Perkins intermittent starting problem

[Tamar]

My Perkins perama sometimes struggles to start as if the batteries are flat, then it will start normally. I've checked the voltage and it's 12.8 on each battery. It happens when the engine is cold or hot. I've cleaned up all the connections and it's still the same. New starter motor perhaps. All advice appreciated.

 

[Bilgediver]

My Perkins perama sometimes struggles to start as if the batteries are flat, then it will start normally. I've checked the voltage and it's 12.8 on each battery. It happens when the engine is cold or hot. I've cleaned up all the connections and it's still the same. New starter motor perhaps. All advice appreciated.

Sounds like a bad connection somewhere. I had a similar problem on a club boat and had checked all the usual places such as battery terminals and connections and then took a jumper wire to the boat and clipped it from the alternator bracket to the battery negative. Engine started easily. The earth connection on the engine had appeared to be clean and corrosion free. However when it was dismantled it was apparent that a combination of aluminium,steel,copper and brass was not a good idea. Once cleaned up all was well.

 

[Tamar]

Sounds like a bad connection somewhere. I had a similar problem on a club boat and had checked all the usual places such as battery terminals and connections and then took a jumper wire to the boat and clipped it from the alternator bracket to the battery negative. Engine started easily. The earth connection on the engine had appeared to be clean and corrosion free. However when it was dismantled it was apparent that a combination of aluminium,steel,copper and brass was not a good idea. Once cleaned up all was well.

Thanks, I'll give it a go later when the sun goes down a bit

 

[Tamar]

Nope, didn't make any difference

 

[LittleSister]

Presumably the 12.8v you measured was with the battery at rest and ,measured across its terminals.

Can you check what the voltage reads while cranking (a) across the battery terminals and (b) across the starter motor terminals?

 

[billskip]

Could be the starter solenoid fitted to the starter motor ( if that's the type you have.
The solenoid pulls a fork back that pre engages the bendix then makes the load across the contacts which then excites the starter motor.

If that is the type fitted.

 

[Tamar]

Could be the starter solenoid fitted to the starter motor ( if that's the type you have.
The solenoid pulls a fork back that pre engages the bendix then makes the load across the contacts which then excites the starter motor.

If that is the type fitted.

Yes it is

 

[Tamar]

Presumably the 12.8v you measured was with the battery at rest and ,measured across its terminals.

Can you check what the voltage reads while cranking (a) across the battery terminals and (b) across the starter motor terminals?

12.8 across the terminals the next day. Thanks for the reply

 

[billskip]

Yes it is

Well check the easy bits first like voltage drop under load and bad connections.
Dont be too quick to change the starter if it's an original lucas, the old ones are solidly built and can take some stick.

 

[Tamar]

I took off every connection this morning, cleaned them up again until they shine, especially the earth when I noticed the earth cable from the battery once I pulled the rubber cover down was a bit loose in the crimped part, so I guess this is not helping. The engine started easily first thing, but then struggled next time, only just catching after turning over very slowly.
Today's job get a new earth cable.

 

[LittleSister]

12.8 across the terminals the next day. Thanks for the reply

I'd be surprised if the voltage remained at 12.8v while cranking.

 

[Tamar]

I'd be surprised if the voltage remained at 12.8v while cranking.

What should a healthy voltage be when cranking?

 

[LittleSister]

What should a healthy voltage be when cranking?

I don't know, to be honest, but unless you have an amazing battery capacity I would expect the voltage to fall somewhat when you apply a big load like a starter to it. Unless the battery is significantly depleted the battery voltage will rise again to 12.8v or something near t that when the starter is turned off again.

The critical thing I suggest you look for is does the voltage while cranking fall further at the starter than at the battery? That would indicate that there is a significant resistance between the battery and the starter. (This would only be revealed when the cables and connections between the battery and the starter are carrying a heavy current, not when at rest.)

The curious thing about your case is the indication the problem is intermittent. If there is an intermittent resistance (e.g. damaged cable or joint that creates alternatively a resistance or not when moved) this will also affect the readings I suggested you take.

 

[Tamar]

it certainly is baffling. I will try all you suggest later when it cools off a bit. I will change the earth cable first just in case. Thanks for the reply

 

[Seastoke]

Do you have a clamp on amp meter

 

[Tamar]

Do you have a clamp on amp meter

No

 

[Seastoke]

Would be a good investment to measure load it would show overload ,.

 

[billskip]

This is where your problem could be...the contacts need cleaning...

 

[Tamar]

This is where your problem could be...the contacts need cleaning...
View attachment 140461

Thanks, I'll give it a go when I get a day off.

 

[billskip]

Thanks, I'll give it a go when I get a day off.

You can easy remove the solenoid if you have access space without removing starter.
There is normally two screws and two soldered connectors to remove the cover.
Take careful notice and mark the position of the cover relative to the body as the solder terminals must be re connected in same position