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MG TD TF 1500 - ignition timing problems
|I am new and know very little. I have a 1952 MGTD that has no history and I live on an island where there is little professional help. I have only had the car for a couple weeks.|
We set the timing at tdc (static) and the car will not start. We advance the timing to where the 12 volt light just goes out and the car will start, but will not accelerate. I suspect the advance but do not know if what I experience when I play with it is normal or not. I have cleaned and oiled it. It seems to be sluggish when I expand it just a little.
Are there other problems I should look at or is ignition probably the cause? If so, do I need a new distributor?
It appears the car has a high lift cam. I have set the gap and dwell for that.
The engine number is original.
|W E Miller|
|Mr Miller, I am assuming that you do not have a timing light, so just continue to advance the distributor body by slowly turning it clockwise until you get the fastest idle, before it starts to stutter, the turn it back slightly. This this should give you a pretty good setting. If there are still performance and other drivability problems, then more diagnosis is required. Hope this helps Phil|
|Do you get any kind of firing? DO you have spark? It could be the dist is not in line with the cam when firing. Mine was one knotch off when I first put it in. Had to pull it out again move it to line up with number 1 firing and then it cranked right up. If it is the dist. Jeff can rebuild here in the states for a reasonable amt.|
|Tom Maine (TD8105)|
|HI Mr. Miller. Welcome to the BBS. This group should be able to assist you. How about giving us a bit more information on your TD? Has it been running? If not, how long has it been setting?|
The advance is under the distributor plate. There are a set of weights and springs under there. It is possible that these are corroded, but most likely not. Try the advancing information others have gave and see if that works.
Keep posting and let us know how it goes.
|Bruce Cunha (1950 TD 4139)|
|Welcome, Mr Miller. There are lots of things that could be going on. What is the story on the car - has it been running at all? Did this problem arise after you tried to set the timing (no shame if it did - that's how we all learned)? Was the distributor out for any reason? It seems like it's a timing issue. What manual are you using for advice?|
1) Take out #1 spark plug
2) KEY OFF - Turn the engine over with the crank until the timing mark is 2" away from the pointer
3) Stick your finger in the plug hole while someone slowly turns the crank, and see if you feel air pushing out of the plug hole - that means #1 is on compression and approaching TDC, and that you have the correct timimg mark. [You can also remove the valve cover and watch the pushrods, but that increases the chance that the valve cover gasket will now leak by 438%.] If no compression, turn the crank 360 until the timing mark approaches, and check as above - you may have the timing 180 degrees off.
4) Then statically time again.
5) Let us know!
Bar Harbor, ME
|When we picked it up from the port, the car started and ran, a little rough, and we drove it home from the dock, about 30 miles. It set for two days and then would not start. We started playing with the timing. A friend who has worked on TD's came over and got it started by setting the points and timing. However, when we drove it, it ran good (not great) for about two miles and then started missing and laboring. The friend would rather not come back to work on it. |
A Calif. British Sports Car Dealer got the car from an estate with no history. I bought it from him and shipped it over to Kauai. It was apparently restored some years ago, including the engine. The carbs are not in good shape and need re-building. The filters are clean.
We can get the car to idle, roughly (carbs?), but not run well enough to drive. The RPM will not increase with peddle pressure. The carbs sound like they are sucking air and the engine wants to stall so we cannot check the spark advance with the timing light. It appears we have the timing advanced about seven degrees just to start it.
Why can't we set the timing at TDC while ideling and then start the car? We tend to do the same thing over and over ( insanity ) trying get it to run (idle) with the idle set properly at TDC so we can check the spark advance. We use the crank to set the car at TDC. We have checked and re-set the point gap many times. The dwell shows it is proper at about 60 degrees for a high lift cam.
I pulled the spark advance weights and springs. Cleaned and oiled them and noticed they had worn a grove where the weights fit over the studs in the bottom of the distributor.
|W E Miller|
|Bill, 90% of carb problems are electrical issues. I think you are in the 10% catagory. Set your static timing back to 5 degrees BTDC. Now lets go have a look at your carbs. Try starting the engine and if it starts let it run until it dies. Turn the key off imediatly. Remove both of the float bowl covers and tell us what you see. Also check that the pistons move up and down freely in the dash pots. Check the bottom of the linkage and make sure that the jets go fully home when you push the choke cable in.|
|Bill, welcome to the fraternity.|
You can static time an engine (which I rarely do) ANYTIME you have the timing marks aligned because you are simply rotating the distributor to alter the point break, which can be done on either #1 compression stroke or #4 compression stroke. This is because #1 and #4 move in concert up and down, with only the valve action determining TDC on either. If one looked at the rotor it will point 180 degress differently, but the point cam will be moving the rubbing block at that point regardless, so knowing if you are at TDC on #1 is irrelevent for static timing.
Some basic things to know: The distributor turns Counter Clockwise (anti-clockwise) and the firing order is 1-3-4-2. (I like to say 3-4-2-1 because that makes more visual sense to me if I think about how the crank turns and the pistons move). On an XPAG, you can mount the distributor ANY way you want in the engine, so NOW do Tom's nifty test and see which way the rotor is pointing. That will be #1 firing point. From there install the spark plug wires CCW 1-3-4-2 around the distributor cap. Going around either way, or from the wrong #1 sarting point 180 degrees out can result in four outcomes; two that will run poorly, one that will run correctly, and one that won't run at all.
The crank pully is 3.75 inches in diameter where the timing mark is located, or about 11.78 inches in circumference. That's .033 inches per degree.The engine turns Clockwise looking from the radiator. I like to dynamically time the engine somehere around 11-14 BTDC on a really well built distibuor, or about 8 BTDC statically. So you can put a mark on the pulley about a quarter inch to the right of the real timing mark on the pulley and static time from there. Then, after the engine starts, have a friend advance the throttle, or do it yourself with pull cord on the throttle, and watch your timing marks with a timing light. At about 4000 RPM you should be fully advanced at about 33 degrees (8 degress plus our 25 degress of advance), or about 1.05 inches before the real timing mark.
It is possible to tighten the center screw in the distributor and lock down the weights. I found the happy place for my center screw and secured it with locktite, before I sent the distributor out for rebuilding... now I can fully tighten the screw.
The condenser can cause the problems you are having, as well as the coil. Check those items out, and then run LaVerne's tests on the float bowls. Make sure you drain the fuel and put in fresh fuel. There are places you can ship your carburetors to for complete rebuilding.
Let us know.
Welcome. You will get fantastic info from this BBS and don't be afraid to ask anything that you don't know as we have all been there. You already have some great responses so I won't ad anything more other than to say what you already know.....You live on the best of the Islands.
We love visiting and travelling around Kauai as it is truly the last of the hospitable and laid back of the Islands. I hope that we can get together on our next visit, whenever that may be.
|Brian Smith (1950 TD3376)|
|Thanks for the input.|
Ignition: We have a new condenser and rotor (Moss) and the coil checks out. we put in new points. Number one is on compression with the timing marks. We have to set the timing about 30 degrees BTDC to get the car to start. The timing does advance (I loosened the center screw in the distributor and the advanced weights work better), however we cannot get the car above 2500 RPM. It runs rough at idle and worse at higher RPM, when we can get it there. We have rotated the dist with the car running to find the smoothest place which is ab out where it likes to start. I am not enough of a mechanic to check,at this point, about the dist being in line with the cam. Remember, the car ran fine for about 50 miles a week ago, then started running rough at higher RPM and starter problems, then I started screwing with it.
Carbs: We checked the floats (they seemed to be ok) and pulled and cleaned the dash pots. Adjusting the forward carb mixture has no effect on the engine. It appears the rear carb was set rich, perhaps to make up for the forward carb. I have a rebuild kit from Moss. Even if I rebuild the carbs right, will that help the timing problem?
I am using "The T Series Handbook". I have the "Workshop Manual and "SU Carburetters Tuning Tips & Techniques" on order. Any suggestions for other books and manuals?
Thanks for your help,
|W E Miller|
|A discharged battery would give the problems you describe. Bad charging system/low battery voltage = bad ignition.|
Make sure your battery is up. Slap a battery charger on it for a spell and while trying to start it (just did that for a bit of insurance on wife's TD today).
Thoroughly clean and inspect your cap for cracks and carbon tracks inside.
Process of elimination!
Why is it you always find something in the last place you look?
...cause you stop looking once you found it!
|Did you install new plugs? Don't clean- use new ones. Make sure all cyls are firing- if you have or can borrow one of the laser thermometers shoot each branch of the exhaust manifold- all should be the same temperature. Or you can loosen the plug wires, and pull one at a time- the speed should drop an equal amount. Any chance the plug wires were switched? How old is the gas? Plug wires and coil wire firmly seated in the cap and coil? Are you sure you have the correct TDC mark- I have seen a couple pulleys with two marks. Two things don't make sense- I don't think it should run at all advanced 30 degrees, and if the mixture adjustment doesn't effect the front carb, maybe those two cyls are not running? So what is the story why your "friend" won't come back- offer him more beer! Carbs: you said you "checked the floats". Did you take them out and shake to make sure not full of gas? What is the fuel level when you take the float chamber lids off? (just wait until the pump stops clicking, turn the key off and physically look to make sure the gas leve is about the same in both. Last, make sure the tach cable/drive isn't shorting the terminal on the distributor. George|
|Did you give it a compression test yet? It almost sounds like the valve timing is off a notch, however, you did mention that it was running fine previously for 50 miles. Phil|
|Thanks guys. We did a compression check and all four are at 140psi.Plugs all show rich fuel and are dry. I adjusted the lifters. It has new plugs. Coil and dist cap should be here in a couple days. Wires will be the only old thing left (except a new distributor). I have new wires but I am lazy about setting them up.|
Thanks Jim, I will look at the battery and charging system in the next few days.
I just got through playing with it some more. It is running a little better and I drove it a couple blocks but it has a hard time maintaining power.
George, If you think 30 degrees is too much. It is now starting and running at 66 degrees BTDC. That is using Dave's numbers. The pully mark was about 2.25 inches before the timing pointer at idle, 800 rpm. As I said before, the #1 is at TDC when the marks are on the pointer.
The floats looked good and the front carb is working but the mixture can't be changed.
I can't help but feel we are missing something simple. I have a tendency to do that.
Nobody told me to NOT re-build the carbs. I will have to go by the book and I have the Moss Video. It's a scary thing to do.
|W E Miller|
George B. in his thread above, asked "how old is your gas". If you have no history on the car, I would suggest that you drain the tank and give it a thorough cleaning. Old and dirty gas can cause all kinds of engine problems. With all the suggestions
from the forum, you have a good start on getting that TD on the road. Good luck and keep in touch with your progress.
|George Raham [TD4224]|
|I'm still believeing your real issue is with the carbs. Since you can apparently start the car and it will idle and you have rulled out a sticking float valve I'd suggest you synchronize the carbs. Might first check and see if both carbs are opening when you depress the throttle. Possibility that the linkage between the two has come loose and you are trying to run on just one carb.|
|From your description of the carburetor mixture adjustment not having effect on front carburetor would make me think it was a vacum issue from either a leak somewhere or possibly the timing chain has jumped a tooth. You might hook up a vacum gauge and check that as well. |
|Easy to miss...as LaVerne says about carb synch. Make sure the throttle activates both carbs. The link between the throttle shafts is an achilles heel. Breaks very easily.|
|Everything in the ignition is new except the distributor. The car does have a new dist cap. |
The fuel pump just went out. It was an Airtex E8012S. I can get a similar one from our local parts store. Does anyone have any suggestions on the choice for a new electric fuel pump?
The carb rebuild is next.
|W E Miller|
|perhaps i missed it in this thread, but how did you check the float level? did you measure the fuel height below the bridge? if you are unable to adjust the mixture..or adjusting for mixture has no effect, the float level could be too high. regards, tom|
|You can't beat an original SU, or the new electronic version.|
|I had identical problems with my YT, after I re-built the carbs, adjusted the mixture, lean needles, fuel pump replaced and adjusted the distributor/timing about 25 times, then someone suggested checking for air leaks - not possible I said, new gaskets only recently !.|
So we tested the idea - Started the engine and squirted a small quantity of water near the carb flanges and inlet manifold flange - engine quit instantly.
Tightened the mounting bolts of the carb flanges and the manifold studs - that fixed it - engine now pulls like a train.
The car had done about 2,000 miles in a week after the carb and manifold gaskets had been replaced without any sign of trouble, and there was obviously some crush left in the gaskets that appeared over time/distance - letting in the air where it was not wanted.
Months later I am still smiling at having "fixed it".
Try the water sprayer test.
|Since I last posted, I have rebuilt the carbs. I, however, can not start the car, apparently, because of the problem in my original post. The problem got to the point where the car would not start before the carbs were rebuilt. We have replaced and doubled checked everything. We have not replaced the distributor yet. It seems to work properly as we hand crank the engine and #1 is on it's compression stroke when the timing marks are lined up. We have tried static timing and just winging it. The engine will cough and backfire sometimes, but not run. Here is the question. Can the mechanical advance be causing my problem. I have cleaned and oiled it. There is some deep groves around the post that hold the weights. The weights can only be opened about one quarter of an inch or less when I turn the shaft. Is that the way it should be? I will send it to Jeff If that seems to be the problem. There just doesn't seem to be anything else to check. The plugs are sparking and the carbs are carbing. We cannot find any air leaks.|
|W E Miller|
|Correction to the latest post my me. The advance weights open only about 1/8 th of an inch. Is that how it is suppose to be?|
|W E Miller|
A quarter inch of movement or less is typical. I don't believe the grove is.
Do you get sparks at all four spark plugs?
The distributor needs a good ground to work properly. They way you describe the problem it does sound like it is going to be something simple. On my website, under mg td15470 Restoration » Engine XPAG TD2 15613 » Engine Start with Coolant are pictures of the inside of the distributor and the weights. They might help you see if yours looks the same. Go to www.dbraun99.com and find the MG TD15470 pages.
When you rebuilt the carburetors did you center the jets? The pistons should lift and fall with a nice thunk right down to the bridge.
|Simple stuff you must check, if not already- before you do anything else: |
1) what is the compression? You need to test that on all 4 cylinders. Must be about 130ish or so in each cylinder.
2) spray some ether starting fluid into the carbs and try to crank. That will rule out a carb/mixture problem once and for all. If it still won't run, must be ignitin.
3)Forget about the advance. If that is way too loose or frozen it will still start and run, maybe poorly, but that isn't why it it won't run.
a)Are you positive the rotor is pointing at the #1 plug wire at compression stroke and not top of the exhaust? Been there done that repeatedly. To check: pull the valve cover, slowly crank it over, the #1 valve (exh) will stop closing just before valve #2 starts to open. At that point the pointer should be on or almost on the pulley mark. That is TDC exhaust stroke. The rotor should be pointing to plug wire 4 (180 degrees) from he #1' wire. Exactly one more rev and the rotor should be pointing at #1 segment and the timing mark.
)Also correct firing order? The rotor rotated CCW, and the order must be 1-3-4-2 (double check this- it is cast into the exhaust manifold).
c)Did you change rotors yet?
d) are you sure carbon brush/spring is in the middle of the cab? That just about covers everything. If it still won't run, I bet a couple of us would come out to help if you will fly us out there and find some nice lodging for a few days! George
| W.E. |
HERE IS A SIMPLE WAY TO CHECK YOUR IGNITION USING A TIMING LIGHT.
Start the engine by advancing the distributer till it starts. Install the timing light on any lead and slightly open the throttle while looking at the timing light. It should show a steady flash for each 2 revolutions. Do this with all four leads.. If the flash remains steady then you do not have a coil -rotor or points problem.
Then advance the timing while turning the distributer clockwise till it reaches max idle speed. twich it back a little bit. Then try to accelerate the car. If it stumbles reinstall the timing light and watch the flashes on all four leads. They should remain steady.
It could be possible that you have a front pulley that is marked wrong. Rare-but possible.
Make certain that both carburetors open together and that both pistons rise equally .
You can still have bad spark-plug leads so I would install your new ones. Check the cap for traces or cracks as under load they will break down.
After that you can fine tune the timing by ear and follow that with a timing light check to verify timing mark.
|Thanks guys. I now have it running really nice. The last three post helped me figure it out. Thanks Dave,George, and Sandy. I had the Dist Cam in backwards. My carb rebuild also was a big success. when it was running before, it had little power or torque. It does great now.|
All you guys are great. Thanks
|W E Miller|
|Bill.. Please tell me how you installed the cam in backwards|
This thread was discussed between 27/06/2010 and 18/07/2010
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