Can't start unless hot-wired

[OS2Dude]

We have a 1985 Catalina 30 SR sailboat with a Universal M25 diesel.

Control panel has an ignition switch, glow plug button (Hold to contact) and a start button (Hold to contact).

Currently the start button does nothing. :grumpy: (Was fine 2 weeks ago.) However, if I short across the start relay engine fires right up. Engine wiring harness was replaced 9 months ago and ends terminated with new connectors.

Tested batteries (Good Charge, Fair to Good electrolytes), voltages at Ignition and Start Button (14 +/-), Voltages at power posts on start relay (From + post on starter and battery and back to - post on starter. 14 +/-), and voltages at relay 'control' posts. (One from start button, other is ground). Here it seemed voltage was only 12 +/- with button pressed.

Removed starter and had tested, Passed. Replaced relay, No Joy. Cleaned ground, still No Joy.

Have run out of ideas. Not a mechanic, so please be complete in your replies.

Thinking of running power via jumper wire to start button post on relay. Do I risk anything doing that?


Thanks!

 

[gm280]

:welcome: OS2Dude to iboats...

If you are able to jumper across the starting relay and the engine starts and runs, then obviously there is your problem. And since you stated you replace that relay and it still doesn't start, then the control voltage that is used to energize that starting relay isn't working. So you need to jumper the control terminal on the relay to see if you can click it in. If you can do that, then the control voltage from the starting switch is either bad or the wiring from that switch. Make sure the starter relay have a good ground on the control terminal as well. There are no other possibilities. JMHO!

 

[StarTed]

It sounds to me like your start push button may be bad. Check the voltage across the button connections before and after pushing it. I would expect full voltage before pressing the button and it should drop to nothing when depressed. If that doesn't happen then you have a bad push button switch. If you don't find any voltage at all then check out the wire between the switch and the starter relay.

 

[wrench 3]

I found three different wiring diagrams for the Universal M25. They all show a 20A fuse in the wire from the switch to the starter solenoid. They show it in the yellow and red wire in the harness at the engine.

 

[OS2Dude]

I found three different wiring diagrams for the Universal M25. They all show a 20A fuse in the wire from the switch to the starter solenoid. They show it in the yellow and red wire in the harness at the engine.

Yes, checked that too, all seems well with the fuse and holder.

 

[alldodge]

Here is the wiring diagram, note the white wire which goes thru pin 3 when start button/switch is energized

 

[wrench 3]

If the switch checks out OK, Look at the harness eight pin plugs. Make sure the metal connectors aren't pushed back into the plugs, the female connectors aren't expanded and not fitting together tight and that none of the wires stretch when pulled. Also check for corrosion.