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MG TD TF 1500 - Help.....PLEASE
| I am having trouble with the TD and hopefully someone will have had the same problem and guide me in the right direction to get it fixed.|
I rebuilt the engine last year and it was sweet, ran like a top. I put it in storage while we were building a new home and once the shop was ready just drove it into the shop until I had some time to work on it.
I did add fuel stabilizer to the fuel but other than that nothing else. Recently drove it to a garage tour and it was terrible! Idled great but as soon as I applied any amount of power or put it under load it missed and bucked like an old bronco.
Today we took it out again and the same thing. Fuel level is good in both carbs, changed the condensor and adjusted points, put on a new distributor cap, cleaned and checked gap on plugs, checked the valves, readjusted the timing (static at 0) and checked fuel levels in floats again. Everything seems good. The subsequent drive showed that it was the same. I should add that I have also replaced the fuel with new fuel on the off chance that this was the problem.
I haven't changed the coil or the fuel pump but everything alse replaced or double checked. The archives gave a fair bit of info and I used this info to do the initial troubleshooting. Does anyone have any further ideas????
|The odds are pretty good its electrical...something breaking down under load.....if you have a spare coil you might try a swap...?|
|Brian, sounds like a fuel problem to me in that there is enough fuel at idle but with the butterfly open the engine is not getting enough fuel and is running very lean. Did you check the filter screens on the carbs? How is the dashpot oil? Vacuum leak?|
Cheers, Hugh Pite
|Brian - Did you have the gas tank sealed with some kind of slushing compound? I had a problem a couple of years ago of the slushing compound dissolving in the gas and gluing the check valves in the fuel pump and the needle valves in carbs shut. The other thing to swap out is the rotor in the distributor, there has been a rash of problems with those recently. Cheers - Dave|
|I had similar symptons. It turned out to be the butterfly connection between the two carburettors had come loose and the engine was trying to work on only 1|
|Dirty fuel or a contaminated system can cause those symptoms (per Hugh and Dave D) And as Geoff says, anytime you are running on one carburetor the engine will act like it is sputtering and unable to go much over 40 mph. So look for dirt in the filter screen at the pump, and then do a simple pump test to see how many pints it can pump a minute. The exact figure is in the workshop manual.|
Then consider the distributor. Check for the rotor fit, and see if oil is making its way up to the bowl. If a Q-tip dipped below the advance plate down to the bottom of the bowl comes up soaked, clean the points with a dry piece of index and try running. Until I got my distributor repaired by Advanced Distributors, I had to sop out my distributor every 300 miles. The oil would film over the points rendering them useless. If the condesor is marginal the car can have trouble running.
Is the fuel pump ticking continuously or with a too high frequency? Does the engine recover by itself, if after these symptoms you keep it idling for a while?
I had a similar problem. After starting ad running properly during some hundreds of meters, the same symptoms as you described appeared. After letting it idling, the engine was able to run fine for the same distance, and again the missing. It turned out to be a clogged fuel line at the bend close to the tank outlet. The limited fuel flow was only sufficient for idling conditions, but when demanding power, the carb bowls run out of fuel, until filling again when idling.
Hope this helps.
|How old is the gasoline? Stabilzed or not, the stuff is getting useless with the ethanol and water absorption after 6 months. Remove the carb dampers (the brass things on top of the dashpots), run it and see if the pistons are moving up and down. We recently spent a couple hours cleaning ethanol/old gas/dissolved sealer gunk out of a TC's carbs. One float was totally stuck to the bottom of the bowl, which overflowed. The pistons would barely move due to the nasty gunk, etc.|
|The hose between the two carbs can break down as well?|
|Lots of great comments. I am going to check out the fuel delivery today. The majority of the fuel is 2 weeks old but I haven't checked the filters yet so this will also be on the list. I have a couple of rotors and changing them hasn't made a difference and the changing out of the condensor also made no difference. I did check for a vacuum leak and this doesn't appear to be a problem and the dash pot oil is good. Sitting in the shop the engine idles sweetly and lifting the lever connected to the gas pedal allows both carbs to open and the engine picks up nicely with no hesitation, it is only when it is on the road that it is a problem.|
My first thought was a float had filled with fuel or a float valve had stuck but checking this out the floats were fine and the float bowls both had the right amount of fuel. My tank was sealed a number of years ago so will still check for this problem. I have a spare fuel pump so will transfer it over but don't have a spare coil. Once I have a new coil I will try this as well.
Really appreciate the comments and will let you know the outcome shortly.
|I had this problem in a Capri once and it turned out to be a bad spring on the points....ran fine at low RPM, but anything off idle the points bounced and the car wouldn't run....drove me crazy. I tried all the things suggested about and finally changed the points because I had done everything else, it then ran fine.|
|A while back I was reading on the O'connor classics site that whenever they have a TD that isn't running right the first thing that they do is change the plugs. Then they go from there.|
I have followed that advice and it often cures the problem.
|Well I am out of the shop once more.......I have gone through the list of potential problem areas listed above now and it runs no better. Changed out the coil, no change, got the old original rotor out of my used parts box, no change, pulled the points plate and checked and cleaned the points and regapped them, no change. The last thing on my agenda was to replace the fuel pump with a new one and once again no change. I drove it out the drive and down the road and it is missing like crazy. This same car ran great last Summer and now it is terrible. I am beginning to think that my mechanical skills aren't enough for this car. My MGB GT has never been this much of a challenge and it has been stripped totally and rebuilt and continues to run great.|
Can anyone think of any further causes that have been missed above????
This is a long shot, but if you have changed your valve guides to bronze ones when you rebuilt you engine, you may have a valve stuck open. This happened to somebody I know, it also was following a long lay up.
If you can do everything that you just listed, your mechanical skills are fine.
Make sure the air cleaner is not squished down so far that the legs are bent and you are choking the engine. It's common.
More fun tune-up stuff:
Take your dashpots off your carbs and raise the pistons and let them fall. Do they land with an nice 'clink'? If they do your jets are properly centered.
Take off your pistons and suction chambers being careful not to mix them up or change their orientation.
How high is the fuel when looking down to where the jet assembly is? It should be .120 to .200 below the bridge. Adjust that by bending the forks on the float lever. Ignore the 7/16 bar stock measurement.
Get a dial caliper and set the jets .070 below the bridge.
Balance the carbs at 1500 rpm, and then turn both idle screws down to 600-800 rpm.
Check to make sure the mixture is right by ajusting the jets until the engine attains its highest idle speed, and then go rich one flat.
The firing order is 1-3-4-2 and the order is counter clockwise on the distributor. I've messed that up before. Make sure 2 and 3 aren't swapped. Put a timing light on each lead to make sure each is firing evenly. When you timed the car, where you at TDC on Compression, or TDC on Exhaust? Simple stuff, but it is often the simple things that trip us up.
|The only thing the guys didn't suggest checking is to make sure the wires, particularly the center wire going into the distributor cap isn't pulled out a little or burned off. Same for the coil end. What about a mouse nest plugging up the exhaust? I have heard of that, never personally seen that. Still suspicious of a sticking carb piston. George|
I know you already changed the condensor, but the symptoms you describe fit perfectly with a bad one. Can you verify the replacement is indeed okay? I've had a couple of them go bad, with the same symptoms you describe -- engine runs okay at idle, but won't pull any load.
I actually pulled all of the wires and confirmed that they were all snug in the cap and the coil.
I have checked the floats, float level and needles as well as double checking the wire filters and all are great. It ran great last year when put away and had in fact taken a long drive to the inlaws place in another community with no problems. I have also checked compression and it is even across the board. Also pulled the air filter completely and no change. Thinking that it "might" have something to do with timing, I double checked that but again no change.
I am willing to try almost anything at this point and I do have a brand new condensor (modern style) that I bought for the TD and never used as it meant modifying the points plate. Now may be a good time.
I can confirm good spark, excellent fuel supply, valves set at .015 with the new cam and everything "appears" to be set up correctly. We are going on a three day run at the end of this month and would rather drive the TD than the MGB GT.
|Hi Brian - I would also hook up a timing light and see what your advance is doing as speed increases. You mention that the car idles well - but breaks up as speed and load increase.|
You may have a broken advance spring or one that has somehow come off of the weight. You may also have a jammed advance - twisting the rotor button will allow you to test this to some degree.
Just a quick thought.
When you swapped out the points plate did you inspect the springs & counter weights for advance? Bad or broken spring could keep advance from kicking in at higher RPM.
|Ok - since we are grasping for straws, check the connectors between the throttle shafts on the carburetors. Had a friend with a TF that had one of the connectors broke - drove him crazy until he found it. Another thing, remove the dampers from the carburetor pistons and lift each on by finger and see if either one is binding somewhere on a bit of dirt. Cheers - Dave|
|Going to throw in one more check. Get a can of some thing combustible and check for leaks around the carb and manifold. You have checked just about everything. But, I also agree with what scott said. Sometimes replacement parts turn out to also not be good.|
I had the opportunity to check that the weights are working properly as it was suggested that I replace the whole distributor and after doing this I went back to the original, neither one made a difference.
The carb connectors are working together but I think that the only thing not checked is the carb pistons. I removed the carb "bells" and the pistons drop with a thunk but I will take of the intake plenum and ensure that they are working with the carb all together. It has also been suggested that I drain the float chambers and then connect the pump to a NEW 1 gallon container of gas. The old gas had been treated with fuel stabilizer and I recently filled the tank but the old gas may have contaminated the new fuel. Nothing to lose trying this as it sure isn't running well now.
I also installed a new condensor on an old points plate and it made no difference so I guess that rules out the condensor.
Thanks for all the help and suggestions all who have responded. This one really has me scratching my head. For such a simple, straightforward engine it sure has me stumped.....must be something really simple!!!!
|with all you have checked and since it is coming out of storage...is the exhaust clear? no mouse condos?? regards, tom|
|Other ideas: Buy or borrow an infared thermometer. Dirve it for a bit hard so it misses, then immediately shoot each branch of the exhaust manifold. All should be the same temp. If one or more much cooler that will narrow down. Definitely get a visual on the dampe movement. While the air intake manifold is off, start it, rev, and place your palm over the carb, the idea is if there is a piece of trash in the jet, or passageway from the float chamber that may suck it through. Did you change the plugs yet? Lastly, make sure there is no way possible the tach drive or cable is swinging around touching the distibutor terminal. A while back, my friend with a TC called and said it would barely run. After spending a couple hours changing about everything, I noticed that the tach drive would move and short out the distibutor. George|
|Hi Tom and George|
Exhaust is clear. I have removed the intake plenum and confirm that both pistons move up together and I held my hand over each one in turn and lifted just before it stalled. Pulled a l;ittle extra gas through the carb. The pistons both drop with a clunk. Once again the engine idles just fine and blipping the throttle there is instant response and no hesitation. Unfortunately I am unable to take it on the road as our drive was just sealed so will have to wait until Monday.
To answer an earlier question the throttle shafts are joined and working together. I will also purchase some new plugs, perhaps some hotter ones on Monday prior to taking it for a ride. Still think that it has something to do with the ignition side but time will tell.
|Getting back to your first post.... other then the fuel stabilizer was there 'anything' else you did...even something small....could mice have chewed a bit of wire somewhere while it was in storage....???|
|Brian - What exactly are you saying here "I removed the carb "bells" and the pistons drop with a thunk but I will take of the intake plenum and ensure that they are working with the carb all together."|
The drop test must be done with the vacuum chamber in place and the dampers removed. In addition to checking that the drop is ok (an indication of correct jet centering), lift the pistons by hand and insure that they are not catching on some grit that has found its way into the vacuum chambers. Cheers - Dave
From the beginning, is seems like you have a very good "handle" as to what to look for to solve your problem, and also tons of good, usefull suggestions from this site.. Very perplexing indeed! One thing that recalled that happened to our TD similar to yours, is that it started to miss under load as yours does, even though it idled fine,,,, after searching, I found that the small screws that hold the "Point/condensor fixing plate" to the dizzy body had worked loose, allowing the plate to rotate a bit. Once it rotated, the timing was way off. It idled fine, but missed when it was on the road. Actually, some of the threads for the screws were partially stripped, allowing this to happen.
Hope this helps,
|Another straw. I had a distributor once where the advance plate wouldn't move with the center screw all the way home. I put the screw in with loctite a half turn up and the advance plate was able to move.|
Did we check to see if the advance is working? A timing light pointed at the pulley and pointer is all that's needed. On a regular rebuilt distributor I time at 8 degrees BTDC static. That's about a 1/4 inch. At 3000 rpm 25 degrees of advance takes me to 33 degrees BTDC which is about 1.05 inch around the pulley. On a Jeff Schlemmer distributor I start at 11-14 degees btdc at low idle and let it take care of itself.
|Dave Dubois - I have taken the plenum off the carbs, leaving the vacuum bells in place and the pistons drop smartly with a clunk. Removing the dampers they really clunk. This car has always had brass pistons but springs as well. Tried running without the springs a few years ago and it wouldn't run well at all.|
Gordon - just fuel stabilizer
Steve - thanks, the distributor points plate is firmly attached and the advance weights move freely.
Dave - I haven't put a timing light on it yet, I have simply used the crank to set the engine at #1 top dead centre on compression which should be 0 and then adjust the dizzy until the points are just opening (static). The pointer lines up with the mark on the crank pulley at this point.
Timing light will come out today!
You did mention fuel tank had been coated, and you have spare pump.
Hows about: rigging a "new supply" from gas can and spare pump?
Did this once with an old Triumph that had a simmular proplem at high RPM. It had a "crushed" fuel fitting that was restricting flow. Car ran great from "temp" set-up and finallly figured out somewhere along the way it had been up on jack/jack stands that had crushed a short section of copper fuel line against the frame.
Also had a 64 tempest that purred like a kitten at idle, but chocked and died when you hit the gas. That one had a ping-pong ball in the tank. Was a great deal for me. The PO had replaced everything, (carb,dizzy,coil,condenser,wires,ect)and was flat pissed-off with the car. I bought it for $20.00 and drained the tank. Had it on a floor jack from the rear end, drained, and a friend leaned on the quater pannel tipping it. That was when I heard the ball roll across the tank. Took the tank off and managed to get it out. Ran great after that.
Talk about a long shot ;-) !
|If you added a new seal to the filler neck of the gas tank, that could be a problem.|
In order for the gas to flow into the gas line, it must not do so from a vacuum. The The T-Series gas tank is designed to leak air around the filler. If the seal is too tight, a vacuum develops and fuel won't flow.
If one looks a a MMM MG, you will notice a small coiled "pigtail" on the top of the tank. This serves the same purpose and allows air to flow into the gas tank.
If you have replaced the cork sealing ring, remove it and start the engine.
|Gordon A Clark|
I replaced all of the plugs with new NGK plugs, pulled carbs apart and checked that everything was clean and set up correctly, put a timing light on the engine while running and it still idles great.
I notice that the engine has a slight miss when I rev the engine (in the shop) so I am beginning to think that the problem has to be in the ignition side. A ride down our street indicated that it still bucks under load and I wouldn't want to take it out for a run anywhere the way it is running now.
I'll keep you updated on progress.
|Brian, Try this- Loosen the plug wires so you can just pull them off with a touch. Then rev it up enough in the shop to have the slight miss occur. Remove the wires one at a time, and see if you can tell which cylinder is missing- if it is just one. The revs should drop exactly the same amount for each cylinder, if one didn't slow much, that would be the problem cyl.|
|Brian, I beg you to let us know what you find! The mind boggles at all the minute possibilities that have been suggested to cure your mis-fire.|
Just a thought,I had a similar problem with my '51 TD a few weeks ago.
To cut a long story short I traced the fault to a loose wire on one of the regulator terminals. It was fine on idle but on the road the wire was making and breaking with the vibration of the engine, then stopping and idling it was fine again, then moving off the engine started to mis-fire again.
Tightening the offending terminal cured the problem, the car now runs as sweet as a nut.
May be worth a try to check it out, you never know you may have the same problem.
|I am really grasping at straws now. I checked and tightened the wires on the regulator (none loose) pulled the plug wires as suggested and with my best half reving the engine until it missed, I pulled each plug wire in turn (twice) and each one resulted in the same hesitation. I also carry an emergency fuel pump that plumbs into the system and I hooked it up and it made no difference. The fuel is not stale and all filters and float bowls are clean.|
As mentioned in a previous response, I had springs in the carb bells even though the pistons are brass so I took them out.....again no change.
I am really thinking that this is on the ignition side but don't know where to go from here. I have two distributors and both gave the same results, the new plugs are getting the same response as the old plugs, timing is good and points gap is .010, the rotor is now an old original as I have 4 of these and changing them has made no difference. I have no way to check the coil or condensor other than change them out and this has been done with no change in miss. The only thing not changed at this time is the plug wires and coil wire, they are actually wire core.
I hope I am not boring you with this saga but I would sure love to get the TD out and use it again. I accept all ideas and will continue to check them out.
Thanks for your understanding
|brian, i am not going back over the things you feel have been checked and are confident they are not the cause. i'm working from the basic premise the only thing this motor needs to run smoothly is compression, good spark delivered at the proper time and and proper fuel/air mixture. it sounds like the idle circuit is working fine, yes? compression is good? if so, as the engine accelerates either the spark is not arriving at the proper time..advance mechanism in distributor, break down in ignition circuit..distributor cap, spark plug wires. |
if the mixture is proper at idle, the things on the fuel side that would effect proper mixture at higher RPM; obstruction in the tank, screens in the fuel system blocked, improper float level due to improper float setting, sinking float, sticking needle valve. vacuum leaks, loose throttle plate, sticking "tickler" pins holding float down.
i believe you will have more satisfying results if you are able test and troubleshoot versus removal and replacement of components.
best of luck. regards, tom
|I haven't seen "voltage" thrown in yet for discussion. Wire a voltmeter in for the time being. I made one that plugs into the lighter for quick checks (I'm presently installing a voltmeter and 2 lighter sockets in a TD).|
Clean battery posts and grounds, too- that doesn't cost anything.
A few months ago, an engineer buddy had to turn around on a trip and drive back a hundred miles when his late model van started missing and running poor- drove right to the Chrysler dealer 100 yards from my house. Paid them $95 and they proclaimed it in perfect running condition. He brought it to me, and 2 minutes later, I showed him his battery had less than 10 volts.
You mentioned that you set the points gap to .010" this is correct for the early distributor with a symmetric cam, for a late distributor with a high lift cam, the gap should be .014" to .016" are you sure you have the early installation?
|I would first put a fuel pressure gauge in the line between pump and carb, such that I could see it while driving. Might have to sacrifice a line to cut for installation of a tee, but at this point...|
Next I'd suggest running a wire straight from the battery to the coil, disconnecting the normal wire. That will eliminate all wiring except the actual IGN circuit. You can have things like a broken wire inside the insulation, etc. Wires that run from the car to the engine (coil - dist) are especially suspect, including engine grounds.
|Fletcher R Millmore|
|Fletcher brings up a good point. |
Be very suspect of any old lucas bullet connectors.
(and newer crimp-ons)
Most of mine were corroded several inches back from the connectors. Replaced them all with new soldier type from Tripple-C. Just about everything on my car was intermitten.
Also I haven't seen anything about tappet adjustment ...you good there?
Since the only thing you changed is adding the fuel stabilizer, before storage, I think I would disconnect the gas line from the fuel pump to the rear carb. Then get a clear glass or plastic gallon bottle and turn the key on. See how much fuel is pumped into it and how fast. Dose it at some point slow down? If so then the fuel stabilizer has loosened up some of the gas tank coating/slouch . A couple years ago I added fuel stabilizer to my leaf blower and string trimmers before storage for the winter. In the spring when I went to start them the plastic gas lines had turned brown and brittle. It dose not take a lot of dirt or sludge to fowl up the screen strainer in the gas tank, where the fuel line connects. John
After chasing this thing and grasping at all of the ideas that came forward the problem did turn out to be electrical after all. I had three points plates with condensors on them (originals) and after checking and rechecking everything I finally modified one of the plates to take a new style condensor and then carefully set the points at .012 and it runs like a top.
I made the decision to assume that at least one of the condensors was good but in the end I was the fool....they were all bum, the brand new one was the only one that worked. I did try it before and I am pretty sure it didn't help but I have since gone through everything so I will guess that there may have been something else as well that I corrected in my checking.
You can probably see my smile from there.
Thanks to all of you, if nothing else I hope that this helps someone else get their car running in the future.
A lot of suggestions listed. Sorry it took so long to pinpoint the issue.
I suspect that your victory was met with mixed emotions. While pleased that your frustratrion is at an end, there is certanly disappointment that the saga has ended. In my opinion your problem is just the type which stimulates this group to search for solutions. In this case the ideas were remarkable and I hope someone will catalog them.
With warm regards,
|That's great news....|
3 bad condensors beat's a stuck/bent valve anyday!
That'as great news indeed!! Congratulations !! But as I read your comment, the mystery still exists as to what the root cause was right? Or did I missread your comment?
>> I did try it before and I am pretty sure it didn't help but I have since gone through everything so I will guess that there may have been something else as well that I corrected in my checking.<<<
Please correct me if I am wrong,,
You are correct. In reflecting upon the procedure I did use a second distributor that was used to test the new condensor/points plate and I am pretty sure that it may have contributed to the problem as it needs to be rebuilt with new bushings and one screw is stripped for the plate attachment. That is sometimes the problem with simply replacing one component for another. So, jobs to do....purchase a couple of new condensors and fasten them to the points plates, purchase a couple of new sets of points and the biggy...rebush and repair the second distributor so it is ready to use should the need arise.
Once again thanks to all who contributed!
It is not clear to me, from your response, if you were able to identify the cam as being a symmertic as opposed to a high lift. You only mentioned that you reset the points gap to .012" If you have a high lift then this gap is incorrect.
|Hi Brian, I think a lot of people, including me, are curious at to whether the condenser was actually the problem. Would it be possible to replace the new one with one of the suspect ones to see if the problem returns?|
Cheers, Hugh Pite
|There is a simpler way to check condensers, just attach the leads from a DVM set at 200K ohms and watch the value rise. When it rises to max, switch the leads and watch it fall. If it doesn't pass this test it is no good. Sometimes it pays to check them hot and cold.|
|Years ago, something like 100, I took auto mechanics in vocational school. Once, the teacher charged up a condenser, can't remember how, and had everyone hold hands. He then completed the circuit and the theory was the last person would get the zap. I wasn't so sure about the whole concept and let go at the last minute and the guy before me got zapped instead. LOL|
I like your idea better than messing around getting it to run poorly again. I hooked up a DVM of my son's last night but not exactly sure what I was looking at. The one I replaced just showed one figure no matter which way the leads were attached. I took a spare that I have for my MGB and noticed that it ran up the scale and when leads were switched it ran back down. Not being at all electrically inclined, is that what designates a good condensor? That almost seems too simple.
It is that simple. The one that did nothing is bad. The one that ran up and then down is good. Not saying though that it isn't getting marginal...
This thread was discussed between 07/05/2010 and 13/05/2010
MG TD TF 1500 index
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