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Discussion Starter · #1 ·
Hello all,
Just signed into the forum, been poking around seeing all the really good info on here and decided you guys may be able to help me out.

I just traded my old truck for my new to me 1985 F250 with a Banks Sidewinder Turbo'd 6.9L.

The truck runs phenomenal. No hesitation, plenty of power, shifts great and running the piss out of her all week, got almost 14 mpg for hilly driving and all highway.

The truck has one issue that ive been trying to some reading on and cant really find a similar issue, It has the weird sound that is very consistent. Sounds like a muffled thunk/thump every revolution of the crank. Im fairly positive its not a IP or Injector issue seeing as the truck starts just fine in all weather so far, when its warm she fires as soon as the key is turned, when its sat for 12+ hours it turns over 3-4 times and fires right up. Ive narrowed the cold starts to glow plug controller and im gonna try to change it over to manual plugs before the winter hits.

But back to the main issue, Like i said before truck runs and drives flawlessly, and sounds exactly like a sewing machine with a serious attitude(im told thats what a healthy IDI sounds like lol) but the thump/thunk sound makes me worry, as the truck is my only transportation at the moment. Do you guys have any suggestions or tips on what to look at? Really appreciate it.:thumbsup:
 

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Thump/thunk sound is really hard to determine without really hearing it.

Can you hear it on a start up. To check it out, pull the wire off the IP fuel solenoid so it won't start, if you can hear the thump, it could be a rod bearing, it would sound loud on the first revolution and get quiter as the oil pressure builds up.

It could be a valve kissing the piston. You'd have to pull the valve covers and check for any damage, like a broken valve spring, bent push rod or things along that line. Do drivers side first, easyest one to remove, pass side, you have to remove a few things then wiggle it off and out.

Do those first then report back with findings.
 

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Discussion Starter · #3 ·
Turns out,covering the hole on the front of the conical air filter completely abates the sound. It's just the sound of the combustion of the engine from the intake tube. Everything on the engine works flawless, except I tried to adjust my fuel set screw for a little more power and the screw was impossible to move, even with channel locks on the hex key. Any tips on how to get the screw to adjust?
 

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Turns out,covering the hole on the front of the conical air filter completely abates the sound. It's just the sound of the combustion of the engine from the intake tube. Everything on the engine works flawless, except I tried to adjust my fuel set screw for a little more power and the screw was impossible to move, even with channel locks on the hex key. Any tips on how to get the screw to adjust?
Don't know what Brand air filter you have, but the guys over at the oilburners forum where talking about the insides of some conical filters were breaking loose, check yours out before some turbo damage is done.

The IP fuel screw might be bottomed out, ya sure don't want to break the screw head off, or this can happen, see pic, the C-ring pushes the rollers out for more fuel, if the screw breaks, the IP will tie up and shear the input shaft.
Try backing the screw out a hex or two, that wil indicate if it's bottomed out.

If the engine has never been timed, ya might wanna do that. Turbo timing is set at 10.5* to 11.5* BTDC.
Are you getting any Black smoke on a hard WOT acceleration?
 

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Discussion Starter · #5 · (Edited)
Checked out the filter, nothing wrong on the inside. Still makes the sound, asked a fellow idi owner in town, he said it's just the pre combustion sound, his truck does the same thing. As for the fuel screw, I'm not getting any smoke at wot unless there's a trailer on the back, then it just has a constant haze. Otherwise no smoke at all. Just little puffs. I tried turning the screw and it won't budge at all. No matter how hard I turned on it, in either direction, it would not move. I stopped trying after the second attempt to make sure I wouldn't damage anything and put it all back together. So I'm lost about the screw not turning at all. Thanks for the reply man.
 

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6.9 or 7.3 IDI?

Hello, I'm looking at buying a good old '89 Super Duty in incredible shape. The seller tells me it's a 7.3L IDI engine...non power stroke. I'm not familiar enough to know...wasn't that non-turbo'd engine (1989,) a 6.9L IH diesel???

I remember my cousin had one in an '87 F-350 that although was a nice enough truck, I though it to be kind of sluggish and understandably so without a turbo.

Anybody tell me if that could be a 7.3L IDI here?

One more question. This truck is pretty unique in that it was really modified by the previous owner with some good engineering and in depth thinking. It has a 2 speed axle hi-low range button on the shift lever, which made me wonder WTH that was all about, so I laid underneath it and saw no signs of a 2 speed rear, but I did happen to find an extra box behind the 5 speed transmission with a wiring harness coming out of it. Is this some sort of OD box that they make aftermarket??? This is a real mystery that I'd like to solve...

Thanks in advance.
 

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It has a 2 speed axle hi-low range button on the shift lever, which made me wonder WTH that was all about, so I laid underneath it and saw no signs of a 2 speed rear, but I did happen to find an extra box behind the 5 speed transmission with a wiring harness coming out of it. Is this some sort of OD box that they make aftermarket???
That would be an aftermarket overdrive unit. One or both of the two brands use a Eaton 2 speed axle shift switch.
 

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IDI came in 3 flavors. First was 6.9 non turbo, then 7.3 non turbo and in '93/'94 7.3 turbo was an option.

Since your looking at an '89 chances are it is a 7.3
 

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That would be an aftermarket overdrive unit. One or both of the two brands use a Eaton 2 speed axle shift switch.

Perfect...that's what I thought. It didn't do anything when I flipped it, but it's probably a fuse or something stupid, I'll find it.

Thanks for the reply.
 

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You're welcome. It's later in the day and my brain is a little more awake. One brand is Gear Venders and the other is US Gear. The Gear Venders uses a planetary unit and US Gear operates more like trans gears (a stronger unit). IIRC the US Gear actually uses the electric shift unit from a 2 speed axle, with a different shift fork of course and possibly a slightly different motor housing.
 
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