25XP Fuel Priming Conundrum

DougM · Feb 9, 2015

I have a friend with the same engine in a Newport 30. He had problems with the engine quitting, resulting in tow ins. He went through the entire fuel system, replaced the pump, replaced filters, cleaned everything, and still had the problem. One afternoon he laid what he thought were perfectly good flexible fuel lines on a countertop and after awhile noticed diesel fuel around the lines. As he picked up the lines to clean up, he happened to flex them and more fuel flowed out of otherwise imperceptible cracks, which were allowing air into the fuel system. Those lines were replaced, and the problem disappeared.

Ron20324 · Feb 9, 2015

I have not yet seen mentioined the screen filter in the fuel tank.

Maine Sail · Feb 9, 2015

Ron20324 said:
I have not yet seen mentioined the screen filter in the fuel tank.

He stated he's got fuel to the secondary filter but this is a good pint and there should not be any screen on the pick up inside the tank.. ..

I suspect this engine has a bypass screw not a bleed screw. With a bypass screw you crack it and fire the fuel pump. When the ticking noise of the fuel lift pump changes from fast to slower the system is usually bled... The only way they will see fuel at the injectors is to bump the engine over while they are cracked. On some engines you need to bump it over with a remote starter switch to get a good bleed but not with the Universal/Kubota's.....

woodster · Feb 9, 2015

Maine Sail said:
He stated he's got fuel to the secondary filter but this is a good pint and there should not be any screen on the pick up inside the tank.. ..

I suspect this engine has a bypass screw not a bleed screw. With a bypass screw you crack it and fire the fuel pump. When the ticking noise of the fuel lift pump changes from fast to slower the system is usually bled... The only way they will see fuel at the injectors is to bump the engine over while they are cracked. On some engines you need to bump it over with a remote starter switch to get a good bleed but not with the Universal/Kubota's.....

i am glad you posted this info as i was wondering about the fuel getting past the pump without turning the engine over as i understood the injector pump controlled the fuel flow to the injectors as it acts like the distributor directing fire to the cylinders one cylinder at a time

Maine Sail · Feb 9, 2015

woodster said:
i am glad you posted this info as i was wondering about the fuel getting past the pump without turning the engine over as i understood the injector pump controlled the fuel flow to the injectors as it acts like the distributor directing fire to the cylinders one cylinder at a time

On some engines the easiest and fastest way to bleed is to use a remote starter switch, close the seacock and bump the engine over as you crack each injector. Fuel will not get past the high pressure pump unless the engine is turning... With Kubota's you don't need to do this....

Stu Jackson · Feb 9, 2015

Maine Sail said:
I suspect this engine has a bypass screw not a bleed screw. With a bypass screw you crack it and fire the fuel pump. When the ticking noise of the fuel lift pump changes from fast to slower the system is usually bled... ........................but not with the Universal/Kubota's.....

Bleeding 101 http://c34.org/bbs/index.php/topic,6377.0.html

for M25 & M25XP engines.

Yes, it is a bypass on these engines, we call it the "knurled knob" 'cuz that's what it looks like.

jibes138 · Feb 9, 2015

So as Maine Sail noted with the knurled knob opened fuel should be flowing freely back to the tank. Listen for the flow into the tank or simply remove the line from the tank return, stick it in a mason jar and turn on the pump. No flow will suggest you start troubleshooting between where you do have flow and where you don't.

Stu Jackson · Feb 9, 2015

captnron said:
Ron,

As addressed earlier, the tank was cleaned, the screen also. Fuel was pumping thru the pump freely. It's the fuel flow problem after the secondary filter that we are troubleshooting.

CR

CR,

In the link I provided is a discussion, actually quite a few

, that note my experience that the nut on the secondary filter needs to be removed until fuel flows out of it. It's messy, but my experience indicates that unless I do this the knurled knob alone doesn't do it when the secondary filter is changed. The knurled knob alone only works by itself when the primary only is changed out. That's why I put a fuel pump shutoff toggle switch in my engine compartment: so I could turn off the pump without having to jump up to the cockpit to turn the ignition switch off, when I change thew secondary, pop the nut and wait til fuel comes out.

That could be your issue. Only one I can think of, given your systematic approach in your discussion.

I, too, agree, that you should check the cutoff handle, but do so at the engine end, too, top end, forward, starboard side.

jibes138 · Feb 10, 2015

Please share your results when you solve this. Never know when the rest of us might have this problem and what to do about it.

jibes138 · Feb 10, 2015

captnron said:
Stu, We did a bleed when installing the secondary filter, a bit of hissing air then fuel flowed. The fuel shutoff was working properly, linkage wise. The one thing I found that needed to be looked at was the de-compression lever that was frozen but in the up position. Checking both positions, you could tell the engine was in compression mode when up & free spinning when held down. We also had the inline valve off the tank closed when changing out filters making it easy to bleed & prime. Jibes, Was hoping to find a post from someone that had the same problem & found the fix but, still waiting. When we find the culprit you betcha, we will post it. Still, the big question, the engine worked fine, shut it down & it would not restart. No parameters or settings were changed anywhere in the system. CR

forget the work you did and focus on troubleshooting. You need compression fuel air and fuel injection at the right time and the right spray volume. I would look at each element but fuel is the big suspect since you monkeyed around with the fuel system. Any chance you caused an exhaust system blockage ? That would be a problem too. Don't keep cranking unless you drain the raw water. Shut off the raw water valve until it starts so you don't flood the exhaust manifold. Maybe the injectors need refurbishment or the injection pump is suspect? Are the glow plugs working?

Jake N Eggs · Feb 10, 2015

CR,

I don't know your engine specifically but here is my take. I assume that the engine shut off is a pull cable. I understand that you have checked the fuel shut off lever position and it is correct. The external fuel cut off leaver usually indexes on an internal mechanism in the fuel pump. It could be that the internal mechanism is stuck in the shut off position. I think that you said that you opened the injector lines at the injectors and got no fuel. If there is no fuel at the injectors the fuel is not passing the injection pump. This would seem to reinforce that the fuel shut off mechanism is stuck in the shut off position.

Hope I understood the process correctly up this point. Good luck.

Jake N Eggs · Feb 10, 2015

By the way, sometimes the shut off act directly on the governor mechanism to push it lower than idle to the fuel shut off position. If this is the case it may be possible to increase the tension on the governor, and thus release the shut off, by moving the engine control to full throttle.

Stu Jackson · Feb 10, 2015

Captain Ron,

I know it's an M25XP, and, as such, should have the simpler wiring. But I wrote this for a constantly recurring issue with newer engines where the "improved" (HA!) wiring had the glow plugs and oil pressure tied into running the fuel pump at startup. If you have the simpler straightforward wiring, forget this, but it's the only other thing I can think of. Good luck. Can't wait to hear. (There is fuel in the tank right?

).

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The newer Catalina and other brand engines have a dual start wiring arrangement where the pump comes on when the glow plugs are energized and then stops until the engine starts AND only resumes when the oil pressure is made. I find this kinda dumb for bleeding, but the engines are supposed to be "self-bleeding." But, "Self-bleeding" works for the primary filter, but doesn't always work on that secondary filter, which is why it makes me think the concept is dumb. There's another downside to this silly design:

...requiring holding the glow plugs via the keyswitch spring position ON while hitting the start button MEANS that there is a continuous draw on the battery bank from BOTH the glow plugs AND the starter motor. Our C34-group experience is that this INHERENTLY leads to tough & rough starting. The Mark I “trick” has always been to RELEASE the glow plug (button in our Mark I case) BEFORE the start button, so that both heavy amperage draws are NOT on at the same time.

and

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Another interesting sidebar to this whole "when does the fuel pump run?" issue just occurred to me after stumbling over this thread: http://c34.org/bbs/index.php?topic=64.0 or any other of the many fuel bleeding posts.

IF the fuel pump ONLY works when the glow plugs are held on with the spring switch OR when the engine is running, bleeding the fuel system is a real PITA. To successfully bleed the system, as discussed here and finally summarized by Ken Heyman (http://c34.org/bbs/index.php?topic=2884.0), it's MUCH easier to run the fuel pump without the engine on, and why would you want to have to energize the glow plugs when you bleed the engine?

Another one of those UNFORESEEN CIRCUMSTANCES and unintended consequences as a result of a "design improvement" that makes things worse, not better.
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and: http://c34.org/bbs/index.php/topic,3347.msg21275.html#msg21275

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Of course, I'm not opinionated about this at all!

In that case, I recommended to our skippers that they re-wire the stupidity out of their systems and just run the pumps all the time.

Here's a perfect example: http://c34.org/bbs/index.php/topic,5078.30.html

Good luck. You'll love that pump when ya need it!

Stu Jackson · Feb 10, 2015

Ron,

Be VERY CAREFUL WITH THAT ASSEMBLY.

One of my friends messed with his and took forever to get it corrected properly because of the little spring either inside or at the edge, maybe even two springs, it's been a while since that happened.

Not a bad idea to check though, but do your homework (as i know you would) before disassembling any part of that starboard upper side housing below the fuel lever.

captnron said:
Jake,

You brought up a good point on the maybe the fuel stop had something failed in the interior. Looking at an exploded view, I doubt this but, that got me to thinking so, I pulled out my 20HP with similarities to the 25XP for a comparison.

The whole assy. is called the speed control unit that includes the governor, speed control lever & engine stop lever. All of these are connected to the lever shaft. The engine stop lever is at the top & is held in place on the shaft with a spring pin.

That got me to thinking that what if the pin sheared, theoretically, that might allow the lever to move looking in working order or, it's just sliding around on the shaft looking like it's working. The exploded view shows the hole for the pin in the shaft so, it's at least worth a look.

It may be a long shot as usually a lever has to be restrained from movement for a shearing of the pin but, at this point, it's definitely worth a second look.

Thanks,

CR