Engine struggling to turn over

slimtim · 12 April 2009, 14:27

So i've re-built my engine and connected up all the electrics again in exactly (as far as I can tell) the same way they were before.

When I came to start it, it initially seemed to turn over fine but then it died off drastically to a point where there just didn't seem to be any umph left in the battery to turn it over. Charged the battery up over night, did the same thing this morning. Tried another fully charged battery that is used to start our tractor and it did the same thing. Somewhere there is something sapping out all the power from the battery before it can get to the starter motor.

The starter motor and solenoid seem to work as I ran the starter with it pulled away from the flywheel. I can also turn the flywheel freely by hand so its not a mechanical restriction.

Any ideas? I'm not too hot on electrics and so far my dad's a bit stumped too

Nos4r2 · 12 April 2009, 15:16

Bad contact somewhere.Look for a hot one. Either that or starter brushes are in need of replacement.

slimtim · 12 April 2009, 20:57

Are there any particular contacts I should check? I have checked the obvious ones and they seem ok (battery, starter motor and solenoid).

Can I replace the brushes in my starter motor myself or does it mean a new motor (=expensive I assume)? The motor seems to run fine when it can spin freely and it seems weird its never given me any problems before or shown any signs of degrading and now decides to just give up after being taken off and put back on again.

One thing that might be worth mentioning was that when I first tried to start it the other day it cranked over fine and actually started on the second attempt. It then stalled after a few seconds from what I assume was lack of fuel (I don't think it had been pumped through properly) and when I tried to then crank it again it got worse and worse until after about 3 or 4 cranks it could barely move at all.

Nos4r2 · 12 April 2009, 21:16

Start at the battery +ve and work your way through the heavy duty terminals. One will be hot. It'll be that one. It's unlikely you'll be able to see it without trying to start it and a multimeter won't test it as it'll only be breaking down under heavy load.
It's also still possible even though it's spinning up when off that your starter motor is the problem. If the brushes are worn out it'll notice under load 1st.
I assume your battery is ok?

slimtim · 12 April 2009, 21:44

we've tried 3 different batteries including a big one which is used to start our tractor (proper big tractor, not a sit on lawn mower!) so short of buying a brand new one we've pretty much ruled out the battery being the problem.

So its looking like it could be the brushes. Can I change these or will it be a new starter motor?

Nos4r2 · 12 April 2009, 22:25

Quote:

Originally Posted by slimtim

So its looking like it could be the brushes. Can I change these or will it be a new starter motor?

Take it somewhere that reconditions them-it'll be a lot cheaper. You may be lucky and be able to replace the brushes yourself, but I doubt it and unless you've done it before it's not an easy job to strip and reassemble without damaging it.

Poly · 13 April 2009, 07:01

Quote:

Originally Posted by slimtim

One thing that might be worth mentioning was that when I first tried to start it the other day it cranked over fine and actually started on the second attempt. It then stalled after a few seconds from what I assume was lack of fuel (I don't think it had been pumped through properly) and when I tried to then crank it again it got worse and worse until after about 3 or 4 cranks it could barely move at all.

Tim, i'm no expert - so feel free to ignore this suggestion especially if someone who is says im talking pish. Starter works OK without load, starter did work OK with a load, starter no longer working as expected with the load... ...could it be the load is too high? e.g. the engine is not turning over smoothly, assuming its 2 stroke, no fuel=no oil which might (will) be bad.

Just a thought before you start spending money on the starter.

Nos4r2 · 13 April 2009, 07:20

Quote:

Originally Posted by Polwart

Tim, i'm no expert - so feel free to ignore this suggestion especially if someone who is says im talking pish. Starter works OK without load, starter did work OK with a load, starter no longer working as expected with the load... ...could it be the load is too high? e.g. the engine is not turning over smoothly, assuming its 2 stroke, no fuel=no oil which might (will) be bad.

Just a thought before you start spending money on the starter.

There'll be enough residual oil in the engine to turn it over. It'd have to be nearly seized before a healthy starter couldn't turn it.

The starter should give good kick in your hand when it starts to spin if you try it off the engine. If it is,look at the starter solenoid instead.

slimtim · 13 April 2009, 08:37

Polwart, I have considered this but I can turn it over by hand with only the resistance of the air compression so it should be fine. I going to check each contact today and clean them even if they look ok and then take a look at the starter, I think the bottom comes off it giving access to the brushes.

Today is a perfect rib day

Poly · 13 April 2009, 08:42

Quote:

Originally Posted by slimtim

Polwart, I have considered this but I can turn it over by hand with only the resistance of the air compression so it should be fine.

Quote:

Today is a perfect rib day

the good news is that this means your engine troubles are completely fixable - and you will be back in action just as soon as the weather changes to being rain/sleet/hail and F9+

Steve Hackett · 13 April 2009, 08:53

Have you checked the main earth connection on the engine block is making a good contact ?

slimtim · 13 April 2009, 09:38

Quote:

Originally Posted by Steve Hackett

Have you checked the main earth connection on the engine block is making a good contact ?

Is that the one that runs from the solenoid?

Steve Hackett · 13 April 2009, 09:53

Quote:

Originally Posted by slimtim

Is that the one that runs from the solenoid?

No, the negative lead from the battery will be connected to the engine block, make sure the connection is clean and tight.

slimtim · 13 April 2009, 11:52

the neg from the battery goes to the starter motor which then grounds to the block through the starter casing. I thought this was the problem but I've just had it off and cleaned it all up and it didn't solve the problem.

I have cleaned all the contacts as best I can and have taken the bottom of the starter motor off to see the "brushes". They appear to be small metal spring loaded blocks but the contact they make is good and they don't appear to be worn at all.

Only thing I can think of is that the Solenoid is stealing the current and hiding it somewhere.

Nos4r2 · 13 April 2009, 12:03

Quote:

Originally Posted by slimtim

the neg from the battery goes to the starter motor which then grounds to the block through the starter casing. I thought this was the problem but I've just had it off and cleaned it all up and it didn't solve the problem.

I have cleaned all the contacts as best I can and have taken the bottom of the starter motor off to see the "brushes". They appear to be small metal spring loaded blocks but the contact they make is good and they don't appear to be worn at all.

Only thing I can think of is that the Solenoid is stealing the current and hiding it somewhere.

In which case, try this. It's a bit dodgy and will create a big spark, so make sure there's no petrol anywhere under the cowl.
Take a big, old, worn out screwdriver and short across the two main contacts of the starter solenoid with it. If your solenoid is duff,the engine will spin up normally on the starter.

slimtim · 13 April 2009, 12:40

yeah was thinking of doing something like that. Just bypassed the starter using a volt meter. With the battery at 12.55v the starter sees 12.2v (the solenoid clicks ok) which then appears to drop off steadily to 12.1v when the key is held in the start position. I'm not sure if it would drop off more than this if the key was held in the start position.

I am going to try cleaning the motor contact with the (carbon apparently, not metal) brushes.

Beach time

slimtim · 13 April 2009, 12:43

Quote:

Originally Posted by Nos4r2

In which case, try this. It's a bit dodgy and will create a big spark, so make sure there's no petrol anywhere under the cowl.
Take a big, old, worn out screwdriver and short across the two main contacts of the starter solenoid with it. If your solenoid is duff,the engine will spin up normally on the starter.

Actually Nos, I can create the same scenario by taking the battery cable off the solenoid and attaching it straight to the solenoid connection on the starter motor right? I can then use my battery master switch as my solenoid giving direct power to the starter to check its ok?

biffer · 13 April 2009, 15:53

try taking the plugs out and turning it over to see if it drops off, but i would plumb for a bad earth as well

slimtim · 13 April 2009, 15:58

Quote:

Originally Posted by biffer

try taking the plugs out and turning it over to see if it drops off, but i would plumb for a bad earth as well

I did that and it still couldn't cope with it. Starter motor has been cleaned up inside and will try that. If it still doesn't work I will bypass the solenoid to see if the motor is ok then it narrows it down to a faulty solenoid I guess.

biffer · 13 April 2009, 16:25

put jump lead straight to starter to see if it drops off, i hate to think that something inside your engine is causing it