This Is The BBC

[sloopjohnrb]

Re 25D4 D istributor
Morris Minor 948 cc

Hello, I recently purchased a 25D4 (red rotor arm) from Simon BBC Distributors, and I have a couple of questions which I hope you can help me with as I'm struggling to start the car.

1.
I'm following the gap settings for both points and plugs as given in the Morris Minor manuals: 0.25 for points, 0.15 for plugs. Are these correct for the 25D4 distributor?

2
I measured the voltage at the coil, on ignition circuit only, with a volt-meter as I wanted to check whether it was putting out enough power for the new 254D dissy. The volt meter gave a reading of: 0.26. Is this a good or bad reading?

I would be very grateful if you could help.
Best wishes
John

[bmcecosse]

You have the gaps wrong way round........... And no - you obviously should get 12 volts at the coil! Is it a standard dizzy - or an electronic one ?

[sloopjohnrb]

Hello,
Yes, sorry, I gave the gaps the wrong way round.

The Dissy is a standard one, with points.

I'm getting a spark at the plugs right enough, but I did read somewhere that it's a good idea to replace the coil with a new coil from Simon BBC so that the dissy and the coil match.

The reading of 0.26 from the coil (ignition circuit on only) was made after the battery had a full charge from the battery charger.
Best wishes

[bmcecosse]

Don't change the coil - it's NEVER the coil........... Where are you measuring this voltage???????

[sloopjohnrb]

Hi, from the screw on terminals on the coil.
Best wishes

[bmcecosse]

Yes - from terminal - to where? If the points are open - both should read 12 volts to earth. If the points are lying closed - the +ve one should still read 12volts, and the -ve one should be virtually at zero. (Assuming -ve earth and non ballast ignition feed). Was the engine running before you swapped dizzies? When you fitted the new dizzy - did the rotor arm end up sitting EXACTLY in the same location as it did on the old dizzy? ie - If it was pointing to #1 lead on the old dizzy - was it still pointing to #1 on the new dizzy ??

[sloopjohnrb]

Hello,
With a volt meter, I placed one probe on negative coil terminal and the other on the positive terminal, the reading was 026.

I will measure the voltage at the points as per your suggestions and see what reading I get.

Yes, car was running before the new dissy, and I have done the Timing at least 12 times.
The rotor arm always comes back to the 8 o'clock posistion.

The dissy fits in with the vacuum unit to the left of the dissy and situated about 11 o'clock.
Many thanks again
Best wshes

[mike.perry]

The distributor drive is offset so that the distributor will only fit one way. It is possible that the new distributor drive is 180 deg out compared to the old dizzy and the rotor arm will then be pointing to no 4 instead of no 1.
Slacken the dizzy off and turn it whilst pressing the starter button under the bonnet (with the ign. on). If the engine starts to fire or kick back then you are somewhere near. If no reaction swap the plug leads along one plug and try again. By the time you have tried this four times you should have found the approx. timing

[sloopjohnrb]

any thanks for your kind advice.
I will be on Gladys tomorrow and will let you know how I get on.
Best wishes

[bmcecosse]

There is certainly no point (!) measuring the volts across the coil terminals.......... Why would you do that? Sounds like you have completely lost the timing - yet you say you have 'done' it?? So - just how are you 'doing' it?
You need to get #1 at TDC with both valves shut. Then turn the dizzy so the rotor arm is pointing to the lead going to #1 plug - and the points just opened. Then 1342 anticlockwise around the cap.

[sloopjohnrb]

Hi
I measured the coil voltage as I wanted to ensure it was sending enough power to the dissy-I now realise this is pointless as you say.

The Timing has been done exactly as you describe, No. 1 piston at TDC, matched with the notches on the pulley, Dissy adjusted to where the points are just opening, gap checked and set, also plugs checked a dozen times!

Best wishes

[bmcecosse]

Aye - but is #1 on the COMPRESSION stroke - and is the rotor pointing to the lead connected to #1 ??????

[sloopjohnrb]

Hi, Forgive me, but I thought that the piston at TDC was the compression stroke?
If this is not the case, please let me know
Best wishes
John

[bmcecosse]

When the crank is at TDC (top quarter in steam railway parlance...) - TWO pistons are at the top of the bore - and only ONE of them is on the compression stroke - and looking for a spark! Which is why I said you need to find the one with both valves shut. Other method involves putting thumb over plug hole and turning the engine (by hand) and so feeling the compression as the piston rises. When it gets to the top - that's when it wants a spark!

[sloopjohnrb]

Hiyas, Right! Number 4 rises same time as Number 1, Derr, I knew that, but just didn't think it through.
I will use your method for feeling the pressure on Number 1.
I'm back on her tomorrow.
You've been really kind, Thank you
Best wishes

[sloopjohnrb]

Right, I seem to have made progres with this Dissy, even though she's still not started.

The rotor is now pointing to one o'clock and the fit is much better all round.
Points perfectly set.

I seem to be on the right path at last.

One question though, when I set TDC, 1 and 4 at the top, inlet valve on 4 just closing, exhaust valve just opening, both valves on 1 closed, I checked the notch on the timing pulley and it was about 1 inch PAST the big timing tooth.

Now, should I crank the engine FORWARD so that the notch matches big timing tooth, which would be almost a full revolution; or wind backwards so that notch and big timing tooth match up? This is probably why she's not catching.Be st wishes

[MarkyB]

I guess the timing chain hasn't been fitted properly, or it isn't an original crank pulley.
I'd put something like a screwdriver in the plug hole to determine TDC, turn the engine back a smidgen and set the points to just open there.

That should be enough to get it running anyway.