Engine Idle

[BTanzini]

I have noticed for several thousand miles now that the idle of the my 1996(cummins 5. 9)when I start it up cold it idles at about 400-500 rpm,as it warms up the idle picks up to about 700 rpm and the throttle response is very poor. Every now and then it will start and idle imediatly at 900 rpm like it did when it was new untill about 45,000 miles when i noticed a substantial decrease in performance,I had it checked out by Chapmans Dodge in Vegas and they said everything was fine. Yesterday I started it up and it idled and performed like it did when it was new for about 60 miles then the idle droped down to about 700 rpm. I'm looking for anyone who might be able to help with my problem. Cat is gutted so I ruled that out. I am not having any problems with any sensors that I know of. Any help will be appreiciated. Thanks in advance.

 

[Macmc01]

Just a shot in the dark... Have you checked your fuel pressure before and aft the fuel filter? If it is low on both inlet and aft it could be the overflow valve or fuel pump. If there is over 5 lbs drop between the two it would be the fuel filter.

Mac

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95 Ram 2500 Auto Std Cab, Cat & Muffler Fell off, New Guages, 130,000 miles.
Bombing Moved Plate & AFC all the way. New 215 injectors.
SMOKE IS GOOD!

 

[Joe G.]

Bill,

Check your fuel return/overflow valve. It sounds like it's shot. Might be the lift pump, but most likely the valve.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,DTT TC/VB,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver

 

[Cooker]

Mine does the same thing when cold. Starts and idles at ~500 then picks up to ~800. I don't notice any other negative problems though.

IMO 900rpm idle is a bit high. I think 750rpm is a bit better and I will be adjusting mine down a bit as well.

I agree with the others. When was the last you replaced the fuel filter? How about air filter?

Check your fuel pressure. If it is out of specs then the overflow valve may be bad and that will affect driveability.

My $. 02
-Ryan

 

['956Wheel]

Mine did the EXACT same thing! When I pulled out the overflow valve the spring was broke. Get a hold of Piers he has them for a LOT less than DC or Cummins... ... wish I knew. My guess is you wind up siphoning fuel back to the tank and a little air gets in the system, runs lousy for a bit till the air gets out.

Mines a '95, same stuff.

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9535hundred

[This message has been edited by Statland (edited 05-06-2001). ]

 

[BTanzini]

Thanks for your replys. RCMC,have not checked fuel pressure,do not have gauge or fittings. Goe G. have not checked overflow valve yet,but will check. Cooker,filter and air filter are all good. Statland,will check overflow valve,may take a few days untill I get a new spring so I can replace if bad. Thanks to all.

 

[BTanzini]

OK guys I checked the injection pump overflow valve and it seems good,spring is intact and is with in specks. Any other ideas other then the lift pump?

 

[HomerDog]

Bill,
Just a guess but I just had a lot of problems with my idle and it was due to an improperly lubed/adjusted throttle cable. It would idle fine at first start but would then be high after driving it awhile. Could also possibly be a streched throttle cable...

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'96 3500 Dually, Black, 4 inch exhaust (no Kitty), chrome kit, Rancho 9000 shocks, '00 Lance camper

 

[BTanzini]

HomerDog,I replaced my throttle cable about 15,000 miles ago,almost a year now and I adjusted the throttle linkage at the same time but I will check again. Thanks for your suggestion.

 

[Joe G.]

Bill,

There are a couple more things to check. Have you lubed the throttle rod ends? There are two screws that fasten the throttle linkage lever to the lever on the pump. They may be loose. It requires an 8mm wrench to tighten them.

Have you checked the coil spring from the pump lever to the block to see what kind of shape it's in?

[This message has been edited by Joe G. (edited 05-13-2001). ]

 

[LarryB]

Next time it idles up where it is supposed to, pop the hood and push and wiggle the linkage around the pump. If the idle drops then you have something hanging up and the idle set too low. Probably not a fuel pressure problem.

You may also try setting the idle up next time it idles too low. If it then decides to ocasionally idle even higher than it probably in not linkage and may be a fuel pressure problem.

My . 02 into the pot.
Larry

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1972 Chinook class C with 96/215 5spd, 4/5" exh, 4"BD, MagHytec, 85gal fuel, K&N RE0880, AutoMeter, 370's, BD gov kit, BD afc kit, 16cm, 16%btdc, yada-yada-yada
www.fostertruck.com/cummins