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The 69 GT just stopped running!

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L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
OK now that I have your attention, I was driving MGB GT at a high rate of speed, and as I came to the top of the hill, I started to slow down the car slowly sputtered to a stop.

I crank the car over for longer than normal and it seemed to want to fire off, it began to run very roughly but had no power and then promptly died.

I towed the car to my garage let it sit for two days and came back to diagnose the problem. I can get it running very roughly after extended cracking of the starter.

My first thought was a fuel starvation problem, so I did and look for the fuel filter which on my car doesn't exist.

Checked my fuel pump and it is operating normally.

One thing I did notice is the coil was very hot to the touch. This is a new coil I put on in the last hundred miles.

Its the 69 with Dual SUs

I can get it to run but it still has no power runs very bad and barely idles.

What is wrong with my car?

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geezer Avatar
geezer Silver Member charles durning
Magee, Mississippi, USA   USA
1958 MG Magnette ZB "Chick Magnette (sold)"
1967 Morris Minor 1000 Saloon (2-door) "Marvin"
1974 MG MGB GT
Check and reset the points and ignition timing first.



Who's version of right are we talking about? When you get 10 LBC owners in a room you'll get 12 different answers.

L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
Forgive my ignorance but how do you do that? If it's in the Haynes book I can figure it out.. I just don't have it in front of me

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rocannon Avatar
rocannon Platinum Member Frank L
Inconveniently located in the wilderness, Oklahoma, USA   USA
1967 MG MGB GT "GT From Hell"
1980 MG MGB "Restored By Photoshop Inc."
And what was the reason for replacing the coil?



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B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, Minnesota, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB
2014 Dodge Charger
Ohm your spark plug wires. High resistance wires can cause the coil to overheat. You want well under 5000 Ohms per wire. Hopefully closer to 1000, or zero if you have copper core wires. Of course the coil IS supposed to get hot so itmay have nothing to do wih your problem.
You can also visually look in the float bowls to see if there's fuel present, or any material that didn't get caught in your non-existent filter.

If you have points and you don't know how to adjust them, that's likely the issue. Remove them, file them, set the point gap at .017" at full lift over the "peak" of each of the 4 cam lobes. Do this on the work bench and reset your ignition timing with a light to roughly 12-14 BTDC at idle.



jeff@advanceddistributors.com

L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
Because I had one in a box it was brand new and when I did change it everything seem to run better

L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
Spark plug wires are brand new

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BillzB Avatar
BillzB William M
Batavia, Illinois, USA   USA
1974 MG MGB
Luke,

I had almost the same thing happen to my 74 roadster. I also suspected the coil because it was hot, but a new coil did not fix it (and later I found the old one was just fine). Hot to the touch does not mean a bad coil, for two reasons; the engine compartment gets hot so everything in it is hot, and most B's have a 3 ohm coil. If you do the math (Ohm's law) that comes to 4 amps which is 48 Watts. A 48 watt light bulb gets hot, just from the current going through it.

OK now that I have your attention (just trying to humor you with that phrase) what I've just said is not completely true because the coil is not carrying current 100% of the time. The points are turning it off and on, but it does carry enough current to create heat on its own, and if your dwell is not correct (if the points are closed for too long a time) it will get hotter than it should. So Charles (geezer) was not off base saying that you should at least check your points and timing.

In my case it turned out to be the points. The insulator that the arm of the points pivots on was worn and the points were shorting to ground. This cause the hot coil and caused the car to stop running.

Bill

L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
This is all great info, I am able to get it started and its not easy, but it still has no power... It seems to run better at higher rpm but its not a happy camper and still no power. Should I tare into the distributor or the carbs first?

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Tim C Avatar
LaGrange, Kentucky, USA   USA
1980 MG MGB "Annie"
Hi Luke,

I would say the points first. In my experience, carbs rarely have a sudden change like you described. Sounds electrical to me.

L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
I did the points, idles better than ever before... super smooth! The problem is when you rev it up... it bogs down... can't get it above 1500rpm... any ideas

Ex-Calif Avatar
Ex-Calif Gold Member Dan D
Cincinnati, Ohio, USA   USA
1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2012 Jeep Liberty "Tank"
2014 Hyundai Accent "Skate"
Fuel Pump...

Remove the line to the carbs and set up a catch can. It should fill a mason jar in about 10-15 secoonds.

Actually from a troubleshooting standpoint you should start at the beginning and check everything rather than shotgun.

- Tappet clearances
- Timing
- Plugs (gap) & wires
- Points (gap)
- Jet heights & float heights
- Fuel filter & pump
- Fuel tank vent &/or vented cap



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B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, Minnesota, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB
2014 Dodge Charger
Now it sounds like you have a bad condenser - beautiful idle but no power?

It could be your timing setting. What is the timing set at?



jeff@advanceddistributors.com

CederholmC Avatar
CederholmC Gold Member Carl E. Cederholm
BROOKLYN, NY, USA   USA
1953 Chevrolet Bel Air "The Sled"
1969 MG MGB GT "Supercharged"
1972 MG MGB "Brooklyn B"
1981 Toyota Land Cruiser
When you get it sorted put a fuel filter on it. Who know what crud you carb is sucking in from an old gas tank.

~ Carl



1972 MGB roadster - 30 over, fast road cam, full peco exhaust, Jeff S. rebuilt 45D Eurospec, Jimmy H. rebuilt HIF4s prestige interior, hood and tonneau cover, Dayton 72 spoke chrome wires, custom center console

1969 MGB GT - Eaton M-45 supercharger, TT stainless exhaust, Jeff S re-curved 25D

L84DNR Luke Clement
Anchorage, Alaska, USA   USA
1969 MG MGB GT "L84DNR"
I'll be the first to admit, I've never touched the timing on this car, it's been years since I've timed anything! It was set up pretty good, so I'm not sure what it all of a sudden would be out of time, so I'm gonna change that condenser.

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