I have had this truck for 3 yrs with a #10 fuel plate and a longer weaker afc spring. The truck has always started easy and idled at 800 rpm. Recently I have added some mods. First was a turbo and 4" exaust, ddp 75 horse injectors, fuel sump and new fuel lines, two weeks ago I put in 4K gsk. Everything seemed fine until today, I ran the truck hard thru the first 3 gears, had to stop for the next light, the truck died. I cranked like usual with no throttle - no start, gave some throttle while cranking started right up. made it home truck seemed to ok but will not idle. Can any one give some advice what to start looking for, Thanks.

 

Stuck or sticking Fuel Cut-Off Valve? I am not a DD expert just have one.
Maybe some others will add suggestions.

 

Sounds like your idle stop is out of adjustment. 10mm loosen lock nut and turn screw in half turn or so then tighten lock nut start up engine and check rpm. Should be 750rpm in gear with ac on. Read TSB


NO: 18-07-98
SUBJECT: Effects Of Incorrect Idle Speed
DATE: Feb. 27, 1998
NOTE: THIS INFORMATION APPLIES TO THE 5.9L CUMMINS MECHANICALLY INJECTED 12 VALVE DIESEL.

DISCUSSION:
Incorrect idle adjustments (either too high or low) may cause many different customer concerns. Following is a list of items that explain the condition/symptoms associated with incorrect idle settings along with component checks and specifications to set it properly.

RPM BELOW SPECIFICATION
Hard Starting/Stalling during cold engine operation.
Engine roughness at idle.
Reduction in the amount of vacuum available during idle from vacuum pump.
Delayed power steering assist when cold.
Excess seat shake and/or mirror vibration.
RPM ABOVE SPECIFICATION
Excess creep at stoplights/signs.
Vehicle does not reduce speed with foot off throttle.
Typically low idle speed is caused by a misadjusted low idle speed screw on the injection pump but high idle speeds can be caused by many items. The following list will help in diagnosing high idle concerns:

CAUSE REPAIR
Idle speed misadjusted Adjust low idle screw on injection pump
Misadjusted throttle/cruise control cable Adjust cables
Throttle linkage binding Clean and lubricate ball connections
Bent throttle rod Replace rod
Broken return springs Replace springs
Throttle/cruise control cable damaged Replace cable


The idle speed specifications for 1994 to 1998 models are 750 to 800 RPM. All idle speed measurements must be taken as follows:

Automatic Transmission In drive with A/C switched on
Manual Transmission In neutral with A/C switched on


When making idle speed adjustments, always use a DRB III, or an optical tachometer such as Cummins 3377462, Snap On MT139 or equivalent to read engine idle RPM.

NOTE: DO NOT USE THE TACHOMETER IN THE INSTRUMENT CLUSTER TO SET OR VERIFY IDLE SPEEDS. THIS TACHOMETER IS NOT ACCURATE FOR READING OR SETTING LOW RPM DURING IDLE CONDITIONS.

 

Thanks for the suggestions, I was hoping it was something easy, I checked linkage , idle screw,fuel pressure, new fuel filter, I'm thinkin it might be some failure in the pump due to the 4k gov springs. I did check the gov springs, and they were still where I set them, maybe time to get that pump to the injection shop.

 

What year truck?

 

It is a 98 dually, 5 speed rwd

 

I dunno, I would personally re-check the gov. spring holders make sure they are at the right tension... maybe back them each off one click and adjust idle. Also make sure the shut down solenoid is holding all the way up, it can hang up and make for a rough idle/low power.

 

No problem with the pump, it's the GSK adjustment.

 

I will back off the gov springs a click and see what happens, the fuel shut off is working full stroke and remains up after it dies, I left the key on and looked. It is odd that it idled exactly the same right after the gov spring change and worked for a few weeks and suddenly went bad. I set the idle screw up so I could keep it running and check fuel pressure, temp gage under the hood. It revs like a common rail truck, revs up quickly and back down slow. Any load with no throttle will kill the motor. Sure don't want to take pump out unless have to. Thanks

 

Wouldn't hurt to check fuel pressure.
http://www.cumminsforum.com/forum/94...-12-valve.html

 

I ended up backing the nuts up 3 clicks each, the tops of both nuts are flush with the tops of the studs.The truck will now idle the a/c doesn't drag the motor down, but I have to give some throttle when I release the clutch or it will kill it. I have to give a little throttle when starting. The truck runs great and is now drivable. Is this typical of the 4K springs? I did check fuel pressure today it was 22psi at 850 rpm and around 28 psi when reved, checked at pump inlet, I have a temporary gage and fitting just for checking. Many Thanks for the good advice, Vince

 

How many clicks do you have on the springs?

 

I'm not sure how many clicks I have left. I did not remove the nuts today. Should I check to see? How many should there be?

 

I think at this point you should turn the idle up.

 

I think so too. Thanks