Perkins Prima M50 - Help with Starting

[keao]

Alright so i've been at it for days now. I can't seem to start my engine properly. If anyone has any knowledge in Perkins Prima engines I would really appreciate your input. this is what's happening:
turn key, wont start.
hot wire it at the solenoid and it starts, when i do this the alternator doesn't charge the battery. and the alternator light doesn't come on at start up or while its running.(I've changed the voltage regulator on the alternator with no w/out success)
trace the positive wire coming off the switch on the engine panel all the way to the starter solenoid and there is voltage in it (including another relay behind the engine).
what i can figure, there is a negative in the system somehow connecting the alternator and starter, or there is another relay i can not find. ANY HELP IN THIS WOULD BE REALLY GREAT!

[Kettlewell]

Sounds like the ignition switch is bad. The field current for the alternator also goes through that switch so you aren't getting any charging from the alternator. But on rereading you say that there is power coming out of the ignition switch to the solenoid when you turn the ignition switch to the start position? It has to be in that switch to the solenoid circuit because you say you can jump the solenoid and it starts, so I would say it is likely the switch. It's not that expensive for a new switch.

[keao]

i checked the ignition switch with an ohm meter, perhaps i'm doing it wrong, but it's a simple push button that connects two wires, i can't see that going bad, but it's possible.

[Kettlewell]

Is there a key switch before the push button starter switch?

[brankin]

I have an M60 and had the same problem. You won't believe it but you have a bad diode in the alternator. The alternator has a circuit that is a negative polarity until it starts and then it turns positive and kills the starting sequence. That is why the panel doesn't work when you turn it on but the starter will fire when it is jumped. Even the experts at Perkins couldn't help me when I had my problem.
Solution...remove the starter and have a starter shop go through it. Re install and it will start like new with the alternator charging like a new one.
Good Luck

[keao]

yes it has a switch.
Brankin, thanks i'll give it a try, i have a spare. when the engine is running and i put a volt meter to it, i get 12.5-13.5 volts. did u get volts coming off it?

[keao]

oh, and all my other instruments on the panel seem to work fine. does that sound familiar?

[brankin]

Look at the wiring diagram and trace the wires from the alternator back to the panel. You can see that if the wire is a negative, the voltage will flow through the panel. If it turns positive, it will neutralize the circuit and turn off the panel.

[Kettlewell]

OK, it sounds like you are now hooked up with someone who knows more about the Perkins M50 than I do. I read somewhere that the M50 has some sort of relay that only hooks up the negative ground to the engine block during starting in order to get the starter to turn over. Not sure if that is on all M50s, but that seems like a possible area to investigate too.

[Rocketman]

I believe the relay that brankin is talking about, is right next to the post on the alternator that carrys the charging current back to the batterys. If you disconect the alternator without turning the power off at the batterys you will fry alot of gound wiring going to the engine. Don't ask me how I know that.

[colemj]

Originally Posted by brankin

Solution...remove the starter and have a starter shop go through it. Re install and it will start like new with the alternator charging like a new one.
Good Luck

You mean to remove the alternator and take it to an alternator shop for new diodes, right?

Mark

[barnakiel]

A very similar problem to things discussed here:

A Perkins started burning the wires between the block and the negative, on its negative earth relay. All other wires are fine except that we too noticed burned earth wires running from the engine to equipment attached to the engine's block.

What is the cause?

barnakiel

[DeepFrz]

barny, it sounds like the alternator is grounded to the block but the block to ground bus has been removed or has a loose of corroded connection or the ground cable is to small.

[barnakiel]

Yep. It definitely may be some wiring issue - either a bad connection or something not wired the way it should. When I came to the boat her starter battery bank was dead, I used the house bank to start the engine and it started fine.

Now with new starter batteries in place we lost the loom. (Twice) At this stage we know what burns and we can see that in later productions Perkins added a fuse in this line (negative earth relay line - wires lead to engine block and to the negative terminal in the connection box). We can also see that others had similar burning issues with ground wires (pun unintended).

We will trace the earth wires, battery wires, etc. now,. If we find the solution I will post here a longer story for the next generation of Perkins' owners.

b.

[JWK]

I have a similar intermittent problem with a Perkins M50 engine and instrument panel. The ignition key is a simple on/off switch that powers up the panel. There are momentary contact push button switches for the glow plugs, starter and stop solenoid. When the key is turned on the alarm buzzer sounds and the "battery" light the fuel gauge come on; depressing the start button activates the starter or nothing happens.

If the starter engages the engine starts immediately but the battery light does not go out and the Tach does not operate. As the engine warms and is operated at normal RPM the Tach eventually comes on and the battery light goes out and everything operates correctly.

The alternator was rebuilt when the intermittent problem first arose; it puts out 14+ volts at an idle. The shop doing the work said they didn’t find anything wrong. I’ve checked and cleaned all the connectors, harness plugs etc., and concluded that the problem is likely in one off the three relays in the system or possibly one or more of the switches.

The switches look ok and appear to function correctly so I’ve ordered new relays assuming that they are the likely failure point. I’d be interested in other M50 owner’s experiences with the panel, switches and relays.

Jim