Sputtering and spitting and then a surge mid gear

[McGIDI]

Ok so i just bought a 85 6.9 and its spitting and sputtering if im just cruising in 4th..... but as i accelerate 2nd and so on there is a surge about mid gear.... like a turbo spooling but of course she aint turbo'd but really hards starts and i think the timing is off so if you guys could give me some insight on where to start...

 

[rhkcommander]

fuel leaking/air intrusion I *think* if I recall correctly can do that. I might be remembering incorrectly but its a common enough problem thats been covered in the past

 

[Wyreth]

Air intrusion almost certainly. Start there before you try anything else. A good test, put some clear fuel line between the lift pump and the filter head. Start it, and see if you get bubbles in it, also rev it up some and watch. Air's compressibility plays havoc with how the mechanical system times its injection points, and will play merry hell with how your engine runs.

Your truck also had the Stanadyne water separator in it. This is a notorious source of air intrusion. There's even a tech article here about it. http://www.oilburners.net/forums/showthread.php?18212-The-Stanadyne-Water-Seperator-Exposed
As a test you can also try bypassing it, or plugging the drain hole on the bottom, and seeing if that changes anything. (do not run it long without some sort of water separation system. If you get water in your IP, you will kill it)

Incorrect timing will not give you the symptoms you're talking about.
however, I had a problem with my advance piston being sticky. Would cause random power surges while accelerating when it would unstick. Was lucky, and after a week of letting it stew in ATF overnight it went away. (everything on this truck was filthy, even the internals apparently)

 

[McGIDI]

so that might be causing the hard starts to as well.... and sorry to ask but what is the advance piston

 

[CaptTom]

Don't forget dirty fuel filter. A plugging filter can give a stall/surge affect. Sometimes the greater load of 4th will cause it to sputter/stall, upon downshift, it gives enough time for the fuel to catch up and now you get surge because your foot's in the throttle.

I'd try air first, but fuel filters are cheap, so why not.

 

[McGIDI]

swet well thank you guys very much.... im a powerstroke guy and had to get rid of all my trucks when i deployed... but now im part of AFSOC again so i will be home and i picked this truck up for 1000 bucks and couldnt beat it... i just want it running perfect so i dont get frustrated lol

 

[Blind Driver2]

or you could just be running out of fuel. a bad lift pump is possible

 

[Wyreth]

so that might be causing the hard starts to as well.... and sorry to ask but what is the advance piston

air intrusion or bad glowplugs are almost always the cause of hard starts.

And DON'T ever be sorry for asking questions! The only stupid question, is the one you didn't ask.
Now lessee if I can answer this one properly.....

Inside the injection pump, there is a ring cam that determines when the pressure spikes that inject the fuel happen. As RPM's increase, this cam naturally starts to lag, and cause the injection pulse to retard. So there is a hydrolic piston in there that uses fuel pressure to advance the cam to counteract that. If your pump sits on a farm for a year or two, or was rebuilt poorly, this piston can either be gummed up, or bind in its bore. Then your timing either jumps around, or simply retards as RPM's increase. Which plays merry hell with how your truck runs.

If that didn't make sense, I posted the shop manual for the injection pump here: http://www.oilburners.net/forums/sh...resting-Reading&highlight=interesting+reading
That might make more sense.

 

[8973]

I had similar symptoms when my fuel pick up/sender started to eff up. At first there was little rhyme or reason to it, but as it got worse I noticed I always happened after a sharp turn (as well as other times).

$.02

 

[id_bowhunter]

Is the arm lever for the advance normally open ( advance pin sticking out) or pushed all the way into the ip?