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MG MGA - Condenser failure

Well had my first break down! Recently started sputtering. I had extra Tune up parts and replaced points, plugs and condenser. Ran fine for a few days and started to sputter again. Crawled back home with the car bucking away. This morning I removed the distributor and cleaned and reset the points and timing. Started out good but ten min in it started bucking again until it finally failed. It will idle real rough but if you give it gas it dies. I really think it is the condenser. But why would two fail? I have a petronic igniter on order but I would really like to have it running correctly before I switch over. If I hold the ohm meter over the old condenser I get nothing. If I hold it over the one in the car it reads .003. Any suggestions?
WMR Bill

Sounds as if it could be fuel/carb problem to me, why do you believe it is the condensor?
How are you measuring the one installed in the car? Were the points open when you did the meter test?
Bob (robert) Midget Turbo

The one in the car was with the meter grounded to the distrubuter housing and the other end on the diconnected lead from the coil. I then turned it over until the points made contact. I have a suspicion that when it starts to heat up the condenser then fails. However, I will start looking at my newly rebuilt carbs. They were running so fine for several thousand miles. I did confirm that they were getting gas from my new elctronic fuel pump. Other than that I have not checked anyother things with the carbs. Any suggestions?
WMR Bill

When the points made contact you were then simply measuring the resistance of your meter leads, which is generally about 3 ohms. Before the points closed were you reading open circuit? as in this condition you would have been measuring across the capacitor and should get an open circuit reading as you have seen with the one you removed.
Curious now, when did you get your new electronic pump and more importantly was the old one faulty?
Bob (robert) Midget Turbo

Bob, I replaced the points and condenser from the ones in my TR3 (They were new) it is still missing real bad. I took apart the bowls to the carb and found a significant amount of dirt in both of them. I cleaned them and sucked all the setiment out with my Vac. Was hoping that was it but I am still getting really bad misfire every tim I try to excelerate. ARGGG!
WMR Bill

Bob, The replacement pump was the replica electronic one from Moss and is about a year old. I did dis-connect the line and filled up a cup at the carb. All seems fine at that end...
WMR Bill

Check the wiring inside the distributor and see whether it is shorting out ( I doube it though). You have a 10 minute problem. There have been a few cases where the coil died after it got hot, check it out. Insure that the condenser screw is tight. Take it for a drive and when it dies, open the fuel filler cap. See whether it improves.
mike parker

Bill - Stick the old condenser back in the distributor. A condenser will usually fail within a few days of installation if it is going to fail at all. Since the car was running ok before you did your tune up, the old condenser is going to be good and will not fail after a few days. I never changed out the condenser in our TD that we have owned and driven since 1974. I kept the original condenser in place since there was never any indication of metal transfer from one contact to the other on the points, indication that the condenser was a correct value for the coil distributor that it was installed in. The condensers used in distributors have a tolerance of 20%, which means that there can be a 40% difference in value between two condensers (if one is +20% and the other is -20%) or anywhere in between. This gives the mechanic the option of trying different condensers until they find one that will eliminate metal transfer between the contacts of the points. Once that is established, the condenser should not be changed (contrary to what is written in the shop manuals). Cheers - Dave
David DuBois

Had similar problem with my TC and MGB both ran well for 20 minutes then when hot started to misfire turned out the coils were overheating replaced the coil and all OK (this was after I had replaced every other ignition part !!!
P D Camp

Well I changed over the Coil, Points, Condenser,Rotor over from my TR. Although it starts, it soon get's back to it's old trick of sputtering. I cleaned all the plugs and as I memtioned before the carberator bowls were I found a conciderable amount of soot! I then removed the needle and cleaned it. Is there any othe part of the carb were the soot might be lodged or at least being sucked into, and creating an obstruction? I'm about ready to trade it in for a Geo!
WMR Bill

Bill as I said earlier I am almost convinced this is a fuel problem.

So one thing that can cause problems when accelerating is a imbalance of carbs. I have seen where some have topped up the dashpot of one of the carbs with different weight oil to the other. This then allows one carb damper to rise more slowly than the other. I was able to find this by removing the air filters and opening the throttles and watching the rise rate of both carbs only to find it different. Cure was simple Empty both out and refill with identical oil.

Just to be clear Bill, if you are out driving and attain a speed of say 40MPH will it cruise fairly smoothly at that speed?
Bob (robert) Midget Turbo

Very puzzling Bill. A colleague in our club with an MGB had similar problems recently and found that the spring on the points gradually twisted round as it warmed up to short on the dizzy base. A change in points stopped it. Unlikely but worth a try.
My own experience with a similar problem on my midget some years ago was a sticking dashpot - I randomly tried everything and then as Bob describes - took off the dashpots, emptied out the old oil and carefully wiped out the inside and around the slider. Symptoms cleared up.
David - interesting theory on the condenser variation and the matching of one to your system. I wonder how many you need to try to find the right one?
Cam Cunningham

Well, I wanted to resolve the problem before my new Petronix points and flame thrower coil arrived but they showed up yesterday. So I decided to just install them and what a difference!! So far it is running like a champ! What a great product so far. Clearly better acceleration and smoother running than the old points and condenser. I have only driven it around the block a few times but so far so good :) I know Barney's not real keen on electroic points, but boy, I am definetely sold!
WMR Bill

This thread was discussed between 22/06/2008 and 24/06/2008

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