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
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.
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.
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.
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. [emoji6] 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!
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.
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!
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!
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.
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.
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.
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.
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.
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.
Sounds like your troubleshooting well. You've eliminated a possible air leak... Good.
Fuel pressure sounds like it is in check. You tried the pinch the return line method to make sure the lift pump is good?
The next thing I would do is look for any evidence the pump has been worked on. Look at the DV holders and see if they've been turned. Look at the governor spring cap. It should still have the safety wire across it.
Did you verify timing is correct? FSM states the drop valve method. Pin timing should get you close enough.
Pinched the return line and the pressure spikes so I think the lift pump is good. Checked timing using the pin method and it was dead on. The safety wire is still across the governor spring cap on the ip. Ill have to take a closer look at the dv holders to see if they have been turned but one thing I noticed is the hex plug on the front of the pump is stripped out. The only reason that it would be removed as far as I can tell is for a dual feed setup but could there be any other reasons?
Yeah not leaking from there it looks like someone tried to remove it but was unsucessfull. I took a look at the dv holders today and it doesnt seem like they have been messed with. What should I look for to verify that they have been turned?
These pumps were painted after they were mounted on the engine and the engine was pained as a full assembly. If they were messed with you'll see a witness mark of unpainted aluminum where the DV holders was moved away from the paint line.
So I pulled the injectors today and did a compression test. I know its not the most accurate way to test for low compression on these motors but the cylinders were all 350-360 so I at least know I dont have a dead cylinder. I was just going to have the injectors tested and possibly rebuilt if one was bad but since the truck has 250,000 on it I figure I might as well replace them with new ones. Does anyone have any recommendations for companies to buy injectors from?
If Rock Auto doesn't have them, check Summit Racing. When I replaced mine, Rock Auto only had 5 - Summit was the next cheapest I could find, so I got the 6th one from them. Though a little more than Rock Auto, Summit was still cheaper than getting one rebuilt by the Bosch pump shop I went to. That was nearly two years ago - so things may have changed since, but still worth checking into.
So I replaced the injectors and the issue is still there. Its definitely not smoking as much but still sounds like it has a slight misfire and has a bad vibration around 1100 rpm. At this point I think it has to be either a burnt valve or something with the injection pump. Would a burnt valve cause a significant difference in readings on a compression test? Im leaning more towards the pump because when I bought the truck the overflow valve was bad and it was running 0 psi. Im not sure how long it was running like that so I think it may have damaged the pump. Anyone have any recommendations for shops to have a pump rebuilt or buy a reman one from?
Unlike the VP44, running with 0 pressure won't damage a p-pump. Have you done a search and read the symptoms other members have had with their '94 pumps?
Ok at least thats good to know. Did a search but none of the symptoms I have seem to exactly match other members. It seems like in most cases ive read the truck will have a hard time starting or the problem will come and go but with mine it seems to be constant and it starts up fine every time.
So I have fuel pressure gauge but never really could read it properly because it was bouncing around a lot due to not having a needle valve. Today I installed a needle valve and noticed the pressure is at 20 psi at idle but never really rises above that. It would actually drop by as much as 5 psi when increasing rpm. When I let off the throttle it will spike back up to a little over 20 and then rest at 20 again. I recently replaced the lift pump with a dcec cummins one and when I pinch the return line the pressure goes up to about 40 psi. So at this point im think maybe there is a restriction in flow like a clogged draw tube in the tank. Im going to test it later by running a hose directly from a jug of diesel to the lift pump but is there anything else that would cause dropping fuel pressure?
This doesn't make a lot of sense to me. My stock OFV ran at 10psi and the truck started/ drove fine with none of the issues you're seeing (the only benefit I saw replacing the OFV and setting it at 28psi is a possible increase in power, but that may be just in my head idk). Also if it was a suction restriction like a clogged draw tube, wouldn't the issue be more present at high RPM / under heavy load when fuel demand is higher, not at idle and 1100 RPM like you're seeing?
I think if you have positive pressure to the injection pump (which you do) and no air leaks (which you've verified with the clear hose) that your low pressure fuel system is not the cause and start looking other places.
So I finally made some progress on diagnosing the issue. Put a new fuel pressure gauge on and saw it was reading about 27 psi at idle so I know the fuel pressure is good. Decided to turn up the fuel pressure with the tork tek ofv and see if the issue got better. Turned it in all the way and the pressure only rose to about 30 psi at idle but the issue got a lot worse. Random misfire out of the exhaust and lots of white/light blue smoke. Since it was doing it constantly I was able to narrow the issue down to cylinder 1 by cracking the injector lines. When I cracked number 1 the smoke almost completely dissapeared and when I tightened it again it came back. Since I just changed the injectors and the issue remained the same im now looking at the injection pump. Im thinking either a sticking delivery valve or warped barrel. One thing to note is when I free rev the engine the fuel pressure will rise but then drop 5-10 psi after a second and then rise again. What do you guys think, throw in some delivery valves or remove the pump and send it to a shop?
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