what am I missing

[kiwi-jim]

I need your thoughts

The rebuild of my 62 TR4 is well on the way and its sort of back on the road....except for the fact the engine is not running well

Heres the story, full engine rebuild, with a tweaked cam, ( wasn't asked for but  seems to be what I ended up with), new distributor,  ( the Indian reproductions  all I can find at present)

new coil, etc.   Car starts easily, but runs really rough, when cold  with backfires, and missing.   when it gets warmed up starts to run better. The carbs have all been rebuilt by a local expert  and fuel seems to be flowing well.  Had the whole set up into a reputed  rebuild and restoration company to tune.  Now one moment  it runs fine, the next it starts backfiring and missing again.  On a road run  we can one moment be running sweetly at 100kms/hr, and the next it will lose power and backfire  and fart around before picking up again and running sweetly again.

I have rechecked timing , gap settings, changed plugs, tried the distributor cap and wires off my TR3 ( it runs fine) but its all still misbehaving intermittently.

So i guess its either spark/ electrics    or fuel  related issue, I'm just lost as to what.

What am I missing or perhaps should recheck. 

   

 

[Ian Vincent]

Backfires suggest timing issues to me.  Do you have anything loose near the distributor that might be grounding the low voltage circuit intermittently?

Rgds Ian

[Z320]

I would first check this: is each plug on the correct spark plug?

But if this is the case you should realise this at once.

[RogerH]

As it runs well one moment and then bad the next it can't be anything that is fixed - Valve timing, etc.

Check ALL the connection in the Dizzy especially the soldered tag on the flexible LT wire.

Check all ignition connector joints.

Have you got oil in the carb dash pots

Roger

[Rob Salisbury]

Condenser? ....... even new ones are not necessarily good ones, ...... try a known good one.

Cheers Rob

[RogerH]

2 minutes ago, Rob Salisbury said:

Condenser? ....... even new ones are not necessarily good ones, ...... try a known good one.

Cheers Rob

.............and rotor and coil

 

Roger

[Waldi]

Like above, my bet is on the electrical system, and in particular woven earth wire (inside the dizzy) or rotor or condensor, or coil. Check if all connections are solid.

If you suspect electric feed, you could connect a multimeter with long wires to the + on the coil and drive the car. If voltage drops when error occurs, you can concentrate on that ( or rule it out).

since it runs rough when cold and does better when warm, mixture cannot be ruled out completely, but I would first concentrate on the electrics.

Regards,

Waldi

[rcreweread]

Indian dizzies don't have the best reputation for reliability so I would try a different one to see if it makes any difference - are you running SUs or Strombergs - if the former, check the oil in dashpots, if the latter check very carefully the diaphrams.

Also check fuel flow to the carbs - is there any **** partially blocking the fuel lines?

Having said all that,  I agree it sounds more electrics related - how about trying a direct cable from battery to coil to rule out any issues with the ignition switch and associated circuits.

cheers

Rich

[Tr4aJim]

I quick thing to try is running the engine with the bonnet open, in the dark. Look for any arcing. Something may be finding an intermittent path to earth.

Jim

[Dic Doretti]

Try fitting your TR3 distributor, a known quantity and see what it is like on the road.

                Cheers Richard

[kiwi-jim]

Brilliant thanks everyone,  like you I do suspect the electrics and in particular the dizzy  somewhere, I will start the process of trying all your suggestions . However it will be a few weeks before I can do it and post a reply off the answer as I fly to Germany for Christmas in 48 hrs.   Thanks again to everyone , I will eventually let you know the culprit.   

Have a great Christmas everyone

cheers 

[ctc77965o]

+1 Condensor

[kiwi-jim]

Hi everyone, your prompt responses got me to race out and try some of what you had suggested.  So I started checking my connections , the lead from the Dizzy to the coil had spade connnections that seemed to easily slip on and off , so I made up a new connection with new spade terminals, plus I changed the condenser for another that was sitting on an old unused distributor.   Flicked the starter and straight away you can see and hear the diffference,  took the car for a short run and it was a different beast.  There is still a bit      of "run on "occurring but your suggestions have really helped. Thanks so much everyone. Have a great Christmas.

cheers 

[ianc]

Don't buy distributor electrical parts (rotor arm, condenser, points) in "Lucas" boxes unless very old stock.  Get these items from Martin Jay (Distributor Doctor), who gets them made to the correct specification.

Some condensers have only half the required material inside the can, some points are made with inferior material in heel and contacts (so wear rapidly), and some rotor arms break down (short).  I had two modern "Lucas" rotor arms fail before Martin produced his rotor arms.

Ian Cornish

[harrytr5]

There is some fake red rotor arms about. I always buy from the source ie..   Martin Jay (Dizzy Doc) who now stamps DD on the rotor arm.( yes they can fake that)

Regards Harry

[Mr Blue Sky]

One other thing that you may want to consider,  is the coil, as they heat up the insulation can break down and give the symptoms you describe.  The previous forumites are right to point out the condenser/rotor arm too.  My wheeled vehicle mechanics course instructors at REME Borden always said check those items 1st when fault finding a misfiring engine.  One last one, if your coil is now on the inner wheel arch as opposed to the block, check the dipstick isn't touching the terminals - don't ask how I know.

Regards, Laurence 

 

[Ian Vincent]

On 12/16/2018 at 8:50 PM, Mr Blue Sky said:

One last one, if your coil is now on the inner wheel arch as opposed to the block, check the dipstick isn't touching the terminals - don't ask how I know.

That's where I was coming from with my original response.  Don't ask how I know either!

Rgds Ian

[Mr Blue Sky]

Ian, my apologies, I had no intention to plagiarise your earlier post.  I have since opened the split section of the dipstick so that it cannot rotate easily.  

Regards,

[Ian Vincent]

21 minutes ago, Mr Blue Sky said:

Ian, my apologies, I had no intention to plagiarise your earlier post.  I have since opened the split section of the dipstick so that it cannot rotate easily.  

Regards,

Not a problem, I was just empathising with your experience. I also had to adjust the split section of the dipstick along with a bit of judicious bending adjustment. 

Rgds Ian