Runs rough when warm, mixing diesel and oil

[CodyBeasom]

Hey all, 

First time posting on the forum, but have used it in the past to fix some of my other trucks issues, some great information on here. 

 

I’ve got a problem with my 1998.5, 2500, 4x4, nv4500, 263k miles. Truck is stock with no aftermarket performance mods, and it is unfortunately a 53 block. I bought the truck recently as a back up for my 1997 7.3 as it just ticked over 500k miles and is gonna need a rebuild soon.  

 

Three weeks after I bought the truck it began giving me hard starts only after it reached operating temp. I falsely diagnosed this as a fried vp44 pump, given the fact that it still had a factory style lift pump, so I put a reman industrial injection pump on it, a fass drp lift pump, big line kit and a mechanical fuel pressure gauge on the truck. Did not fix the issue. After installing the pumps, I changed my oil and found an extra 1-2 qts of diesel in it as well. So, I bought a set of rv275 hp injectors(only aftermarket performance mod truck has), and crossover tubes.

 

Truck would fire up and idle just fine when it was cold, but began to idle rough when it warmed up, also the rpms would bounce from about 900 to 600 back and forth only going down the road when you popped it out of gear and into neutral like if you were gonna coast to a stop. This got progressively worse to the point where taking your foot out of the throttle from any rpm and shifting to neutral would stall the truck. 

 

Got a opinion from a friend who is a diesel mechanic, and he said the hard starts were because of a fried ecm, and the running issues were injector related. Got another ecm and it solved the hard start issue. Still had the same running problems though. I figured I made a mistake when installing the injectors and tubes, and removed them, cleaned them, checked the nozzles, put new orings and copper washers on them and the crossover tubes, reinstalled. Torqued the injection lines first, then injector hold down bolts second. 89 inch lbs. Drove the truck around yesterday and today. Same result, truck still idles rough only once it’s gotten warm, rpm will bounce when going from a load to neutral, and attempts or sometimes manages to stall when going from a load to neutral. Also still getting diesel in my oil. No visible diesel leaks anywhere either. Tried to torque the injectors again thinking maybe they might gotten loose through a couple heat cycles, and it made one difference. Starts up in a bump, and doesn’t smoke excessively on start up or going down the road aside from a little puff of black smoke when shifting into the next gear, but I believe that’s normal. 

 

To my knowledge there’s really only three likely places on 24 valves to mix fluids. Injector body cracked, injector seals, and front shaft seal on vp44 which seems pretty uncommon. If that doesn’t change anything I might have to pull the injectors again and have them tested just to rule that out. I’ve replaced injectors on these trucks before with no issues, so I’m not sure what I’ve managed to miss twice. I’m also not sure how to test the front shaft seal on the vp44, and pulling the inspection cover with the engine running seems sketchy. Guy I bought it from doesn’t want to return my calls, starting to wonder if there’s something wrong with the head. 

 

Sorry for the novel, any insight would be appreciated. Thanks 

[dripley]

Have you checked for any trouble codes?

[CodyBeasom]

Hasn’t thrown any codes. Checked with my friends snap-on scanner. 

[Silverwolf2691]

There is one other way to get diesel in oil.. blown out/worn piston rings. They allow fuel to wash the cylinder down. Simple test: start engine, and take the oil cap off and place either upside down over the hole or gently rest in the hole. If it doesn't pop off you should be fine. When its really bad the blow by smoke will look like a steam train coming out of the filler hole.

 

But the part I'm stuck on is that a warm engine would make this occur less because of tighter tolerances, but you are saying the issue only occurs once warmed up.. 

[Mopar1973Man]

Warm engine with low pop pressure injectors can product a misfire or stumble. I know he changed injectors. I've seen injectors with low pop pressure do weird things. The funny part was the set I had this problem with was RV275. Only different was mine I had test the first time and they were barely 300 bar. I cleaned them up internally and ran fine for about a year. Then failed again with stumbling and misfire. 

 

I would look at having those injectors tested. If a injector is stuck open it would explain the fuel mixing in the oil. Also bad injectors can wash out the rings too. Hence whay I dropped the RV275 and when to +50 HP and got them pop tested and flow matched. Can't do that on Bosch stock or Bosch RV275. Those are just 6 random injectors picked off the shelf.

Edited July 16, 2021 by Mopar1973Man

[CodyBeasom]

I did the oil cap blow by test when I bought the truck and it has no blow by. Well, not enough to move the oil cap anyway. 
 

I was doing some research into pop off pressures last night and it seems like something funny could be going on. It’s almost like the fuel injection timing isn’t quite right. It’s strange though because the running condition is a gradual decline, relative to engine temp, not an instant all the time failure. Leaning toward a stuck injector. 
 

I think I’ll pull them out this weekend and have them tested. 

[Mopar1973Man]

Right out of the Dodge FSM book...

 

So if you look stock is 310 bar (4,500 PSI). Then the lower limit is 293 bar (4,250 PSI) then the upper limit 327 bar (4,750 PSI). 

 

Little secret I did on my current injectors. I've got 150 HP DAP injectors popped to 320 bar (4641 PSI). This is something you can do with custom built injectors (but no Bosch stock or Bosch RV275's) The higher pop pressure does limit the flow a bit but the spray is much finer and economy is good to fair depending how you drive. Just remember pop pressure below 290 is most likely a total failure. I did the high pop pressure for longevity being all the past injectors only lasted mere 70k to barely 100k and started to either misfire or smoke excessive. You have to remember as pop pressure goes down the timing advances for the firing event. With my 320 bar injectors the timing is retarded but since I'm running a Quadzilla I can add those couple degrees back to the injector and get it back on time. 

 

One last thing to mention its possible to lose about 10 bar of pop pressure just in the break in period of the injector. Just something to consider...

 

[CodyBeasom]

Interesting, thanks for that information, that pretty much covers what I wanted to know about pop off pressures. Starting to wonder if pressures on mine are too low. 
 

So to be clear, if I have these injectors tested, will the pop off pressures for each be provided, or is that gonna be something I have to request? Only had injectors tested once a few years ago and don’t remember if I was given that information. If one or more are found to be too low, because I can’t have these popped to a different pressure, are they worth having rebuilt? Or should I just maybe move on to a different injector being that these aren’t customizable. I don’t really plan on running a tuner on this truck for the moment, I just need it to run properly. 
 

[Dieselfuture]

Any shop that knows what they're doing should be able to pop test and adjust pressure to whatever you tell them to. It's simply comes down to how much someone cares to help you. With everyone's having a smartphone a guy that does pop testing can easily lay them out on a piece of paper saying what Pop pressure each injector was and is now.

[CodyBeasom]

Okay sounds good. I’ll have them tested and adjusted if necessary. 

[Mopar1973Man]

7 hours ago, CodyBeasom said:

Only had injectors tested once a few years ago and don’t remember if I was given that information. If one or more are found to be too low, because I can’t have these popped to a different pressure, are they worth having rebuilt?

 

They should be all popped together to be matching in flow rate, and pressures. What good is to have one cylinder flowing more fuel and the other cylinder could be lower amount or higher volume yet? This is one reason I do not suggest Bosch stock or Bosch RV275's. Now all injector shop will start out at a +50 HP injector. Now you able to flow match and set pop pressure. Now I will not suggest adding extra pop pressure till your up in the +100 HP or higher. There is no real gain for small injectors being popped higher pressure. 

 

Give you an idea typically I see stock injectors that are newish idle with about 6-7% engine load. My DAP 150 HP injectors (7 x 0.010 @ 320 bar) when I fired up and was watching the Quadzilla it idles at about 13% engine load. This gives me an angle of longevity because once an injector set finally reaches 1% or 2% for engine load at idle they are basically done and wore out.

 

Why the change in engine load?

 

Ok that's easy when the injector is new like what I've got set at 320 bar the ECM calls for more throttle 13% just to make it idle because of the high pop pressure. Now as the injectors wear and the pop pressure falls now the engine load will get down to 6% to 7% like stock injectors might see. As it continues to wear out the pop pressure falls below 290 bar the engine load will drop to 0%. Now you see idle speeds rising above 800 RPM which the ECM is programmed too. ECM can't cut any more fuel because there is nothing left to cut. Being the injector is opening easy and early the idle speed will rise. When I finally gave up on my factory stock injectors at 150k miles the idle speed was 875 RPM and engine load was 0%. Now this is why I say to replace injectors between 100k to 150k miles because most injectors are well below 290 bar for sure by that time!

 

My old +75 HP injectors I got from Vulcan Performance they falled at 75k miles and they started life at 305 bar. So it didn't take long for those to get below 290 bar and idle again was rising above 800 RPM and the engine load floating 2% to 0%...

[CodyBeasom]

That makes sense. So a higher pop pressure forces a higher engine load at idle, increasing the longevity of the injector. In your case, at idle with 13% engine load, double the stock load, you’ve essentially increased the life of your injector roughly two fold. When the engine load decreases past the stock 6-7%, the now looser injector will allow the engine to idle faster due to it popping faster and easier, above 800 rpm. My truck idles just under 900 rpm. 
 

Curious though, if longevity of the injector in this case is based on engine load at idle, wouldn’t a higher load accelerate injector wear? Because injector wear rate isn’t a constant, would having injectors that idle at a engine load of 13% wear down to the stock 6-7% at a faster rate than the time it takes to wear down from 6-7% down to 0%? 
 

Just to clarify, I can’t have my rv275s popped to the same pressures and flow rates matched after they’re tested. Is that what you meant when you said you don’t recommend them anymore? 

Actually never mind on that middle paragraph. I answered my own question, just didn’t see it at the time. 

[Dieselfuture]

You can pop them a bit higher, maybe 310-315 just my guess. I went with 320 and I'm betting now I'm around 300-305, my load is around 6-7 now was 12-13 few years back.

[CodyBeasom]

Finally have an update, been a hot minute since I’ve been able to get back to the truck. This past month has been pretty crazy. 
 

Got the injectors tested, and they are all perfect. Pop off pressures are the exact same for all six, and within spec. None were stuck or hanging up, or leaking. I went ahead and popped the injectors and connecting tubes back in the truck, but haven’t torqued anything down yet. 
 

The tech at the diesel injection shop told me to check my injection pump and make sure I had that key indexed right and didn’t smash it or it didn’t shear off. He also told me to check for a restriction in my return system. I haven’t heard of a restricted return system building up enough pressure at the pump to blow diesel by the pump shaft seal, but I suppose it’s worth checking. 
 

Pulled the inspection cover and checked the key. It looked to be indexed and seated in the gear just fine. Went ahead and pulled the pump anyway just to be sure I didn’t mash it. Key is just fine, not mashed or marred anywhere, and the key way on the gear is just fine too. Verified that the key matched the numbers on the side of the pump. The shaft seal looks just fine. There’s some diesely oil on it though, but not just straight diesel. I don’t know a good way to test that seal, and I know the chances of it being bad are slim. 
 

I suppose I’ll reinstall the pump, but I’m wondering if I should have it tested. I’d have to ship it off to do that though. Sort of at a loss for the moment. 

[Great work!]

Air hose about 20 psi and soapy water or you can add dye to the fuel kind of late now for that. Could have a cracked head but very rare.

[MikeH]

21 hours ago, CodyBeasom said:

Verified that the key matched the numbers on the side of the pump.

Did you happen to check the arrow on the key? It should be pointing towards the pump. Timing could be off if it was installed backwards.

[CodyBeasom]

The arrow is pointing toward the pump. 

[CodyBeasom]

Reinstalled the pump and ran the truck this weekend. Fresh oil change and filter. Same problem. Runs rough as soon as it starts warming up, likes to stall returning to an idle and still mixes fluids, no white smoke, no coolant loss. In less than 40 miles of driving and idling in my driveway for about 20-30 minutes, then shutting it off and letting it settle, the level on the dipstick was about a 1/2” past the safe mark, green and smelling of diesel.

 

 I took off the inspection cover for the vp44 shaft nut to see if it had any fresh diesel on it and found it covered in diesel. I ran the truck with the cover off and I could see diesel spraying off the nut and all over my inspection mirror. Looking like the shaft seal might be my culprit for mixing fluid. Not sure why I didn’t think to do that earlier but oh well... 

 

Pretty sure I can replace the seal, but I might still send the pump off to have it checked. Maybe the psg has a malfunction when it starts getting warm that’s messing with my fuel injection timing. 
 

 

[MikeH]

On 7/15/2021 at 7:05 PM, CodyBeasom said:

I put a reman industrial injection pump on

Why don't you contact Industrial Injection and tell them what you found. Warranty or not they might back up that job if they did the reman.

[CodyBeasom]

That’s what I plan to do tomorrow, don’t know if I’ll get a hold of anyone today. Hopefully they’ll work with me. 

Edited August 29, 2021 by CodyBeasom