MF1250 Compact knocking after fuel inject pump rebuild

[IndyJay]

I have a 1994 MF1250 that I sent out for Injection pump and injector rebuild. Came back 4 months and $2,800 later with a bad engine knock. I've had the tractor since it was new and had never heard it knocking. Any idea what it could be? I know, 27 year old tractor, hours are unknown since tach hasn't worked for probably 20 years but looking for some things to check.

Iseki TK532, 91.4ci/1.5L 3cyl 34HP

Thanks!

 

[irvingj]

Sounds like the timing of the injector pump is off, assuming this tractor's old enough to have a straight mechanical injector pump. On older diesels, the injector pump can be rotated (after loosening a bolt) very much like a distributor on an older car engine, to set the injector timing.

Three possibilities: 1) loosen bolt & rotate yourself until it sounds "right"; 2) take it to someone who has experience in this and have them do it "by ear"; 3) take it back to the folks who did the pump repair (did they re-install the pump??) and have them do it the "official" way, which entails taking off the timing cover and aligning appropriate marks on rotating parts. (This can be a rather involved process.)

 

[IndyJay]

Sounds like the timing of the injector pump is off, assuming this tractor's old enough to have a straight mechanical injector pump. On older diesels, the injector pump can be rotated (after loosening a bolt) very much like a distributor on an older car engine, to set the injector timing.

Three possibilities: 1) loosen bolt & rotate yourself until it sounds "right"; 2) take it to someone who has experience in this and have them do it "by ear"; 3) take it back to the folks who did the pump repair (did they re-install the pump??) and have them do it the "official" way, which entails taking off the timing cover and aligning appropriate marks on rotating parts. (This can be a rather involved process.)

Thanks Irving, this tractor is being serviced by a MF dealer. They removed the "common rail" injection pump and injectors and sent them out to a rebuild shop (in January). It took them 4 months to have the parts fabricated and shipped from Japan. When it went back together it had this knock. Dealer says they have checked and rechecked (gear driven) timing marks.

Thanks, Jay

 

[irvingj]

Does the dealer still have it? Sounds like the next step would be to determine if it's an ignition issue (pre-ignition) or a mechanical issue, like a rod bearing or other mechanical "slop".

 

[irvingj]

How'd you make out? Did you try a mechanic's stethoscope to try to localize the knocking?

 

[IndyJay]

How'd you make out? Did you try a mechanic's stethoscope to try to localize the knocking?

Haven't spoken to them yet, will follow up tomorrow with request to verify timing marks. I mentioned earlier in thread that they did pull the head and drop the pan. There is some wear but according to their mechanics nothing you wouldn't expect from a 27 year old tractor. They said they have seen worse without there being a loud knock.. I will update when I learn more. Thanks!

 

[IndyJay]

Followup... got a call from the Dealer today. The owner got involved and took it over himself. Confirmed that the timing marks were correct but discovered that there was an additional step for this model to do a "spill port timing adjustment". After he performed those steps the tractor fired up without the knocking. They are looking to deliver it early next week. Again, I appreciate all who commented with suggestions and ideas of where to look.

 

[irvingj]

OK, learn something new every day! What I was referring to above -- older mechanical systems-- are Indirect Injection (IDI) diesels; what you have is a Direct-Injection (DI) system.

I was under the impression that all DI systems used electric solenoids or piezoelectric actuators to control injection (in turn controlled by the engine computer), but apparently early DI systems were in fact mechanical, using what's called a "spill port" in each injector to control injection timing and volume. This is apparently the type of engine the 1250 has.

So it was in fact the timing of the fuel injection that was the issue, but that's resolved by going through a "spill port timing" exercise.

Yeah, I use to turn a wrench, but I've been out of that field for a number of years. Although I do read up on developments, I missed the transition between IDI diesels and fully-electronic DI engines, the "spill port" (but still DI) diesels.

Thanks for the opportunity to learn something new, and glad you got it fixed!