Engine not starting - advice urgently needed

[ProDave]

UPDATE
-------------
Shorting out the solenoid with a screwdriver did not do anything.

There is only 7.15V at the big red wire on the solenoid and the same voltage at the red/white terminal on the key switch. (This is testing it with a multimeter with the - ve lead earthed on the engine block)

The voltage is the same on the engine start battery, on the domestic batteries or on both (I have a 1/2/All switch)

Where should I look next?

(All other electrics, lights, instruments, Webasto) are working fine)

That suggests your batteries are flat. Highly unlikely ALL of them.

So repeat your measurments with the -ve probe of the multimeter on the battery -ve terminal.

Also measure on ohms between battery -ve terminal and any metal part on the engine block.

Report the findings.

 

[Sea Change]

That suggests your batteries are flat. Highly unlikely ALL of them.

So repeat your measurments with the -ve probe of the multimeter on the battery -ve terminal.

Also measure on ohms between battery -ve terminal and any metal part on the engine block.

Report the findings.

I don't think it does. A Websto is pretty voltage sensitive and wouldn't start if the battery was flat.

 

[ProDave]

I don't think it does. A Websto is pretty voltage sensitive and wouldn't start if the battery was flat.

He says he only has 7.15V reaching the input terminal of the solenoid. Where is he measuring that with respect to? Engine block or battery -ve terminal. That is what I am trying to get at. It could be flat batteries (unlikely all of them) Faulty 1/2/both switch or engine earth strap failed for example.

And it should be pretty easy to determine which.

 

[webcraft]

Well, it was a loose earth connection at the domestic batteries, which of course is also the earth for the engine start battery (only the lives are switched)

Two seconds with a 13mm spanner and all was well.

Particularly galling because
a) I installed the brand new batteries myself less than 3 months ago

and

b) 1st mate had suggested a loose battery connection but I didn't believe it could be that simple and instead went down a rabbit hole.

Thanks to all who responded, I have learned quite a bit.

- W

 

[Mistroma]

Well, it was a loose earth connection at the domestic batteries, which of course is also the earth for the engine start battery (only the lives are switched)

Two seconds with a 13mm spanner and all was well.

Particularly galling because
a) I installed the brand new batteries myself less than 3 months ago

and

b) 1st mate had suggested a loose battery connection but I didn't believe it could be that simple and instead went down a rabbit hole.

Thanks to all who responded, I have learned quite a bit.

- W

Just glad it was an easy fix. All the signs were in favour of just a bad connection somewhere. Finding the somewhere is the time consuming bit. Inside a switch, crimp, corrosion, etc.

 

[dunedin]

Well, it was a loose earth connection at the domestic batteries, which of course is also the earth for the engine start battery (only the lives are switched)

Two seconds with a 13mm spanner and all was well.

Particularly galling because
a) I installed the brand new batteries myself less than 3 months ago

and

b) 1st mate had suggested a loose battery connection but I didn't believe it could be that simple and instead went down a rabbit hole.

Thanks to all who responded, I have learned quite a bit.

- W

Glad you got sorted so quickly.

And presumably a bottle of red for the 1st Mate, now also promoted to Chief Engineer

Back to Mousa? It is worth it if not overrun by trip boat folk. Climbing inside the walls and walking round the roof walk, which makes other castles seem like modern builds.

 

[webcraft]

Glad you got sorted so quickly.

And presumably a bottle of red for the 1st Mate, now also promoted to Chief Engineer

Back to Mousa? It is worth it if not overrun by trip boat folk. Climbing inside the walls and walking round the roof walk, which makes other castles seem like modern builds.

Sadly it's gusting 20kts right into the anchorage, so we are heading down to Sumburgh for an early stsrt to Fair Isle tomorrow.

 

[penberth3]

Well, it was a loose earth connection at the domestic batteries, which of course is also the earth for the engine start battery (only the lives are switched)

Two seconds with a 13mm spanner and all was well.

Particularly galling because
a) I installed the brand new batteries myself less than 3 months ago.....

Fit and forget? Had you checked the batteries in the last three months?

 

[webcraft]

Fit and forget? Had you checked the batteries in the last three months?

I fitted them less than 3 months ago!

 

[penberth3]

I fitted them less than 3 months ago!

Is that an admission you haven't checked them in three months? This should be a regular thing e.g. every time you check the engine.

 

[Sea Change]

Is that an admission you haven't checked them in three months? This should be a regular thing e.g. every time you check the engine.

So you honestly check the terminals on the battery every time you start the engine? Fair play to you. I certainly don't.

 

[PabloPicasso]

Check fuses first.
Check fuse connections.
If in doubt, replace.

Do you have 7volts at the battery terminals? That won't crank anything

With electrics be methodical

Start at the battery, if good, move to the next connection (? Fuses?).

Check beforw & after fused joints. Then work up all connections in order until you find where there's no power. Thats how to isolate the fault.

 

[PaulRainbow]

If all else fails, short the two large terminals on the starter solenoid with an old spanner or hefty screwdriver.

This will not work. The motor will spin, but the starter will not engage.

 

[PabloPicasso]

So you honestly check the terminals on the battery every time you start the engine? Fair play to you. I certainly don't.

Lots of people have voltage monitoring displays on, or near, the main switch panel which are easy to check

 

[Chiara’s slave]

So you honestly check the terminals on the battery every time you start the engine? Fair play to you. I certainly don't.

We have a volt meter on the main switch panel. If that says we are low, then I’d investigate. Otherwise ours remains ‘unchecked’ indefinitely.

Simultaneous post. We are one of those people.

 

[PabloPicasso]

We have a volt meter on the main switch panel. If that says we are low, then I’d investigate. Otherwise ours remains ‘unchecked’ indefinitely.

Simultaneous post. We are one of those people.

Anyway, gkad it was a simplemfix and you got it sorted.

Well done.

 

[PaulRainbow]

A loose negative on the domestic batteries should not stop the engine starting, something isn't right with the wiring.

Do you have a battery monitor ?

 

[webcraft]

A loose negative on the domestic batteries should not stop the engine starting, something isn't right with the wiring.

Do you have a battery monitor ?

It means a poor earth connection to the engine, surely? Just at the battery end, not the engine block end. I would have thought the effect was exactly the same.

(The engine start battery negative goes to the same terminal on the domestic bank. Batteries are selected via the 1-2-both switch, which only has the positives connected)

 

[Mistroma]

This will not work. The motor will spin, but the starter will no engage.

Unless he managed to find an antique inertial engagement starter.

Even I only remember them faintly, so must be truly ancient.

 

[awol]

This will not work. The motor will spin, but the starter will no engage.

Having succesfully started my old 2GM (oft discussed problem activating solenoid) with an 8mm allen key across the solenoid M8 studs, I disagree. As to the circuit which causes the solenoid to activate during this I neither know or particularly care. If I can be bothered I may investigate with the redundant (2GM long gone) spare in the garage.