Slow cranking when hot - any advice please?

[starbiscuit]

Hello all,

Sorry to keep posting questions.

My bus starts great when it's cold. Good cranking speed, fires quickly.
But if I try to stop and restart once it's warmed up, the cranking speed is much much slower. Sometimes it fires, sometimes not.

When it's in this "slow cranking" state, if I can get the battery voltage up from normal 12-ish to 13 or 13.5 by jump-leads from another (running) car, or jumpstart powerpack, it cranks faster and it starts fine again.
And if I leave it to cool down for half an hour or so, it cranks at normal speed and fires up.

It's a bog standard 1600SP. Some-time-in-the-past not original pistons/barrels, but still standard capacity. As far as I could tell, standard everything else apart from an alternator conversion, but the "hot slow crank" problem came first.

The battery is relatively new. To check, I swapped it with a bigger one off my other car and it's the same deal.
The battery + and ground leads are new due to the old ones being corroded and insulation cracked.
I have removed and cleaned the battery ground chassis connection near the rear lights, replaced the transmission ground strap, cleaned the connections on the starter.

I've read a fair bit about hot start relays, lots of strong opinions (of course) both on "do" and "don't" fit one :roll:
I might fit one anyway, to reduce the current through the starter switch, but I'm not sure how, if the starter actually spins, that the relay would help it spin faster.

Every other car I've owned has always started better hot than cold, so I'm a bit out of my depth here.

Before I go and chuck £60-80 at a new starter, is there anything else I should check?

Thanks for reading.

 

[gas1man]

Check in the search section for .....Hot Start Relay.... it's a good place to begin.
With a cup of tea of course. :lol:

J & P

 

[gvee]

High resistance in the starter motor wiring.
Check the gearbox earth area
strap and consider reps
replacing the live feed. Hot start relay (standard 4-pin) will help.

 

[starbiscuit]

I have renewed the gearbox earth strap, the battery lead to the starter and the battery earth.
The problem existed before and is the same after.

I read a lot about hot start relay and I understand about voltage drop from the battery up to the ignition switch and back through the "crank" wire to the starter, leaving too little voltage to operate it.

But this isn't the feed that spins the starter motor, it only engages the solenoid (which throws the starter pinion into mesh and energises the starter)

So I don't see how a hot start relay would make the starter spin faster, because it doesn't directly feed the starter motor itself.
How does the voltage on the solenoid affect the current to the starter windings?

I do understand that it can make a difference if the solenoid won't engage at all, and that it is a good idea to take the load off the ignition switch contacts, which should make them last longer.

Maybe I'll fit a hot-start relay anyway and see what happens. 40A relays are only a few quid.

 

[ozziedog]

Just a thought :? When was the last time you checked your gearbox oil ???????
And if not that,,, maybe just see how hot the starter is when you have this issue before you crank it, then maybe have a look at a little refurb of bearings or just see how it is inside. Just had another thought, is it possible that the starter is staying engaged ? That would make it nice and warm :shock:

Ozziedog,,,,,,,,,,,,,,, :mrgreen:

 

[dustrat]

I had a similar problem a few year ago. Your starter motor does not have bearing but bushes either end. One of the bushes is in gearbox where armature shaft goes in and the other is starter motor housing at the other end. Through time these wear. I replaced both of these bushes and never had any more problems. Might not be your problem but worth checking.
Robert

 

[starbiscuit]

Before I have the issue, everything is pretty hot to the touch - starter, bellhousing, heat exchangers (very)

But if the engine has only run a few minutes, choke off, warmed up, but not "as hot as it gets", it's generally OK.

Gearbox oil is recent, I think.

Bushes are a good shout. I just came across that suggestion while trawling some more of the "hot start relay" threads on here.
The one in the bell housing seems to be favourite, and cheap, which is a bonus.

Is there a knack to getting it out?

And if I replace that, I may as well take the starter apart and see how bad it is, while it's off the bus.

And I may as well try a "hot start" relay, even as a temporary lash-up.

Thanks for the tips.

 

[dustrat]

Use a junior hacksaw blade and cut in in half. With a bit of luck you will be able to pull it out. If any of the bush drops into bell housing don't worry as it will get broken up by flywheel and do no harm. If you are going to refurbish starter motor may as well replace other bush and brushes.
Robert

 

[Moseley]

Or easier still for removal of that bush - run an M12 / M14 (can't remember which) tap down it. Once the tap bottoms out, the bush just threads its way up the tap until it is free.

 

[dubdubz]

I had a similar problem a few year ago. Your starter motor does not have bearing but bushes either end. One of the bushes is in gearbox where armature shaft goes in and the other is starter motor housing at the other end. Through time these wear. I replaced both of these bushes and never had any more problems. Might not be your problem but worth checking.
Robert

+1

this is most likely the cause - happened on both my buses. The tap trick also works - or you can knock it in.
Its a phosphor bronze so soak it in clean engine oil overnight as its porous it helps maintain the lubrication!

I only had to do the bell housing one not the other end

 

[starbiscuit]

Thanks all.

I've ordered the starter bellhousing bush and bits to rig a hot-start relay.

And I think I have the right sized tap to draw out the old bush, but I don't want to try it until the new part arrives.

I will post an update soon I hope.

Cheers

 

[starbiscuit]

So I can confirm that replacing the starter bush while the engine is in the van is a fiddly job.

That upper mounting bolt on the starter-motor is a sod. The nut is somewhere between the fan housing and the front tinware, which involves contorted blind groping.
Some people pay for that, I suppose.

An M12 tap is the right tool to get the old bush out.
And I found that the upper starter mounting bolt is ideal for knocking the new bush back in.

I spun an M10 nut onto the bolt to the length of the bush, then wrapped some insulation tape around the threads to hold the bush, slid the bush onto the taped threads and tapped it home with a hammer on the D-bolt head.

I stuffed a rag into the bellhousing in case I dropped something, but I didn't need it.

 

[StuF]

How old/recent is the starter itself?
When we first got the bus it would start perfect when cold but nothing when upto temp
Replaced the starter with a GSF item and no issues since

 

[starbiscuit]

Starter is from 1987 if the Bosch stickers on it are to be believed.

It cranks fine cold, and was very sluggish when properly hot. Not dead, just dead slow.

While it was all apart I wire-brushed the mounting bolts and flanges until they were shiny, because that's the current path to earth, and it does spin faster now.

I haven't got it properly hot yet, so I don't know if I will need a new one like you suggest.
At least the new ones are self-supporting, so a sloppy bush in the bellhousing isn't an issue.

Slightly annoyed at GSF "sale" games: now they have jacked their prices you can only shop there on 42%-off days.

 

[StuF]

Starter is from 1987 if the Bosch stickers on it are to be believed.

It cranks fine cold, and was very sluggish when properly hot. Not dead, just dead slow.

While it was all apart I wire-brushed the mounting bolts and flanges until they were shiny, because that's the current path to earth, and it does spin faster now.

I haven't got it properly hot yet, so I don't know if I will need a new one like you suggest.
At least the new ones are self-supporting, so a sloppy bush in the bellhousing isn't an issue.

Slightly annoyed at GSF "sale" games: now they have jacked their prices you can only shop there on 42%-off days.

Yep - I have noticed that about GSF and the continual "special offer" emails are getting tedious!
Fingers crossed you have cured it though!

 

[Purplemonsta]

Might be worth taking the end off your starter and giving it a clean out as well....mine's was full of black carbon dust from the brushes!!
Cleaned it out - and the commutator (and the grooves) and it's been great ever since
There's a clip on You Tube that shows you how - I only cleaned the brushes end and it sorted mine out