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Author Topic: '69 B-GT Backfiring and Losing Power  (Read 703 times)

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'69 B-GT Backfiring and Losing Power
« on: May 10, 2020, 01:09:12 PM »
I have been dealing with trying to diagnose a problem with my '69 B GT. It was running great up to a few months ago, then coming back from a run it started backfiring and losing power to the point I had to stop and get a tow. I checked the points and they look good, set them again, then went on to the fuel system. I took off the fuel lines before and after the in-line filter to check for flow and can hear the tick of the fuel pump and have good flow. I even replaced the fuel lines and filter under the hood with new but it doesn't seem to matter. The car will start but seems starved for fuel, idles rough, and when stepping on the gas it wants to cut out. Even feathering the accelerator doesn't seem to work very well. Took the K&N air filters off to examine and they look good, no airflow issues here. Thoughts?

John Hale


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Re: '69 B-GT Backfiring and Losing Power
« Reply #1 on: May 10, 2020, 01:38:23 PM »
My two cents is that this is one of those "Back to Basics" kind of problems. Like that old saying "If you hear hoofbeats, think horses, not giraffes"--the same applies to car symptoms. Hit the basics first, not the esoteric possibilities. How good is the spark? Did you use a fuel pressure gauge (you can have a squirt, but not enough pressure)? What is your compression? Did you test for vacuum leaks with carb cleaner or smoke? Did you do a cylinder balance test?

Joseph Troise
American MGB Association
phone/text: 773-769-7084

North America's oldest and largest club for all MGBs, MGB-GTs & Midgets.  A nonprofit organization founded in 1975 and offers color magazines, emagazines, technical advice, member recommendations on service shops, registration of your MG, a tradition of service & FREE member classified ads that appear in the magazine & on the website.


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