Newbie needs help with his first diesel (Please)

[gandalf]

WHOA!
...and then let off the throttle.
...
It died, but just before it did, there was like a "blip" of power--a jump in RPMs, and then it quit. ...
Anyway, I checked the schrader valve again, and got a hiss of air, so it's evidently sucking air from somewhere.
But the most alarming thing, was that diesel was pouring out of my tank. I noticed that it was dripping the other day after I filled it up, and I just assumed that the tank either had a rust hole or a bad bung gasket or a leaky filler neck. But, it has evidently been dripping since Wednesday, and when I cranked it up today, I'm clearly getting pressure in the tank. When I cracked the fuel cap, diesel gushed out. What would be causing my tank to pressurize, and are these things related?
What have I gotten myself into, here??

Sounds to me like you may be dealing with two separate and distinct problems here.

First problem: let up on the peddle to go to idle and the engine dies. That's the classic sign of a sticking metering valve in the IP. The immediate fix, and hopefully one which will last for a while, is to remove the fuel filter and fill it with ATF. Be sure to fill it through the OUTER ring of holes only, so that the ATF will be filtered. Put the full fuel filter back in place and start the engine. Let it run for a few minutes, until you hear the engine sound change slightly. That can take anywhere from 30 seconds to a few minutes. Once the engine sound changes, shut the engine off and let it sit overnight. The IP will be filled with ATF, which is a good cleaning agent for the IP. The next day start it up and drive it like you stole it. Take a short drive, maybe 10 miles. If that doesn't clear the metering valve, then there may be a deeper problem

Second problem: fuel pressuring the tank. That's probably not what is actually happening. It sounds to me as though the Fuel Selector Valve may be stuck. Your engine does not burn all the fuel it sucks from the tank. The unburned fuel is returned to the tank from which it came. Now, you have two tanks, and the fuel selector valve determines which tank to draw from, and to return fuel to the same tank. If the return selector portion of that valve is stuck, you may be drawing from one tank and returning to the other. If the tank receiving the return fuel is full, then the fuel returning might easily overfill it and appear to pressurize it.

The FSV is located on the frame rail, about at the rear of the driver's door.

Got to run. My daughter just called, and reported she is out of propane, and people arrive in an an hour for a big BBQ.

 

[Mad Maxine]

Yes, I think that's the issue with my gusher. That valve may be the problem with my supply as well.
Is there some way to just bypass the fuel selector valve and only run one tank?
I'm not taking this rig across the Alaskan Highway; one tank will do me. At least for now.

 

[gandalf]

Yes, I think that's the issue with my gusher. That valve may be the problem with my supply as well.
Is there some way to just bypass the fuel selector valve and only run one tank?
I'm not taking this rig across the Alaskan Highway; one tank will do me. At least for now.

Some members have eliminated the FSV and run only a single tank. If you have only one tank there is no need for the FSV. Ba absolutely sure that you have the lines correct, so that you draw from the tank you want, and return to the same tank. I'm not sure how you want to connect the selected lines at the FSV. I'll let somebody else tell you that. Basically, it should be a simple matter of putting in two 6 inch splices, one for feed and one for return.

I'll toss in another picture here, of the FSV on my '92 CCLB. I've labeled the lines, if you read carefully. Not all the labeling is clear. BE AWARE, my picture is from a '92 model year truck. Your '86 may be different. I don't know. My '86 is 3000 miles away, so I can't look.

 

[whitehorse]

When I pulled one tank off cause my selector valve took a dump it would read empty all the time...... Maybe I done it wrong...dunno but the valve is like 90 bucks on rockauto...

 

[IDIoit]

i did a 33 gallon rear tank.
the fuel and return line is a fairly easy switch.
one is 3/8" and the other is 5/16.
you need special inserts for the nylon line, where you stick the hose in hot water to swell it and then install the insert.
they work great.
as far as the electrical, there are diagrams all over, basically what you do is connect the black wire and the yellow striped wire to the incoming corresponding wires from the dash harness.

mine works great, if it reads full all of the time you have a ground issue.
if it reads empty all the time you have a sending issue.

 

[bbjordan]

Air Intrusion

It died, but just before it did, there was like a "blip" of power--a jump in RPMs, and then it quit.

That is classic symptom of air intrusion. There are a couple of places to check for that. The Water Fuel Separator could be letting air in. Another is the bit of rubber fuel hose between the hard line and the fuel pump.

You can disassemble the Water Fuel Separator and clean it up. It is not that difficult. A lot of folks bypass the WFS, but it has a function.

Another suggestion was to replace the fuel filter head with a 7.3 head. I wouldn't for a few of reasons.

1) the 6.9 filter is finer. It is rated at 6 microns. The 7.3 filter is rated at 10 microns.
2) the 7.3 filter head head has more holes to leak from. ie. the fuel heater connection.
3) the water in fuel indicator will have to be rewired.

An electric fuel pump is a good upgrade. I just did put in a carrier pump and I love it, by time the glow plugs are hot, the system is primed.

That reminds me, the 6.9 glow plug system sucks. It is 8 burnt glow plugs waiting to happen. A manual glow plug system is an upgrade in my opinion.

Just my 2 cents worth.

 

[BDCarrillo]

Tanks can get pressurized if the little breather valve on the very top is clogged. Had to clean several out, the hoses were full of dirt. Before the cleaning the tanks would actually swell from the pressure.

Pop a little cheapo fuel filter on the end to keep dirt and crap out.

 

[Waystro]

Well I'm against removing the fuel water separator
it was put there for a reason.
Mel has a thread on Cleaning/Repairing it in the Tech Articles
but I would get a aftermarket like a Racor and be done with air intrusion all together

 

[Mad Maxine]

Thanks guys!

Well, indeed the fuel selector valve was stuck, and flooding the rear tank with diesel. The replacement valve--as you all know--doesn't have the horseshoe connector barbs, just a regular hose barb. In any case, I've about decided to just run one tank and get rid of that possible source of a headache for good. Maxine is an old gal, and I'm not going to be running her any great distances where I can't find diesel.

Speaking of, does anyone know what the capacities are for the saddle and rear tank? Are they approximately the same?

The saddle tank from the get-go wouldn't take fuel. The bed is a "retro-fit" off of a '92 model truck, and the fuel fill hose had all kinds of twists and turns to make it work with the '92 bed. The rear tank takes fuel just fine without spitting up. Unfortunately, the sending unit in the saddle tank worked, but the rear tank is dead. I'm going to drop it anyway to see if the showerhead is still intact. Probably no. I'll look up a wiring diagram for the fuel gauge and see if I can figure out how to tap into the appropriate wires. Guess I'll use the saddle tank sending unit in the rear tank if that'll work (?)

Gandalf suggested I bypass the water separator temporarily just to see if that was my source of air leak. Well, someone had already done that for me. So, now I guess I need to get me a good water separator.

"you need special inserts for the nylon line, where you stick the hose in hot water to swell it and then install the insert.
they work great." IDIoit--what is that, and where do I get them? I assume the insert is some kind of barb that couples the nylon hose with rubber fuel line?? Or is that used to splice two nylon lines together? I'm going to need to do that unless I run rubber all the way from the back to the front.

Thanks again!

 

[Waystro]

The Front Should Be a 19 gallon
The Back Tank is 18 gallons

At least that's how it is on my 86

 

[83ford]

Does anyone know if I can still get a stock sending unit from Ford?

We bought acouple from ebay I think it was that we're brand new acouple months ago they were for the back tanks only but we took a second one and used the parts from it on the front sending unit.let me do some hunting and try and see if they are still listed


Sent from my Iphone using Tapatalk

 

[Mad Maxine]

Well, I got ol' Maxine up and running. Thanks for all the help, guys! Seems the selector valve was the source of both the introduction of air into the lines and the flooding of the rear tank.
Wound up deciding to just run the rear tank. Went back and forth about getting the 38-gallon tank for the rear, but in the end decided just to run what I brung. She's an around-town kind of truck anyway. Have a sending unit on order from LMC, and a new water separator, too.
Now on to the next issue--
Front hub bearings.

 

[FarmerFrank]

Ah the front hubs and bearings aren't too bad... after you've done 100's of times. I still fight with te wire snap ring on the outside. You'll see what I'm talking about soon enough.

On your sending units an 87+ one will work, but the sending unit reads different ohms than an 86. Also your FSV is what controls your gauges so if it's messed up it might be what's wrong with your gauge. You can direct wire it in at the FSV if you plan on never going back to a 2 tank setup.

 

[Mad Maxine]

Also your FSV is what controls your gauges so if it's messed up it might be what's wrong with your gauge. You can direct wire it in at the FSV if you plan on never going back to a 2 tank setup.

Yeah, I jumped the wires on the FSV pigtail, and she still no workee.
I'm hoping that the sending unit I bought from LMC will be correct. I guess I'll find out.