Problem with the automatic box on a 150?

Saloons
1

My 150 still has the original BW automatic transmission and I only have a vague understanding of how it works!
Some years ago I replaced the original distributor with a new one that incorporates an electronic ‘module’ which replaces the points and condenser. It was fine, made the car much easier to start. Then the module failed and the supplier gave me a new one.
After I’d fitted it the car didn’t start so easily. More importantly, as soon as I put it into gear the engine died straight away. I found that if I used the throttle to get it idling at about 1200 rpm, instead of its normal 750 rpm and then put it into gear, engine speed dropped a lot but it didn’t die and was ready to go. All of this done with the foot on the brake.
So is this a gearbox problem or just another fault with the ‘new’ electronic module?
My take is that when you put it into gear with the brake on, the engine should obviously still run, it’s just churning over the oil in the torque converter. So if the engine dies at normal idle speed it means that the engine is so low on power at this speed that it can’t overcome the drag in the torque converter. So it’s an ignition problem not a gearbox problem.
I know the easiest test is to replace the distributor but I’d like to understand what’s going on first!
Any opinions wecome please.
(Posted on XK and Saloons forum)
Bramshill

2

you say you put the car “in gear”…then it is not just spinning torque convertor, but also the box is engaged to move the vehicle ?

This can/will stall it if the engine is “out of tune” for any reason

check your ASC (start carb) is working

is your GB a type DG250 ?

3

Tackle the basics first. I have a 150 with the DL250 BW tranny. I don’t think the tranny is your problem.

  1. Make sure the mechanical advance is oiled and moving. Grab the rotor and twist against the spring. It should snap back.

  2. Make sure both carb pistons are free by raising them with the lifting pins.

  3. Check the timing.

  4. Check carb mixture with the 1/8 inch lift test. You may have a vacuum leak. The brake servo may be the culprit (air piston seal).

Pat H

4

If it is a petronix module, they have a pdf with several tests to make sure the module is working correctly. Their customer service is VERY good. Just email and ask for the document. It does sound like a vacuum leak which could be in many different places. Do one test at a time so you are not all over the place.

Gerard

5

Was the car statically or dynamically timed when the module was changed over? Slow idle (apart from your footwork) and less power sounds like retarded ignition? Paul

6

Did you try a lower Idle, 500RPM would give less drag when shifting into drive.
I have a XK140 with a DG250 and a S-type with a DG250 also.
I think 750 RPM gives to much drag when shifting into gear.

Regards,
Peter Jan

7

Thank you for your help and suggestions everyone.
Confirm it is the DG250 box and rather a ‘tired’ one at that.
I haven’t yet had the chance to try anything but I think the first move will be to borrow a known good distributor and see if that’s the problem.
I can’t get away from the fact that this problem did not exist before the electronic module failed, needing the car to be recovered home. All that changed then was that I took the cap off and replaced the module. Not necessary to re-time it. Put the cap back on and started the engine. Allowed it to warm up and it died as soon as I put it into gear - several times.

8

that is what I would do, in fact a complete spare points dizzy, kept in the boot can be installed in a few minutes roadside, should an electronic one fail. As a plus, once you have that spare, the electronic one will probably never fail

9

Today I took the car to my mechanic who replaced the electronic distributor with a points and condenser set up. Car started fine but still tended to stall when put into gear. During a short test run the coil ‘blew up’ in his words. The insulated (terminal) end cracked open. The coil was replaced by my very original (1960) coil and everything is now fine - so far. It idles at a better speed, runs nicely and will still run nicely (as it should) when in gear with the brakes on. So subject to a much longer run tomorrow, now it’s home, I’ll be very happy.
I shall stop trying to figure out exactly what the problem was but a poor performing, and ultimately failing, coil seems to be the culprit …