Engine STOP button won't stop diesel engine

[SailingDownhill]

I have a Perkins M50 engine that periodically refuses to stop when the STOP button is pushed on the cockpit panel. The engine tried to stop - hesitating over and over. I suspect the fuel shutoff is not completing. Could it be the switch or the relay (and which of the 3 on the engine)? Any ideas?

[Cheechako]

It sounds like you have a stop solenoid on that engine and it's not pulling hard enough, or needs adjustment. But if it was working previously likely you need to replace that solenoid.

[Northbound44]

I support the fact that the solenoid is defective. I do have a Perkins M50 since 10 years now, best engine I ever had but the three solenoids that come with the engine are too fragile. Replace them with stronger ones and put them in a dry location.


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[barnakiel]

Test the switch up first. It may be old worn and interrupting. They do get worn over time.

Next test the solenoid without the switch. Just run a long + wire and touch where the signal wire enters. You should hear a very distinct click.

The same exercise on moror running tells you if the solenoid is OK or dirty/faulty.

b.

[rwidman]

Originally Posted by SailingDownhill

......... Could it be the switch or the relay ...........

Yes it could. Nobody on a web forum can tell you which. Test them.

[rwidman]

Originally Posted by rwidman

Yes it could. Nobody on a web forum can tell you which. Test them both.

BTW: It could be faulty wiring or connections as well.

[DeepFrz]

Check the wire going to the solenoid and the ground. I once had an engine that wouldn't stop and found the ground wire was broken. You may have a bad or loose connection in the wiring. Could also be a loose connection at the switch or a connector not making good contact.

Or, it could be a defective solenoid or switch.

[hoolie]

I had a similar, maybe worse, problem with our M50 when it refused to stop at all with the STOP button. It was a bad contact in the Schlegel ATL contact block behind the button.

They're not readily available now, so while I tried to source a replacement I wired in a temporary momentary contact on the panel connections. Now replaced, but I think if you're careful you can disassemble the ATL and clean the contacts.

[GordMay]

Greetings and welcome aboard the CF, SailingDownhill.

[SailingDownhill]

As suggested by Barnakiel I removed the panel enough to access the remove the STOP switch. Tested continuity at rest and when depressed. Saw no obvious signs of corrosion so I'm on to checking continuity to the solenoid. There are 3 relays, all Lucas 33RAs with different part numbers. Green Start? relay; Blue Glow Plug relay and Blue Negative Earth relay. I assume (I'm not an electrician) that the Green relay both starts and stops the engine. If that is the case I'll replace the Green relay.

[Kalinka1]

I had the same problem tis past summer on my Beta. I McGyvered a fuel shut off with a piece of small line and a small block from the fuel pump to the engine cover. Worked like a charm. Then the electric stop miracleus started to work again! so now have both if needed and the Gremlins are confused which I think is a good think! Same could be done with a choke cable but not as much fun.

[01kiwijohn]

Before you go replacing things, test each component AND check the wiring for continuity. I can't tell you how many times I have been called out to look at problems and found a bunch of replacement parts recently installed, and then I've located a wire or connection the was the actual cause.

[Northbound44]

Now I remember, the negative earth relay ( item 5 on the attached schematic) was defective.
In my case, the wire harness feeding the engine stop solenoid was also corroded. Follow the black and blue wire from the stop switch to the solenoid and check the ground relay ( item 5).
Good luck

[CapnCrunch]

01kiwijohn basically hit the nail on the head. When dealing with electrically powered devices (starters, shutoffs, pumps, etc.), ALWAYS check the simplest possible problems(i.e. connections, relays, fuses) first. I have seen many boaters (and vehicle owners) replace a starter, alternator and or battery only to find out that the problem was a bad connection.

[Cheechako]

Yes, could be a corroded terminal and resulting in low voltage to the solenoid.