Misfire then temporary loss of all power

[AndyC 4A]

Yesterday, I did the longest continuous run since complete rebuild, which was 40 miles through the New Forest completed faultlessly. Parked up outside all day then attempted the return, different story. After about 4 miles I felt a small intermittent misfire, it disappeared then a minute or so later it came back as if I was firing on three. Revving it seemed to clear it but after another 5 miles or so it re-appeared and felt like I was down to to firing on two so was forced to stop. Bonnet up, coil, distributor cap, leads, all seemed ok, in fact they were new. After about 5 minutes, tried again, started fine, running on all 4, so off i went. another 3 miles and then the same thing happened.

 

Whilst waiting for Towergate I tried everything again, fuel was present (hand primed the pump to into the fuel filter), spark at points when manually opened, all connections sound, so was a bit flummucksed!. After about 20 minutes, I tried again and wanting to move the car off the verge of a busy A road, I decided to see how far I got this time, but did not close the bonnet fully and off I went,

 

Well this time I completed the remaining 20 miles fault free, only stopping in a lay-by to cancel the recovery.

 

So I would welcome thoughts as to this, my limited knowledge suggest that perhaps this is temperature related, cool morning run, fine, hot (ish) afternoon run and OK with through flow with bonnet open....something is breaking down...Coil perhaps.

 

Sorry for the ramble but has anyone had a similar situation or could offer suggestions?

 

Andy

[derekh]

i had something similar a few months ago. Eventually traced to the LT lead between the coil and the distributor having an internal break near the spade connector which sometimes would connect and sometimes not.

 

Derek

[John Morrison]

Condensor.

 

John.

[Motorsport Mickey]

As above with the LT lead, when the engine torque moves the engine or Distributor working loose and altering the timing, check the timing again and nip the distributor up a little tighter.

 

Mick Richards

[RogerH]

Hi Andy,

it does sound heat related but don't be fooled by the apparent 'facts'.

 

For heat things - check by swapping - rotor arm, coil, dizzy capacitor.

Replace odd things like the Coil/Dizzy LT wire.

 

Also have a look at the dizzy internal LT wire. Remove and inspect the contact between wire terminal.

Mine was crimped on the insulation and soldered on the terminal. The solder had failed but was almost impossible to see.

 

Roger

[TR 2100]

Did Towergate manage to catch up with you?

 

AlanR

[Paul Harvey]

Buy a condenser from a known source.

This fault is common and for pennies you will know immediately.

[AndyC 4A]

Thanks all, sound advice as always. I will work through the components and check connections etc. Taking it out for a spin this evening so will have a final check after that.

 

Interestingly I noticed that the dizzy doesn't have the plastic insert with the spade terminal on, solid wire direct from points to coil, but have found an insert on another unit.

 

The condenser was new, from "Motorist Discount Centre" so may need to change, at least have a spare in the car.

 

As for Towergate, they took details, reading from a script, ....... was it diesel or petrol, was it a saloon or estate, etc, which didn't inspire confidence so bit my tongue. Then they phoned back to say they couldn't get anyone with the knowledge to fault find so would send a recovery truck. Also I wasn't aware, probably my fault, that the recovery was only "local", within 10 miles form home.

 

Do we prefer copper HT leads or the flexible carbon jobbies?

 

Andy

[RogerH]

Hi Andy,

for a fairly standard engine either copper or carbon leads work OK.

Apparently I've had carbon leads for the last 150K miles with no problems. I actually thought they were copper.

 

Roger

[Geko]

condensor if heat related or that nasty rotor arm spinning loose and/or missing the tiny spring. Quick visual check is to look for filing scraps inside the dizzy cap.

[AndyC 4A]

Hi Geko,

 

Interesting you should mention the rotor arm as what I failed to mention, as I thought it irrelevant at the time. was that as a security measure, I removed the rotor arm. Was this a coincidence or did I fail to put it back correctly, didn't think you could as it worked or it didn't ?? Also, where is the spring you mention?

 

Andy

[Geko]

on the inner face the rotor arm there's a nick in which a tiny square shaped spring is inserted and prevents the rotor from wobbling on the axis. Removing the rotor frequently can cause wear and the spring can drop without you noticing it.

[littlejim]

Fits fuel starvation too.

(e.g. bit of crud intermittently covering tank pickup or fuel bowl pickup, drops off for a while after you stop.)

Could be worth a look, if the electrical fixes don't solve the problem for you.

[AlanT]

Carbon leads were introduced to prevent the sparks from causing radiated interference to the TV pictures.

 

This was before we had UHF TV. Then the VHF TV pictures would show white spots as a car went past.

 

I suspect the TV dont do this anymore but you may get noise on your FM radio. You won't if you are gettinga stong signal. But if you are in an area of weak FM reception you may get an "engine noise" in the background.

[ron88]

Ok, I had a problem very similar to this on my Kharman Ghia (a while back= 30 years!). The longer I let it sit - the further I drove. Ten minutes = one mile. One hour = 5 miles, and so on. Overnight I could do about 30 miles. After two months of agony, it was a very simple thing - dirt in the needle jet. One blow through and problem solved. Seems the colder it got the more it "settled" - the warmer it got the higher it rose and the more it blocked.

 

Those of you who read this forum often will note that I had something similar recently with my 4A. The first thing is check the plugs to see how fouled they are and consider replacing all as a first step prior to the second (one or two of mine were so fouled that a good clean didn't do much). Then, I disassembled both floats, checking for float leaks, and blew through all fuel lines. Then I checked the jets were working properly and blew through those areas as well. Reassembled and so far - so good. Worth a simple try.

[ianc]

Buy points, condenser and rotor arm from the Distributor Doctor (Martin Jay) - then you'll have the proper kit.

Inside the centre of the distributor cap, there is a carbon brush which is spring loaded. This provides the electrical link for the HT from the coil to the spinning rotor arm. The brush (which is a carbon rod) is a 'service item' and gradually wears away - Martin can provide replacements.

Ian Cornish

[AndyC 4A]

I have checked the distributor cap and the carbon brush is is free and hardly worn as I would expect as it has only done a couple of hundred miles, but understand that new does not necessarily mean fault free, bathtub graph of reliability! I have inspected the rotor arm with a watchmakers eyepiece and I cannot see a nick or spring. It has the number 2 embossed on the underneath directly behind the locating lug, and on the top has a symbol of a C with what looks like an I vertically across it with Made in England in a circle around it.

 

As for fuel, I have noticed that despite having the Fuel tank steam cleaned etc, the paper fuel filter is now quite dark, so will change that shortly and check the float chambers as well for crud etc.

 

Will be my last post for a while as flying out the States to drive Route 66 tomorrow, any one got any good suggestions on what automotive places of interest to recommend??

 

Andy

[Geko]

Your rotor must be different: this is a standard Lucas fitting a 25D dizzy.