Madinventions
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| posted on 19/2/10 at 09:50 AM |
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Sluggish cranking
A friend of mine has a Sylva Mojo with a 1600 CVH engine that cranks very slowly when cold. We've fitted a brand new fully charged battery
(260CCA) which didn't make much difference. During cranking, the voltage at the battery terminals drops to around 11V so this should mean that
the earthing etc is ok as reading at the battery will ignore any wiring losses. The resistance between the battery negative and the engine block is
<0.1 ohm.
The engine itself is fairly modified with Kent cams, Pumaspeed head, larger valves, Webber 45's etc.
At tickover, the battery voltage is 14.1V (measured with a DMM at the battery terminals) so the alternator seems fine although the battery light will
come on if you leave it to idle for 5 minutes or so. A quick blip on the throttle makes it go out immediately. The idle speed is steady with no
hunting.
When the engine is warmed up, the cranking seems somewhat faster and the engine catches much more quickly (1-2 revolutions). When cold it can take a
few goes of 10+ revolutions for it to start.
So - has anyone got any ideas what we could try next? It seems that something is loading the starter heavily so my next guess is the starter motor
itself or something as simple as really thick sludgy oil although it did look ok from a quick wipe of the dipstick. Maybe it's just the way
modified CVH engines are? I must admit, I'm more used to the quick starting Zetec SE engines so this is unknown territory for me! 
Your help would be appreciated as always!
Ed.
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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cd.thomson
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| posted on 19/2/10 at 09:55 AM |
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cranking advance? what ignition is he using?
This will have a more noticeable effect when cold
Craig
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Bluemoon
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| posted on 19/2/10 at 09:57 AM |
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I would guess thick oil, as it's cold.. Is it the correct grade? Also CCA of 260 is probably a small car battery, so in combination this maybe
why.
Dan
[Edited on 19/2/10 by Bluemoon]
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Jenko
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| posted on 19/2/10 at 11:48 AM |
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Get some jump leads and ground the battery (gound) then try it - This will tell you for sure if you have any grounding issues.....
If your feeling brave you could also try a jump lead to the starter...again, it it acts differently, it's the battery / starting wiring...
Ditto comments on the advancec - If he has a distributor, then try coming off the advance to see if it helps......
Also, check the sparks are good at initial cold cranking....
I've a 'more' modified CVH, and it starts on the button every time (although I have electronics ignition and fuel injection).
MY BLOG - http://westfieldv8.blogspot.co.uk/
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steve m
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| posted on 19/2/10 at 11:48 AM |
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i had similar problems on my car
<<<<
And thought it was more engine related with cams and modifying the engine timing etc
Turned out to be the earthing stap from engine to battery and chassis
so replaced with a new cable
Engine spins over fine now !!!
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les g
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| posted on 19/2/10 at 12:35 PM |
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you have ruled out battery,leads and earthing problems............
only leaves the starter
thats what i would look at next
what you describe can be a symptom of a failing starter
cheers les g
[Edited on 19/2/10 by les g]
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Danozeman
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| posted on 19/2/10 at 12:56 PM |
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Starter or earth lead i would say. A jump lead as an extra earth whould show this up.
We'v had loads of starters at work which turn slow when theyr cold. Its actually quite a problem with fords.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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Bluemoon
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| posted on 19/2/10 at 12:57 PM |
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Remember 0.1Ohms is a high resistance at 100A.. That would be 10V drop! So high it would not crank over at all (the resistances are so low a DVM is
useless to check this on the resistance range).. so I don't think you can eliminate that in the way you have tried.. You could measure the
voltage across the starter when cranking, but doing this safely may prove difficult..
Dan
[Edited on 19/2/10 by Bluemoon]
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britishtrident
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| posted on 19/2/10 at 01:51 PM |
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Battery is way undersized for cold cranking but my gut feeling is too much static ignition advance
Also check the volts drop between the engine and battery negative when cranking and the voltage drop between the main starter terminal and the
battery positive when cranking.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Bluemoon
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| posted on 19/2/10 at 01:53 PM |
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Might find this handy:
linky
Dan
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madrallysport
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| posted on 19/2/10 at 03:24 PM |
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Bad earth, or starting starting to give trouble, i fitted a geared starter to my mates anglia rally car it was expensive (£185) but unreal at cranking
the engine over, the used to have 24v starting to crank it over due to high compression ratio.
UNDERSTEER is when you hit the wall with the front of the car.
OVERSTEER is when you hit the wall with the rear of the car.
HORSEPOWER is how fast you hit the wall.
TORQUE is how far you take the wall with you.
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Richard Quinn
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| posted on 19/2/10 at 04:15 PM |
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In the dim & distant past I had a highly modified Pinto that was a very lazy starter due to compression. That ended up on 24V starting.
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britishtrident
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| posted on 20/2/10 at 06:51 PM |
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quote:
Originally posted by Richard Quinn
In the dim & distant past I had a highly modified Pinto that was a very lazy starter due to compression. That ended up on 24V starting.
Root problem is usually static ignition advance, With an old fashioned distributor the traditional cure is to modify the advance curve to give more
total centrifugal advance and retard the static timing by the same amount so the ammount of ignition advance at cranking speed is less but the
ignition advance over 1000 rpm is unchanged.
With old fashioned distributors the problem gets worse as the advance mechanism wears and the springs stretch.
For good starting no more about 5 degrees static advance is a the golden rule. Modifying a distributor to get additional centrifugal advance is
done by stripping the shaft out the distributor and cutting or grinding back the stop buffers for the centrifugal mechanism.
Of course with Megasquirt and the like it is just a couple of key strokes.
[Edited on 20/2/10 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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