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Join Date: Sep 2006
Location: North Salem NY
Posts: 59
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1973 mfi backfire
I have a 1973 911 MFI. I was going up a small hill and cd player cut out twice for a second or two and then there was a loud backfire. I pulled over and the car stalled. It restated a minute latter. I had one more loud backfire / loss of power on way home. any thoughts as to the problem (s) ?
thanks cros
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Cros |
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08-03-2008, 04:40 AM
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Location: North Salem NY
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Thought I should include a photo...
Cros 
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Cros |
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08-03-2008, 04:45 AM
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Well, I'll state the obvious. Seems you lost the electrical circuit momentarily, and the unignited fuel ended up firing on its way through the exhaust. Lots of possible causes- I've been through many myself- but more driving to try to replicate the problem may be in order. An exhaust backfire, while somewhat scary, shouldn't cause any real damage. If it did, my engine block would be a mass of molten metal by now... Anyway, try to note everything during the occurrence- temps, speed, how long into your drive, what's on, did the tach drop out, etc. All these things may help in the diagnosis. Once you've done that it should be easier to start to pinpoint the cause, and will be helpful to all the MFI gurus on this site.
You may want to check what circuit the CD is hooked to. Having the electrical diagrams (available on the this site) will help. I'll also throw in a plug for the Check, Measure, Adjust manual for Bosch MFI. It's a step-by-step procedure to tuning the MFI. The first parts are just the basics- plugs, compression, pump timing, ignition timing, dwell, etc. I've found many problems are because these are out of whack, and if not at least knowing they are correct will eliminate them as suspects. You need to do these regularly anyway so it won't be wasted effort. Jeff
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Jeff Jensen 1973 911 |
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08-03-2008, 05:54 PM
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(the shotguns)
Join Date: Feb 2006
Location: Maryland
Posts: 21,550
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how about the ground strap at the tranny?
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***************************************** Well i had #6 adjusted perfectly but then just before i tightened it a butterfly in Zimbabwe farted and now i have to start all over again! I believe we all make mistakes but I will not validate your poor choices and/or perversions and subsidize the results your actions. |
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08-03-2008, 06:25 PM
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Join Date: Sep 2005
Location: So. Cal.
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Check the ground strap on the battery (ies). Might need to tighten the wing nut.
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David 1972 911T/S MFI Survivor |
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08-04-2008, 09:48 AM
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Join Date: Jun 2007
Location: Sheboygan, WI
Posts: 147
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You didn't have Snoop Dogg, Kenny Chesney, or Madonna in the CD Player did you. I have a hard time running to those artists as well!
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08-04-2008, 12:11 PM
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