Poor Starting from Cold on twin H4's

Post any technical questions or queries here.
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

Thanks, yep I have already added fresh petrol as I was worried it may have gone stale.

I think the winter may be a bit of a red herring, although it is worse to start in the winter, it's never easy to start from cold at all. It's 'easier' if it's been run the day before but still not easy.
ianh1968
1275 Cooper S
Posts: 1012
Joined: Sat Nov 03, 2012 6:00 pm
Location: West Sussex

Re: Poor Starting from Cold on twin H4's

Post by ianh1968 »

sclemow wrote:It's been very reluctant, even in the summer, so I don't think it's simply damp and cold weather.
rich@minispares.com wrote:my car was doing this - getting worse and worse to start, it was the engine earth strap
If it struggles in the summer, it sounds like a battery wiring issue to me.

You can check for voltage loss to the starter like this:
Firstly, make sure the battery is good and fully charged.
Get a voltmeter and connect it between the engine/earth and the feed tag to
the starter motor.

Crank the engine over.

We are looking for 12 volts under load, and if there is an appreciable drop
here we need to work out which side of the circuit to investigate. That is,
do we have a bad earth, or a bad feed?

The concept is the same for +ve earth and -ve earth, but I'll use -ve as an example.

Get your voltmeter and a long piece of wire, an assistant would be handy.
Now, a voltmeter actually measures "potential difference" in volts and we
normally use it to check that the PD/Voltage is between a feed and the earth,
like we did in the first test.

What we will be doing here is to use the meter to measure the "Potential Difference"
or "Voltage Drop" from two points on firstly the negative side of the circuit, then the
positive. It may sound odd connecting it to two negatives or two positives, but trust me
here, we are measuring a "potential difference"...

Have your assistant hold one end of the long wire DIRECTLY on the negative terminal
of the battery, not the wiring tag, the actual stub on the battery.

Connect the other end of the cable to one side of your meter.

Set the meter to a low voltage scale, say 12v.

Using the normal test lead in the other side of the meter, connect this to the
engine as close to the starter motor as possible.

So now we have both sides of the meter connected to -ve, one at the back of the car,
and the other at the front. You should have a reading of Zero Volts.

Now, crank the engine over and watch your meter: If it moves negative, swap the leads
round on the meter and try again.

If you get a small reading, try changing to a lower voltage scale.

Crank the engine again....

The reading will show you how many volts you have "lost" in the -ve side of the circuit.

Now the other side....

Have your assistant hold the long wire on the positive side of the battery.

Connect this to one side of your meter.

Connect the other side of the meter to the starter-motor main feed tag.

Spin the engine over (swapping the leads and/or adjusting the scale as above if necessary)

The reading will show you how many volts you have "lost" in the +ve side of the circuit.

The concept remains the same here for wherever you connect you meter, for example,
at the front end, connect the short lead, before, then after the solenoid. If the loss happens
at the output of the solenoid, but not before, this component is suspect...

As I have said in another post, because so many of the cables (read, virtually all of them)
are only crimped, it is possible to get a bad connection between the cable/braid and the tag.
This is why I always solder ALL my battery leads.

If you lose a bit in each side, like rich says, you can end up with severe coil-robbing and
either a very weak or no spark.

Good Luck,

Ian
BRI MK1
1275 Cooper S
Posts: 827
Joined: Tue Sep 25, 2012 10:44 pm
Been thanked: 3 times

Re: Poor Starting from Cold on twin H4's

Post by BRI MK1 »

Also check valve clearance as this can cause bad cold starting but I am probably wrong but worth checking.
mricsman

Re: Poor Starting from Cold on twin H4's

Post by mricsman »

Wrong grade of oil in the carb dashpots...?
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

I had a brief look at the electrics the other day. It looks like it is losing volts somewhere along the line. I'll delve further .....

Thanks guys.

Simon
abri
998 Cooper
Posts: 746
Joined: Tue Jun 29, 2010 4:25 pm

Re: Poor Starting from Cold on twin H4's

Post by abri »

I had these exact same symptoms on my S a while ago (when it was winter here in the South). I also thought it was maybe the cold and lack of driving....until I took out the year old Champion 9y plugs and put in a used set of NGKs.....fired right up on the first swing!
User avatar
mk1coopers
1275 Cooper S
Posts: 2005
Joined: Thu Jun 24, 2010 2:14 pm
Has thanked: 2 times
Been thanked: 1 time

Re: Poor Starting from Cold on twin H4's

Post by mk1coopers »

I had the same sort of thing on my car, NOS starter that was robbing the voltage so that the spark was weak (got to the point where it didn't start at all), I've put a powerlite hi torque 1.6 KW starter in it now, hopefully that will be the end of the problem (it had the odd bumpstart in the top paddock at Wiscombe last year to get it going :lol: )
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

Which Wiscombe?
I was at the sept 5 clubs event, saturday with my single seater, sunday with the S.

I suspect it's a bad earth, I need to dig it out and follow the voltages through.

Simon
User avatar
mk1coopers
1275 Cooper S
Posts: 2005
Joined: Thu Jun 24, 2010 2:14 pm
Has thanked: 2 times
Been thanked: 1 time

Re: Poor Starting from Cold on twin H4's

Post by mk1coopers »

Yes I did those days with the DEWS club in my S, was your S parked over with the single seaters on the Sunday ?
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

Yes, that's the one. I broke my rear suspension on the single seater on the first practice run on Saturday, so brought the S out on the Sunday. It's not really prepared for hill climbing but didn't do too badly for a road car. :-)
User avatar
mk1coopers
1275 Cooper S
Posts: 2005
Joined: Thu Jun 24, 2010 2:14 pm
Has thanked: 2 times
Been thanked: 1 time

Re: Poor Starting from Cold on twin H4's

Post by mk1coopers »

Nice looking car you've got :D
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

Thanks, with a 3.1 diff, no lsd, dunlop R7's and those horrible wet conditions it wasn't very competitive at all. Still I built it as a road car.
This is my usual hillclimb stead ....

http://www.hillclimbandsprint.co.uk/photo.asp?PID=2016

From one end of the results to the other!! :-)
User avatar
mk1coopers
1275 Cooper S
Posts: 2005
Joined: Thu Jun 24, 2010 2:14 pm
Has thanked: 2 times
Been thanked: 1 time

Re: Poor Starting from Cold on twin H4's

Post by mk1coopers »

Looks like that would be slightly quicker than the Mini's :lol:
vegar
850 Super
Posts: 137
Joined: Fri Jun 25, 2010 8:05 pm

Re: Poor Starting from Cold on twin H4's

Post by vegar »

abri wrote:I had these exact same symptoms on my S a while ago (when it was winter here in the South). I also thought it was maybe the cold and lack of driving....until I took out the year old Champion 9y plugs and put in a used set of NGKs.....fired right up on the first swing!
I bought a mk2 998 a few weeks ago. It was very hard to start, but when warm it started OK. Changed the spark plugs, and now it starts imediatly, even in sub-zero temperatures :)

Image
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

Had a go through it today and found I was dropping quite a few volts when turning it over on the starter. I've been through and cleaned and checked all of the high current leads to the starter along with both engine earth straps. I'm now dropping a lot less volts so hopefully that and a fresh set of plugs should sort it out if not it'll be a new solenoid!
User avatar
sclemow
998 Cooper
Posts: 338
Joined: Thu Jun 24, 2010 1:02 pm
Location: Bristol, UK

Re: Poor Starting from Cold on twin H4's

Post by sclemow »

Thoroughly going through the electrical connections and new plugs seems to have improved it a lot.
Cheers Guys.

S
Post Reply