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Engineer of profanity
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MFI fuel pump for carb not working.
Justin here, I pulled my MFI fuel pump out of my 1970 911T. With the help of a thread called MFI Open Heart Surgery I removed just the pump off of the front. I sprayed carb cleaner into the pump and spun the shaft and the motor runs with a battery.
The problem is that after I reinstalled the pump and o-rings, the pump still doesn't work. The the motor in the pump spins up good, but the pump isn't sending fuel to the carbs. Under the pump mechanism on the front of the pump there is a steel ring to hold the star wheel and rollers in. The plate has a small indention on one side. Which way does this indention point? I should have marked the side of the pump to the relation of the ring and the pump before disassembly but I forgot. Any pictures of each side of one of the pumps or just personal experience would help me. Thanks pelicans. You guys are a super forum. Justin |
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04-16-2011, 11:25 AM
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Engineer of profanity
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The indention is on the outside of the steel ring plate under the pump and the 1st o-ring. All I need to know is which way to point the indention.
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04-16-2011, 11:31 AM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,189
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I just took a pic of one a couple days ago...
 the notch 
__________________
Everyone you meet knows something you don't. - - - and a whole bunch of crap that is wrong. Disclaimer: the above was 2¢ worth. More information is available as my professional opinion, which is provided for an exorbitant fee. 
Last edited by island911; 04-16-2011 at 11:38 AM.. |
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04-16-2011, 11:34 AM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,189
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you may have missed my edit and second pic. ... the indentation is up.
__________________
Everyone you meet knows something you don't. - - - and a whole bunch of crap that is wrong. Disclaimer: the above was 2¢ worth. More information is available as my professional opinion, which is provided for an exorbitant fee.
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04-16-2011, 01:11 PM
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Engineer of profanity
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Yes this must be a rebuilt pump? The ring behind the pump is square on this pump. Mine is round and it has an indention on the outside of the ring. It doesn't look to matter where it is, but my pump won't work even though it spins up freely on a battery. I wonder if it's the pump valve inside the pump itself. I cleaned it with carb cleaner too but still no pumping.
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04-16-2011, 01:14 PM
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Engineer of profanity
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Oh, right on! I see the indention! Maybe this is why my pump won't work. Back to the shop. Breakdown #3 maybe she works the next time. The third time is the charm I hope.
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04-16-2011, 01:17 PM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,189
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the pic above is a new (old stock) pump for a '73 911S (MFI).
The operation of these type of pumps is simple --constantly squeezing the fluid to the outlet- but if the inlet & outlet are in the wrong place, it won't pump. ...if the eccentric opening is in the wrong place, it won't pump sounds like you have it now. 
__________________
Everyone you meet knows something you don't. - - - and a whole bunch of crap that is wrong. Disclaimer: the above was 2¢ worth. More information is available as my professional opinion, which is provided for an exorbitant fee.
Last edited by island911; 04-16-2011 at 01:23 PM.. |
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04-16-2011, 01:21 PM
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Engineer of profanity
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Thanks so much sir! Maybe this will get her juices flowing again.
I would advise anyone trying to undertake this job to service the pump half. Spray some carb cleaner in the housing hole and spin the shaft by hand 5 or 6 times. Then hook your battery up and see if it spins. You might not even have to service the motor. Also, the o-rings are not rubber and look to be manufactured flat. If the the pump half is not leaking when you take it apart, put some WD40 on the seals to swell them up and put them back in if you have to. It's a little harder to find the seals than you think. Of course you will have to monitor the pump for leaks often because there is no telling how long this will stay sealed. |
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04-16-2011, 01:37 PM
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Engineer of profanity
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Oh and tighten the #%^* out of it if you use old o-rings. The pump half was on mine very tight when I first took it off.
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04-16-2011, 01:41 PM
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