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MG TD TF 1500 - Pertronix Installation Problem

I installed a positive earth unit this morning and am now in trouble. As per instructions I joined the black ignitor lead to the ignition switch wire, the black & white ignitor wire to the negative coil terminal and earthed the positive coil terminal to the chassis. I adjusted the timing statically using a 12v bulb and a colortune plug which sparked in number one cylinder exactly on TDC. When I pulled the start switch the engine it turned freely with the ignition off, but laboured slowly with it on. It sounded as if there was far too much compression. The firing order is the correct 1-3-4-2, New NGK plugs were fitted and I checked the coil resistance at 2.1 ohms before attempting to start the engine. After refitting the points the engine won't fire. Another check on the coil showed zero ohms. I dont know enough to trouble shoot the problem and would appreciate any help available.

PS. Could someone also give me the correct sequence of nuts, washers etc on the primary dizzy terminal. Working outwards on mine I've got: Square nut head-condenser connection tag-Lshaped square fibre washer-base plate vertical flange-3/8"plastic spacer-washer-nut-black/yellow lead-washer-nut.
Thanks
John
John James

Further to my last posting, I had the moving point strip touching base plate flange, so allowing it to earth. Further thoughts on the slow turnover with ignition on lead me to think the ignition must be grounding somewhere.
John James

The only way ingnition on would change turnover speed is if the timing is way off, probably too advanced. Loosen the distributor clamp, and turn it counter-clockwise 25 deg. or so at a time, and try again. Are you sure you were static timing it correctly? Very easy to do backwads.
George Butz

Thanks George
I set number one piston at TDC using the previous rotor head setting to distinguish between 1 & 4 compression strokes. After some thought I'm beginning to think number four might have been on it's compression stroke when the colortune plug sparked in number one cyl at TDC. It would slow the engine down for sure. Tomorrow I will use my compression tester to confirm number one is on the correct cycle and run another test on the coil. Fingers crossed.
John
John James

Eureka!
I case anybody else has the same problem, I had to retard the distributor in stages by almost 90 degrees before the engine fired up. It is interesting that I checked No 1 cylinder with a compression tester and set it at TDC on the compression stroke, then I used a colortune spark plug to set the number one spark timing spot on. When I tried to start the engine it still slowed down as soon as the ignition was switched on. It must be somehing to do with the way the pertronix sensor times the sparks.
John
John James

John,
Pardon my reluctance to chime in at the beginning of this thread. My experance with Pertronix install was not unlike yours in that my dizzy is off-set about 90 degrees from where it was when points installed. I discovered that one of my advance springs had rusted and broke in there so I had removed the dizzy for a good cleaning and to replace the springs...I just figured I had put it back in wrong after I did that work so I didn't say anything at first. I did end up taking it out again and doing a bit of re-wiring to get the dizzy around to a "workable" install with the post in a place that shorting on the tach drive unit would not be an issue (covered in an earlier thread on this post) and the plug wires were not twisted around the cap! For what it's worth...after the install I had a power loss at higher RPM that was disturbing. I followed Bud's advise from here:
http://home.earthlink.net/~budkrueger/Pertronix_Into_TD.html
(don't think he will mind me sharing)...and re-timed at 3000RPM with a 30 degree advance using a timing light with advance adjustment and setting at TDC.
Car has run great since and starting is much improved.
In fact, I have only had to use the choke twice to start since the install and that was on days the temp was 20 F.
Cheers,
David 55 TF1500 #7427
David Sheward

Thanks David
I've got Bud write-up. The thing that threw me was was the large error in the timing having carefully set it up as described earlier. I had visions of a burnt out coil, faulty sensor etc, etc. Had to go out with her indoors today, so I hope tomorrow's forecast of wind and rain is wrong so I can annoy the 4X4 brigade when fine tuning the timing on the local lanes.
John
John James

Having installed the positive unit on my 51 TD and a negative ground on my other car (61 TR3A), I found that I had to adjust the timing up to 60 degrees on the TD and 15 degrees on the TR. I helped a friend install one on his TD and found we had to adjust the timing only slightly. When I switched the magnetic pickup ring with my TD,the settings were reversed. It appears that there is a small quality control problem in the placing of the magnet in plastic casting. Jim
J.W. Herbert

My '37 TA has a XPAG that has been running poorly, and on a part time - when it wants to basis since I got it over a year ago. I installed a pos. ground Pertronix system and used the static timing method described in "the books", having the light come on when you cranked it to tdc. The car would almost try to run backwards! After asking several sources if I had put something in the advance together backwards, or put something else together wrong, and being afraid of running the car with something so far from what I read it was supposed to be, I stumbled into another internet site discussing this same problem. They said that instead of the light coming on at tdc, you adjust timing so the light is just going out. Must be something in the way the pertronix causes the field to collapse and fire the plugs. Anyway, I came home the next day and spent a few minutes setting up, and when I put it all back together and hit the starter, it started quick and sounds better than ever. Waiting for a warmer day to road test and adjust if needed, but it starts now without even using the "choke".
D. Holm

Here's another way to static time your electronic ignition. I have a Crane unit on my TD, but I am sure that it would work with the Pertronix type.

Disconnect the high tension wire from your coil. Replace it with an old spare wire and secure the other end about 1/4" to 1/2" from a ground.

Turn the engine with the hand crank until the timing marks are aligned, with the rotor facing the contact for #1 cylinder.

Turn the ignition switch on, and rotate the the distributor untill you hear a loud "snap" (the spark)

Since the position of the pick up unit is adjustable, you will have to make sure that when the spark occurs, that the rotor is still in the vicinity of the contact for #1 cylinder in the cap. Regardless of how you time the ignition, I think that this is where people are running into problems when installing new ignition systems...by the time they get the tming right, the rotor is between contacts, or even facing the wrong contact.

Try it it works!
Mark Evenchick
Mark Evenchick

Mark
I used a similar system utilising a gunson's Colortune plug which has a visible spark when fitted in a spark plug hole. I aligned the distributor to give a spark in number one cylinder at TDC and then encountered the problem I described earlier. I had to retard the ignition almost 90 degrees before the engine would start.
John
John James

This thread was discussed between 10/01/2004 and 21/01/2004

MG TD TF 1500 index

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