Ive been on this forum for 10 plus years but in the V-10 and 6.2 sections. I just bought an old 1986 stake truck with a 6.9. It runs well but if it sits for several days, it wil start but then stall a few seconds later. Then I have to crank it like crazy before it starts. It will always fire up if I start it every day. Also there is an electric fuel pump by the brake booster that I'm assuming isn't stock? It doesn't smoke like crazy or anything but I'm pretty sure It burns a little oil. Should I replace the injectors and return lines for the heck of it? A few of the return fittings leak a little. I found a starting fluid can behind the seat. That worries me a little. I'm not sure why because even in the cold it will always start, I changed the oil on it. Any other things I should look over or service on it? It's got 85000 miles on it. Been a farm truck its whole life but I can tell its been worked hard its whole life also.

 

Text book air intrusion. Would do return lines. The electric fuel pump is not stock, someones attempt to fix the air intrusion.

 

Ok I'll replace the return caps and the lines. Should I ditch the electric fuel pump? I removed the PCV valve on the back of the intake under the air cleaner. I was told they can get blocked but I could blow air through it and didn't see anything in it.

 

Sounds like air intrusion, especially since there are leaking return caps. Order a return line kit to replace them. Kit will have the caps, o rings, and enough fuel line to do the repair. It's easy and fairly quick to do.

 

If the electric pump is a cheap one I would ditch it for a better one or go back to a mechanical.

The faucet duralift seems to be a pretty popular electric pump that people here use.

They have that pump where the lines to the water seperator used to run. It's probably bipassed because they were known to leak air

 

Is the water separator that thing on the firewall next to the brake booster on the corner of the firewall? Its a little clear tank with fuel line in and out and what appears to be water connections. If so then that's exactly how this electric pump is connected. Although I believe the mechanical pump is still connected. Is it ok to run both?

 

I wouldn't recommend it, but I've seen it setup that way several times as most cheap electric pumps won't push enough fuel by themselves to feed the motor. They can supply enough volume, but not enough pressure.

The factory water separator was an all metal unit, so it may have already been replaced on yours, if so that's money you won't have to spend.

 

Pictures are worth a 1000 words they say. Dont know if thats still the case being the economy is so strong, might be 1200 words.

 

Could I just bypass the mechanical pump and run a hose directly to the fuel filter front the electric pump? I'm ordering a facet Duralift pump to replace the existing electric pump. If I could run all electric I would prefer that route.

 

Sounds like you might already have a facet pump. Ive always preferred the mechanical myself, never much luck with electric, especially with diesel. That said, yes you can. Make sure you have a filter pre pump or you will toast the electric. The epump wont fix the air intrusion, just makes it a little less hard to start after it dies.

 

Yes you can bypass the mechanical pump. While I have a 7.3, I think it is much the same on your 6.9

I bought this it appears to be the most recommended pump on the forum
for covering the hole left from removing the mechanical pump
The above two were in a "Frequently bought together" option

and a couple brass fittings Where the pump gets mounted will probably determine which fittings (90* or straight) to use

I also picked up a 12v relay, and an inline fuse.
The relay is powered by a wire that is hot when the key is on and the relay powers the pump from battery power through the fuse.

Since your return line caps are leaking, I used this but check first you might want to use the older caps have the in/out connections inline and the newer ones connections are to one side.

I have only done the leaking caps so far, but the difference is night and day in ease of starting.

I would do your glow plugs too. Especially since you will be right there changing the return caps. Get the Motorcraft ones.

 

Could I just leave the mechanical pump on the motor? Or do I have to put a block off plate on it?

 

You can just leave the old one, but there is a small potential for contamination of the engine if the diaphragm fails.

 

You can leave the old one, just disconnect the fuel lines from it. I have done that on some industrial engines without an issue.

 

Had a buddy that did exactly this with a 7.3, one day the electrical quit, luckily we had a piece of air hose and plumbed the old mechanical back in, not only did it still work, but it got us home and he never touched it again. Still worked when he sold it.

So if anything, think of it as an emergency back up