Rough as a badger's....advice please!

[Westy]

I took my TR4A out for a long weekend run in the Cotswolds with friends and it ran perfectly. That was a month or so ago. Now, however, it's not. I can't think what has changed. It fluffs and hesitates under acceleration and feels really quite rough when it used to be silky smooth. When warm it would idle smoothly at just under 1000 rpm, now if falters, coughs and splutters. Last time I experienced a similar problem I put in a new mechanical fuel pump - that was less than 2 years ago. I have done the following to try and cure the issue: -

• Put in new NGK spark plugs and set gap at 25 thou'
• Swapped out condenser, rotor arm and contact set (from distributor doctor) and adjusted points gap to 15 thou'
• Checked for spark to each plug with inline whatchmacallit thingy
• Crudely checked vacuum advance by sucking down pipe (seems to work OK)
• Ignition coil is relatively new and battery is good
• Checked for fuel supply through glass inline filter that I added when I renewed fuel pump (yes, the glass bowl of fuel pump is full with no debris). I disconnected the fuel line, put a plastic container underneath and turned over the engine and saw fuel spurting out of the fuel pipe. The float chambers were full of fuel too. The mechanical primer under the fuel pump, worked on release of the lever, not actuation - is that right? Maybe the fuel supply is a bit erratic? Maybe I should consider fitting an electric pump?

So not sure where to go from here. Any advice anyone? Please........

[RobH]

The only thing you haven't mentioned is putting in fresh fuel...........

Have you perhaps topped up recently with something contaminated - or if not, could the stuff in the tank have gone stale?

(Yes the priming lever pumps as you let go, not when you press it. )

[keith1948]

7 minutes ago, RobH said:

The only thing you haven't mentioned is putting in fresh fuel...........

Have you perhaps topped up recently with something contaminated - or if not, could the stuff in the tank have gone stale?

(Yes the priming lever pumps as you let go, not when you press it. )

Rob beat me to it. Two of us had a similar problem with a 4A and a 3 after filling up at a supermarket about 3 or 4 years ago. Fresh fuel from a different garage and all back to normal.

Keith

[TR4Tony VC]

Hi

Worth blowing out the fuel lines with compressed air if you have it as I’ve had a similar issue many years ago which turned out to be a small piece of paint / tank lining rotating in the pipe causing irregular fueling. This could extend all the way to the float chambers on your carbs (check the float and pins too).

My other thought is your coil, leads and end connectors - It’s worth swapping them in and out individually to rule out an intermittent fault with a new part. Some new parts are not that great and move about and get loose .Also, if not 100% secure the dizzy retaining bracket allows the body / pedestal to move / cap moves upwards with revs, pulling the leads around and wrecking the sprung contact inside the cap. Worth checking that all is tight and not moving at all under load or with low rev vibration.

regards

Tony 

[roy53]

All good advice above.  I have had problems in the past with dodgey NGK new plugs . Also check tappets whilst you are going through everything.

Roy

[Andy Moltu]

Lots of fake NGKs in circulation

Check that your carb floats are operating the valves ok.

[RogerH]

Hi Westy,

 did you change all those tings in one go- .  Always, where possible, change one thing at a time.

I had similar problems with NGK plugs back in 2018. I now use Champion L87.

Check the SU dash pots for oil level.

Roger

[Westy]

Thanks - I'll work my way through the list. Didn't think of the fuel but yes, could have filled up at a supermarket (my memory is hazy these days). Changed one thing at at time and no noticeable difference each time. Had NGK spark plugs in there and swapped for the same NGK BP6HS from The Green Spark Plug Company. Will let you know how I get on...

[Charlie D]

Do you have Strombergs on your car?

If so check the diaphragms as your symptoms are similar to those I had once with a split diaphragm.

Charlie.

Edited September 13, 2022 by Charlie D

[tthomson]

A few years ago, I had a similar problem where my TR4A ran perfectly well below 40 mph, but above that if lost power, badly misfire, and would hardly accelerate.

The problem was due to the HT connector on the coil. The threaded insert that held the HT lead into the coil had become broken, and the lead was not making good contact with the coil, and therefore creating a spark gap at the coil output. As the revs increased there was insufficient energy at the spark plugs to maintain the spark, so lots of misfiring under load.

So always worth checking for HT breaks of any sort, and since you have a newish coil, that is suspect.

TT

[Z320]

Hi Westy,

I guess the problem is the glass inline filter you added.

They are fake filters, I had the same problems like you with this nightmare product.

I wrote a post about anywhere at this forum 2 years ago.

Ciao, Marco 

 

[Z320]

I found it via a Google search, not possible via the TR Register search

[John Morrison]

Hi Westy,

this is why we have TR's,  old car's in general can be challenging at times. its part of the fun!

I would go back to the coil.

Check out the pinned information provided by Rob in our general technical on coils.

then buy the recommeded one, many of us carry a spare anyway, try it on the car.

If no success this time you'll have the spare anyway.

John.

[Phil Reade]

On 9/13/2022 at 9:12 AM, Westy said:

Thanks - I'll work my way through the list. Didn't think of the fuel but yes, could have filled up at a supermarket (my memory is hazy these days). Changed one thing at at time and no noticeable difference each time. Had NGK spark plugs in there and swapped for the same NGK BP6HS from The Green Spark Plug Company. Will let you know how I get on...

Hi Westy,

A word of caution regarding your NGK Plugs. I bought a set from the same place as you and started having running rough issues after a few hundred miles. Checked the details on the plug body and found they had been made in some country which I can't remember, but I suspected have dubious Q.C., than Japan. Bought some more NGK from elsewhere and problem was sorted.

[Ralph Whitaker]

9 hours ago, Phil Reade said:

Hi Westy,

A word of caution regarding your NGK Plugs. I bought a set from the same place as you and started having running rough issues after a few hundred miles. Checked the details on the plug body and found they had been made in some country which I can't remember, but I suspected have dubious Q.C., than Japan. Bought some more NGK from elsewhere and problem was sorted.

If you look up Fake NGK Spark Plugs on the internet you will find that NGK have posted a guide on how to tell fake from real, but  the differences are very slight and hard to see.

I have to say that I would be very surprised if the Green Spark Plug co are selling fakes, they have a good reputation to uphold.

Responders seem to have missed the point in Westy`s post that all the work he has done, came after the problem developed, and the trouble he is having is not a consequence of the changing of parts, however the filter was fitted 2 years ago, and are known to be dodgy, as Marco has discovered.

Not sure what carbs Westy is running, but I had similar symptoms on my 3 when the choke stuck on slightly on one carb. Just a thought.

Ralph

[Westy]

Hello all,

I thought I'd give you all a bit of an update on progress. I haven't gone through the full jobbing list but I have: -

• Swapped out the NGK plus for Champion L87 but that has made no discernible difference
• So, too when I took out the fuel filter and replaced with a single uninterrupted length of fuel pipe
• Checked both float chambers (a few small metal filings but nothing serious) and valves closing OK when I manually raised the float and blew down the open end of fuel pipe
• Checked the ignition coil as per technical advice posted in this forum by RobH May 2021 using an ammeter/voltmeter
• The central lead from the distributor to the coil looked well connected but I opened up the push-in fitting to ensure a tight fit. I have some Magnecor KV85 ignition leads on order just in case
• Not sure how to check the SU dash pots for oil but I unscrewed them both and push back in and with about 1cm to go, met resistance/damping. Does that seem right?

My car is fitted with twin SU carbs, not Strombergs. Next I will empty the tank and put in some fresh fuel as suggested early in this thread, check the fuel lines are clear back to the tank even though I did this a year or so ago when I experienced a similar issue and replaced the fuel pump. Talking of fuel pumps, TR Shop in Chiswick mentioned that a few of the fuel pumps they used to supply (with plastic screw nut below the fuel chamber - like mine incidentally) have reported as failing and they now supply a pump with a brass screw nut. I ordered one, just to eliminate that from my enquiries. So think it must be bad fuel or perhaps the fuel pump. Getting closer but no cigar just yet.

 

[Z320]

He Westy,

do you check the result after every modification?

Ciao, Marco 

[Westy]

Yes, I did Marco

[Z320]

Good.

Btw I remember a club mate’s TR4A failed because on his mechanical fuel pump the bolt holding the pump lever moved out of the pump housing.

You can feel that when you touch for it, all around the pump could be very oily.

Ciao, Marco 

[Ralph Whitaker]

On 9/17/2022 at 3:16 PM, Westy said:

Hello all,

I thought I'd give you all a bit of an update on progress. I haven't gone through the full jobbing list but I have: -

 

• Not sure how to check the SU dash pots for oil but I unscrewed them both and push back in and with about 1cm to go, met resistance/damping. Does that seem right?

 

 

Sounds like the dampers have enough oil, but to check, take out the damper rod and fill the inner tube that is visible to approx 1cm from the top. There is a proper oil for this, but 20/50 engine oil will do.

Have you checked that the chokes are going fully off on both carburettors?

Ralph

[rcreweread]

On 9/17/2022 at 3:16 PM, Westy said:

Hello all,

I thought I'd give you all a bit of an update on progress. I haven't gone through the full jobbing list but I have: -

• Swapped out the NGK plus for Champion L87 but that has made no discernible difference
• So, too when I took out the fuel filter and replaced with a single uninterrupted length of fuel pipe
• Checked both float chambers (a few small metal filings but nothing serious) and valves closing OK when I manually raised the float and blew down the open end of fuel pipe
• Checked the ignition coil as per technical advice posted in this forum by RobH May 2021 using an ammeter/voltmeter
• The central lead from the distributor to the coil looked well connected but I opened up the push-in fitting to ensure a tight fit. I have some Magnecor KV85 ignition leads on order just in case
• Not sure how to check the SU dash pots for oil but I unscrewed them both and push back in and with about 1cm to go, met resistance/damping. Does that seem right?

My car is fitted with twin SU carbs, not Strombergs. Next I will empty the tank and put in some fresh fuel as suggested early in this thread, check the fuel lines are clear back to the tank even though I did this a year or so ago when I experienced a similar issue and replaced the fuel pump. Talking of fuel pumps, TR Shop in Chiswick mentioned that a few of the fuel pumps they used to supply (with plastic screw nut below the fuel chamber - like mine incidentally) have reported as failing and they now supply a pump with a brass screw nut. I ordered one, just to eliminate that from my enquiries. So think it must be bad fuel or perhaps the fuel pump. Getting closer but no cigar just yet.

 

 

Hi Westy - I sent you a PM (Personal Message) a few days ago about fuel pumps which I can see you haven't yet opened - your personal messages go into your forum mailbox which is the envelope icon in the top right hand corner of a forum page - if it has a message inside which you haven't read, there will be a red tag attached to the icon - click on the icon and it will open your mailbox and you will be able to see any messages in there, which you can then reply to if you want.

Cheers Rich

[Westy]

Final report and perhaps the end of this thread. I found the fault. Without exchanging the fuel pump or replacing the fuel. It turned out to be.....spoken in a hushed tone...a dodgy HT lead on cylinder 2. Connections at either end were good but I suspect the lead had broken down in the middle. I will fit replacement Magencor KV85 leads when they arrive - in 6 weeks! Thanks for all your advice. I learned a lot. Not least, to try one thing at a time and start with the cheap fixes before spending any money!

[ianc]

Old-fashioned copper HT leads do not fracture.

And they are inexpensive.  Just buy an appropriate amount and cut to suit each.

Ian Cornish