Help with Universal M25 Diesel - 1983 Catalina C36

[bomberhart]

This has been the year of diesel upkeep.

We have done the following projects already:
1. Changed Oil
2. Changed Transmission Fluid
3. Replaced Fuel and Oil Filters
4. Added solenoid from started to glow plugs to decrease glow plug time and ease starting
5. Replaced glow plugs
6. Replaced Air filter
7. Replaced Fuel lines and a couple other softs that were cracking / breaking
8. Replaced Impeller pump - the body, as well as the rubber

And most recently,
9. Replaced Fuel injectors.

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 ofter 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.

My mind is telling me to 1) adjust the idle up to 1000-1200 rpm (I think it is around 750-800 now), 2) let her run for a while - maybe even take it out for a multi hour cruise to make sure the system is totally clear and then reevaluate?

What would you do in this scenario? What am I missing? Any and all comments are appreciated.

[donradcliffe]

Mechanic's rule number one. Change one thing at a time, then test. Usually learned the hard way. My vote would be the likely problem is the fuel lines you replaced are leaking air.

[bomberhart]

You're right. I have been banging my head against the wall for this one...

Any ideas on how to rectify?

[olepedersen]

IT is a very good engine tie to the dock put it in gear and let it run. while running you can
check fuel lines, and injectors

[donradcliffe]

The first thing I would try is to crack the injector lines one at a time when it is running rough. If cracking a cylinder does not make things worse, then that is the cylinder which is not firing. If you find one cylinder is the problem, then it is probably the injector on that cylinder, and not the fuel lines.

[Ken Z]

new injectors, I have had to run my engine for about 3 hrs under load to clean up the injectors and starting cold a few times after that it would be smokey but eventually cleaned up. I always try to use hwy. diesel rather than the ruby red.I use injector cleaner.

[Tetepare]

I didn't see anything about the water separator. If you don't have one, install one.

Check or replace the impeller. Always have a spare impeller and belt.

[Stu Jackson]

Originally Posted by bomberhart

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My mind is telling me to 1) adjust the idle up to 1000-1200 rpm (I think it is around 750-800 now), 2) let her run for a while - maybe even take it out for a multi hour cruise to make sure the system is totally clear and then reevaluate?

What would you do in this scenario? What am I missing? Any and all comments are appreciated.

Your idle is horrendously low. Period. All the rest of the things you've done are simple, good maintenance issues.

Idle adjustment is easy: nuts with lock wires on the forward starboard top of the engine.

**********

Engines 101 - The BIGGEST & BEST collection of M25 Series Universal Engine Information on the Internet, plus some M35, too

Diesel Engine - c34.org

[boeing1]

I agree with low idle,

[Seas the Day]

Just had my marine mechanic in for a service. My M35B was idling too fast so he set it back to around 1,000 RPM. Easy to do.

[bomberhart]

Originally Posted by Tetepare

I didn't see anything about the water separator. If you don't have one, install one.

Check or replace the impeller. Always have a spare impeller and belt.

Definitely have a water separator. I cleaned it and reinstalled when I changed the fuel filter.

Impeller is new and in good shape.

[jimbunyard]

According to Westerbeke, the idle on the M25 should be between 1000-1200 rpm, specifically to avoid drive plate chatter at idle in gear. In my experience with these engines that makes it shift harder, but if it saves wear and replacing damper plates, then I guess that's the lesser of two evils. It just grates against my mechanical nerves to hear a transmission slam into gear...to me a proper small engine idle is around 700-800 rpm.

Regarding your rough running engine, why did you change the injectors?

How was the engine running before you changed them?

Did you drop one of the injectors while installing it?

It sounds a little like you may have an air pocket in the injection pump that needs to be bled out, or possibly a small leak on the suction side of the lift pump. This is of course (mostly) ruled out if the engine was running ok before you changed the injectors.

I wouldn't change the idle until you've fixed the roughness issue...

[bomberhart]

Originally Posted by jimbunyard

According to Westerbeke, the idle on the M25 should be between 1000-1200 rpm, specifically to avoid drive plate chatter at idle in gear. In my experience with these engines that makes it shift harder, but if it saves wear and replacing damper plates, then I guess that's the lesser of two evils. It just grates against my mechanical nerves to hear a transmission slam into gear...to me a proper small engine idle is around 700-800 rpm.

Regarding your rough running engine, why did you change the injectors?

How was the engine running before you changed them?

Did you drop one of the injectors while installing it?

It sounds a little like you may have an air pocket in the injection pump that needs to be bled out, or possibly a small leak on the suction side of the lift pump. This is of course (mostly) ruled out if the engine was running ok before you changed the injectors.

I wouldn't change the idle until you've fixed the roughness issue...

The engine was running ok beforehand but had problems starting. I was checking everything and found some corrosion on the high pressure lines to the injectors. When I changed those I checked the injectors and they were a carbon mess so I opted to change them thinking it would help... And here we are.

I don't believe I dropped one but they were shipped so it could have taken a knock without me knowing.

[bomberhart]

Originally Posted by jimbunyard

According to Westerbeke, the idle on the M25 should be between 1000-1200 rpm, specifically to avoid drive plate chatter at idle in gear. In my experience with these engines that makes it shift harder, but if it saves wear and replacing damper plates, then I guess that's the lesser of two evils. It just grates against my mechanical nerves to hear a transmission slam into gear...to me a proper small engine idle is around 700-800 rpm.

Regarding your rough running engine, why did you change the injectors?

How was the engine running before you changed them?

Did you drop one of the injectors while installing it?

It sounds a little like you may have an air pocket in the injection pump that needs to be bled out, or possibly a small leak on the suction side of the lift pump. This is of course (mostly) ruled out if the engine was running ok before you changed the injectors.

I wouldn't change the idle until you've fixed the roughness issue...

The engine was running ok beforehand but had problems starting. I was checking everything and found some corrosion on the high pressure lines to the injectors. When I changed those I checked the injectors and they were a carbon mess so I opted to change them thinking it would help... And here we are.

I don't believe I dropped one but they were shipped so it could have taken a knock without me knowing.

[jimbunyard]

Jostling around in shipment shouldn't hurt an injector, you'd have to drop it so the tip landed on a hard surface to damage it.


Did you replace the copper washers when you changed the injectors? Did you remove the old copper washers first? A leaking or imperfect compression seal around the injectors could cause the symptoms you describe.


Can you define 'problems starting'?