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Help! Weak spark
Folks,
Just rebuilt a pair of A calipers to replace my S calipers which have been giving me issues. So I fire up the car to go on a test drive and bed the pads and she starts but is incredibly rough. The car is firing on 3 or 4 cylinders only. How do I know? Well a friend came over with an infra-red thermometer and we pointed it at each exhaust header. My # 1, 2 and 5 are not firing. They are 80 degrees and the others are 300. We pull a few plugs and they look fine. We then checked the spark on each wire and I'm getting juice to each. But when we looked at the actual spark on the plug it is very weak. I think it is not strong enough to fire the fuel/air in 1-2-5. We took the same plug and fired it using his Corvette and difference was remarkable. It was like a mini fireworks display! Given that I'm getting power to each cylinder, what could be the cause of a weak spark? We tried two different coils each with the same results. I have a MSD-6A ignition box and a new (rebuilt) Bosch distributor with points. Any ideas? I have today and Friday to get this car back running so that I don't miss my last track day of the season at Road America. Thanks in advance. Tristan PS. I will be checking the MSD per their instructions today. I'll post results. Last edited by Ho Hum 74; 10-11-2004 at 04:02 AM.. |
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10-11-2004, 03:54 AM
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Designer King
Join Date: Mar 2004
Location: Toronto, ON Canada
Posts: 5,499
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Did you try a good plug wire on a bad cylinder to see if it made a difference?
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Paul Yellow 77 Sunroof Coupe/cork interior; 3.2L SS '80 engine/10.3:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rods; Bilstein B6; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Firestone Firehawk Indy 500s; PCA/UCR, MID9 Never leave well enough alone |
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10-11-2004, 05:20 AM
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Friend of Warren
Join Date: Oct 2000
Location: Lincoln, NE
Posts: 16,483
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What Paul said. I would try swapping plug wires.
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Kurt V No more Porsches, but a revolving number of motorcycles. |
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10-11-2004, 05:29 AM
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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Beru connectors can be a pia
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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10-11-2004, 06:59 AM
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1974 Porsche 911 2.7 RS Spec
