Poor Starting from Cold on twin H4's

[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]

It's been very reluctant, even in the summer, so I don't think it's simply damp and cold weather.

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]

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

[mricsman]

Wrong grade of oil in the carb dashpots...?

[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]

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!

[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 )

[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

[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 ?

[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.

[mk1coopers]

Nice looking car you've got

[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!!

[mk1coopers]

Looks like that would be slightly quicker than the Mini's

[vegar]

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

[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!

[sclemow]

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

S