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mfi adjustments
hey all. my car is a 73 911e. I just did a top end rebuild. I went with a slightly larger piston and cylinder. im having a little troublt adjusting my pump. car starts up great and was at idle, having a very gasy exhaust fumes coming out the exhaust. I leaned out the idle adjustment and seems to be fine. I was having a slight miss driving the car around 3000 rpms. I pulled the plugs and all are very sooty. so I assume its running rich
now when I have the car idling, it seems to be fine. but when I rev it up, I get a little bit of black smoke out the exhaust. which means its running rich. what adjustment would that be? idle or part load adjustment? would running rich make the car miss? I also was having a hot start problem, so I cleaned the thermostat. it was dirty and seemed to take care of the warm start problem. would the thermostat make it miss also? I never adjusted a mfi pump before. do you really need a co2 or gas analyzer to correctly adjust the mfi pump? everything is all adjusted. dwell and timing. all plugs wires cap and rotor are new.. throttle bodies, linkages and air correction screws are fine. this is driving me crazy. been working on this a few weeks now. any help would be great. |
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08-28-2013, 03:34 PM
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Max Sluiter
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If you go by the Check, Measure, Adjust manual you need a carbon monoxide sniffer. Sounds like you might need a main rack adjustment.
Some info: Ultimate MFI resources thread MFI Pump - Open Heart Surgery
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1971 911S, 2.7RS spec MFI engine, suspension mods, lightened Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance Last edited by Flieger; 08-28-2013 at 05:03 PM.. |
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08-28-2013, 04:59 PM
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Join Date: Dec 2008
Location: San Antonio, Texas
Posts: 3,591
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The MFI system is good and reliable, but won't tolerate unknown fiddling. Strict adjustment procedures must be followed. Do you have the CMA adjustment manual? What mods did you do to your engine? When you took your thermostat apart did you put all the washers in the exact same positions?
At this point you need to take the pump off and ship it to Pacific fuel injection with the injectors and the description of your engine specs. Mark Jung is excellent too, so i've heard. You could be chasing your tail for quite awhile and destroy your engine in the process, too much fuel and you'll wash your cylinders down. Once properly setup you won't have to touch it for years. From your description, your thermostat isn't working and your throttle bodies aren't balanced. Eurometrix is in your area of the country and they do excellent work too.
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1973 911S (since new) RS MFI specs 1991 C2 Turbo |
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08-28-2013, 05:04 PM
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the only mod I made was I went to a 85 mm piston. up from 84mm. the thermostat is working now. I did replace all washers in the same order. the car starts when warm .
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08-28-2013, 05:31 PM
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Registered
Join Date: Dec 2008
Location: San Antonio, Texas
Posts: 3,591
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PM me and I'll email you the CMA. Meanwhile here is a link to the master.
http://www.911mfi.com/index.html
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1973 911S (since new) RS MFI specs 1991 C2 Turbo |
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08-28-2013, 05:55 PM
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I still cant get the pump adjusted right. I just ordered a gunsom gas analyzer. so hopefully by next weekend I cant figure this out. also im back to having a warm start problem. the car starts fine after a few minutes off, but wont start if left sitting warm , more then about 5- 10 minutes. I think the thermostat is working fine. could this problem be because the pump isn't adjusted right??
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09-01-2013, 07:15 PM
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Join Date: Oct 2006
Posts: 315
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On my 73S with MFI, with warm to hot starts and sitting for 10 min, I put pedal to floor and crank. Under the same warm/hot condition and sitting for over 20 min to an hour I pull up on the throttle lever and while cranking and I feed the throttle pedal to the floor slowly and usually the car fires up before the pedal hits the floor stop.
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09-02-2013, 04:17 AM
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I would rather be driving
Join Date: Apr 2000
Location: Austin, TX
Posts: 9,108
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the car when cold will likely be lean. Do not adjust the pump until the car is fully warmed to operating temperature. This will give you false readings of mixture.
How much have you adjusted? Did you keep track of your adjustments so that you can return it to baseline? Did you change anything else besides that piston diameter ( 84 to 85mm?)
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Jamie - I can explain it to you. But I can not understand it for you. 71 911T SWT - Sun and Fun Mobile 72 911T project car. "Minne" - A tangy version of tangerine #projectminne classicautowerks.com - EFI conversion parts and suspension setups. IG Classicautowerks |
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09-02-2013, 06:23 AM
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that's the only change I did. the p&c's. as for adjustments. I really didn't keep track of my adjustments. I know stupid me. I was actually adjusting the idle when I thought it was the part load adjustment. the car ran good before the rebuild. I was told since I was going with a little bigger p&c's, to just enrichen it a turn or 2 on the part load. im sure when I get my gas analylzer, I should be able to set it perfectly. right?
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09-02-2013, 09:54 AM
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Max Sluiter
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If your throttle bodies are good and you follow the Check, Measure, Adjust you should be able to get it very close if not perfect.
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1971 911S, 2.7RS spec MFI engine, suspension mods, lightened Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance |
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09-02-2013, 11:37 AM
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1971 Porsche 911S
