Oil and fuel mixing in ppump - Dodge Cummins Diesel Forum
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post #1 of 49 (permalink) Old 05-22-2019, 09:02 PM Thread Starter
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Oil and fuel mixing in ppump

Hi all, I recently bought a 94 2500 12 valve 5 speed manual and am having a fueling problem that I cant seem to figure out. To start off the truck seems like it has a slight misfire and will shake a little at lower rpms but will clear up once it gets past around 1500 rpm. It blows white/blue smoke sometimes at idle and while accelerating but other times there is no smoke at all. There is little to no blow by coming from the vent tubes and the coolant level/temps have remained normal. When I first started diagnosing the issue I installed a fuel pressure gauge on the side of the pump and noticed it was reading 0 psi at idle. It turned out to be the overflow valve so I replaced that and its now reading 20 psi at idle. I took the truck for a drive after I replaced the overflow valve and it was running good. It had plenty of power and acceleration was a lot smoother than before. So I thought I had fixed the issue but then when I went to drive it a couple days later it was exactly like it was before I replaced the overflow valve. Fuel pressure was still at 20 psi but it had all the same symptoms as before. I then proceeded to replace the lift pump, fuel filter and fuel pre filter. I also deleted the fuel heater and replaced a couple leaking banjo washers. Problem still remained. I then thought it had to be the pump timing so I checked the timing using the engine and pump pins and it was dead on. One thing I noticed though is that when I pulled the plug on the pump a bunch of very thick dark oil came out. When I started up the truck I'm assuming it refilled it with fresh oil which is a lot thinner than what came out. I didn't change anything except draining the old oil from the pump but the problem got a lot worse. The truck was sputtering randomly and blowing out a lot of white smoke that smelled like oil. It almost seemed like oil was being injected into the engine. Sorry for the long post but my question is, is it possible for oil to mix with fuel in the pump and be injected into the engine? Also if anyone has any idea what this could be suggestions would be greatly appreciated. Thanks

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post #2 of 49 (permalink) Old 05-22-2019, 09:13 PM
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I honestly think if it were an issue like that the fuel would be mixing with the oil and raising the oil level. I'm thinking you've dropped an Injector but I've also seen governor springs cause the engine to do weird things as well. Any pinging or knocking at idle? 12v it's kinda hard to tell haha. It just seems to me like your either dumping fuel causing a miss fire or not getting enough. When it's misfiring does the tach drop or raise? Usually a misfire will cause it to raise an injector drop would lower rpm or atleast from my experience.
Hope this helps.
If it's not a daily I'd yank injectors and send them to a shop for rebuild etc. Plus a good balance makes a nice difference.


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post #3 of 49 (permalink) Old 05-22-2019, 09:33 PM Thread Starter
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Thanks for the reply. Im hoping its an injector and not the pump because I was planning on putting new injectors in soon anyways but the main thing that has me confused is the oil smell. This is my first diesel so Im still trying to figure everything out but the smoke smells like fresh oil like if you stuck your nose in a brand new jug of oil. Is it possible that the smell is just unburnt diesel? No pinging or knocking and no major tach fluctuation. The main area I can tell the misfire is from the exhaust. The engine doesn't shake too much but the sputtering from the exhaust is loud and will puff smoke every time it sputters.
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post #4 of 49 (permalink) Old 05-22-2019, 10:00 PM
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Thanks for the reply. Im hoping its an injector and not the pump because I was planning on putting new injectors in soon anyways but the main thing that has me confused is the oil smell. This is my first diesel so Im still trying to figure everything out but the smoke smells like fresh oil like if you stuck your nose in a brand new jug of oil. Is it possible that the smell is just unburnt diesel? No pinging or knocking and no major tach fluctuation. The main area I can tell the misfire is from the exhaust. The engine doesn't shake too much but the sputtering from the exhaust is loud and will puff smoke every time it sputters.
Hey no problem, anything to help Alittle. Diesel is oil in a sense. Once it's heated by the engine and not ignited it does kinda smell like oil, it almost smells like an old dirty engine kinda smell. Hard to explain. The only way I could see oil getting in to the fuel on a p pump is through the pistons that compress the the fuel but the pressure would be so immense you'd be adding fuel to your oil for sure. Could crack ur lines at the Injectors and see if the fuel has oil in it. Should be fairly evident. The rough cold start still makes me think injectors. Luckily they're cheaper than a 24v or dirtymax.

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post #5 of 49 (permalink) Old 05-22-2019, 10:31 PM Thread Starter
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Very true one of the reasons I went with a 12 valve over a newer diesel haha May just end up pulling the injectors and inspecting them at least till I can buy new ones. I did notice what looked like oil seeping out of one of the line fittings on top of the #5 injector but I agree with you that if there was oil and fuel mixing then there should be fuel in the oil which it doesn't really seem like there is. I did add some power service diesel kleen to the tank before I did checked the timing and the problem got worse so that might have something to do with it. I also noticed when I did the lift pump that it had red diesel the fuel bowl for the pre filter which from what I understand is off road diesel. I have filled up the truck twice since Ive owned it both at big chain gas stations so I thought that was kind of weird.
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post #6 of 49 (permalink) Old 05-22-2019, 10:40 PM
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Yeah farm diesel is not bad as long as filters are regularly changed. I ran that in my diesel lots as it's much cheaper. Shh

I can't see the power kleen doing anything but making you smoke more as it's cleaning stuff. When I add Lucas to mine it smokes like crazy. Now low to mid range power? When I first got mine I had a boost line broken the one that goes between 4-5 valve cover its steel and that cause a bit of issues can't see it causing what urs is doing but something to keep in mind as well. You're going bigger Injectors what are you doing for air? I've got the bd big single and love that thing!

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post #7 of 49 (permalink) Old 05-22-2019, 11:05 PM Thread Starter
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I want to go with a bigger turbo but unfortunately my next priority is fixing the infamous nv4500 3rd gear grind. Also the previous owner bolted on an hy35 for god knows what reason so I was probably just going to go with some slightly bigger injectors for right now so it doesn't get too hot. Do you have any injector brands you would recommend? I was looking at the industrial injection oe bosch 300hp ones.
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post #8 of 49 (permalink) Old 05-22-2019, 11:12 PM
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Industrial injection is the way to go. If I wasn't so far in the boondocks I'd get my injectors built and balanced by a local shop and have them put 100% over nozzles in. If Ur like me right now drop ins are your best bet. If your going with 300s I'd dial the fuel pump wayyy back. Especially if you're fighting heat now. Diesel is opposite of gas. More fuel = more heat less fuel in most cases is less heat. This makes me suspect injector(s) are a culprit if your fighting heat. But a hx30 is pretty small for any performance. Not saying it's doable but the turbo effeciency map is something like 33psi anything over just makes heat and kills performance and thee volume is mid range. If you have the 4500 apart do the 5th gear mod, the nut likes to come loose and it goes south fast from there. Also look into killer dowel pin fix definately don't want that happening either!

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post #9 of 49 (permalink) Old 05-22-2019, 11:29 PM Thread Starter
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Coolant temps seem fine but I really need to install an egt gauge. I do like the instant spool of the hy35 but by 2000 rpm power just falls off. I will definitely look into the 5th gear mod. The killer dowel pin fix was actually the first mod I did to the truck. Good thing too because it was already a few millimeters out!
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post #10 of 49 (permalink) Old 05-22-2019, 11:33 PM
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Anyone who has idle quality issues, sputtering, white smoke from a 94 or early 95 160/175 pump I always inform them that it's a possibility the IP is developing warped barrels.

It sounds like you've dine your fuel pressure checks. 20psi at idle is good. The only other thing to check for is any air leaks from the suction side of the lift pump.

Otherwise, the last confirming test of an issue with the IP itself is to run some cold water over it when it starts to act up. If it clears its time to look for a replacement.

Oil from the pin nut cover is normal.

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91.0 D250 A727 w/ 216k on the clock. i/p replaced 20k ago, lift pump 2k, 1 turn fuel, 2 turns smoke, ground & polished AFC pin, timing bump, 366 spring 94 2500 4x4, 49k miles, Farrell Diesel rebuilt 215 pump, PDD 5x12 SAC, SXE 362, built 47RH
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post #11 of 49 (permalink) Old 05-22-2019, 11:35 PM
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Originally Posted by Dieseldave94 View Post
Coolant temps seem fine but I really need to install an egt gauge. I do like the instant spool of the hy35 but by 2000 rpm power just falls off. I will definitely look into the 5th gear mod. The killer dowel pin fix was actually the first mod I did to the truck. Good thing too because it was already a few millimeters out!
I thought u had an egt already. That speaks volumes having that.

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post #12 of 49 (permalink) Old 05-22-2019, 11:54 PM Thread Starter
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Thanks I will try that. Before the problem got worse it would start blowing smoke around 10 seconds after first start up. It would start it up and it would be clear with no smoke and then it was almost like a switch was flipped and it would start smoking. Now it seems to start smoking right away.
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