About a year ago I bought a 86 F350 with the 6.9 motor. It ran kind of funky (tempermental) so I replaced the Injectors and Pump. It ran better but still had issues when very cold out. I traced that problem to a bad firewall mounted water/ fuel seperator allowing fuel aireation on cold days. That was replaced and corrected the problem.
This truck runs perfect but has a habit of using about a quart of oil every 200 miles.
One other thing that confused me was that the motor was colored red. I ran into the previous owner and asked him about the motor color. He told me that the guy he bought it from had put a "crate motor" in it.
I'm thinking that the rebuilder could have done a poor job on the bores so it might be wise to keep an eye open for another good motor.
I found one in the local "Wheeler Dealer" magazine for $500 dollars. It was a rusted out wrecker (sans wrecker part) with 62K on it. It even was clean. The garage owner told me they never used it so it just sat and mother nature reclaimed it!
When he went to start it had to crank it for at least 1 minute before it started. He said it was always hard starting but ran excellent.
When I got it home I was backing it off the trailer and it died. With a 5 gallon can (IV) feeding the mechanical fuel pump, it had no pressure. I put in a new fuel pump and had some (weak) flow, still started hard but ran good.
I'm thinking this motor has a bad fuel pump eccentric on the cam?
At 62 K miles???
A couple of weeks later I went to move the truck and it wouldn't start for nothing, even with an electric fuel pump feeding the inlet to the injector pump. The fuel solinoid was clicking so I figured the injector pump was bad.
Must obtain another pump.
Meanwhile I drained the fuel/ sugar combination from the main fuel tank!
(the garage I bought it from must have an unhappy customer!)
I found another complete motor from a scrapped F350 that was already out for $200 dollars.
When I went to get it I was surprised it was so clean! The guy told me it was a good running motor but the truck was too rusty to save! I handed him the $200 and they loaded it into my trailer. (score, I thought)
I found out that the motor was rebuilt, however full of water and the bores were too rusty to save. Damn! I wish they had covered it! At least the injector pump worked good on my other (sugared) motor.
During teardown of the watered down 6.9, I found all of the new looking glow plugs were burnt out and the fuel pump eccentric was worn down!
Are these motors known for bad fuel pump eccentrics (cams)?
What I have done with my 62K mile motor to move it around the yard was to install a low pressure electric fuel pump on the passenger side inner fender untill I swap it into my good truck. (it starts quick now) Then I will replace the cam!
Has anyone out there run into this issue?
I have 3, 6.9 motors and 2 of them have worn out camshaft fuel pump eccentrics.
It can't be just me!
Steve G.

 

Not many cam problems really over my several yrs........ but lots of members on other sites are going to electric pumps just ahead of the FSV (selector valve). Holley red or a cheaper one from NAPA that works fine. If you do an electric no need to fool with the cam....

 

I have the same problem with one of mine . I have an electric pump on it and it runs fine . It had the electric fuel pump on it when I bought it , which I thought was a little odd . I put a new manual pump on it and it would not pump a drop . So I went back to the electric pump .

 

If it runs good, don't bother replacing the cam, an electric pump makes life alot easier, especially when it comes to bleeding the system after a filter change/run out of fuel, etc....

 

I have seen the cams go but they generally have more miles. I would probably go with the electric pump also. You don't have to replaced the cam but you still have to tear into the motor.

 

I'd suspect the fuel/sugar concoction has done some damage to the IP/Inj's?

Run a HIGH dose of Fuel Additive (1 qt/10 gal's) thru it, and see how it reacts.

 

Fonefiddy,
That is why I picked up the last motor, for it's injector pump!

To all,
It makes much more sense to use an electric pump after the fuel selector valve and remove and cap the mechanical fuel pump block opening.
The original design keeps the entire fuel supply line, FSV and water seperator in a negative pressure. Even the slightest leak will cause aireation of the fuel and reak havoc with the performance of the truck (as in my case).
This would only happen when it was really cold out and never dripped a drop of fuel from anywhere.
If this would have happened with the fuel system in a positive pressure it probably would not have affected the operation of the truck and just been an obvious leak. Or maybe not even a leak because fuel is thicker then air.
I'm all for the fuel pump ahead of the FSV, just make sure the lines to the FSV are in perfect condition.
This makes more sense that the way the factory did it!
One of the neat things about the Diesel fuel systems is that all the fuel that runs thru the lines, goes thru the Fuel Heater and a portion of that (un-used) returns to the tank from which it came, warming the fuel in that tank on cold days.
This is just the opposite of the "Hot Fuel Handling" on the 460 gas engined trucks. The Hot Fuel Handling keeps the fuel moving from the tank, up to the vapor seporator near the carb and returns a large portion back to the tank constantly. This is accomplished with an "in tank" electric fuel pump and eliminates "vapor lock" from overheated fuel by keeping a constant supply of "cool fuel" at the carb.
People used to insulate their underhood fuel lines with tinfoil to delay vaporlock. The trick is just to keep the fuel moving with a fresh, cool supply.
Thanks to all!
Steve G.