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Old 28-06-2017, 21:20   #1
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Help! Universal M25 Fuel Injector Problems

I recently installed new fuel injectors into my Universal M25. First, it knocked and pinged like crazy because one of the injectors was stuck open. Then (once I got the replacement), it started right up and sounds great. It revs up beautifully, but when in gear it won't go about 1200-1400rpm.

The fuel is new. The fuel filters are new - so I know it's not that.

The oil is jet black and replaced 20 hours ago.

I installed a new air filter this year. I also installed some new soft rubber fuel lines to ensure the connection is good.

The copper seals were replaced with the new injectors. The glow plugs were replaced earlier this year also.

What could it be????
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Old 28-06-2017, 22:09   #2
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Re: Help! Universal M25 Fuel Injector Problems

Check stop lever moving back to 100% run position.
Check throttle lever moving correctly at Fuel pump, not turning on shaft.
Old copper washers removed from hole.
Prop fouling growth. Affect exaggerated on static pull. [Tied up]
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Old 29-06-2017, 13:08   #3
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Re: Help! Universal M25 Fuel Injector Problems

Every thing Shakey Doug said, plus 1 more. I've seen soft rubber fuel lines peel off the inner layer and block the flow of fuel. Many years ago I remember a mechanic being fired for making up a new oil supply line to a turbo and didn't check it. No oil to turbo and burned it up. Inner liner peeled off and blocked flow of oil. (no it wasn't me) But I've done just as bad or worse.
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Old 29-06-2017, 20:56   #4
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Re: Help! Universal M25 Fuel Injector Problems

I'm assuming this is the same problem from your previous post, so to repeat;


"Did the engine sit up for a long time in it's recent life?

If you're sure that there are no vacuum leaks in the suction side of the fuel system (fuel wouldn't be obviously leaking except possibly when the engine is off), then the problem sounds more like an injection pump or governor issue.

For the injection pump; either internal sealing issues or sticking p&b(s), on the governor/governor linkage; a missing, broken or stretched spring or corroded governor bearings. Either of these conditions would be best diagnosed by an experienced on-site mechanic.

As an aside to the previously mentioned 'specified' idle speed, I still think 700-800 rpm is the appropriate idle for a small engine, and know that shifting at 1200 is detrimental for the gearbox, so an easy workaround would be to set the idle at the lower speed, shift at that speed and then immediately run up to the appropriate speed to avoid chatter. And then of course remember not to run the engine in gear at less than the 1000-1200 speced by Universal..."


The inconsistency described thusly, from your previous post,

'The new fuel injectors are giving me a little problem. The motor now has a really rough idle. I suspect that the idle speed is low, but it kind of burps along and every so often will rev up 50 or so RPMs and then cool down again. I haven't been able to get it to run consistently clean without burps of white exhaust.'

seems to describe erratic fueling, which could be caused by internal failure of a rubber fuel line as described above, but if the problem predates the changing of the fuel lines, probably not.


Another thing that hasn't been mentioned (though it wouldn't explain white smoke, which is usually indicative of over-fueling [if compression is good]), is a blocked fuel tank pickup or a blocked tank vent.


The blocked vent fix is easy and self explanatory.

Not so easy for the blocked fuel pickup. For some unfathomable reason, fuel tank manufacturers often install a fuel screen on the lower end of the fuel pickup. This usually winds up getting clogged, restricting flow. To solve this problem the tube has to be taken out, which can be difficult (or impossible) in the (usually) confined spaces in a small boat, and the screen cleaned, or better yet, removed. A shot of compressed air will probably blow the clog off the screen as a test to see if this is your problem before trying to remove the tube, but the problem will eventually return as the sludge washing around in the tank gradually re-collects on the screen.


The previous suggestions are all good, a simple test is to disconnect the throttle cable and stop cable and see what max rpm is, out of gear, with the throttle lever operated by hand at the engine...
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Old 30-06-2017, 14:32   #5
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Re: Help! Universal M25 Fuel Injector Problems

Should rev to 2600 rpm out of gear. If you've got that governors probably ok. Full throttle in gear tied to the berth maybe 1700 rpm and black smoke, no black smoke would indicate fuel starvation. A fouled or wrong size prop will bring revs down but will black smoke as well. What colour is the exhaust ?
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Old 30-06-2017, 21:43   #6
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Re: Help! Universal M25 Fuel Injector Problems

I had a recent problem with a Perkins diesel. I found the issue was insufficient bleeding of the injector lines. First bleed the fuel line to the injector pump with the motor off. Get the motor running and bleed each injector until there are no bubbles at the bleed point. Then run the motor at least 2/3 max rpm and repeat.
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Old 30-06-2017, 22:26   #7
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Re: Help! Universal M25 Fuel Injector Problems

One item i very seldom see mentioned in possible RPM issues and poor running in general is the one issue i have just repaired, My engines issue was one of not being able to achieve full RPM in or out of gear but apart from that started well and ran well until around half throttle,every thing had been replaced in the way of filters/lines/lift pump/etc but the problem still existed-the answer was in the return line fuel restriction plug-(it was missing) we dont know how or where it went but it was not there, every diesel engine has this restriction device located some where in their system, other wise the lift pump pressure will just return to the tank and not pressurize the injector pump to the correct pressure causing starvation of fuel when most needed!
Many restriction devices are located in the fuel banjo hollow bolt that locates in the injector pump or some times (like GM) in the fuel return line itself, there fore (all though normally secured in place) if lines or banjo bolts have been removed for any reason these can be lost (with out noticing them). In our case the engine had been reconditioned and felt the restriction plug had been lost during cleaning of all parts,
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Old 01-07-2017, 06:47   #8
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Re: Help! Universal M25 Fuel Injector Problems

Ok - here's an update... I traced the problem to the fuel injector pump. After a hand full of phone calls I found a refurbished one in Seattle for about $350.

I was able to pull the old one out and get the new one in. It looks like it needs some shims as the aft injector gives off a perfect mist when cracked. I'm getting nothing from the center and too much from the front one....

So, a shimming we will go.
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Old 01-07-2017, 15:41   #9
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Re: Help! Universal M25 Fuel Injector Problems

Sounds like you still have problems either with air in the system, blocked fuel supply or injectors. Could also possibly still be problems with the 'refurbished' pump.

That one out of three injectors appear to be working OK seems odd with new injectors.

Shimming the pump affects the timing of the injection on all three injectors simultaneously; it should have no effect of the spray pattern of individual injectors.

Have you tried moving the #3 injector to the one and two positions to see if the good spray pattern follows the injector?
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Old 12-07-2017, 19:46   #10
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Re: Help! Universal M25 Fuel Injector Problems

Another update...

Turns out the refurbished injector pump was bad, argh! So I had mine rebuilt and put it back in. I bled the lines to the pump, and then it started right up, but still the same problem, AAAARRRGGHHHH!!!

I then decided to re-check things. So I started with the water separator, and the diesel in it didn't look great - kind of cloudy. Any ideas there? I drained the tank today, will go back tomorrow with fresh diesel, new fuel filters, compressed air to clean the intake and the fuel vent and try again...

Heaven help me...
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Old 12-07-2017, 21:08   #11
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Re: Help! Universal M25 Fuel Injector Problems

Cloudy fuel is obviously bad what ever quite commonly caused by water particles mixed with diesel and or accumulation of crud/bacteria and if all your new diesel/new filters/cleaning the lines/breathers dont help then go back to the previous suggestions and answer these questions
1) Is the propeller clean of barnacles
2) Does the shaft turn freely out of gear
3) Does the engine rev freely and responsive out of gear
4) DID YOU CHANGE THE FUEL LIFT PUMP!!!!!
5)Suggest you disconnect the fuel return line and check the amount of fuel flowing back to tank, if flowing to much (more than a dribble) then the fuel restriction orifice/valve is not working or lost from the system.
6)Are you sure the injection pump timing is correct 100%
7) Un likely but consider the gearbox may have an issue

If there's any "not sure answers" or NO answers start there
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Old 13-07-2017, 05:45   #12
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Re: Help! Universal M25 Fuel Injector Problems

You might also try running the engine directly off the jug, then you'll know for sure you've got fresh clean diesel...an outboard-type primer bulb comes in hand here...
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Old 30-09-2020, 17:02   #13
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Re: Help! Universal M25 Fuel Injector Problems

Quote:
Originally Posted by bomberhart View Post
Ok - here's an update... I traced the problem to the fuel injector pump. After a hand full of phone calls I found a refurbished one in Seattle for about $350.

I was able to pull the old one out and get the new one in. It looks like it needs some shims as the aft injector gives off a perfect mist when cracked. I'm getting nothing from the center and too much from the front one....

So, a shimming we will go.
Bomberhart, I know you didn't have any luck with the refurbished one from Seattle, but do you remember the company's name you got it from. I am getting quotes of $1500 for the injector pump.
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Old 30-09-2020, 19:15   #14
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Re: Help! Universal M25 Fuel Injector Problems

Quote:
Originally Posted by Jops74 View Post
Bomberhart, I know you didn't have any luck with the refurbished one from Seattle, but do you remember the company's name you got it from. I am getting quotes of $1500 for the injector pump.
If you have the plain M25, the base engine is a Kubota D850. Kubota p/n for the pump for that engine is 15531-51010, these people

https://oregonfuelinjection.com/shop...obcat-6599004/

show a new OEM one (Zexel) for 686.00 USD.

There are others available, starting at 252.00 from China.
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Old 01-10-2020, 22:13   #15
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Re: Help! Universal M25 Fuel Injector Problems

Its actually the Universal M-25XP which is the Kubuto D-950. Thanks I'll look into it.
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