I've got an 86 F250 with a 6.9 w/ Banks Turbo, and a c6 automatic transmission, that I'm having a little bit of trouble with...

I have to keep the accelerator pressed almost to the floor in order to cruise at highway speeds. I didn't think much of it originally, because I had heard these engines were slow... But as last winter came, I noticed MUCH better throttle response in the morning, while the cold start solenoid was active. And as the solenoid turned off, I suddenly had to press the accelerator another couple inches to maintain speed.

Alright, figured the issue was just timing, I knew it was off, so I wrangled up the tools this summer and timed it. The engine sounds better, I haven't gotten the mpg difference yet, so it's possible I'm off still, but the throttle pedal remains the same, having to be almost at the floor to keep cruising. It definitely accelerates a bit better now though...

Prlbably a related symptom, is when I was timing it, using the turnbuckle method for throttle control described in akaMacgyver's videos, I couldn't get it to hold at 2k rpm. I would very carefully turn the turnbucke a tiny fraction, and at about 1800 RPm, the rpm's suddenly took off to 2300. Trying to back down from there had a similar problem, it hit about 2100,then dropped like a rock to 1500....

Any idea what's going on here? Please don't say injector pump is bad X.x

 

Sounds to me like the injection pump and injectors need replaced.

 

Sticking and stretched throttle cable? Can you try playing with the RPMs with the cable disconnected to see if the symptoms still exist?

Just throwing that out there, I understand the turnbuckles should keep the RPMs steady.

 

I had the same problem with the RPM during timing. At idle it was fairly steady, but when I accelerated it to 2000, it would jump.

I use a pulse meter and found that I needed to clean the injector line more, wipe it down and make sure the pickup is secure. The meter's manufacturer suggested I turn the pulse adapter around 180 degrees. I am not sure if it was the cleaning of the line that made the difference or turning the adapter, but it worked fine after that. I was able to set it at 2000 rpm steady and got a steady advance reading.

 

Need MOAR timing advance!

 

*plugs ears* BLAH BLAH BLAH, not listening! Blah blah blah! X3

****, I really don't want that to be the case... the parts alone would cost me almost what I paid for the whole truck X_X It runs fine aside from those two things. Its idle is smooth, it accelerates pretty nicely now that I got the timing advanced... There's no missing... I haven't tried towing anything yet, so I can't say what it does under load, aside from the 3.5 tons of the truck itself...

Hmmmmmm..... Worth looking into I guess... I don't think that explains the timing issue, but that's small potatoes :P Plus, I have another less catastrophic potential reason for the timing fluke. I'll try and peak at the cable in the next few days and see if there is any slop in it.

Well, I'm using the lummy method, not the pulse meter. It's not just changing of numbers on a screen in my case, the engine very noticeably revs up, and down. It goes from a fairly loud noise, to a roaring freight train in the matter of a few seconds XD

I'm.... assuming you're joking? My timing was way retarded, but, I bumped it up 1 degree in advance over recommended because I have the Banks Turbo, and I read that you add a little advancement with the turbo bolted on...

The result being, the cold start solenoid no longer has such a massive change in power. I get good power when the solenoid is active, and when it is not. And when it kicks off while driving, I have to push the gas pedal only about an 1/16th of an inch, instead of the extra inch or two I used to have to press it...

 

No joke. More advance.
Set it by ear.

 

If you're getting more power with the cold advance ON, you aren't advanced enough. Basically, the sweet spot where you want to be is where you get maximum power out. Too late and you lose power, too early and it clatters.
You should have it give maximum power once warmed up and cold advance off. With the cold advance on, it should clatter quite a bit, until it clicks off.

 

The pump and injectors are wear items, idiperformance.com has good prices for the mild upgrade stuff. A stock pump is slightly cheaper at the green auto parts store, but not as capable.

 

I'm not familiar enough with diesel engine opperation to tune it by ear ^^; This is the most time I've ever spent around one... But, I'll give it a try... Only one way to learn, right?

Hmm, okay, I'll turn it up a bit more this weekend. It does have alot of clatter when the cold advance is on, kind of wished it sounded like that all the time, I love it XD

I think part of the problem was operator error too ^^; My ginormous feet were pressing my toes against the accelerator arm when depressing it.... I moved my foot down a few inches, and there's a bit more room in the throttle than I thought ^^; Plus, I've got 4.10's in the back, which really limits throttle to speed ratio...
Thanks I was wondering where to get upgraded parts... I do plan to beef up the engine eventually, but I don't have the funds for it at the moment. So, I'd really prefer not to replace my pump now with a milder one then I will want later on...

 

you'll know it when you hear it.
She'll crackle nice!
You can't get it ***** on but you can get it pretty darn close!

They say "never adjust it while running".
I have.
Either way will work. Just don't let it get away from you while it's lit.