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Diesel mechanic help
Posted on 9/12/25 at 9:49 pm
Posted on 9/12/25 at 9:49 pm
Just changed out fuel injection pump. New pump in and exhaust has blueish white smoke coming out of exhaust now. Mechanic said he thinks it’s fuel on the piston. Is this major or easy fix? Trying to figure out if it’s just old fuel that was leaking from bad pump and will eventually burn off or bigger problems. Old pump was bad and I know fuel was in oil. Changed oil today before using since pump was changed.
6
Posted on 9/12/25 at 9:51 pm to shoelessjoe
Not necessarily major right now. It could just be leftover fuel/oil mix that needs to burn off.
If the smoke doesn’t improve after a couple hours of use, or if it worsens, then it’s likely either a timing issue or cylinder wear from past fuel dilution Both need attention but aren’t instant engine death if caught early.
If the smoke doesn’t improve after a couple hours of use, or if it worsens, then it’s likely either a timing issue or cylinder wear from past fuel dilution Both need attention but aren’t instant engine death if caught early.
Posted on 9/12/25 at 9:53 pm to OysterPoBoy
Could a bad injector cause it as well? It doesn’t smoke when idling, does it when I accelerate. I used it for about an hour today and it was steadily smoking.
Posted on 9/12/25 at 9:55 pm to shoelessjoe
Could be fuel dilution in the oil washed the bearings. Could be rings. Run it and at some point could check compression. Blue smoke typically is never good.
Posted on 9/12/25 at 9:55 pm to shoelessjoe
No smoke at idle, but smokes on acceleration/load classic sign of an injector problem (leaking, dribbling instead of spraying a fine mist, or overfueling).
If it were just old fuel on the pistons, you’d normally see smoke even at idle until it burned off.
If it were oil burning from bad rings, you’d typically see at least some smoke all the time, and often a puff on startup.
If it were just old fuel on the pistons, you’d normally see smoke even at idle until it burned off.
If it were oil burning from bad rings, you’d typically see at least some smoke all the time, and often a puff on startup.
Posted on 9/12/25 at 9:56 pm to OysterPoBoy
I feel like I should tell you this was from ChatGPT.
Posted on 9/12/25 at 9:57 pm to OysterPoBoy
Gotcha. I am thinking of changing the injectors to see if that works.
Posted on 9/12/25 at 10:00 pm to OysterPoBoy
quote:
I feel like I should tell you this was from ChatGPT.
Why you say that?
Posted on 9/13/25 at 12:02 am to shoelessjoe
Check your points or better yet just change out your entire distributor.
Could also be a carburetor* issue.
*French word meaning “don’t frick with any set screw”
Source: ChatBTR
Could also be a carburetor* issue.
*French word meaning “don’t frick with any set screw”
Source: ChatBTR
Posted on 9/13/25 at 12:06 am to shoelessjoe
I’m thinking fuel on a piston would be an injector pissing. What were your symptoms thst made you bring it to the shop? Best case would be an injector problem. You just change those out like a spark plug. Don’t run it too long with a bad injector, or you’ll melt down a piston.
Fwiw…white smoke sounds like a possible head gasket to me.
Fwiw…white smoke sounds like a possible head gasket to me.
Posted on 9/13/25 at 12:26 am to shoelessjoe
Did you have this bluish white smoke prior to changing the injection pump? Blue in smoke is typically oil. Also, why was the injection pump changed out?
Posted on 9/13/25 at 2:45 am to Spankum
Injector pump was bad. Was running on only two cylinders. Changed out injection pump and now it started smoking. Didn’t smoke before pump was changed. I wonder if the cylinder that was not working was the same cylinder that has the bad injector in it. The pump wasn’t pumping fuel in that injector so I couldn’t tell anything. Now that pump is changed and all three cylinders are being used, I wonder if that’s why it’s smoking. That cylinder had the bad injector but wasn’t getting fuel to it because pump was bad, now that it’s changed, the injector is bad as well.
Posted on 9/13/25 at 2:48 am to windmill
Injection pump was changed out because one of the little plungers in the pump wasn’t pumping fuel working. Only getting fuel through two cylinders. Changed pump and now it smokes. Makes me believe since fuel wasn’t getting through all three cylinders, could diagnose bad injector since it wasn’t smoking. Now that the third injector is getting fuel since injector pump is changed, it shows bad injector as well now, that’s why it’s smoking.
Posted on 9/13/25 at 6:56 am to shoelessjoe
This is all called “throwing parts at it”
Could really be anything. Up to this point I’m not sure I even know what engine we are dealing with. Cat? Cummins, Detroit?
Is it in a truck or equipment
Could really be anything. Up to this point I’m not sure I even know what engine we are dealing with. Cat? Cummins, Detroit?
Is it in a truck or equipment
Posted on 9/13/25 at 7:25 am to shoelessjoe
Why didn’t your “mechanic” time it right?
Because surely, your “mechanic” has tested the injectors, so you know they are right.
Because surely, your “mechanic” has tested the injectors, so you know they are right.
Posted on 9/13/25 at 7:28 am to subMOA
quote:
Why didn’t your “mechanic” time it right?
This.
Take the pump back off and put it back together again, correctly.
Posted on 9/13/25 at 1:17 pm to LSU Neil
John Deere diesel mower.
Posted on 9/13/25 at 1:19 pm to OysterPoBoy
quote:
puff on startup.
Thought that was generally valve guides?
Posted on 9/13/25 at 5:19 pm to shoelessjoe
What fuel pump do you have? Cp4?
Posted on 9/13/25 at 5:54 pm to BFANLC
Not sure. All I can tell you is that it’s a Yanmar 3 cylinder diesel.
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