuel out of the front tank, and move it to the back one. So, first, I went to the fuel station to add about 5 gallons to the rear tank just to make sure it didn't leak as well... I put the nozzle in the hole and start pulling the trigger, and a few seconds later the diesel is geysering back out at me. I thought maybe the fuel was displacing too much air in the empty tank, so I gently pulled the trigger, and left a gap at the top for air to get through, and it worked fine for about half a gallon before it errupted again, and continued to do so for a half second or so after I cut off the fuel flow. Once I got home, I went ahead and shoved my electrical fish-tape down the tube to see if there was some obstruction in the line, but it went into the tank fine. This is the first time I've owned, or opperated a diesel engine. So the first time I filled the front tank, (bringing it home last night) I had a little trouble with the fact that the nozzle doesn't go INTO the shoot like on gassers. But after a few minor spills, I got the front tank topped off so I could bring it home. Is there some special technique I'm just not getting? Or is there something wrong? Thanks.

 

I have a problem with my rear filler also. Depends on which station I go though, some are OK. I believe it has something to do with there is supposed to be an inner and outer filler tube in the rear. I am wondering if the inner came loose on mine.
On your front, the spout should go all the way in. I am wondering if some one changed your bed/filler opening. I am pretty sure the "Gas" neck has a slightly smaller opening.

 

Also did you check to make sure the rear tank is not full. It could be/ but the transfer switch is not working and you can't read or pull fuel from rear tank.

I had an 84 F350, the guy I bought it from said he didn't use the rear tank. I went to put fuel in it, the tank was missing. At least you have 1 to start with.

 

Well... I suppose it's possible, but it seems very unlikely. Both the front, and the rear have the same nozzle doesn't fit in thing... The end of the Diesel nozzle has this odd bell on it, and it mates up with the ring in my truck almost perfectly, but it doesn't let it through... How odd... Maybe I'll just take a hole-saw to it and open it up a little more :P I don't see anything as far as an inner/outer... it just looks like a metal tube, with a rubber furnco spliced in the middle to allow for flexing... I took my bright flashlight and pointed it down the tube, but I couldn't see very far...

 

Just did some checking. Looks like they used same filler 80-86. Mine is an 89, that is why they are different.
P.S. LMC truck Truck Parts and Truck Accessories is a good place for research. Good pictures, helps with difference between years. Not the best price, but sometimes the only place to find it.

 

Neat! Thanks for the link.

 

Hmm.. from the diagrams on LMC... it looks like the size of the port is determined by the end of the filler neck... They have one listed for Diesel specifically... but $150 seems kinda crazy for a small section of tube.... I think I can do better at a salvage yard >_> Or, again, the afore-mentioned hole-saw will work fine as long as I take it off first to keep from getting shavings in my fuel tanks.

 

Looks to me like that only applies 87 on. 80-86 uses same for gas or diesel, best I can tell.
Yeah, that's what I was saying about price. But if you are going salvage yard hopping you know what years/models will work.
Or check Rock auto they have good prices, if they have the part.

 

Well... I stumbled onto this site that has filler necks... and only filler necks o.o (Seems like a strange thing to build a company around but... if it works....)1980-1986 Ford F Series Pickup Fuel Filler Neck (REAR TANK) DIESEL | Filler Neck Supply Co.

And they specifically have diesel filler necks, both front, and rear. At a much more reasonable $60. Buuuut... I'm betting a salvage yard can beat that, if I can find a salvage yard with a Diesel F-series pickup of course XD

Compounding this, is the fact that I've got a dually pickup. So I'm not sure if they had custom necks made for this purpose... Or if they just added more rubber... The front filler is on the fender.

I'll have to check on the rear tank potentially being full... It seemed to be empty when I put my fishtape in there, it sounded that way anyway, but I'll climb under there tomorrow morning and knock on it directly.

Will it cause any issues if I switch it over to the rear tank, if the switching mechanism isn't working? As I understand, if the tank runs dry, it's a royal pain to get the truck started again afterwards. If I drop my front tank to weld on it, am I going to have to bleed the entire system somehow?

 

You don't want to run injection system dry. That is hard on the pump and then you have to bleed the lines to get it restarted.
The switch or more correctly the valve is located on the frame rail in front of side tank and is solenoid operated. If it is bad several things can happen when you switch.
1. everything switches, cool we are happy.
2. Nothing, bummer
3. Fuel gauge switches but fuel lines don't.
4. Worst case I have heard of, fuel pickup changes but fuel return doesn't or vice-versa. Truck can suck out of 1 tank and return to other.

I think the gauge switch from dash switch not valve on frame but would have to check wiring diagram when I get home.

 

Try using the auto diesel pumps instead of the truck pumps. The truck pumps have the larger nozzle and also a higher flow rate.
If I try to use the truck pumps I have the same problem you are describing.

 

Ahhh... Yeah, I was using the semi truck pumps... but, at the stations I was going to, those were the only available pumps... When I topped off my front tank, it took like... 20 seconds to throw 10 gallons in...was nice While I was at the pumps yesterday, there was a modern Dodge with a Cummins filling up there... Are modern truck ports larger now? Maybe I should try to find something newer to get parts from so that I can use the large nozzles, at least on the front tank... I'm pretty sure I know where there's a diesel pump in the same area as the gas pumps... I'll try filling up there. The slower flow might combat the geysering.

 

So, it's just if I run it dry? All the way to the injectors? If I drop the tank, weld it, and put it back in with a full tank, I should be able to switch back to it without any serious difficulty?

 

The dodge may have a larger fill tube. I only use the pumps with the smaller nozzle.

 

I suppose that makes sense. I was rather surprised when I learned that our tanks only had 19 gallons each... I've heard of Fords that had dual 100 gallon tanks, I was really hoping it would have a setup like that :P I'm sure the Dodge has much larger tanks, and maybe more justifiably uses the larger filler.