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MG MGA - Crossed Plug Wires?

Is it reasonable that my nos. 1 and 2 sparkplug wires were crossed for more than a yr (1500 miles) and the MGA still ran well? I found this when trying to find the reason for the car suddenly not wanting to start (turns over, hits and dies with what sounds like a muffled near backfire.) When I reversed the two plug wires to the order shown in the diagrams I have seen (Mike Ash's Tech Sessions page 160, for example) the car almost doesn't hit at all. I'm inclined to put the plug wires back like they were and keep searching for another explanation for the car not starting. Anyone have any experience with crossed plug wires, and how the condition would not cause a noticeable problem with how the car runs?
Gary Poe

Gary. I do not have any idea about what you are writing of. Perhaps if I can give you my understanding of how things work you can give us some more information?

The firing order of the B series engine is 1-3-4-2 with the engine being timed off the number one cylinder. The distributor, when you are looking at it from the right (passenger side in the US) rotates counter clockwise. The normal position for the distributor cap terminal firing number one cylinder is about the "2 O'Clock" position. To the left, when facing the distributor from the right hand fender area, will be the spark plug terminal for the number three cylinder at about the "11 O'Clock" position. Below that, at about the "7 O'Clock" position will be the terminal for the number four spark plug. The remaining terminal, at about the "5 O'Clock" position goes to the number two spark plug.

As to the car not starting, it needs three things--spark, fuel, and compression. My website, has, under the MG section, then "articles" tech articles on how to test all three areas. They might be of use to you in attempting to diagnose your problem. At least, they will provide us with a common frame of reference for you to use in describing your test results. I can be reached though the website on the ignition and compression check articles. David DuBois has his tech articles on the fuel system with a hot link to contact him directly. Contact either of us if we can provide further assistance.

Les Bengtson

When I first tried to start my MGA 36 years ago after rebuilding the engine, I could get to to start but it would not idle and I would have to run it at about 3000 RPM. I could have sworn that it was wired 1 4 3 2 for firing. Thw problem was I wired the cap while looking at it from the inside. When the cap went on, it was 180 degrees off. We switched two wires and it ran like a charm

To answer your first and last question, it is not reasonable to think your sparkplug wires were crossed if it was running well.

Jeff may have the answer as to why you thought they were crossed in the first place. And Les' info should get you back up and running.

This thread was discussed on 30/04/2007

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This thread is from the archive. The Live MG MGA BBS is active now.