Question for diesel gurus (strange failure 6.9idi)

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67charger383

67charger383

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Haven’t started my truck in about a week.
It was 50* out so I didn’t use the block heater.

(it’s a ‘87 F350 dually. 6.9 idi/t19 4 speed)

Started right up after a few cranks, then I had it idling for 5ish minutes. I do this a lot with this truck because it doesn’t have tags yet.
Had it warmed up and went into low idle like it should.

Anyway, it randomly started revving up without me touching the pedal, and I immediately killed it with the ignition. Only did this for about 1-2 seconds before I cut it off.

Looked over everything, no leaks, didn’t blow up, nothing got sucked in the intake.

waited about 5 minutes and went to start it again, seemed like it was cranking faster than normal so I stopped.

What the hell happened and how do I fix it?
It’s a low mileage truck, but I suspect it might be injection pump failure or lift pump failure?
 
67charger383 said:
Haven’t started my truck in about a week.
It was 50* out so I didn’t use the block heater.

(it’s a ‘87 F350 dually. 6.9 idi/t19 4 speed)

Started right up after a few cranks, then I had it idling for 5ish minutes. I do this a lot with this truck because it doesn’t have tags yet.
Had it warmed up and went into low idle like it should.

Anyway, it randomly started revving up without me touching the pedal, and I immediately killed it with the ignition. Only did this for about 1-2 seconds before I cut it off.

Looked over everything, no leaks, didn’t blow up, nothing got sucked in the intake.

waited about 5 minutes and went to start it again, seemed like it was cranking faster than normal so I stopped.

What the hell happened and how do I fix it?
It’s a low mileage truck, but I suspect it might be injection pump failure or lift pump failure?
Click to expand...
I worked at the Navistar Indy Engine plant back when the 6.9 was built. I can guarantee you that engine saved the employment of a couple of thousand employees directly and untold thousands indirectly. With that said, to your problem,,,
Check the fuel filter and air filter, an unsteady idle is an indication that the motor is starving for fuel or air.
If your truck has OBD II, check to see if it has set any codes. Your engine is mechanical FI, so it may not have OBD.
There are a lot of 6.9’s still in service so if you don’t get good direction here at FABO look for help at a 6.9 diesel forum.
www.binderplanet.com
Is forum that deals with all products made by IH/Navistar.
 

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Check your oil level . I think that engine has a low oil monitor that will effect how it runs .

Maybe someone installed an optimized idle sysytem on it ? Did you buy it new ?
 
I know the answer to all your truck problems.

Send it to me. I will give it a good home.
 
mbaird said:
Check your oil level . I think that engine has a low oil monitor that will effect how it runs .

Maybe someone installed an optimized idle sysytem on it ? Did you buy it new ?
Click to expand...

it’s an entirely mechanical engine, no computer, mech injection. Non turbo.

No, 2nd owner. Has 160,000 miles was only used for towing horse trailers. Bought it last year.
 
In all seriousness, it sounds to me like what diesel guys call "air intrusion". That's air getting into the intake "somewhere" it ain't supposed to be. I would check all of the intake hoses, gaskets and whatnot. Maybe make sure a rat ain't chewed through somethin or somethin ain't rotted or cracked.
 
67charger383 said:
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Click to expand...
This won’t help with your problem, but did you know the IH/Navistar 6.9 has a bit of a connection to Chrysler.
The engine that became the 6.9 was developed as a 446 ci gas engine known within IH as the MV8.
During development Chrysler expressed an interest to purchase that motor for use in motor homes and large trucks as a replacement for its own discontinued big block motors. The MV8 launched in late 1974 in the midsts of the 70’s gas crisis and Chrysler was cutting product lines and they dropped any interest in the MV8. From the mid 70’s to the early 80’s IH made a only couple thousand MV8’s there was no market for that gasoline motor. In the mid 80’s IH initiated a plan to change the MV8 into a diesel motor as diesels were gaining popularity. Many design changes were made, but the way IH designed engines back then the basic architecture stayed, as it was plenty strong. There was a new cylinder head, pistons,,,,, the machining and assembly lines were retooled. And the 6.9 worked well. IH signed a contract with Ford. And Ford put the 6.9 in their F250 and F350 trucks and the 6.9 started a line of engines that went from the 6.9IDI to the 7.3L to the 7.3T to the 7.3IDI to the 6.0l to the 6.4L. As mentioned earlier, provided good paying jobs to a lot of folks for nearly 25 years. Today the plant where that string of engines was built is completely gone, flattened.
New construction is going on there for a distribution terminal.
 
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How high did it rev before you killed it ?

(I know my diesel goes in high idle on its own from time to time...and I presume this is a new truck to you)
 
diymirage said:
How high did it rev before you killed it ?

(I know my diesel goes in high idle on its own from time to time...and I presume this is a new truck to you)
Click to expand...
I didn’t rev it. It was idling and revved on it’s own.

it did a Christine

probably 300ish more rpm, didn’t redline or anything
 
mbaird said:
Check your oil level . I think that engine has a low oil monitor that will effect how it runs .

Maybe someone installed an optimized idle sysytem on it ? Did you buy it new ?
Click to expand...
The 6.9L, 7.3L and 7.3T were mechanical FI
The 7.3DIT and the 6.0 were the HEUI Injectors, Hydraulic Electronic Unit Injector FI
The 6.4 used PCR, Pressurized Common Rail FI
 
I had a 85 F250 4x4 with the 6.9 in it.

One day i was changing the glow plugs and one snapped off. I thought about it and just put the new one in.
I let the engine eat the old plug.
They are hard to kill.
 
1WildRT said:
6.9 IDI, a good place to start is this kit.... Fact is the three items they show as frequently bought together are all good routine maintenance items...

https://www.amazon.com/dp/B002M1BRYI/?tag=fabo03-20
Click to expand...

I will 2nd on servicing the return fuel lines it is a common failure item on IDI 6.9 and 7.3 engines, maybe the reason for the idle speed increase was that the controller decided the engine wasn't warm enough, so it raised the idle speed.
 
Cope said:
I had a 85 F250 4x4 with the 6.9 in it.

One day i was changing the glow plugs and one snapped off. I thought about it and just put the new one in.
I let the engine eat the old plug.
They are hard to kill.
Click to expand...

These engines have a prechamber for the glow plug and it would have most likely have trapped any serious piece of the glow plug and it would have eventually broken up and passed out of the engine.
 
Glow plugs are another common failure on these engines you can ohm's test them by unplugging them and test them for continuity, even in warm weather they don't like to start if the glow plugs don't work.
 
the 6.9 wasn't half the engine the 7.3 was . i had both , the 6.9 near ruined me on diesels .
 
jimjimjimmy said:
the 6.9 wasn't half the engine the 7.3 was . i had both , the 6.9 near ruined me on diesels .
Click to expand...
Assume that you are speaking of the 7.3 DIT.
The 6.9 IDI was normally aspirated. Although many were upgraded with aftermarket Banks Turbo kits.
The 7.3 T is the 6.9 DI with a slight over bore to increase displacement and the factory added the turbo.
The 7.3 DIT was a clean sheet of paper new design. The only part carried over from the 7.3 T / 6.9 IDI were the roller lifters.
Along with the design being completely new, the machining and engine assembly and test were also all new and state of the art for 1993 when that engine launched.
The 7.3 DIT is truly a work horse.
 
I had an '89 with a 7.3. First I'd check or replace your injector return lines. Have you replaced the fuel filter lately? Make sure that's sealed good. You may also need to have the pump rebuilt. I believe Stanadyne still rebuilds them.
 
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