I just replaced my lift pump. Installed 80 HP injectors. New over flow valve and a new ATS manifold. Truck runs good in the upper rpms. But my truck idles rough.. And when I take off from a dead stop I have to give it more pedal than normal. Seems to be under fueled when I take off and also when the truck comes to a stop. I had the same idle issues before I installed all the new parts. So it seems like it could only be the Injection pump or bad rubber fuel lines? Any thoughts or suggestions?

 

The most frequent cause of bad idle is low timing. When the P pump fails you lose power at the upper rpm ranges first. Since it is still handling the new injectors and running good in the upper rpm range, that just reinforces the timing issue.

It is possibly bad fuel lines, or even a leak at the fuel heater. However, when those things start causing bad idle the rig is generally a real bear to start too.

Another thing to check is the lift adjustment on the fuel shutoff solenoid lever. Sometimes when they are swung to the side to replace the fuel plate they get slightly bent and will hold the follower from fully opening. Another item could be the follower on the actuation arm is running under the AFC stop and jambing it a bit at low rpm, a quick adjustment will fix that.

 

Tell me more about this? I have had a few issues with the AFC screw being a little tough to srew forward. I looked at the AFC housing put did not see anything unusual?

Also I had my local Cummings shop replace the lift pump for me. The service manager said that he had never heard a Dodge idle like mine. The mechanic that fixed my truck said it screamed at the high end. But did not think it was a timing issue. My rough idle get worse then gets better. But never is perfect. Truck has a noticible shake at idle. And the old "just let the clutch out" and the truck will take off from a dead stop is no longer. I have to give it some pedal because of the poor idle.
Thanks....

Dave

 

There's your problem. You need to find a Cummins mechanic. Cummings is owned by Ford

 

hey WCI,
dont mean to hijack your thread, but your truck is still lookin good w/ the black wheels/tires. i finally got mine on a few weeks ago. i'll try to get some pics on here soon.

l8r.

 

Rodeo thanks for the compliments. At this point I would take running good over looking good....

Dave

 

You don't list what year your truck is in your sig. That would help a lot in diagnosing your problem, if we knew what we are talkin about.
Nice lookin truck by the way.

 

Sorry Scott, I thought my year was in my sig. Fixed now, 94. My truck is surging/choking when I take off. And it idles rough. And now it seems as though it is a little rough through out the entire RPM range. It defenitely has a fuel problem.

New 80 HP injectors. New overflow valve. And new lift pump. Did the same surging and bad idle before I installed the new injectors, overflow vavle and lift pump.

So I am thinking bad rubber fuel line/connectors or bad injection pump.....

Dave

 

Here is a video of my truck idleing. Can you notice the rough idle?

http://www.proworkz.com/dodge.wmv

Dave

 

So I have now replaced my rubber fuel lines and my truck is still idleing bad and running rough. I have been told by several DTR members that it could be a simple timing slip. But my local Cummins shop told me that timing rarely slips on 94's? I do not want to keep dumping money into my truck and finding out that I have just replaced a perfectly good working part...

So I will refresh my scenario....

Truck started idleing rough one day..... around 550. I installed 80 HP injectors and it did not change anything. Changed overflow valve. Had local Cummins install a new lift pump. No change.... But fuel pressure was at specs after new lift pump.

Then I changed the rubber fuel lines. No change. I even droped my new rubber fuel line in a 5 gallon bucket to see if I had a issue from the rear of the tank. No change in idle.

And other then the idle the truck has lost some power. I can no longer just let the clutch and and go. I have to stay on the go pedal to get the truck to run smooth from a stop. And once moving the truck seems like it is surging or running on 5 cylinders. I also checked the temp of my exhaust manifold at each cylinder with a heat gun and they where all with 15 degrees of each other at idle. So I figured that would rule out a dead cylinder.

Thanks guys..... I am at a lost .....

 

Recheck filters, if new then I would think about an injector sticking. Pretty easy to have pop tested and cleaned if necessary. You may have knocked some crud loose when you put them in. It's all too easy to do. Just a thought.

Paul

 

dave, where on the west coast are you?

 

your valves adjusted? what are u idling at? 700-800? or are u still idling at 500? air filter decent?

my truck had made aterrible racket kinda like yours at idle and would get better as i increased rpms and it was loose TC bolts...but u dont have that since u have a manual...

 

this might be really stupid but have u fully inspected ur fuel shut-off solenoid? maybe its in need of an adjustment and kinda hangs around at idle not allowing u full fueling...maybe the wire running to and from it is corroded or not properly connected...it will cost u nothing

ps on colder mornings when u start ur truck does it snap crackle and pop for a few seconds and puffl white smoke and then settle down? if so a timing bump will will get rid of that completely...i used to have that with mine...now its smooth as butter even in buffalo winter

 

Im no mechanic by all means, but it sounds like its doing exactly what mine was doing and i changed my fuel filter and it runs better now than it ever has.