Power issue--Posted for VTCUMMINS

[ISX]

VTCUMMINS sent this to me, figured you guys could jump on it as well since I seem to be losing time available to me.

i have a 96 dodge cummins with a #100 fuel plate and the star wheel backed off. the truck doesn't want to sit an idle it just stalls, but if you keep the RPM's up it will continue to run, it also seems to have a problem driving up hills, I've changed the lift pump because i thought that might be the problem but turns out not to be, hopefully you can give me some direction....? p.s. the problem came well over a year after the fuel plate...

As for the stalling thing, you need to adjust the idle set screw. I imagine if you let off it tries to idle at 400RPM or something.

That thing should run really good up hills and since you replaced the lift pump then the overflow valve could be shot. Could also have a clogged fuel filter. Does it smoke at all? Is it an auto or 5spd? The more info you can give or symptoms you can describe, the better we can assist

[VTCUMMINS]

sry about the lack of info on the truck... yes the truck does smoke but its always a dark black fuel smoke which should be due to the fuel plate and star wheel... the truck is a 5 speed with a gear vendors over under drive running off staight diesel no bio diesel and has over 330000 miles, ive read some things on the over flow valve and the symtoms seem to be the same, the truck doesnt want to idle and will stall, it also starts hard and i would have to tap the throttle to get it to start. these symtoms came slowly and eventualy got worse till the truck became impossible to drive....

[ISX]

sry about the lack of info on the truck... yes the truck does smoke but its always a dark black fuel smoke which should be due to the fuel plate and star wheel... the truck is a 5 speed with a gear vendors over under drive running off staight diesel no bio diesel and has over 330000 miles, ive read some things on the over flow valve and the symtoms seem to be the same, the truck doesnt want to idle and will stall, it also starts hard and i would have to tap the throttle to get it to start. these symtoms came slowly and eventualy got worse till the truck became impossible to drive....

How high of RPM do you have to go to get it to not stall? Mine idles around 550-600, or between the 2 middle lines. Mine also has the issue with not starting right away if I don't step on it a little, otherwise it takes maybe 5 cranks, I changed the overflow and it didn't change a thing startingwise, still have to step on it to get it to light instantly. I am wondering if this issue can go both ways though, like you changed your lift pump but not the overflow, I changed the overflow but not the lift pump.. So maybe it will solve the issue if I changed the lift pump, but I am not sure. Fuel pressure is up to normal with the new overflow so I didn't see the need for a new LP, but I am thinking it might be a little worn so at cranking speeds it doesn't pump much, whereas yours would pump but the overflow would just be relieving it all.

[VTCUMMINS]

as soon as it starts to stall i step into the throttle and it will stay running, i dont think it takes much more to keep it running but it needs help either way..but im thinking that i should try to change that over flow valve.

[ISX]

Have you tried messing with the idle screw? Just get the truck warm and set it in between the 1000RPM line and the line below it. If it is cold and you set it in the middle of those 2 marks, it will be at 1000 when warmed up.

[VTCUMMINS]

where is the idle screw?

[ISX]

where is the idle screw?

Hmmm, give me 10 min and I will show you how to mess with it.

--- Update to the previous post...

Well they did a better job than I could since it is night here. Anyhow, on the back of the pump, pretty well straight down from where the starwheel is, you will see all the levers that pivot for fueling. On the back of the on that is directly under the starwheel is a screw that stands straight up. You loosen the locknut then start the truck and turn the top part of the screw until it is where you want the idle to be, then hold the top of the screw so it doesn't move and tighten up the locknut.

If you need more info, let me know and I will make a youtube of it tomorrow.

[VTCUMMINS]

what makes you think that the low idle screw has something to do with the issue? ive never touched it befor so im not sure how it would come out of adjustment?

[ISX]

You say it stalls unless you step on the pedal a little, if you bumped up the idle, you wouldn't have to hold the pedal since it would be idling higher.. It has nothing to do with the issue but will keep it running. You would have to hook up a fuel pressure gauge to know for sure if the overflow or fuel pump was causing the low power. There is also other concerns, do you have any gauges (Egt, boost, etc.) if so what do they read going up these hills?

[Terry C]

Check to make sure that the shut down solenoid is pulling ALL the way up. I had one here that would start OK, but not great, want to stall and not have much power. I pulled the solenoid and cleaned everything up and it ran like it was supposed to again.

[VTCUMMINS]

yah ill check the solenoid and make sure thats its comming all the way on but im not going to screw with the idle adjustment and camofloge the problem,...what should the fuel pressure be if i test it?

[Mopar1973Man]

yah ill check the solenoid and make sure thats its comming all the way on but im not going to screw with the idle adjustment and camofloge the problem,...what should the fuel pressure be if i test it?

http://mopar.mopar1973man.com/cummins/2ndgen12v/fuel-pressure/p-fuel-pressure.htm

[Zacharynels]

400 rpm is too low and is bad for your cam actually, with the low end torque the engine puts out. If it's a 5speed it should idle somewhere around 800 at idle. Maybe a little less with the AC on. Make sure that someone has not messed with the high end idle and that you are adjusting the low. Overflow valve could be bad too though. If it were me, I would hook a good tach up to it and adjust the idle or have someone who knows how do it quick. Only takes about 2 minutes with two tools to adjust it, while the truck is OFF. Also, once there is no more lope in your idle, from being turned low, listen to the truck as it idles, it should be constant if you here a lope you may have a pissed off injector. Another thing to check for, make sure that none of your fuel lines are bulging under pressure, if they are replace them so they don't collapse and clog the filter or fuel pump. Check the fuel heater pre-screen delete, repair or replace the heater element (middle section) because those will also draw air into your fuel. Obviously try replacing the fuel filter and overflow after you have checked all fuel lines and heater first. No sense in wasting money when it just might be dirty. Before you perform the fuel line and heater check run some Diesel Kleen through a tank of fuel. (I recommend only running Diesel Kleen and never put seafoam in your cummins.) And, see if that helps at all. After running the additive change out the filter and screens. If that fails sounds like overflowHope this helps