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Discussion Starter #1
Ok so I have only ever owned Fords (7.3, 6.0 PS) but I decided I wanted a cummins and found a great deal on a 2004 HO ram 3500 nv5600 I am suffering from a loss in fuel pressure and long cranks and barely starting (if it even starts). Here’s the run down of what I checked/replace (Fuel filter and water separator on the air dog, made sure the pump was running and good flow, high pressure relief valve, back of the head banjo bolt, check the fuel lines, new cp3). Basically what’s happening is the pump will kick on and the pressure gauge will go to 15-16psi then then slowly drop or drop fast if I try and start the truck. When the truck runs it runs great and smooth. Any help would be appreciated and if you need anymore info let me know like I said I’m new to cummins haha
 

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:welcome:
Do you have a way to monitor rail psi while starting?
If the lift pump is losing psi when cranking, 1st guess is a problem with the LP itself.
Is LP still getting 12v when cranking?
Do you still have the OEM underhood fuel filter?
 

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Discussion Starter #3
Yes oem filter housing and filter is still there. I don’t have a way of checking rail pressure when cranking And I am going to have to check the voltage on the lift pump when cranking I do notice when I get it started at idle I hear a slight chirping sound (I don’t have a better term for it) I’m not sure what a downed injector would sound like but the truck runs great
 

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Discussion Starter #4
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Do you have a way to monitor rail psi while starting?
If the lift pump is losing psi when cranking, 1st guess is a problem with the LP itself.
Is LP still getting 12v when cranking?
Do you still have the OEM underhood fuel filter?

Also when the truck is running I seems to have 0 pressure on the gauge. I forgot to metion
 

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You should have minimum 9-10 psi from
LP at idle.
 

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At cruise speed, you should still have anywhere from 6-9 psi and at WOT 3 psi or more.


Looking more like the LP is .crapped. out or bad wiring or ECM power to LP. You could wire in a relay to power 12v straight to LP with key on
 

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Discussion Starter #8
At cruise speed, you should still have anywhere from 6-9 psi and at WOT 3 psi or more.


Looking more like the LP is .crapped. out or bad wiring or ECM power to LP. You could wire in a relay to power 12v straight to LP with key on
Ok with the weekend here I am gonna try and tackle it and see what I can do Thanks for the help
 

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Also I would ,
Check for codes??
Any smoke ??
fuel in oil??
why new CP3??
make sure good batteries 12.6+ volts and their connections are good, need 150 rpm to get compression to start properly.
check function of belt/ac compressor /alternator/power steering/water pump and/or fan all which can effect cranking
If good, try plug in truck to block heater, if starts easier hate to tell you, injectors are most common issue, perform cap /return test to verify.
Buy only NEW Bosch or BBI injectors and new connector tubes, if replacing to avoid reman injector issues.:wink2:
 

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Discussion Starter #10
Also I would ,
Check for codes??
Any smoke ??
fuel in oil??
why new CP3??
make sure good batteries 12.6+ volts and their connections are good, need 150 rpm to get compression to start properly.
check function of belt/ac compressor /alternator/power steering/water pump and/or fan all which can effect cranking
If good, try plug in truck to block heater, if starts easier hate to tell you, injectors are most common issue, perform cap /return test to verify.
Buy only NEW Bosch or BBI injectors and new connector tubes, if replacing to avoid reman injector issues.<img src="http://www.cumminsforum.com/forum/images/CumminsForum_2016/smilies/tango_face_wink.png" border="0" alt="" title="Wink" class="inlineimg" />
I’ll go out and see what codes are thrown. The dealer I bought it from did the cp3 right before I bought it then I believe them kinda just gave up on trying to fix the issue. I’ll get back to you with the codes and I’ll double check everything you mentioned
 

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Discussion Starter #11
Just wanted to let you guys know I found out the problem. Was driving down the street and it started running weird. Pulled over and all I saw was white smoke. And wasn’t running right so I’m gonna be putting injectors in. But thank you for everyone’s help
 

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Discussion Starter #13
Should check compression, could be more issues then you think<img src="http://www.cumminsforum.com/forum/images/CumminsForum_2016/smilies/tango_face_wink.png" border="0" alt="" title="Wink" class="inlineimg" />
Yea that’s what I’m afraid of. I checked for blowby and there is none so I’m hoping there no hole in my piston
 

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Discussion Starter #14
Also would a hole in the piston cause diesel to trickle into the oil? Cause I don’t smell diesel in the oil. Also there is no blowby so I’m not sure a hole would cause that either?
 

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Very hard/almost impossible to melt thru Cummins piston tops, are meant to hold 17.2 to 1 compression.
Diesel usually gets in oil from cracked injector body or really leaky injector ie fuel out exhaust manifold.
Best to send out proper oil sample if any doubts.
Depend how hot it got, usually rings crack first cause issues, should check compression if low and you have a true SO/HO then leak down for valve/seat issues.
 

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Discussion Starter #16
Very hard/almost impossible to melt thru Cummins piston tops are meant to hold 17.2 to 1 compression.
Diesel usually gets in oil from cracked injector body or really leaky injector ie fuel out exhaust manifold.
Best to send out oil proper oil sample if any doubts.
Depend how hot it got, usually rings crack first cause issues, should check compression if low and you have a true SO/HO then leak down for valve/seat issues.
Thanks I am gonna look Into getting the test done just to be sure
 

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Discussion Starter #17
Ok guys. Replaced the injectors. I fixed the starting issue. Fires right up. But I still have a misfire and white smoke Any ideas? There is no blowby or any sign of engine damaged (knocks or sounds) Any help would be appreciated
 

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What injectors did you get? new crossover tubes?
 

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Discussion Starter #19
What injectors did you get? new crossover tubes?
I had an engine builder that has a shop in my town that had a set of stock injectors that he used for an engine but only put 1000 miles before he upgraded (but they came out fine and running). It was the only option I could afford as I can’t have this truck down for long periods of time and I didn’t have the money with these hard times. But i did use new cross over tubes and made sure all torque specs were done properly
 

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ECM controls fueling, Check for codes?
Perform compression test?

I would cap off individual injector, find dead cylinder, then swap injectors to see if injector or cylinder issue,
keeping in mind the more you run it the more damage you could be doing. :wink2:
 
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