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  #1  
Old 06-19-2011, 07:04 AM
busymountain busymountain is offline
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Default Dodge Cummins running rough: injectors, pump, other?

I have an 03 Dodge Cummins that began to lose signifigant power when accellerating. It got so bad I had to baby it to get it back home. I first thought fuel filter - changed it but now it idles really rough. I am thinking fuel supply pump. Bought the truck from a RV transporter type so it has 320k. Been running excellent prior to this.

I will check to see if it has old stock lift pump on back of fuel filter but I don't think so. I understand those only hold up at best to around 150k or so. Another thing is the fuel filter did prime when I changed it so I figure the pump must be working unless the big pump was able to pull the fuel to start it.

It is not smoking which I believe is tell tale of injector problems. Some time ago on another 03 I had the local Bosch guy explained to me that injectors can also leak? I really don't know what I am looking for.

We have a scanner though limited- is there any codes I should look for or other symptoms. I am at a loss as to what to try next. Any assistance would be great!

If it helps the truck is an 03 4x4 dually 6speed.

Last edited by stodg73; 09-21-2012 at 08:39 AM.
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Old 06-19-2011, 08:28 AM
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MnTom MnTom is offline
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Well, I guess the first thing to do is scan it for codes. Then I would want to look at the rail pressure. It may be low due to the pressure regulator failing. Try that and let us know.
I just thought of another thing to check. Pull your dipstick and see if the oil level is increasing. You may have an injector or two leaking.
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Last edited by MnTom; 06-19-2011 at 08:48 AM.
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Old 06-19-2011, 09:34 AM
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also unscrew the oil fill while its running and make sure it doesnt have a ton of blowby. The cap should stay down in the hole and float lightly. If it bobs up and down you may have a common problem in CR engines of broken rings which will cause low power. 9 out of 10 guys who bring their trucks in thinking they have injector issues actually need an engine rebuild due to broken rings. if this is the case shop around for a mechanic. A good one can rebuild your engine for less than a junkyard engine would cost...generally between 3200 and 4000 pulled, rebuilt, and installed back in it.

Good luck!
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Old 06-19-2011, 12:14 PM
busymountain busymountain is offline
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Default Thanks for the tip!

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Originally Posted by CSnyder View Post
also unscrew the oil fill while its running and make sure it doesnt have a ton of blowby. The cap should stay down in the hole and float lightly. If it bobs up and down you may have a common problem in CR engines of broken rings which will cause low power. 9 out of 10 guys who bring their trucks in thinking they have injector issues actually need an engine rebuild due to broken rings. if this is the case shop around for a mechanic. A good one can rebuild your engine for less than a junkyard engine would cost...generally between 3200 and 4000 pulled, rebuilt, and installed back in it.

Good luck!
I checked on the cap trick and it stays down. I can feel a little pressure coming from the hole but thats it. It is definatley not bobbing up and down with a lot of pressure.

So - that being the case do you like injectors or supply pump as the issue. its starts easy and does not smoke noticeably. I am wondering about the pump unless it could be some sensor or other electric. - what do you guys think?
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Old 06-19-2011, 12:23 PM
busymountain busymountain is offline
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Default leaking injector adding oil to crankcase

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Originally Posted by MnTom View Post
Well, I guess the first thing to do is scan it for codes. Then I would want to look at the rail pressure. It may be low due to the pressure regulator failing. Try that and let us know.
I just thought of another thing to check. Pull your dipstick and see if the oil level is increasing. You may have an injector or two leaking.


Thanks for your assistance here- I thought that if injectors leaked it would be hard to start, is that the case or not necessarily?

What I am getting from your comment about the truck making oil is you think that the fuel may be running into the crankcase from the injectors. I pulled the stick and it looks about right however the problem just started and I only drove it about 8 miles after the problems began so I may not notice much increase in that short period.

?A question on the rail pressure: is the rail pressure from the supply pump or after the big pump? You mentioned it may be low due to the pressure regulator failing - Sorry about the novice questions but where is the pressure regulator?
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Old 06-19-2011, 05:00 PM
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I mean rail pressure as in what the injectors see (after the CP3). However, this problem just started out of the blue? Has the truck been sitting for a while or driven daily? Been working at all (towing)? What was the fuel level in the tank and had you run it that low before? Sometimes it helps to go back and look at all things again...
Tom
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Old 06-19-2011, 11:54 PM
busymountain busymountain is offline
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Yes the problem started out of the blue - has been driving regularlly for the last 2 weeks almost daily. Has been pulling a trailer but not when condition started. The fuel level in the tank has not got below 1/4 for along time as we keep it topped off for work.

I just had a guy from the cummins forum tell me he thinks its the fuel supply pump. He also said he has seen them run without good fuel pressure to the big pump - sounds chancy to me.

What do you think Tom - supply pump or to many unknowns?
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Old 06-20-2011, 06:02 AM
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I guess if it was me, I would check the fuel pressure before the CP3 and see if the lift pump is failing or has failed. The CP3 isn't as fussy about incoming pressure like the VP44, but if it was a supply problem the truck should still idle smooth. It just may be a combination of things. Try getting your LP pressure and we can go from there.
Tom
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1996 RAM "Custom Ground" 100 plate 3/4 forward, 300 injectors, 16.5 timing, Goerends Auto = 365HP, 833TQ Third Gen Rims, Aluminum Headache Rack
Duct Tape can't fix stupid, BUT it can muffle the sound
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Old 06-20-2011, 08:13 AM
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Good to hear you dont have alot of blowby. You could make sure the FCA is good by unplugging it while its idling. If its bad it will continue running the exact same and if its good you will notice a change in engine sound. Just dont run it long with the FCA unplugged.
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