I had the 86 Ford 6.9 Diesel out in the slush today and it has a new unhappy habit. While driving the engine will speed up briefly then lose power as if it is starving for fuel. Does not shut off. After a few seconds it returns to normal operation. This did start just after a new tank of fuel. Any experience with this?
How are the fuel lines? There is a kit that includes the o-rings, lines and fittings. Also, fuel filter?
What temperature does diesel start to gel? Sounds like it was colder than normal for you.
I am going to start with the fuel filter and some anti gel goo. Then off to another station for some fresh (hopefully) Diesel. I don't think that it is leaking at the orings. No diesel smell under the hood.
YOu won't necessarily smell diesel under the hood. A small leak will affect it. The kits are ~$25 and easy to install. I have a spare for my 7.3 IDI.
Sounds like one of the times my Cummins broke (there were many...). In that case, it was the shut-down solenoid.
I think you likely have some water in the system somewhere. I don't remember if those engines have fuel/water separators. If so, just have to drain it. If not, water tends to accumulate in the fuel filter. If you do throw a fuel filter at it, be sure to prime it with good diesel fuel, or ATF. ATF is nice in that it cleans out the injection pump and injectors.
In reply to Brotus7 :
I think the water separator was on top of the engine on mine. The bottom of the canister had a small thumbwheel that you unscrewed to drain.
"Lose power"? I didn't think the Ford 6.9L had any power to lose.
There is a large cannister filer on the firewall. Separator? And a smaller filter just in front of the air filter. I think this is the filter. It has a shrader valve.
I owned a 6.9/5spd very briefly. It was a truck with no title that wouldn't hold brake fluid that i bought for $200 bucks. Someone had put a really tall shifter with a metal bulldog shift handle in it and a glasspack was the only exhaust. It was fun to drive, even without brakes. I only sold it because someone offered me $500 and i didn't have to do anything to earn it. 
In reply to Brotus7 :
Not sure on the 6.9, but on an IDI 7.3 there is a drain.
SPG123 said:There is a large cannister filer on the firewall. Separator? And a smaller filter just in front of the air filter. I think this is the filter. It has a shrader valve.
The smaller one is the one I had to drain. If it wasn’t done regularly ice could start to form in cold weather.
I THOUGHT that the canister on the firewall in my 84 6.9 was the separator. But unscrewing the bottom petcock of that seemed to drain diesel gas rather than water.
I owned my 6.9 for probably 8 years and never had a single engine problem, so I'm not much help. Well actually I replaced glow plugs once.
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