Poor Starting from Cold on twin H4's

[sclemow]

I've got a poor starting problem with my 1275S running on twin H4's. When it is cold it is an absolute ***** (pain) to start.
It will only start when turned over a lot, then only when turned over on full choke, then the choke put in completely.

It runs beautifully when warm, and has recently been set up on Steve Harris's rolling road so there are no major issues. The chokes seem to be operating correctly.

Any ideas of where to start with the starting?

Simon

[Pete]

I'd say it depends on the level of tuning, compression etc. Most competition engines have to be coaxed into life in Autumn / Winter temperatures, usually with a comp starter !

[foxy52]

I've got a poor starting problem with my 1275S running on twin H4's. When it is cold it is an absolute ***** (pain) to start.
It will only start when turned over a lot, then only when turned over on full choke, then the choke put in completely.

It runs beautifully when warm, and has recently been set up on Steve Harris's rolling road so there are no major issues. The chokes seem to be operating correctly.

Any ideas of where to start with the starting?

Simon

...prob nowt to do with the h4,s.. most old minis don't like the cold or damp this time of year... the only issue I ever have with starting is points/condenser.. keep the distributor clean and use moisture repellent....my car will start first time everytime even if left out for a week in the cold and wet...as rgds to yer min turning it over and over due lack of spark will effect other components not least the battery... I use a Unipart jobbie inexpensive and I have found it to be first class....I have only had 2 batteries since 2000 !!...happy winter mini-ing..foxy52

[sclemow]

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

It runs electronic ignition and a new NOS starter motor. It's using the physically largest battery that will fit in the battery box so is cranking ok and it's not a points/condensor issue.

The engine was built by Steve Harris and approximates the Downton Stage 1 spec, it's running a taurus head with pretty large valves, a 276 and 1:5 rockers. The pistons are dished and from memory it doesn't run a particularly high compression. It's got a lucas gold coil.

What plugs do people tend to run? A thought that went through my head is that the plugs are a bit cold for it?

Simon

[rich@minispares.com]

a quick test is to wait until its cold, then put a slave 12volt battery direct onto the coil (so all its running is the coil and the coil is independent of the demands placed on anything fitted to the car)

if it fires right up you know that the starter is 'stealing' voltage from the coil, a lot of electronic ignitions are very intolerant of voltage drop.


my car was doing this - getting worse and worse to start, it was the engine earth strap - the separate battery trick worked a treat to diagnose it

[FCV.66]

Have you spoken to Steve about the problem? I have an identical Steve Harris unit in my S, also with H4s. You need only look at the key in summer and it starts. In winter a couple of turns and it is away.

Garry.

[FCV.66]

I recon Rich is right.

G.

[sclemow]

Yeah, I've spoken to Steve about it. That was why it went back on the rolling road this summer.
He and I hillclimb regularly together so don't worry he's had his ear bent

That's a good plan with the electronic ignition, worth a shot, although I doubt it's the issue as it's not a true electronic ignition, just the lumenition kit that replaces the points.

S

[foxy52]

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

It runs electronic ignition and a new NOS starter motor. It's using the physically largest battery that will fit in the battery box so is cranking ok and it's not a points/condensor issue.

The engine was built by Steve Harris and approximates the Downton Stage 1 spec, it's running a taurus head with pretty large valves, a 276 and 1:5 rockers. The pistons are dished and from memory it doesn't run a particularly high compression. It's got a lucas gold coil.

What plugs do people tend to run? A thought that went through my head is that the plugs are a bit cold for it?

Simon

for my six penneth I always use Champion 9y,s..i don't think it matters much in truth but as long as they are clean and show no signs of fouling etc etc...ill replace mine at least every 9 months...the head,cam,crank,roller rockers,pistons,valves etc etc on mine are heavily modded but the points/condenser being dirty/knackered was the only issue,.thats the only starting prob I ever had in truth....so I always keep a spare set just in case....but as one other said there are a myriad of reasons as to why minis get the gremlins !!!!.especially in winter !!!...foxy52

[carbon]

Simon,

Other cause of poor starting in cold weather can be 'summer' petrol left in the tank if a car has not been used much.

The petrol sold on forecourts varies slightly throughout the year, with more of the volatile components being used in blending for the winter months. This winter spec petrol can help with starting from cold.

[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.