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Discussion Starter #1
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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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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Discussion Starter #3
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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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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Discussion Starter #5
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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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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Discussion Starter #7
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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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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Discussion Starter #9
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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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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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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Discussion Starter #12
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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I've never seen so many wrong theories and misinformation typed into one thread before. Where do I start?

The oil in the p-pump is constantly being changed while the engine is running. It isn't separate from the engine oil, it is the engine oil.

Pin timing is only good for getting the engine started. The cam timing pin is adjustable, so if you want to find TDC I suggest you perform the procedure in the factory service manual. We refer to it as the drop valve method.

Throwing parts at a problem wastes money. There is a very good fuel system write up in the beginners thread. https://www.cumminsforum.com/forum/94-98-powertrain/287781-beginners-thread-read-first.html
https://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html
I suggest you read both.

Red diesel is exactly the same as normal ULSD, it has dye in it so the tax man can see if you are cheating the gov't. You might be seeing the result of some moron putting ATF into the fuel. There are those who think it is an injection cleaner/fuel lubricant. It is neither and over time will damage an engine. If the PO used it a lot you might be seeing the results.

Forget the 300HP or 100% over designation for injectors. The size is written by number of holes and hole size i.e. 5X12 300 HP is a meaningless term.

If 5th gear come of you have a 4 speed. It is something to address if the transmission is apart, but not something to worry about. The only true fix is a fully splined shaft and gear assy. All the other "fixes"are temporary.

Pay attention to what hemirunner426 said. Warped barrels has been addressed in many threads.
 
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GAmes is correct as far as red dyed offroad diesel is concerned.

It has been the same as 15ppm ULSD pump diesel these past few years.

The only diesel with a higher sulfur content these days is locomotive diesel; marine diesel went the ULSD route not too long ago.

I'm waiting for when 2 stroke oil gets added to the recommendations in this thread.:doh:
 

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Discussion Starter #16
I've never seen so many wrong theories and misinformation typed into one thread before. Where do I start?

The oil in the p-pump is constantly being changed while the engine is running. It isn't separate from the engine oil, it is the engine oil.

Pin timing is only good for getting the engine started. The cam timing pin is adjustable, so if you want to find TDC I suggest you perform the procedure in the factory service manual. We refer to it as the drop valve method.

Throwing parts at a problem wastes money. There is a very good fuel system write up in the beginners thread. https://www.cumminsforum.com/forum/94-98-powertrain/287781-beginners-thread-read-first.html
https://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html
I suggest you read both.

Red diesel is exactly the same as normal ULSD, it has dye in it so the tax man can see if you are cheating the gov't. You might be seeing the result of some moron putting ATF into the fuel. There are those who think it is an injection cleaner/fuel lubricant. It is neither and over time will damage an engine. If the PO used it a lot you might be seeing the results.

Forget the 300HP or 100% over designation for injectors. The size is written by number of holes and hole size i.e. 5X12 300 HP is a meaningless term.

If 5th gear come of you have a 4 speed. It is something to address if the transmission is apart, but not something to worry about. The only true fix is a fully splined shaft and gear assy. All the other "fixes"are temporary.

Pay attention to what hemirunner426 said. Warped barrels has been addressed in many threads.
Thanks for the info. I understand the oil in the ppump is engine oil but I just did an oil change recently and the oil that came out of the pump looked like it was 5 years old. Im not sure if the oil in there was not mixing with fresh oil or what but It was a lot darker than what was on the dipstick. I really hope the previous owner didnt put atf in the tank but I may drain it just to be safe since it seems like the truck was sitting for awhile before I bought it. I'll look back for threads on warped barrels too.
 

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Thanks for the info. I understand the oil in the ppump is engine oil but I just did an oil change recently and the oil that came out of the pump looked like it was 5 years old. Im not sure if the oil in there was not mixing with fresh oil or what but It was a lot darker than what was on the dipstick. I really hope the previous owner didnt put atf in the tank but I may drain it just to be safe since it seems like the truck was sitting for awhile before I bought it. I'll look back for threads on warped barrels too.
It is only your perception that the oil is darker. There is a constant flow of oil through the p-pump.

If it has been sitting a long time I believe it is a good idea to drain the tank. Putting good fuel on top of contaminated fuel (if it is contaminated) only makes the engine run poorly longer, and also clogs filters.
 

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Discussion Starter #19
Yeah I think im definitely going to drain the tank next. I have a feeling the previous owner ran into fueling issues because of the worn out overflow valve and dumped something in the tank to try and fix it. If it doesnt fix it at least I will know its clean when I eventually get injectors.
 

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Discussion Starter #20
So update on the truck; I drained the tank best I could without removing it and filled it with fresh diesel. Still had the same problem. I then thought there might be air getting in the fuel so I bought the clear fuel hose that goes from the filter housing to the injection pump from larryb's. Installed it and there are no air bubbles whatsoever. I tried pinpointing which cylinder was causing the misfire by cracking the injector lines but they all seem to change the idle about the same. There is only a very minor difference that I can tell. So now im looking at either the injection pump or the injectors. Im leaning more towards the pump but could it be anythin else? The truck starts right up every time and has decent power. The main problems are loping at idle, hesitation around 1100 rpm and blowing white smoke.
 
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