‘86 6.9idi smoke

[RWettstein]

I have an 86 F350 with a 6.9idi and only 65+K miles but a lot of years. Had a lot of white/grey smoke that would increase to the point it would hardly run. A mechanic friend told me to check the check valve on the IP and it was full of debris (metal and fiber). Cleaned it out and it ran pretty well. Then it would do it all over again and I would have to clean it again. Replaced the IP and runs better but still smoking and running rough at higher throttle but doesn’t want to stall. Nothing in the check valve anymore. Lift pump only has about 4 1/2 pounds pressure when running from the tank at idle. It drops to zero and probably negative when increasing throttle. I’m sure that’s to be expected. All the lines are clear back to the tank and new filters. Runs a little less smoky out of a clean jug of fuel direct to the lift pump. I have not checked the pressure while it is running from the jug. I cracked the lines loose at each injector one at a time and they all seem to make it run worse. Also, no discernible sound difference from one to the next when holding a rod to the injector. I don’t know if the lift pump is too weak(I doubt it has a couple hundred miles on it) or if there is debris in some or all of the injectors. I only make a few deliveries of mulch a year with it anymore. A little help would be appreciated. Thanks

 

[IDIBRONCO]

My first guess is that the lift pump sounds like the issue. You have to realize that they, like many other parts for our trucks, are made with poor quality these days. Sine the pump pumps faster as engine RPM rise, it should make more or at least the same pressure while revving in park/neutral. That may drop off at the top end of the RPM. Since the pressure drops as you rev the engine (assuming that the transmission is in park/neutral). There's more load on the fuel system as you're driving then when in park/neutral. Even when driving empty. To me it sounds like the lift pump just isn't able to keep up. This is why electric lift pumps are so popular these days. A cheap electric pump also won't be able to keep up with the demand for fuel. I no longer recommend Holleys because they don't seem to last. I had one the was a blue (mid line pressure and volume). It didn't quite last for one year. Right now, I'm using one for a 24v Cummins and it's been doing well enough since last December. There's another guy on here who's running an electric lift pump for a 2nd gen 7.3 PSD and it's doing pretty well as far as I know. He uses his for high load work most of the time.

 

[RWettstein]

Thanks IDIBRONCO. That makes sense regarding the pressure increase. I just assumed that the IP would over power it and draw a vacuum at high rpm’s. I’ll try to find that pump. Way cheaper than injectors Thanks again

 

[IDIBRONCO]

A IP will draw some fuel to an extent. My personal experience was driving around the block when the Holley quit working. It's also not good for the health of the IP for it to do that very much.
A IP needs a certain amount of fuel to cool it down and for internal lubrication. Lack of fuel also affects the timing by retarding it. A bad mechanical lift pump wiped out a good IP for me which is why I used the Holley. I didn't realize what the issue was. I had to drive back home on a drive that normally took about 4.5 hours. It took about 6.5 hours that time. The IP kept running out of fuel so I had to stop for a few minutes when it did and let everything "catch up" as I though about it. If I drove 65, I could drive for about 20 minutes. If I drove 50-55, I could drive for about 45 minutes. I made it, but boy was that ever a LONG drive! The internals wear in a way that makes too much fuel go through the return back to the tank. Even new, with the regulator wide open, the Holley blue couldn't keep up and it's rated at 110 GPH which is more than twice what a N/A engine like mine requires. That's just an idea of how bad low fuel pressure/volume can be on a IP.

 

[RWettstein]

Gotcha. Thanks again

 

[RWettstein]

Well, that didn’t work!!! Mounted a Facet Duralift 40222N. 9-11 lbs and 120” lift. Put it on a cross member 3’ from the tank. Ran all new 3/8” line from the tank to the pump, to the water separator, and then around the back, above the motor to the filter. Still smoking and running rough at higher throttle. Haven’t checked the pressure yet. Had to tap the pump with a rubber mallet to get it to turn though. Now seems to be running ok.

 

[IDIBRONCO]

Duralifts are known to be poor quality. Some are bad right out of the box. How was your fuel pressure?

 

[RWettstein]

Barely 4 lbs with just the key on. Drops to zero when I start it

 

[RWettstein]

Took the bowl off the pump and made sure that the check valve up inside was moving and that’s fine

 

[Nero]

Barely 4 lbs with just the key on. Drops to zero when I start it

That is too low. You want 4-7psi across all rpm range.

 

[RWettstein]

I bypassed the water separator, also ran it straight from a jug to eliminate possible issues there and always the same result. I can’t imagine there is too much going out of the return to not allow it to build pressure. I’ll call the company in the morning

 

[RWettstein]

Tried to get tech support from facet and all he could say was that it wouldn’t have left the factory if it didn’t make 9-12 psi. I got it from Amazon (Pegasus auto racing) and it’s going back. The mechanical pump is still in place (just bypassed) so I’ll reconnect it with new 3/8” fuel lines and decide which mechanical pump to replace it with. Carter, Delphi Sparta, whatever. I still have a bad feeling it’s going to be the injectors with crap in them causing the problem since it didn’t smoke until the injection pump started breaking down. This motor isn’t worth going crazy on with the front and rear seals leaking and I don’t put that many miles on it.

 

[RWettstein]

Installed a new mechanical lift pump and have decent pressure at the Schrader valve. Consensus then seemed to be that the injectors were bad so I just replaced them with reman injectors. Blew out all of the injector lines and returns and caps. Still smoking but interestingly at a slightly increased throttle the white smoke would come and go for a split second on occasion. I decided to run it out of a jug again to rule out my old crappy saddle tank (removed the rotted original tank years ago) and it still smoked the same. I’m thinking maybe it’s the reman injection pump as there was maybe some debris in the lines when I first installed it?