7.4 MPI won(39)t start...-gctid817855

[Jeffw]

Start battery and house bank new last year, charged and tested. Tried MBSS 1, then 2, then both, just a "clunk," like the first noise when turning over. Oil is clear (20 hrs. since service) and full. Tried turning flywheel with breaker bar, no problem. I have not checked for loose connections beyond the batteries yet, and my other thought is starter solenoid. Any thoughts? Thanks as always...

[itsabowtime2]

Jeff, I just had the same problem.

I first checked all connections, starter, batteries, switches.

Then checked power at the ignition, which was fine.

Then I checked power at the starter, fine.

Power at the solenoid, fine as well.

(of course checked the 50amp breaker and fuses at the panel as well along with "is it really in neutral")

I went forward with removing the starter and having it bench tested. Starter was bad.

The old hit it with a hammer trick did not work either.

[builderdude]

After verifying good clean connections at the battery, engine block, and starter motor I'd look at test jumping the slave solenoid first, these often wear out internally and will cause the issues you've described. If no go test jumping the slave then it's likely a starter solenoid or starter motor issue. In that case I'd recomended replacing the starter with a new unit as it'll need to come off the engine anyway.

Like Phil said, you can try the tap on the starter motors solenoid to see if she'll crank over, if it does then you've found the problem.

[Guest]

If you think it is a connection try this:

Run one digital voltmeter lead to the +12 battery post.

Run the other to the +12 solenoid post

Watch the voltmeter while engaging the starter...no volts, no connection issue

Move the lead from the +12 of the solenoid to the output of the solenoid if possible(where it enters the starter...some are accessible, some are not...)

Try again (see if the solenoid is working)

If that's ok, do the same trick from the -12 battery post to the case of the starter

***Note: If there is an open in the starter motor (Rare) it will befuddle this test.

Chay

[Ruffryder]

Meter for 12VDC between the two small prongs at the slave solenoid with the ignition switch on starting position...

[Jeffw]

Thanks all. I have young skinny friend diving into the bilge today at beer thirty...:cheer:

[builderdude]

"Ruffryder" post=817901 wrote:
Meter for 12VDC between the two small prongs at the slave solenoid with the ignition switch on starting position...

This is a great way to tell if there's "trigger power" being delivered to the slave via the ignition switch through the neutral saftey switch etc. but me thinks it won't help diagnose a slave thats not closing the circuit to the starter motor.

Jeff says he hears the "clunk" like the first noise when turning over" so it's likely the slave is closing and the starter motor or the starter motors solenoid is the issue.

[Ruffryder]

It will help to diagnose a slave that is not closing the circuit to the starter motor.

Measure the primary big terminal first...that should be constant 12V + HOT, then with the ignition key on Starting position, measure the secondary big terminal, should be hot if the slave is closing like they're supposed to.

If not hot, we know that the slave is faulty.

Slave closing, but nothing happens then we know it's the starter that's faulty.

[builderdude]

Agree completly Joon but you said small prongs initially :P

[Ruffryder]

Thought you knew bro,

Guess I'm just too lazy to type LoL

And I'm about to put a starter in my 4.3 OMC...

What a PITA.

[Jeffw]

OK, Joon's small prongs aside...

Seriously, the guys at the shop will be on it first thing Thursday morning. It was so hot and humid Wed. afternoon, and the beer was ice cold... They're doing the trailer bearings, and one of my young skinny friends is going into the engine bay to figure out the non-start issue. I'll let you know what they find, thanks for all the replies!:cheer:

[Chief_Alen]

a skinny bilge rat is the ticket, just don't feed em too much.

I second the slav, jump it with a screwdriver with a rubber handle, if she turns you know it's bad.

Not a marine specific part, capiche ?

Be well .

[Jeffw]

"Chief Alen" post=818027 wrote:
a skinny bilge rat is the ticket, just don't feed em too much.

I second the slav, jump it with a screwdriver with a rubber handle, if she turns you know it's bad.

Not a marine specific part, capiche ?

Be well .

But if it's the starter, that should be ignition protected/marine, right?

[builderdude]

Yes, and the slave will also be an ignition protected part that you may find at an auto parts supplier for le$$.

[Jeffw]

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