• Untitled Document

    Join us on March 29rd, 7pm EST

    for the CBEC Virtual Meeting

    All EYO members and followers are welcome to join the fun and get to know the guest speaker!

    See the link below for login credentials and join us!

    March Meeting Info

    (dismiss this notice by hitting 'X', upper right)

M25 Rough Engine Operation

Dan R.

New Member
The Universal M25 (5421) on the Ericson 33 I sail has not been starting easy or running normal since launch in May. Once started, it coughs and chokes at idle to the point it stops running, but if we keep the RPM at 800 or above it runs OK. We added injector cleaner to the fuel tank to help if it's a clogged injector, but no noticeable change until a few days again. Now, after operating in this manner for 3-4 weeks, the engine will only turn 1900 RPM at wide open throttle. Running the engine at 1500, we cracked the nuts on the three injector lines and had a big decrease in engine performance on the #1 and #2 cylinders, but the engine operation did not change when the fuel flow to the #3 cylinder was interrupted. Pulled the #3 injector and compression tested the cylinder; 250psi. Tested #1 cylinder as point of reference, also 250 psi. Thinking of taking the injectors to a shop to be cleaned and tested...

So after that long story, I'm looking for guidance on next steps and if anyone knows what the compression should be for the cylinders of the M25. I found two different compression ratio's in the manual I've found on the internet (22:1 and 21:1).

Thanks in advance for any help!
 

Baslin

Member III
I would check prices on new injectors from kubota...I think you can find 3 new ones for less than having them serviced. You can also do a leak down test on the #3 cylinder but seeing that you have good compression, I think you are on the right path with an injector problem.
 

e38 owner

Member III
Sounds like fuel to me. I would start with fuel filters. Crack in filter housing or hoses
 
Last edited:

Alan Gomes

Sustaining Partner
Sounds like fuel to me. I would start with fuel filters. Crack in filter housing or hoses
Yes, but the fact that he saw no significant degradation in running when he cracked the line to injector #3 vs. when it did it for #1 and #2 suggests to me that something is wrong with that injector or the flow of fuel going to that injector specifically. Given that piece of info, that's where I'd start. If it were the fuel filter generally I would not expect to see a cylinder-specific issue.

As always, I'd make only one change at a time and see what happens.
 

debonAir

Member III
The #3 injector seems like the culprit if de-fueling it doesn't make any change to operation, and doing the other two make obvious changes. Of course there could be a generic fuel issue as mentioned if it is really rough-running. Any leak on the pressure side would be obvious, so check filters and look for leaks on the suction side (does the lift pump give you bubbly fuel on the output side?)

A new OEM injector is about $70 at Messicks. You can get (probably clones) on eBay for about $40.

A new nozzle, to fix your injector, is about $110 (at Messicks), which of course begs the question of why anyone would ever buy one, especially as there seems to be dozens of "adjusting washers" inside the injector body just begging to roll into dark corners if you took one apart to replace the nozzle.

I don't know how a rebuild shop could compete with a $40 new unit from eBay unless they're somehow junk.

I'd order new OEM fuel overflow lines (the short flex tubes between each injector) to have on hand when replacing injectors. Even if you buy full-price injectors you probably want to do all 3 while in there too.

On the subject of smooth idle.. While adjusting my throttle I think I got my 5424 down to about an rpm where I could basically hear each individual cycle, like maybe 100rpm, and it still ticked along quite smooth and happy. I was surprised how hard it was to get the thing to stop. You really have to cut off all fuel to it.
 
Last edited:

gabriel

Live free or die hard
have you checked your diesel tank for algae? if it's growing there it will make its way into the filter and clog it enough so it will run but you can't develop full power.
 

Alan Gomes

Sustaining Partner
have you checked your diesel tank for algae? if it's growing there it will make its way into the filter and clog it enough so it will run but you can't develop full power.
Again, the question would be: How would "algae" explain the problem that's specific to cylinder #3?

Of course, there could be multiple problems going on. He might have an issue with bacterial growth in the tank AND an injector issue. And four or five other things. It is best, though, to tackle one thing at a time, otherwise when there is a change (whether for better or worse) you would not know just what effected it. Since there seems to be a clear issue with cylinder #3, it really points to something amiss with that injector and that would be the place to look first.

DebonAir's advice is, I think, spot on.
 
Last edited:

Dan R.

New Member
Yep, bubbly fuel on the output side and replaced both primary and secondary fuel filters and started with a fresh tank of fuel on launch day (empty it every season for lay up. Haven’t seen any fuel in the bilge.

I’ll check Messicks and keep following the thread for any other advice, thanks.

The #3 injector seems like the culprit if de-fueling it doesn't make any change to operation, and doing the other two make obvious changes. Of course there could be a generic fuel issue as mentioned if it is really rough-running. Any leak on the pressure side would be obvious, so check filters and look for leaks on the suction side (does the lift pump give you bubbly fuel on the output side?)

A new OEM injector is about $70 at Messicks. You can get (probably clones) on eBay for about $40.

A new nozzle, to fix your injector, is about $110 (at Messicks), which of course begs the question of why anyone would ever buy one, especially as there seems to be dozens of "adjusting washers" inside the injector body just begging to roll into dark corners if you took one apart to replace the nozzle.

I don't know how a rebuild shop could compete with a $40 new unit from eBay unless they're somehow junk.

I'd order new OEM fuel overflow lines (the short flex tubes between each injector) to have on hand when replacing injectors. Even if you buy full-price injectors you probably want to do all 3 while in there too.

On the subject of smooth idle.. While adjusting my throttle I think I got my 5424 down to about an rpm where I could basically hear each individual cycle, like maybe 100rpm, and it still ticked along quite smooth and happy. I was surprised how hard it was to get the thing to stop. You really have to cut off all fuel to it.
 

Dan R.

New Member
Update with Partial Solution: After hours of trouble shooting based on conversations with a (relatively) local Kubota engine repair shop, and a final consult from the local yard mechanic who had a spare minute, the problem was the engine driven injector pump. Parts deep inside the pump had failed allowing fuel to continuously flood the #3 cylinder. Once repaired and reinstalled, the engine roared back to life.

Thanks all for your responses to the post.

Yep, bubbly fuel on the output side and replaced both primary and secondary fuel filters and started with a fresh tank of fuel on launch day (empty it every season for lay up. Haven’t seen any fuel in the bilge.

I’ll check Messicks and keep following the thread for any other advice, thanks.
 
Top