Slow cranking after a long lay-up

Technical advice Q&A
User avatar

Topic author
ALAN COCHRANE
Posts: 637
Joined: Sun May 06, 2012 9:37 am
Location: Fife
Great Britain

#1 Slow cranking after a long lay-up

Post by ALAN COCHRANE » Wed Nov 11, 2020 3:34 pm

Hi Everyone

I finally managed some time in the garage so I thought I'd tackle a slow cranking issue I'd been having this year.
If the car has not been started for a period of time the engine slow cranks and fails to start. After this it starts on the button with my battery charger connected and set to the start function.
Today I swapped the battery (less than one year old) for the GT6 battery which made no difference-so the battery was removed from the list of suspects. I then noticed that it cranked slightly faster with the under bonnet starter switch than the ignition switch. The ignition starter button operates the starter switch electrically via a relay in my car -so the starter switch became the new suspect.
I finally managed to start the engine and let it run up to full operating temperature. After this the engine cranked at "full speed" both with the starter button and the ignition switch-so the starter button earned a reprieve.
Is this possibly symptomatic of a bad earth. I've checked the battery to bulkhead and bulkhead to bellhousing straps and they were both tight and in good condition. Despite this I was wondering if the bellhousing connection may have some resistance when cold but not when hot. The other earth strap is not affected by the heat from the engine.
Or is the high torque starter motor on the way out? The E-Type and GT6 starter motors are identical high torque units so I could swap them over as well but time did not allow for that today.
I will start the car again tomorrow and then again in a week to see if this recurs.
In the meantime any/all thoughts would be greatly appreciated.

Thanks in advance
Alan Cochrane

1962 S1 OTS-850389,1968 Triumph TR250, 1971 Triumph GT6 Mk3, 2008 Porsche Boxster RS60 Spyder

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

madjack4
Posts: 114
Joined: Tue Aug 18, 2015 8:24 pm
Location: wakefield
Great Britain

#2 Re: Slow cranking after a long lay-up

Post by madjack4 » Wed Nov 11, 2020 10:48 pm

Hi
First you can put a good heavy duty jump lead from earth on battery to a good earth point on engine that will eliminate a bad earth.Another thing is what oil have u got in engine if its old or too thick that believe it or not will cause so much drag it will slow the engine down on cranking when cold.If the battery is good starter leads or starter i would get batterys checked both could be down on cranking amps need checking with a modern digital battery tester
Regards

Link:
BBcode:
HTML:
Hide post links
Show post links


christopher storey
Posts: 5074
Joined: Sun Mar 09, 2008 3:07 pm
Location: cheshire , england
Great Britain

#3 Re: Slow cranking after a long lay-up

Post by christopher storey » Wed Nov 11, 2020 10:53 pm

My experience is ( only with standard starter motors ) that this is typical after a long lay up . You do not say what battery you have but the cranking amps of modern batteries - often only 400 to 500 CCA is frequently not up to the standard of batteries of yore - IIRC something like 660 CCA . Further, even a small dip in voltage below that of a fully charged ( as opposed to say 85% charged ) battery will produce your problem, which is why a high voltage/current charger alleviates this. I would give your battery a 24 to 48 hour slow charge before the next time you try . These engines are not easy starters after a layoff, not least because of the long inlet tract

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

Topic author
ALAN COCHRANE
Posts: 637
Joined: Sun May 06, 2012 9:37 am
Location: Fife
Great Britain

#4 Re: Slow cranking after a long lay-up

Post by ALAN COCHRANE » Thu Nov 12, 2020 2:55 pm

Thanks for the replies.
Both batteries were fully charged before starting via intelligent chargers. In addition they were checked with my battery tester and both were healthy. The E-Type battery previously cranked the engine quickly so the CCA rating is not an issue.
The GT6 battery cranks the Triumph very quickly and the resultant current draw is almost identical on both cars- checked with my Fluke meter and CT ring.
I still think it may be an earth issue with the temperature being the only variable.
I may try the jump lead directly from the battery negative and that may indicate the problem.
Alan Cochrane

1962 S1 OTS-850389,1968 Triumph TR250, 1971 Triumph GT6 Mk3, 2008 Porsche Boxster RS60 Spyder

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

mgcjag
Moderator
Posts: 6034
Joined: Fri Jul 09, 2010 6:15 pm
Location: Ludlow Shropshire
Great Britain

#5 Re: Slow cranking after a long lay-up

Post by mgcjag » Thu Nov 12, 2020 3:14 pm

Hi Alan.......take the earths and live lead off clean them up with a thin smear of vaseline......if your sure you batteries are good then it can only be a high resistance earth or live lead to the starter or the actual starter itself...Steve
Steve
1969 S2 2+2 & Building a C type replica

Link:
BBcode:
HTML:
Hide post links
Show post links

Post Reply Previous topicNext topic