12v Cummins help

[gr8shot]

Well cumminsforum hasn't been real helpful so maybe you guys can help me. I have my cummins swap like 99% done. Its driveable and everything. Probably put 1500 miles on it so far. But its developed a really bad misfire/chug at pretty much all rpms. Its really bad when I put a light load on it at low rpms. Bad enough that it shakes the whole truck. But with heavy throttle it isn't as bad but still very noticeable. I've since parked it until I get it fixed for fear of further damage.

http://static.photobucket.com/playe...lbums/ii285/gr8shot49/VID_20111110_165126.mp4

Hopefully the video works. I took it the last day I drove it, about two weeks ago.

Here's all the info I have... it starts instantly, first piston over. Still has good power. No oil/coolant mixing, no fuel in oil. Brand new overflow valve so fuel pressure should be good. No sticking valves or broken springs. I pulled the valve covers and everything is perfect. Valves were adjusted while the motor was out of the truck. I was told to loosen the injector lines at the pump, and if a dv holder spins then its a broken barrel, but none of them spun. Timing seems to at least be in the ballpark still, no excessive smoke after it warms up, but no full exhaust system yet so I can't tell 100%.

Basically it almost has to be either injectors or pump im thinking but I'm at the end of my troubleshooting knowledge to figure out which, and don't have a ton of $ to throw at it. I will have a little but I can't afford to waste money on something that wont fix it so I'm trying to narrow it down before I spend the money. Short of taking it to a shop, is there anything else I can do to try and narrow down the source of the problem?

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[gr8shot]

Crap I should also mention that Its a 95 cummins with a 175hp ppump and nv4500. Stock fuel system only mods are fuel plate slid forward and starwheel turned forward a tad. Otherwise bone stock. If I forgot anything else just let me know.

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[madmatt]

crack lines loose one at a time to see which cylinder the miss is on. once you determine that, swap that injector with another and see if the miss follows the injector or stays in that cylinder, if it moves you know it's an injector issue. if it stays put do a compression test on that cylinder. passes move on to the pump. pull the dv holder and inspect the spring and poppet underneath the holder. good inspect the DV for damage. nothing found there remove pump and take it to a shop cause it's gonna be a plunger or barrel issue. somethings broke and that plunger may be stuck

 

[gr8shot]

I'm pretty sure the miss is on #3. When I loosened the injector lines at the pump I did em one at a time. It got worse each time I had one unscrewed but with 1 and 3 there was only one misfire. With 2, 4, 5 & 6 I could hear one big misfire and the same faint one as before. But even with 1 or 3's line cracked the misfire would get more pronounced.

Ill try swapping a couple injectors around and see what happens. I hadn't thought of that. Hopefully its injectors because I've never had a pump apart other than the afc housing so I might be in a little over my head with the dv's and such.

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[Turbo Performance]

How does it rev? Does it want to pull the top end? Stock timing? I would start with what Madmatt said. I'm thinking either timing slipped or an injector issue. Can't really tell in the video but a stuck plunger would sound worse and wouldn't really get any better with RPM. Does it idle okay?

 

[gr8shot]

It idles great but you can still hear the slight miss even at idle. Once the boost comes up it pulls hard til it gov's out close to 2500rpms and the miss isn't as easy to hear at full throttle. But that's probably also partly due to next to no exhaust right now.

The one weird thing it does do is when I rev it, if I only use part throttle its fine, but if I try to rev and give it full throttle it'll kinda spit and sputter. Also when its cold and I take off it will spit and sputter and not rev above about 1800rpm in second gear. As soon as there's a little heat in the motor it goes completley away though. I though that might be an air leak, but it has all new fuel lines, starts perfect and doesn't sputter or die at idle, it'll idle happily all day long and start right back up after shut down.

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[madmatt]

i didn't watch the vid but i guess timing coulda slipped but every time I've had that happen the were a MF'r to start but the issue where you can't snap rev it does kinda sound like a timing issue.

 

[madmatt]

I still really think it's an injector issue. Got any pump shops around?? Ours here will pop test them for me for free since they're so easy and quick to do. May be worth a shot just to have them all tested real quick to be safe.

 

[gr8shot]

I don't know of any shops anywhere within driving distance. (Central Nebraska) But I'm new to the cummins game so I wouldn't know anyway really. I'm not above getting em tested and the pop pressures reset, but I just want to spend the $$ once and have it fixed as I can't afford to throw $ away Hoping to fix it. But I'm going to try swapping the #1 and #3 injectors with others (one at a time obviously) and see if the misfire moves or stays in the same spot. That ought to tell me what I need to know I imagine.

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[gr8shot]

Swapped the #3 and #4 injectors this morning. Didn't seem to make any difference. Still seemed like the miss was on #3 cylinder after swapping the sticks. Guess that means it's probably the pump

I'm going to run an ass load of stanadyne through the rest of the tank and see if I notice any difference, but I'm not too optimistic.

 

[TNeill]

Have you checked fuel feed pressures to your injection pump. No less than 9 psi at idle . Check right at pump inlet. Just an idea!

 

[Bonestock]

On first startup hold your hand on the exhaust manifold by each cylinder one at a time. You will be able to tell if you have a dead hole or two just by the difference in heat. You can also use an infrared heat gun.

 

[gmguy]

I don't know of any shops anywhere within driving distance. (Central Nebraska) But I'm new to the cummins game so I wouldn't know anyway really. I'm not above getting em tested and the pop pressures reset, but I just want to spend the $$ once and have it fixed as I can't afford to throw $ away Hoping to fix it. But I'm going to try swapping the #1 and #3 injectors with others (one at a time obviously) and see if the misfire moves or stays in the same spot. That ought to tell me what I need to know I imagine.

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Call the guys at Midwest diesel in beamer Nebraska. They are top notch in cummins fuel systems.

I have a pop tester also. Your only an hour and a half away from me, pm me if you need any help. 12 valves are my specialty lol

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[gr8shot]

Well the guys at husker diesel are working on it for me. Pump is off and injectors are out. Pump is getting benched this week and injectors are getting the pop pressure reset. They're also going to do a compression test just to be sure but pretty sure its all in the pump. Should have some answers next week! Pretty excited to have the beast back before too long!

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[gr8shot]

Verdict is in. Injectors were SHOT! Pump was benched and came back good. Got everything recalibrated and set up nicely on the pump while it was on the bench. Bought new stock injectors to go back in. Timing is getting set to 15.5* for the best highway mileage too. Also going to try and get a 5" exhaust put on while its in the shop. It ought to run like a new motor when I get her back!

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[cdbright]

send pics of truck w hood open

 

[gr8shot]

send pics of truck w hood open

There's probably over 100 pictures here:

http://www.duramaxforum.com/forum/diesels/93398-my-build-thread-project-red-betty.html