TR4/4A TR4A missing a beat

[Adrio]

It seems like my TR4A wants to keep me busy. Every time I solve one problem and feel like I am home free it throws up an other "challenge".

This time it started skipping and running rough. At first it was just one or two missed beats when I was driving along at low RPM and at low throttle position. It would run fine if I was at hight RPM and/or at full throttle. But today it became constant and even stalled and would not start. After a few minutes it then started again but ran rough again (still better, but not perfect, at full throttle). The coil, points plugs cap, condenser and wires are all new this summer and have under 300 miles on them.


Anyone have any suggestions or ideas.

 

[LarryK]

If it ran decent before the points. coil and condensor, check point gap, and wires leading into distributor to the points, any wear will short and cause miss as timing moves. Also, try replacing new condensor with old etc. until you find cause.

If you changed things because of a miss, you might check carb adjustments and fuel, vacuum leak and valve lash etc.

 

[tr6lover]

this may sound stupid, but grab the distributor and see if you can twist it like your setting timing. ive had an mgb spit one out while i was driving and i know that the distributors they used in some of the 4 cylinder british cars are prone to moving because they get worn on the area where its clamped down because of overtightening.
randy

 

[Bugeye58]

Check the low tension lead between the coil and distributor.
They've been known to break and make intermittent contact.
It'll drive you nuts until you find it. After that it will be one of the first things you'll look for. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
I used to deal with a parts store that practically wouldn't sell you a set of points without selling you one of those!
Jeff

 

[PeterK]

Recheck the points.

 

[TR3driver]

i know that the distributors they used in some of the 4 cylinder british cars are prone to moving because they get worn on the area where its clamped down because of overtightening.

Not just worn, it's actually fairly easy to break that part of the casting ! The pinch bolt can exert a LOT of pressure, but it grabs just a thin lip on the casting which can't take much pressure.

 

[Bugeye58]

Not just worn, it's actually fairly easy to break that part of the casting ! The pinch bolt can exert a LOT of pressure, but it grabs just a thin lip on the casting which can't take much pressure.

And a good way to fix that problem is to fill the cavity between the thin side of the body, where the clamp fits, and the main body with epoxy. Another trick is to put a spacer, or washers, on the clamp bolt, between the ears of the clamp to prevent overclamping.
Jeff

 

[Adrio]

Thanks for the advice. So far I have tried a few of the suggestions and it seems the "new" condenser may not have been so good. I put the old one back in (it was only a few hours old but they points that came with it melted where they rub against the cam so I changed them both but kept the condenser). It seems to be working OK but I have only driven about 2 miles as it was late by the time I got that far and I did not want to risk going to far afield after dark until I was confident of the car. I will take if for a long test drive before dark soon to confirm the repair is for real.

In the mean time I will order a new set of points and condenser.

 

[RonMacPherson]

Buy a Crane/Allison shutter wheel points replacement kit. Fits right into the distributor, and then you never have to change points and condensor again. Works nicely, even if the distributor shaft bushings are worn some.

 

[DNK]

got a used 1 to sell cheap

 

[Tomster]

Crane/Allison shutter wheel points replacement kit
?? Can you supply image and info. on this?
Adrio, what ever happened about the carbon explosions from the exhaust that you were experiencing last spring? Same issue?

 

[Adrio]

As regards the carbon explosions.

The first bunch were in the fall and that went away with new points and condenser (the old points were melting on the cam). Then once that was solves I had an extremely rich mixture even with the jets all the way up. The answer was that the floats were sinking just a bit. They were not leaking but must have gotten heavier over the years some how. I replaced them and the fuel level in the bowls went down near a 1/4 inch. SO after the new flats I was able to get the mixture down to the proper level (and the jets are not fully up) and the plugs are now nice light brown (and not fuzzy black like they were and back then I had the carbs set at full lean). In amongst all that I had the fuel pump problem.

The teething pains on this car are something. Just as I solve one problem I find an other. I still don't trust it

 

[RonMacPherson]

Tomster,

Opened Google, typed in Moss Motors, Hit TR4a, performance, igntion system, then clicked on the XR700 Crane

https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=32646

HTh. Also Crane Cams used to have a pretty good pictorial on installation, but it's been several years since I did an in depth of their site. I prefer the Crane over Pertronix, as no matter how long you leave the key on you shouldn't have a problem burning it out. When they were Allison they came with a liftime warranty(I put mine on in 87 ish and it's been going strong ever since). When they sold to Crane, Crane reduced the lifetime to 1 year. The only ones I've seen fail have been because the installer didn't allow enough slack when placing the primary pigtail in the distributor and after beaucoup years the insulation wore through.

 

[Tomster]

Thank you for the link

 

[NickMorgan]

I had a new condenser do exactly the same thing after only about 300 miles. Seems to be quite a common problem.
I have also had new point close up if the plastic heal is not sitting nicely on the cams. The heal then seems to wear very quickly.

 

[RonMacPherson]

If you go with points make sure you place small amount of ponts grease on the heel of the point rubbing block, on the side where the lobe meets the points block first. Standard Blue Streak tube is still in my tuneup drawer in my tool box, should be able to get any parts house to order it for you.