Resurrecting a boat diesel engine - Ford Lehman

[Tony]

Been down the boatyard today helping out a mate with a boat he's acquired that has sat for some time full of rainwater.

The engine isn't seized and turns by hand no problem (injectors out - each pot is full of rainwater from the exposed inlet).  He thinks it's a 4.1 diesel of some description, from a truck?

Removing the starter revealed a flywheel with rusty gunk stuck to it at the lowest point, now all cleaned off.

Engine has been flushed with diesel to clean it up a bit.

The starter though, she won't spin up when connected across a battery (linked after the solenoid, which seems to work).  Just draws 100A or so and twitches.  I've turned the shaft by hand using a pipe wrench but this doesn't seem to help it spin up on it's own.   Sprayed a load of WD40 into it but no luck.

Anyone got any experience with DIY repairing starter motors?

It's quite a hefty beast!

[greasemonkey]

If you can pull a pump apart, you can pull a starter motor apart.

My guess would be that the commutator is heavily corroded, the brushes are stuck in and/or shorting to earth. Worst case the field coils, or the armature windings are shorting.

Without seeing it, I'll hazard a guess that you need to pull the plate off that bolts against the bell housing, or whatever is on there. Under there, you will likely see some gubbins, like a bearing and the drive gear. You will probably be able to pull the whole lot out of the casing in one piece, armature and all, once you have unscrewed the plate.

Clean it all up, and then when you come to put it back together, you will have to work out how to retract the brushes. Either they will be removable, so you can put them back on after you have reinserted the armature, or there will be a tiny hole in them somewhere. You push the brushes back in, put a piece of wire through the hole, and then reinsert the armature, then pull the wire out to let the brushes shoot out onto the armature.

It's not the end of the world if the coils are shot, they should be fairly easily available. You'd know how to test them better than I would though.

IIRC the field coils should be earthed to the body of the motor. Obviously, if the earth is heavily corroded, then that will cause problems. Better check with someone else on that one though.

Has it got a solenoid mounted on the side of the motor body? With some of them, the solenoid moves a lever inside the motor, which engages the gear into the flywheel. This can also jam. The shaft in the solenoid can seize, it can also seize the mechanism that moves the gear, among other things. You'll see it once you get it apart.

[Tony]

Thanks for the info - yes it has got a solenoid on the outside, this goes clunk when the start wire is connected to 12V and voltage appears on the motor side of the solenoid.  Not sure if it has a connecting mechanism.

So these starters, no permanent magnets just field windings on the outside and a brushed commutator on the inside?

The gear that should fly out to engage the flywheel we've moved by hand ok but obviously if there is some lever inside that shoves it out we've not tested or moved this.

[Dickjotec]

Don't forget it may be 24v if it is a truck engine. It will have field coils and an armature with a commutator.
Dick

[greasemonkey]

Not sure on the permanent magnets, you'll have to take a look.

After what you have said, I'll take another guess.

That solenoid does two things. It pushes the gear out, and at the same time, it pulls a plate back against two contacts. When the plate hits the two contacts, it gives the charge to the brushes, by which time, the gear is engaged with the flywheel. That is the solenoid bit of it. The cylindrical bit is an electro magnet that moves the bar back.
The whole lot could be corroded up, the plate and contacts are probably copper, so very likely to be heavily corroded.

Personally, I'd just strip the thing, clean all contacts and commutator, all moving parts, and stick it back together.

Biggest problem is the plate and contacts, they need to be contacting at exactly the same time, other wise it will ark on one side, and over time, burn a small hole in the plate, thus loosing contact. Basically, be careful gentle it up, try not to distort it. Finish it with some fine wet and dry, so its nice and shiney.

[Tony]

Since there is a big copper bar between the external solenoid and the motor I tried jumping that directly to 12V, this draw 100A and it felt like it twitched inside.  I assume bypassing the solenoid in the manner should spin the motor but probably not throw out the gear to engage the flywheel?

[greasemonkey]

I would hazard a guess that the starter you have may well be working on the same principle as this one.
It is post five if the link doesn't take you directly to the diagram.
You can see the gear and lever assembly, and the contact plate, although obviously they may be arranged differently in the motor you have.
http://forums.rennlist.com/rennforums/993-forum/643024-starter-question-is-lubricating-bendix-possible-without-removal-done.html

[Tony]

Ah!  Perfect diagram

[greasemonkey]

Since there is a big copper bar between the external solenoid and the motor I tried jumping that directly to 12V, this draw 100A and it felt like it twitched inside.  I assume bypassing the solenoid in the manner should spin the motor but probably not throw out the gear to engage the flywheel?

Not nessaserally. (How do you spell that word?)

Im not to sure where you have put the charge to, but if the bar in the electromagnet does not throw, then it will not send power to the brushes. Even if you have sent power to the brushes, by bypassing the solenoid, then the commutator could be so corroded that its not getting through. If it has been left in a salty and damp environment, then I would bet anything copper is green with corrosion.

Just strip the thing, you wont get into trouble with it. They are relatively simple once you get into them. If your in doubt, take plenty of pictures as you go along, so you can refer to them when you rebuild.  Thats what i do if I'm a bit dubious of getting something back together.

Edit: I'm guessing that the copper bar you are talking about actually charges the field coils, hence the twitch.

[photoman290]

what he said. suspect the brushes are stuck or the brush rings have corroded. the brushes need to slide in and out of the holders easily. if they stick due to the comm not be concentric when you turn it by hand the brushes move in their holders and lose contact with the comm.
as a rule it is not a good idea to try powering up something that has been in water for long time. it might be perfectly fine till you power it up. much better to take it apart and clean it up first.

[greasemonkey]

I'd almost guarantee that every bit of copper and every contact is corroded. Strip the lot down and clean it all up. Maybe test the coils and armature first. I don't know how to do that though.

[Glycer-rides]

I would think if the liners have been exposed to water for sometime they'll need honing as a minimum to remove the corrosion that will destroy the piston rings' sealing surface seconds after it starts.

[greasemonkey]

I would think if the liners have been exposed to water for sometime they'll need honing as a minimum to remove the corrosion that will destroy the piston rings' sealing surface seconds after it starts.

Totally agree. Whip the head off, and have a good inspection. Take a look at the timing gear, cams etc. It would be a shame to wreck something just for the sake of giving it a good clean.

[Tony]

This is a push-rod engine - the top end (rockers etc) seem to be fine.  The engine was submerged in rain water only to a certain height, the water in the bores is from the air inlet which was not adequately protected against the elements.  Unable to say what corrosion has happened in the bores - I'm wondering whether to try starting anyway and if it drops compression then have the head off and fit new rings on the pistons.  Might just be fine anyway!

[greasemonkey]

At least drop the sump oil first. Replace or reuse depending on what it looks like. Maybe fill the bores with something to loosen up any corrosion. Leave for 24 hours or so. I was going to say WD40, but diesel might be cheaper, maybe even Bio. Might want to turn it over once or twice in 24 hours. Spin her over with the injectors out before you start her, to clear the diesel out. Could be somewhat messy, but I would say it is worth it.

Get some pics.....