Diagnosing engine issues - Universal M25

[Dave96734]

Hi,

My 1984 C30 has a universal M25 that won't start. It cranks just fine. Steps I've taken so far: replace secondary fuel filter, bleed fuel lines (at secondary filter and at bleed screw just proximal to the injector pump), confirm starter is receiving charge. I unscrewed the injectors and did not observe any fuel spurts when the key was turned & fuel pump engaged. To my understanding this isolates the issue to the injector pump. Does this diagnosis sound correct? Is there anything else I should consider?

Many thanks!
Dave

 

[jssailem]

High Dave...
It is a challenge. You need to start somewhere with a fuel issue. Your engine is supposed to be self priming. Till it isn't.

Sounds like you want to start at the injector pump. Test to see if you have fuel to the Injector pump. Try loosening the fuel line that supplies fuel to the Injector Pump.. Turn on the electric fuel pump. If fuel squirts from the line then you know you have fuel to the injector pump... It could be that air is trapped in the injector pump. You need to bleed the injector pump. Your manual should tell you how. Basically it is opening the bleed screws tilll fuel flows to the injectors.

If no fuel leaks from the line you loosened, then the problem is between that point and the fuel tank. You need to work your way back from there to the tank to find where it is fouled.

Good luck. Be methodical One step at a time.

 

[Ward H]

This is the bleed screw on my M25XP. It should bleed any air out of the injector pump. Is yours the same?

I unscrewed the injectors and did not observe any fuel spurts when the key was turned & fuel pump engaged.

This doesn't sound like you cranked the engine, just turned on the ignition to let the pump run. Doesn't the engine need to be cranked for the injector pump to pump fuel?

 

[sailme88]

Dave, in order for the engine to fire it must not experience any back pressure. Back pressure happens when the exhaust elbow where the raw water and exhaust gasses meet. Over time this will occlude. Eventually it is clogged. A secondary problem may now exist.. If you have repeatedly cranked the engine with the raw water valve open and no way for that incoming water to be pushed out with the exhaust it can back up into the head and flood the engine with water. Check your crankcase oil for water.. If present, you might be looking at a rebuild.

 

[jviss]

Be careful. High pressure diesel is dangerous. It can penetrate your skin and poison you, in addition to other damage. Wear safety glasses.

 

[Ralph Johnstone]

Doesn't the engine need to be cranked for the injector pump to pump fuel?

Thanks Ward. That's exactly what I got from the OP's description of what he did to clear any air from the injector pump. The injector pump will only turn over if the engine is turning over and from what I understand, the engine wasn't turning over, only the electric lift pump.

To bleed the injector pump of air, you must have someone crank the engine while you crack an injector fitting (or open a bleed screw as per @Ward H) to reduce the back pressure acting against the injector pump and allow air to be forced out of the pump.

 

[jviss]

Thanks Ward. That's exactly what I got from the OP's description of what he did to clear any air from the injector pump. The injector pump will only turn over if the engine is turning over and from what I understand, the engine wasn't turning over, only the electric lift pump.

To bleed the injector pump of air, you must have someone crank the engine while you crack an injector fitting (or open a bleed screw as per @Ward H) to reduce the back pressure acting against the injector pump and allow air to be forced out of the pump.

You can save the battery, too, by securing the compression release as you do this. Also, make sure you frequently drain the muffler so you don't get water backing up into the exhaust manifold.

 

[Ralph Johnstone]

Also, make sure you frequently drain the muffler so you don't get water backing up into the exhaust manifold.

And if you don't have a drain on your FG muffler (most of us don't), shut off the thru hull supplying cooling water. The raw water pump CANNOT go dry, contrary to the old wives tales which abound on these pages. It may boil after running for a short time but it won't go dry.

JVISS ........................ ?

 

[jviss]

JVISS ........................ ?

What? My Catalina 36 muffler had a drain petcock. But, yea, you can close the seacock, too, I guess. Just remember to open it! I used to hang my key on the raw water seacock, to make sure I always opened it before starting the engine.

 

[Ralph Johnstone]

I used to hang my key on the raw water seacock, to make sure I always opened it before starting the engine.

I'm not saying my memory is getting any worse (at least not from what I can remember) but I don't even trust hanging the key on the seacock.

Finally installed a flow detector on the raw water inlet line, just in case one of the mottley crew members missed it .

In fact, I've heard the flow alarm wailing away once or twice indicating that someone grabbed the key and didn't open the cock. All in the name of getting away in a hurry.

Talk about thread drift. Subtle, mind you, but still there.

 

[RitSim]

Agree with all above. Had similar issues with my C30. You can temporarily use a piece of clear tubing in the fuel line feed up to the engine. The clear tubing lets you see if any air is getting in the suction. I also had to remove the injectors from the engine (still connected to fuel) and crank the engine till I saw fuel spray. Even though I had cracked the fuel line on top if the injector and was getting fuel, I still couldn't start. If you remove the injector, you may need to replace the copper crush washer. After you are all done, check the well around the injector for leakage.

 

[jssailem]

To bleed the injector pump of air, you must have someone crank the engine while you crack an injector fitting (or open a bleed screw as per @Ward H) to reduce the back pressure acting against the injector pump and allow air to be forced out of the pump.

That is why I installed a start push bottom in the engine room so I can crank the engine from the engine compartment not just the cockpit.

 

[jviss]

That is why I installed a start push bottom in the engine room so I can crank the engine from the engine compartment not just the cockpit.

I use one of those remote starter switches you can get at the auto store or Amazon:

Remote Starter Switch | Heavy Duty | Wired Start Crank | 6V-12V Car Truck Van SUV |

 

[Dave96734]

Thanks for all the great comments and discussion! I tried starting with the raw water seacock closed and it started up like a dream.

In retrospect, I had done a lot of cranking /failed starts before changing a battery several weeks ago. I had gotten a successful start since then, but it was the back pressure after all. Fortunately no evidence of corrosion.

Also, with regard to the injector pump, I had not cranked it, just let the fuel pump run. Learned a lot about my engine, and only missed a few days of sailing.

Mahalo,
Dave

 

[Ralph Johnstone]

Learned a lot about my engine, and only missed a few days of sailing.

C'mon .............. where else can you get a free education on diesel engines like this from SBO ?

 

[sailme88]

Thanks for all the great comments and discussion! I tried starting with the raw water seacock closed and it started up like a dream.

In retrospect, I had done a lot of cranking /failed starts before changing a battery several weeks ago. I had gotten a successful start since then, but it was the back pressure after all. Fortunately no evidence of corrosion.

Also, with regard to the injector pump, I had not cranked it, just let the fuel pump run. Learned a lot about my engine, and only missed a few days of sailing.

Mahalo,
Dave

Dave, have you pulled your dip stick? If any water made it into the engine it would find it's way to the oil pan. The oil will froth into a yellow foam. If present, immediately drop the oil pan and flush the engine with fresh oil.. SOMETIMES the oil doesn't get frothed. In this case, stop at an automotive store and get a reagent. They come in pastes, end strips that resemble pH test strips.. This is a very inexpensive test that could save BIG dollars

 

[Dave96734]

Dave, have you pulled your dip stick? If any water made it into the engine it would find it's way to the oil pan. The oil will froth into a yellow foam. If present, immediately drop the oil pan and flush the engine with fresh oil.. SOMETIMES the oil doesn't get frothed. In this case, stop at an automotive store and get a reagent. They come in pastes, end strips that resemble pH test strips.. This is a very inexpensive test that could save BIG dollars

I did check the dipstick: no foam, no bubbles. An oil change was on my to do list, and it has now made it's way to the top of the list, just to be safe!

 

[Dave96734]

Well, I may have celebrated too early. Back at the boat ready to change the oil but again the engine won’t start. Same symptoms! Tried with the raw water seacock closed. No difference. I am increasingly concerned about damage to the crank case from the water that was left in the circuit. Thoughts on next steps before getting on a marine diesel mechanic’s waiting list? To recap: I was able to start it once I closed the seacock. I let it run for five or six minutes.

 

[jviss]

Opening or closing the raw water seacock will have no effect on starting your engine.

 

[jssailem]

1. bleed fuel lines,
2. confirm starter is receiving charge.
3. I unscrewed the injectors and did not observe any fuel spurts when the key was turned & fuel pump engaged.

If you do not get fuel to the injectors (evidenced by opening the injector fuel line and seeing fuel escape - along with air) then the engine has not been fully bled of air.

Check that fuel is being pushed past the High Pressure pump to the injectors.

The seacock is kept closed till the engine starts. Water will be needed to cool the engine if you run it. So once started open the sea cock to provide a way for the engine to not over heat.

Since you ran the engine dry for "5-6 minutes" it would be wise to inspect the neoprene blades on the raw water pump. This is to assure the raw water pump impeller was not damaged.