Diesel Running Rough

[djcturner]

Hello,

I have a 2002 3500 Ram. Before I state my problem allow me to mention I changed the lift pump 2 years ago. The PSI is set correctly. I just notice I had 2004 as the year, this was incorrect, sorry.

The truck is doing this.

If I floor it at take off the truck gets up to around 40 MPH and starts to act like its locked in a vacuum until I left off the pedal and apply it slowly again and its clears up.

This started about 7 months ago. Now the problem will still happen but it has progressed to where if I just take off from a light at normal driving speed and acceleration. It will start choking and shuddering between 40 and 50 MPG when the truck needs to shift. Once it shifts it stops spitting and choking.

A diesel mechanic during the summer told me he thought it might be something he called a ECV valve in the trans. I'm not sure if I got the name correct.

I drove the truck again later today and it didn't give me any trouble other than the problem if I floor it from a dead stop. I guess the problem during 40-50 MPG didn't happen because it was warmer outside. It was about 40 degrees this morning and 75 this afternoon.

Any thoughts?

Thank you.

Dave

 

[cerberusiam]

Sounds like it is starving for fuel and\or air.

Have you chnaged the filters lately? Air and fuel?

What is you LP and rail pressure pressure at idle? When it starts stumbling?

Have you checked the rail PRV to see if it is bad?

What is boost doing when this happens?

Without gauges your are trying to find Atlantis in the Atlantic, not an easy chore.

FYI, there is nothing in the transmision that will cause th enegine to defuel or choke. Those systems are totally spearate.

 

[djcturner]

Thanks for the reply

I just installed a glowstick gauge and found I wasn't running good pressure. In fact it wasn't even moving the needle. I set the PSI at 16 idle.

Sitting in the truck at idle it now runs at 16psi and when I gun the peddle it drops to around 10psi.

Then I took it out for a run and it runs great, or at least better than it has all year. I no longer have the choking problem. Shifting is good, all is good now. Turbo boost is okay, always has been. I bought a glowstick boost gauge this week to install too.

I did see that if I take off hard the PSI drops to 0 and stays there the whole time while I am flooring it hard and gaining speed. Is this normal or is the psi suppose to hold at a certain level?

Thanks again

 

[mweiman]

You should be maintaining positive pressure, there may be some opinions about it but I would say if you are dropping below 5 psi you have an issue. What are you running that you are adjusting fuel pressure?

 

[djcturner]

I dont know what you mean by asking me what I am running?

I'm in the forum under dodge cummins 5.9 engine.

I have a 2002 3500 SLT duelly. I installed a airdog FP 2 years ago. I used a GAS pressure gauge to set the pressure on the FP but I guess it was a very inaccurate Gas gauge. It has been running great until 6 months ago. My diesel mechanic told me he thought (the above stated problem) it was some kind of overdrive value ECV or something like that was going bad.

Since my posting I installed the GlowShift (not glowstick) gauge yesterday and thats when I found it wasnt even registering any PSI on it. SO I turned the setting until I started seeing the PSI go up and now everthing is running great.

The one thing in question is the pressure dropping down to 0 when I floor it and hold the pedal down to the floor. Once I let off it runs at about 8-10 PSI.

So the question is, is this normal when flooring it or taking off hard for the pressure to drop to 0 until I let off the pedal to normal driving?

 

[mweiman]

I meant what are you running for fuel lift pump which I see is an air dog. Like I said if you are dropping to 0 psi you have an issue. Are the fuel filters new?

 

[djcturner]

The LP is a Raptor FRRP 100. No the filter is not new, its black, might need to be changed. I was going to change it too. You say filter(s), there is more than 1 fuel filter? I had it changed on the last oil change.

Now that the PSI has been set to 17 at idle and even though it drops to 0 on a heavy load. To me it seems to be running great. If its not, I would love to see what its like when it runs correctly. It was my father truck until he passed away on 2009. It seems to be running the same as it did new now. I do find it amazing that if the LP wasnt running at the proper PSI for the past 2 years since the LP install. I would think, from all the postings I have read, the injector pump wouldn't be working at all.

So I mean if there is an issue how would I know since it is running good as far as I can tell?

This is mind boggling.

I have been searching on the net and I am finding so many different postings on what the PSI should be running. This is ridiculous. I seen one say it should be 10PSI at idle and drop to 7-8 PSI at load. I see some say 20 at idle and 10 at load. With all these different replies it is hard to figure out what is correct. lol

 

[djcturner]

I found this site.

http://www.bluechipdiesel.com/lift_pump_diagnostics.html

Great information there, very nice.

 

[PWong]

Assuming you are measuring the lift pump pressure after the stock filter, how about check the pressure again after replacing the stock filter with a new one to see if it drops to zero psi at WOT?

 

[djcturner]

Yes I will be doing just that today.

I just got off the phone with a rep from Geno's garage and hes telling me that the problem very well could be the sending unit its self. He suggested I pick up a needle gauge from the hardware store and try that to measure the PSI. I installed one on a 1975 CJ I owned and its was great. Its right there under the hood and can be seen while making adjustments too.