Engine cranking speed

[WNX700H]

In one of my cars , I have a 1380 engine 285 cam around 9.75to 1 CR.

I have problems starting the car in terms of getting it to crank at sufficient speed to get it to start ....

a) When cold

and

b) When I have used the car in anger on a rally , if I stall it, it is almost impossible to get it to turnover. If I wait 40 sec or so eventually it will reluctantly turnover , as soon as it cranks it fires .

What are the likely causes ? Have gone thro several starters but no real difference , changed wiring etc no difference.

Suggestions ? Cant use a geared starter as am running in historic classes.

Thanks

David

[littler]

battery / charging issue?

has it allwase been like it or is it getting worse?

i think youre ok running a gear reduction starter with historics .

[WNX700H]

The car has always been like it . Does not appear to be a charging issue . Have fitted a bigger battery but problem remains. Can cost me up to a minute if I stall it on a stage .

[mk1coopers]

Earthing fault?, have you tried doubling up on the engine earth

[greyghost]

X2 on the earthing issue.

but pull apart every connection, from the battery and the starter, and clean them.
and check your solenoid.

[IAIN]

Is the problem a long running fault with the car or has it only been with this engine unit ?

Another thing to check is the starter motor for worn bearings/bushes. Swap it to eliminate it.

[mini13]

Ok a few tips/things to try for you,

Get a volt meter and measure the volt drop on the cables during cranking, and make that sustained cranking, pull the coil lead off before you start, and also give the cable you are measuring a wiggle while your measuring to check for broken cores.

anytime a cable drops voltage it gets hot and limits/wastes energy that should be going to the starter, a mini starter consumes about 2.5-3kw if you have a cable in the line with 1v of drop that cable will be disipating about 250watts,

I would say any cable thats droping more than 1/4 to half a volt you should replace, Also on the subject of cables, the std style battery cables are prone to the cores breaking if there is any movement in the cable due to them having 8-10 thick copper (or aluminium) strands, I have moved to multistrand cable, all my cables are 10mmcore made up of about 30 or more copper strands, the cable is much more flexible, and less prone to fatigue, I got mu cable from a boat suppliers, they use it for electric bow thrusters on larger boats.

Also another thing worth looking at is your cranking timing, I had a ,look at a car recently that wouldnt start, I checked all the cabling as above, and found that during cranking the battery (and large booster pack) were being pulled down to about 7 volts, put a known good battery on and the same... the up shot was there was too much advance on cranking, so the starter was fighting the enine trying to run backwards, It sounds like your in historics so will be running bobweights, could be a sticky bobweight or weak spring?