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Your Old Cummins Won't Stop Running?

81K views 36 replies 25 participants last post by  Starchief_59 
#1 · (Edited)
If you recently turned up the fuel on your 89-93 Cummins and still have the stock injectors and now your engine won’t stop running when you turn off the key, this is write up will hopefully solve your problem.
The first part of this write up is the same as another write up I did, but I figured I could kill two birds with one stone and do a write up on the Fuel Shutoff Solenoid (FSS). It’s just removing the injection pump top. Maybe I’ll do a 3200RPM spring install write up as well…

First, if you own a 91.5-93 with an automatic transmission with overdrive, you’ll need to remove the three bolts holding on the throttle position sensor and move it out of the way. Then remove the throttle rod by simply popping it off. Also remove the two banjo bolts making sure to not lose the washers behind them.


Next, loosen this bolt thing and remove this plate thing. :D


STOP!! TAKE A MINUTE TO MARK, TAKE A PICTURE, OR JUST NOTE WHERE YOUR THROTTLE INDEXING IS. IT WILL SAVE YOU FIFTEEN MINUTES OF FIDDLING WITH IT LATER WHEN YOU TRY TO START YOUR TRUCK.
Lift out the plate, the plastic pieces and spring noting how it all goes together.


With a ball end allen wrench (if you don’t have one, get one. It makes life so much easier. That being said, it is possible, harder though, with a regular allen wrench.), loosen the four bolts that hold on the pump top. The fourth bolt can be a pain and is where the ball end allen comes in handy. You may have to remove the idle screw. I don’t but it’s not the stock piece anyway…


Lift the pump top off and push the throttle rod through partway. Pull it the rest of the way from the bottom so you don’t lose parts.


Now you can get to the FSS. I’m guessing there’s a special tool to remove it but I use a good ole crescent wrench at an angle. Unplug the wires and unscrew the solenoid.


Now I removed the spring and plunger quite awhile ago so I don’t really remember what it looked like before but this is what it needs to look like after. Now I’ve heard of guys sanding down the plunger or removing the rubber from the plunger all together and the FSS working again but I’ve never done it so I can’t say. I just wish I’d have heard of that before I tossed it… You can find out more information on it or replace the solenoid all together (although until you get bigger injectors to relieve the pressure in the injection pump or turn down the fuel, the solenoid will probably fail again.)


Screw the FSS back in. Tighten it as well as you can and you’ll know it’s pretty good when the spades are back in the original position.
If you don’t go the replacement FSS route, you can always install a pull cable on the manual fuel shutoff lever. I have heard of people cutting of the top of this bracket in order to get to the FSS easier but as you can tell, it’s not necessary.


Now back out the fuel screw while counting the turns so you can put it back where it was and reassemble the pump.
If I missed anything I’m sure someone will chime right in! I hope this helped someone like I’ve been helped so many times on CF! Stay Classy.

EDIT: READ THIS ENTIRE THREAD AS THERE ARE OTHER WAYS TO GO ABOUT DOING THIS. THEY ARE DESCRIBED IN OTHER POSTS THROUGHOUT THE THREAD AND THEY MAY BE HELPFUL. THERE'S MORE THAN ONE WAY TO SKIN A CAT!! :D
 
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#31 ·
If I scraped the plunger off and then installed it with the oring and left out the spring. Will this work to bypass the FSS?
 
#34 ·
I'm new to diesels so let me ask an ignorant question or two. If connecting a cable to the fuel shut off lever is used to shut the engine off. How wouldn't it shut off a run away engine? Aren't they the same thing?
 
#35 ·
A diesel engine in a runaway situation will pull fuel from anywhere it can. It may be oil from the crankcase, or fuel that is already in the atmosphere, like at an oil/gas field. You need to kill the air to the engine to shut it down.
 
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#36 ·
I guess I didn't realize a diesel can run off it's crank case oil. Still doesn't seem likely for a Cummins to me. Maybe a Detroit? Anyone here with personal experience of having a run away? Lots to learn here. Thanks,
 
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