Something has most likely broken in the injection pump and has logged it self in some of the linkage. My injection pump had a piece of one of the internal springs kicking around and it would idle high some times. Your external linkage is connected to the internal linkage via a spring so when you Lett off the throttle there is nothing forcing the internal parts back besides the governor it self. So it is vary easy for debris to hinder the return movement. You need to pull the "pump top" off and investigate. Make sure to soak up all the fuel that is in the governor area and look vary carefully for pieces or stuck parts.

 

When you say that blipping the throttle has no effect: do you mean it doesn't raise the rpm either? or just won't drop rpm?

I had an 89 360 where the kickdown linkage stuck at WOT. Ruined the crank when it went WOT dead cold.

Also, is this maybe part of the injector pump recall from way back?

 

A PO could have maxed the power screw, back it out a 1/2 turn or whole turn if the collar is removed.

If it has sat for sometime run some diesel fuel conditioner in it.

 

thank you for your responses. i drove it gently for the 2 100-200 mile trips i went on before it was parked and the only problem then was that it would die when suddenly letting off the throttle. no abuse no high rpm driving. then it got parked. fixed the fuel line and now it starts fine. unless something broke in the IP while sitting something has seized in there and yes a running a recirculating can of seafoam which has worked wonders for me in sitting Rabbits with the 4 cyl VE pump.
BUT, how do i safely run a sufficient amount of fuel conditioner with the engine to unstick the IP internals with the engine revving like mad?

-blipping the throttle has absolutely no change on rpms, up or down.
how could i find out about this recall to get more info and determine if it is my problem?

-no one but me has touched the truck. i have done no work to the engine or ip.
i have also not touched the power screw.

 

http://www.cumminsforum.com/forum/8...rum/89-93-tech-articles/1618-possible-injection-pump-recall-information-ns.html Recall info.

Is the throttle arm going to the idle screw and staying there when it's running?

Take the AFC top off and see if the fuel pin is up? Push down on it to see if it moves free and returns up.

 

removed the AFC top and with an aluminum rod pushed down onto the cup shaped part that the bottom of the tapered diaphram-plunger unit would actuate during pressurization/activation but pushing down it is solid and it does not rebound at all - is it stuck? if so is there an easy way to unstick?

have not started truck today. i am afraid the high rpms are causing damage so i try to minimize until i have a better idea!

i have an 89 so the IP recall should not effect me. i will check numbers regardless...

 

If you pushed down on the bolt thread that is in the center of the diaphragm and it stuck then that's not good. There is a spring under the diaphragm that pushes the fuel pin up at no boost.

Take the spring out and put the pin back in and see if you can push the fuel pin down and pull it up easy.

 

sorry miscomunication - my mistake. i took out the diaphragm/shaft assembly
as well the 1" dia spring below it, all move freely up and down no obstructions.
i was referring to the steel hole (female plug) which the bottom of that plunger mechanism pushes onto, it does not move up or down.

 

Sorry I still don't follow the female plug that the plunger pushes onto part. What plunger are you talking about?

 

There is a pin that comes from the front side of the bore that should shoot out when you press the throttle when the diaphragm and fuel pin are removed.

 

fuel pin?

is there an exploded view i could reference to? found it: http://www..com/1st-generation-dodg...ion-dodge-cummins-89-93/13543-89-93-ve-pumps-rotary-pump-breakdown-diagram.html

the diaphragm/rod or plunger spring combo according to this drawing are completely hidden in the altitude compensating unit/IP cover. they slide up and down in an unobstructed manner.