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MG TD TF 1500 - Jumping Timing Mark TF 1500


www.youtube.com/watch?v=Q1UFf_2SXvg&feature=youtu.be


Here is my MG TF 1500 with a timing light on it. It is running at 3000 revs the timing is 'averaging' at 30 degrees advanced which is about right. If you watch the timing mark on the pulley ( you can't see the reference point on the sump in the video) you can see it is jumping around . Probably +/- 15 degrees.

At idle the car is running about 8 degrees advanced. You can see some jumping but not as bad since I guess the advance mechanism is not really kicking in at that point.

I took the distributor out. Cleaned up the centrifugal weights area ( not really dirty but enough perhaps to interfere). The drive cog looks great. No real wear. There is no side to side play in the drive shaft either. Some up and down. The mechanism all looks in very good condition. I think it must have been refurbished by the PO. There is a repair to one of the mounts for the cap spring clips. I have a pertronixs electric ignition fitted.

So - A : is this as bad as it looks ? Car has been running hot on the motorway. Plugs have brown crusty deposits on them.

B: since the only other part that can wear is the springs holding the centrifugal weights should I just change them ?

I could send it off to Advanced Distributors but it is a long way from Ireland ...and I haven't been able to contact them.

Thanks.

Dave


D Moore

Pic of one of the timing weights after I cleaned it up


D Moore

Pic of the base of the centrifugal mechanism after cleaning. Marked for 12 degrees ?


D Moore

Dave
I guess it could be any of the things you suggest, but it might also be the timing light - if it is of the inductive pick-up type. I also get some jumping around of the timing mark with my engine and I am using a new distributor (MGB type) from Advanced Distributors in the USA with conventional points. I am thinking its caused by the proximity of the inductive pick-up when on Lead 1 to the Alternator (in Dynamo case).
Dave H
Dave Hill

if you think its the weights, then wire them shut, check the timing, if it varies then it isnt the weights. the shaft should only be a few thou up and down to ensure mesh constant, so maybe try a shim or two to test.


the video looks rather jumpy as does the flash, try it on cylinder 4 and is it looking down or up at the timing marks?

Dave most likely has a point
mog

What kind of spark plug wires do you have? If solid copper, that and the Pertronix ignition can cause what you have happening there.

Also, if your plugs are brown and crusty you may be running a bit lean which would account for the car "running hot".

Gene
Gene Gillam

Hello Dave -

I was experiencing the same issue - I solved it by fitting resistor spark plugs - this eliminated the jumping around that I was seeing on my timing light strobe.

I had a steady mark on the crank shaft pulley for the number 1 plug lead, but 2,3,and 4 were jumping around - I have the Pertronix Ignitor I unit and used solid wires.


The plugs solved the problems with 2,3,and 4 - and I am switching over to the graphite core wires as well - per advice from Pertronix.


I agree with Mog - wire your weights together and re-check - I also agree with Dave and Gene - you could have electrical interference from the wires or plugs.

Good luck!
DLD

Dave, which Pertronix module do you have installed. Bud
Bud Krueger

I'll second what Dave Hill said. There is a lot of interference from the spark plug wires. The inductive type timing light will probably be subject to this interference.
I have had the same problem in the past.
I bought an old non-inductive timing light on ebay and do not have that problem anymore. I had it with both the points and the Petronix. The direct connection timing light cured the jump on both points and the Petronix.
I use my in line spark plug checker and just clamp the timing light to the exposed section of the lead.

http://www.harborfreight.com/inline-ignition-spark-checker-69014.html

Mort 50 TD

I solved the same problem by wrapping the clamp-on pick up with aluminum kitchen foil. ,on my neighbours TR7

You could try it maybe it helps to avoid interference
from the other leads,

Gerard

Gerard Hengeveld

I have conventional copper wires on the HT leads. Made up of perhaps 10 or 12 strands of copper. Is this a 'solid' wire ?

I tried the light on my MK2 jag. Also positive earth - timing marks showed up steady as a rock so the light itself is not faulty.

The shaft moves more than a few thou up and down.

I'll measure the movement to be sure.

I'll wire the weights.

I think I have an 'R' for resistor plug in my used collection I can clean up and try.

I'll report back.

Thanks guys for all the suggestions.

Dave
D Moore

Dave,

Yes, copper stranded wire is the "solid" we're talking about. Your Jag probably has a more modern type of spark plug wire.

I'm not sure switching to Resistor plugs will help - the interference is coming from the wires.

Gene
Gene Gillam

Dave, again -- which Pertronix model are you using? Bud
Bud Krueger

Dave if the clamp of your timing light is not firmly attached to the wire ( wire thickness ) you'll will get a erratic reading

Gerard
Gerard Hengeveld

Trying to time my MGA the light not only jumped around, but I could see the timing mark on the pulley from all four spark plugs. I drove it over to Jeff's Advanced distributors and watched as he put the distributor with my cap and wires on his scope. When he spun up the distributor spark was going every where! Jeff put on a new cap and wires and the scope showed it was perfect. Car purrs like a kitten.
S E Bryan

Bud my unit is an LU 146 P12

Looking at the archives looks like you are probably the expert on working combinations of wire/plug/cap and unit :-)



Dave
D Moore

One of my lights (digital with an advance setting) shows the timing mark in it's right place and a second jumping pretty much all over the place. My static light (no advance setting) is steady as a rock. Pertronix igniter, copper wires.

Some light designs/pick-up are going to be more sensitive than others.

....
MAndrus

Dave,

If you timing chain is worn, the timing mark will jump around at idle, but will steady at higher revs. As the oil pressure increases, the tensioner exerts more pressure and the timing will stabilize. How many miles on your beast?
A Peddicord

Dave, that Pertronix model (LU-146) should be fine with solid wires. Have you looked into the distributor cap? See http://www.ttalk.info/Failure.htm for a possible cause. Check the inside of your distributor cap for carbon dust. Is the carbon brush in the center of your cap functioning? You probably don't want to send your distributor to Jeff. He abhors Pertronix. Bud
Bud Krueger


I taped up the wieghts and the light still jumps. Maybe not as big a range. I am guessing since the advance mechanism is removed from the equation and the timing sticks to its idle position this might be expected

I tried wrapping the pick up in foil. Didn't help.

I also tried the light/pick on all the wires. They all had some level of jumping. #2 perhaps a little less.

The cap looks good and I have cleaned it already - see attached photo.

There is a small amount of carbon and some wear on the rotor - see attached photo. There is definitely contact there - too much ?

The timing mark is more erratic looking at higher revs ( A. Pedicord)

One other thing I noticed - looks like the car could be timed of #4. See the last pic.- does this matter. I guess it is just 180 degrees out.

Still to try - taping the pick up in place - Gerard pointed out if it loose then it may be moving.

Still to try resistor plugs.


Dave



D Moore

Rotor


D Moore

Spark plug for good measure


D Moore

Oh dear, that plug looks rather strange, not only deposits, but oil on the last section of thread, is the tf a short reach plug?
mog

And finally rotor is pointing to #4 wire when timing marks are at TDC - an issue ? The issue ?


D Moore

Actually just to answer some of the other earlier questions I forgot...

The milometer reads 38,000. I would guess it since it was rebuilt by the previous owner it has less than this. Maybe as low as 15,000

There is very little up and down movement when I pull straight on the rotor when the distributor is installed. A couple of thou. If I pull and twist in the direction the cog meshes with the engine I get a little more - maybe 1-2 millimeters.


D Moore

to get to tdc for timing ( static start ) the no 1 piston should be at tdc when viewed through spark plug hole, with both rockers 1 & 2 loose, when turning engine over to tdc using a wrench: no 2 rocker ( inlet valve) should be watched through the rocker oil cap and should have opened and closed. at this point the rotor arm should point toward no 1 on cap.

no 4 piston is at the same level as 1, it fires at 180 deg off cam timing but the same point of crank
mog

That poor spark plug is fouled up. I would change them all.
It also looks like you have a cylinder head for 1/2" reach plugs but you are using 3/4" reach plugs. Look at the dark line on the threads.
Sandy
Sandy

You are looking at it 180 degrees out. The easy way to find TDC (the marker and pulley will align twice - but only one is TDC) is to remove #1 spark plug and turn the engine over with the crank until the pulley mark is quite a bit before the pointer. Stick your finger into the spark plug hole, and keep on turning - if you feel air compression you are approaching TDC; if not, you are 180 out. Then make sure the rotor is pointing to the #1 wire, and all is well.

I agree with Sandy - you (desperately) need a set of the correct plugs! Check the casting number on the front corner of the head, and be sure you have the correct 1500 head, using a 3/4" reach plug. You may well have a replacement earlier head, needing 1/2" reach plugs. An XPEG head will have the casting number AEF 118; a TF1250 head will be numbered 168425, with the final digit stamped. 22952, and you have an earlier head.

Let us know!

Tom Lange
MGT Repair
t lange

Another note(s):

When setting up for timing I use a socket wrench to turn the engine. With the #1 plug removed I put my thumb over the spark plug hole. As my pulley approaches the TDC mark I can feel either expansion (sucking in of my thumb) or compression (pressure pushing on my thumb).
You want to be in the compression cycle when approaching TDC.
At that point your rotor should be in the vicinity of the #1 plug wire. If you don't like the orientation of the distributor just raise the shaft to the point where the gear disengages from the cam shaft and rotate the shaft to the desired position.

I find trying to get contact at exactly TDC to be a waste of time. You are going to rotate the distributor to give you your desired advance at elevated RPM. The the mechanics of your distributor will determine the static timing. If I recall when I got my Pertronix the relationship between static timing and advanced timing were set for my drive set up.
At 30 degrees advance @ 3,000 RPM
That gives me about,
At 10 degrees advance @ 1,000 RPM
Mort
Mort 50 TD

This is the timing light I think you should be using:

http://www.ebay.com/itm/VINTAGE-CHROME-SEARS-PENSKE-TIMING-LIGHT-244-2115-Parts-or-Fix-LQQK-/161442445122?hash=item2596b83742&item=161442445122&vxp=mtr

or

http://www.ebay.com/itm/Vintage-Penske-DC-Power-Timing-Light-244-2115-Made-In-U-S-A-for-Sears/201167458385?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29979%26meid%3De3c6080f4d7d418492e17b8e174ad7c0%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D161442445122

Mort 50 TD

SOLVED!

The answer was electrical interference with the timing light pick up.

I researched the archives and bought some NGK BPR6HS. Short reach half inch resistor plugs to fit my 'wrong' TD head.

( I had by the way replaced the plugs I showed in the earlier photo as the first thing before starting to work on the timing... with lovely new Champion plugs but 3/4 inch... Anyone want them for the price of postage ?).

The timing marks were steady and she is timed to 8 degrees advance at idle and 30 degrees at 3,000 RPM.

Just to confirm I put one of the Champions back in #1 and the flicker was there on #1 but not #4.

I then dug up an old timng light from 20 years ago I had forgotton about and repaired the wires. It was the type you suggested Mort with a connecter over the plug itself.

On both the original Champion without supression the timing was steady.

So good news - dizzy is in great nick, timing is great. I can only hope now the new 'correct' plug lengths are a fix for the overheating and fouling of the plug was cause of me starting this exercise. If not then at least I know I start working the carbs with a sound electrical base.

I had been running with the 3/4 lengths ever since I got the car so luckily never had any issues with them hitting the top of the pistons.

Gents - thanks for your expertise and assitence with this. I was stumped by the quality of the pratical advice. In particular one thing stood out - the idea to wire up the weights in the dizzy to eliminate wear in the advance mechanism from the problem. Sounds simple but in a million years I would never have thought about that.



Dave

D Moore

Dave,

Glad you found the problem and it wasn't too serious!

Having the pistons hit the longer spark-plugs is one issue with them, the other is to have the threads so carboned up you can't remove them from the head.

Gene
Gene Gillam

Got her our for a short spin today.

Engine is definitely smoother, accelarates with a little more power. No pinking when hitting the accelerator going up hill in 4th.


Car took a little longer to warm up - used to be able to back off the choke very quickly. Once warmed up idles smoother. I had thought I was running rich before since I was able to back off the choke so soon.

She is running a little cooler overall.

Also didn't have any run on when switched off which indicates the elimination of hot spots in he combustion chamber maybe caused my the wrong longer plugs?

I'll be keeping an eye on the plugs for the next while to check mixture.


I have posted a separate question just to check my block+head+gasket combination.

So far so good.

Thanks again.

Daave
D Moore

This thread was discussed between 14/07/2015 and 17/07/2015

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.