I have a 1988, #584 with a Universal M 25 XP and as I posted previously, I've been experiencing slow starting for a couple of years. I decided to replace all the glow plugs and when I tried to get started today, I could not remove the middle nut holding the wire on as it ran up against I believe the air intake manifold. With all the discussions about glow plugs, I never saw this mentioned. What I assumed would be a quick boat upgrade (when are the ever quick?) was aborted as I didn't want to get in over my head 2 weeks from launching. I can't believe it's designed this way but do I seriously have to remove the manifold to get the glow plugs out? Anything I need to be aware of once I start this boat surgery? Thanks in advance for any guidance. Brian McPhillips
I struggled to replace them without removing the intake manifold but in the end I pulled it and the job went off without a hitch. I wouldn't hesitate to do it that way again.
If the gasket(s) is in good shape, it's okay to reinstall them/it.
On my M25 im SURE i didn't pull the manifold, although it was too many years ago to say that 100%.
Maybe my plugs were shorter???
Is it a matter of trimming off the stud so that the nut can back off?
Trimming the stud is something that wouldn't have occurred to me. Very tight quarters so not sure if I can get my Dremel in there but maybe a file. The new NGKs have almost a 1/2" of stud above the nut. If the current plugs have close to that, I think it might work. Fortunately it's only one of the three plugs
What i did was to purchase a 1/2 inch socket.
And then I ran it thru a grinder
Fit slick as you know what
I also used a small winch handle with a hinged neck that I bought at Lowes
Works great now. Even my diesel mechanic friend was impressed
Cliff—Please post pics of your "small winch handle" from Lowes. I am a bit confused...
Brian : Look at the condition of the two plugs that you did get out. I'm sure that the middle one is in the same condition. You could just replace the two that you got out and I'm sure that if the slow starting is a glow plug problem - then the new two will help.
A thought
Quote from: Analgesic on April 26, 2022, 04:16:54 AM
not sure if I can get my Dremel in there but maybe a file.
I was thunking just a hacksaw blade (you don't need to buy a close-quarter hacksaw.)
One of my grandfather's go-to tools (he had an auto shop) was one of the shorter blades with a duct tape "handle" on one end.
Brian : That nut is either bronze or brass. I'd put some Blaster/Penetrating oil on it and let it set for awhile. Then use a 6 pt box end or socket and it should come off.
A thought
Thanks to all. Clarification to Ron and others, I can loosen the nut of the middle glow plug but in unscrews to the point that it runs into a part of the air intake manifold. There is not enough room to turn it the final turns to remove the nut so I can't get the wire off so no point in removing the plug so far. On the first and third plugs, the net comes off so the wire can and then the plug should be straight forward. As Ken suggested, if I cut off some of the middle plug's nut, I might get enough clearance to remove the nut, then wire , then plug. TBD when I visit the boat this weekend.
I had forest/trees vision.
You wouldn't need to perform precision surgery to be able to unscrew the nut all the way. Just unscrew it some and hack off the nut and stud. Since it will be trashed it doesn't matter how you get it off - you could work the stud back/forth with a needle-nose locking pliers and snap off the stud.
More important is how the stud is shortened on the new plug so it can be installed.
IIRC my old plugs had a round nut with an offset slot on the face for a flat blade screwdriver to fit into and turn it.
Brian : If you don't want to do as Ken suggested or remove the manifold then - then do as i said. If the two glow plugs that you removed are NOT burned to a nub then just replace those two and worry about the other one for a later time!! With 2 new glow plugs the engine should fire up immediately - if glow plugs were really the "slow staring problem?!?"
A few thoughts
Update: after looking closely at the middle plug, it seemed clear that trimming the stud might allow nut removal but the angle is such that I don't think the plug would fit backing it out. Removal of the entire air manifold was too intimidating 2 weeks before launch (plus at least two of the nuts looked extremely difficult to access). I went with Ron's suggestion replacing glow plugs 1 and 3 and the engine started up nicely. Maybe I'll take on the manifold removal to replace #2 next Fall with the luxury of many months to recover from whatever disaster I create and the back pain from the extreme boat yoga required. Thanks again for all the helpful advice as always! Brian
Fired her up on Monday with new glo plus and new batteries and never started so well!
Fancy!! Glow plugs are on my list. Even with a glow relay I have one cylinder that takes a bit to come along with the other three before they all run together.
Alex : When was the last time you ran a compression check??
A thought
I haven't but I dont have any reason to think it is low at this point. The condition only presents itself on a cold start. After the engine has been started once, it stats right up with all 4 cylinders, which points to glo-plugs.
Alex : If the engine starts on 3 cylinders and it takes some time for the 4th cylinder to kick in - it well might be that the glow plug is NOT the problem!!
A thought
Sounds good Ron. I'll make sure to call my mechanic first thing Monday morning and have him get started right away. ;-)
That said, it isn't near as dramatic as you are projecting. It takes about one or two ignition strokes and it lights off just fine. This is why I suspect glo plugs.
Ron
I'm interested why you don't buy into the glow plug theory?
That would be my guess not ever having experience running into that issue.
I'd think that the cyl could mis fire until it gets up to temp and the fuel properly ignites. I suppose but don't know if low compression would rectify itself after she warms up?? But if every cylinder doesn't fire what would be the first suspect - compression or preheat?
It's simple to verify if one has a bad glow plug!!
Ken & Guys : When the cylinder piston of a diesel is at TopDeadCenter the distance between the top of the piston and the bottom of the head is the thickness of a piece of paper! Boyles Law states that when a gas is compressed it raises in temperature!! So when the air diesel mixture reaches TDC (and a hi temp) there is an explosion driving the piston down (so no need for a spark plug!!). If the piston reaches TDC and that mixture is NOT ignited it could be that mixture is NOT compressed (like it is in the 3 other cylinders?). Hence, I'd check the compression on that cylinder.
If the other glow plugs are heating how likely is it that one plug is not?? My opinion is that it's slim.
My thoughts
Ok, I agree about how diesel ignites. But how/why does that cylinder ignite ok once the engine runs a bit?
And if the engine is still warm why would that cylinder not misfire if it's low compression?
I'm missing how those two situations relate to low compression.
If the glow plug is ok, I'd also suspect an injector that's "acting up" at startup.
Check the temp and the resistance of that plug compared to the others.
Guess we'll all just have to wait for Alex to tell us how he/his mechanic fixed the lazy 3rd cylinder problem!!
A thought
Prob not going to be for a while as it really isn't a problem. I am the mechanic that will do it and it will mostly be a process of replacing the glo-plugs for "known good component" as the boat is new to me. It is a process I go through with most mechanical things I acquire. I often replace service parts JUST to know their age vs getting stuck with a problem due to a part of an unknown use life.
Alex
VERY simple.... Preheat 30 secs (unless you have a preheat solenoid then 10 secs); feel each plug - if you can constantly hold onto a plug it's not heating enough. See if you feel a noticeable difference to the suspect plug.
Measure the resistance from tip to engine ground of each plug (at least the suspect one) or as many as you can get the wire off. See if the suspect is noticeably lower than the others (or zero -shorted, or very high -bad winding.
Being new to it, even if you systematically replace parts J.I.C. it's always better to know the condition of what you're replacing if there's an issue. Otherwise you might NEVER locate the root cause of a problem and never make more than one related change/replacement at a time.