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MG TD TF 1500 - Same problem, different day!

I have had an old problem rear its ugly head once again. 1950 TD with early engine appropriate for the year. Went on a club run and it ran very well but on the way back it was rough and "lumpy".

I have since checked all valves, compression is 135 across the board, timing set statically at zero on #1 compression tdc, unlit propane torch directed at shafts, intake manifold etc with no change. Noticed carbs leaking a little fuel so installed new kits, ensured floats at 7/16, new steel needles and seats, checked carb and pump filters, balanced carbs, still no luck. Just installed new coil so chenged the distributor and cap, the installed new spare condenser. Replaced the NGK plugs with Champion plugs from my spares.

I had new needles and seats so installed them and centred so that Pistons drop with a clunk.

Can't get the car to run without a miss and is running rich.

Even charged battery to ensure full charge available. I have run out of ideas now. I have two new spare condensers but they are the small new style.......would it be possible the replacement condenser I installed is not working?

Brian
Brian Smith (1950 TD3376)

Is miss steady or irregular? Try pulling one plug wire at a time to isolate cylinder (s). Is the rotor a red one? Black ones are junk. Many reports of bad condensers, read archives. Carefully remove dashpots/pistons, turn on key, make sure fuel not running out of jet. If not, eyeball the level below the bridge, should be a little below. I would bet on ignition issue. George
George Butz

George, the rotor is a black one, I have a few that were new old stock that came from a dealer who closed in the late 70's. Should have stated previously that I have new metal core plug wires and I used my timing light to confirm each wire had current. Fuel level appears good but fact that it still runs rich indicates it may still be too high. I will rig my NOS condensers tomorrow to test. One is unmarked, the other says made in Canada.

I am sure this car has a mind of its own and loves to see me struggle. I have gone through old posts and recommendations and while it was successful previously, not so this time around.

By the way, all filter screens were clear.
Brian Smith (1950 TD3376)


Use your timing light to see if an ignition miss is related to a single cylinder or if they are all missing about the same. Just watch the light as its running to see any miss.

If all are the same, it might be the condenser, however, a single cylinder might relate to a single bad plug.
Richard Cameron


Do you have a ground wire on the distributer like shown in the photo?

Richard Cameron

Richard, tried the timing light on each plug lead and didn't see anything out of the ordinary. The champion plugs replaced the NGK with no change as to how it ran.

I don't have a ground wire as in your picture but isn't the distributor grounded to the block anyway?

Brian
Brian Smith (1950 TD3376)

What I didn't see on your list is the first thing I check/clean/gap/time (unless you run electronic ignition), the points.
JRN JIM

I think those ground wires did come on the t types. Don't bother trying to put at the logical place of under the screw that holds down the points place. You will never get the clip on to hold down the cap.
R Owen

Jim, missed that, I did check and clean points and recapped. Haven't seen that ground wire before but easy enough to install so will do it in the morning.
Brian Smith (1950 TD3376)


Brian, Please take the time to make up a ground wire. The distributer actually floats in its mount on the early TD. As things get well lubed, the distributer can get intermittent ground. The wire shown in the picture is a factory item that is often thrown away during rebuilds.

If your misfire is caused by an ignition problem, you should be able to watch the timing light strobe and actually see the miss as an un even strobe when it occurs.
Richard Cameron

Brian, If you possess a set of jumper leads make a direct connection between the battery post earth and the engine block, run engine and see if the fault is removed, if not also try this;

Obtain a suitable length of insulated wire to connect between the coil supply terminal and the active battery post, fit alligator clips to the wire ends and attach between these points, this provides a direct current path to the coil and bypasses the normal ignition coil supply circuitry,run engine and see if the fault is removed.

These tests may isolate your problem to a poor earth path or to ignition switch circuitry.

I would confirm continuity of all the wiring and connections in the primary ignition circuit.Pull your plugs and check for carbon deposits, because the car ran fine for a period of time the performance of a component has degraded with time.

Hope you are not running ethanol based fuel.

Graeme
G Evans

Thanks to all who helped. Richard I had never seen that ground wire on a car before but it did make a difference. Also tried a new condensor but no change. Still had a bad miss and pulling plug leads numbers 1 & 2 had no effect.

Back to the basics, checked the front carb, float level good, piston drops with a clunk, gasket between carb and manifold looked a little dodgy so I changed it and things started to sound better. Replaced gasket on rear carb and the motor is running great.

Should I have a need to do this again in the future it will be one thing at a time.

Brian
Brian Smith (1950 TD3376)

This thread was discussed on 11/06/2016

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