1972 911 MFI runs for 2 seconds then dies

[rowingone]

So was in the process of adjusting the main rack and was almost there . . turned it lean about three clicks and now the car will start . .run for a second or two . then abruptly stall. I talked with Mark at MFI Werks and he assured me three clicks would not cause the car to not run so the problem must be somewhere else. I checked coil resistance, ok . fuel pressure . .ok . . ignition wiring . . ok . . it has the 123 ignition . . all ok. What am I missing!? I am showing the car next week to a potential buyer so . . I need to fix this!!!!!!!!!!!!! And yes I did turn the rack back to where I started and still the same symptoms.

[stownsen914]

Agreed that 3 clicks on the main rack won't do that. Are you sure nothing else got messed up while you were making the adjustment? Seems an odd coincidence the problem started after making that adjustment. Maybe a quick visual check of the area near the MFI pump where you were working. One thing that comes to mind is insufficient fuel. Enough to kick it over but not really run.

[76FJ55]

Does it have a ballast resistor in the system? I'm not intimately familiar with the 123 ignition. if so try temporarily bypassing the ballast resistor and see if that keeps it running, and if so replace the resistor. it could be that it is only getting power during the starting process off pin 50 of the the starter.

[rowingone]

no ballast resistor with the 123

[rowingone]

Could a bad fuel pump relay cause this?

[Jeff Higgins]

Can you hear the electric fuel pump running when you turn the key to the ignition position?

[john walker's workshop]

Try taking the wire off the pump solenoid, just to eliminate that system, for test purposes.

[stownsen914]

To test fuel flow getting to the MFI pump, a convenient way is to pull the return line off the fuel filter stand with fuel pump running, and run a separate piece of fuel hose from there into a fuel can. If everything is working properly, you should get full fuel pump flow from there.

[rowingone]

Yes I can hear pump is running . . fuel pressure is to speck. I wondered about the pump solenoid . . I will so as suggested.

[Jeff Higgins]

A lot of us convert the bypass solenoid to manual control. The whole thermal time switch method of triggering it seems to be a point of constant problems. With you controlling it, through a momentary contact switch placed somewhere on the dashboard, you can eliminate the tendencies to provide either too much fuel when the engine is still warm or too little fuel when it's cold.

I placed a momentary contact switch in an unused hole in the dash right next to the steering wheel on the right. It even looks like it might belong there.

Being that you are selling the car, however, this might not be an option if the buyer is looking for originality. Probably more something you would do on a "keeper".

[rowingone]

Ok so everyone says " dont touch the mfi pump!" . . and I did and i did not get things right . . evidently when I was searching for the slot in the rack adjustment I was actually turning the adjustment screw and not realizing it . . John Eisenbud was kind enough to get me back to where I needed to be . . he is a master at MFI .. I evidently am not! Thanks for all the suggestions! This car is a screamer even with only 140hp!

[r lane]

Not clear on what happened here. The slot in the end of the rack is the adjustment screw. You have to know what it feels like because you can get the little screw driver skewed and you may think you are making and adjustment and actually doing nothing, so don't know what you might have done. Was going to ask, ''did you try to make the adjustment when the car was running''. Bob

[Jeff Higgins]

Originally Posted by r lane

Not clear on what happened here. The slot in the end of the rack is the adjustment screw. You have to know what it feels like because you can get the little screw driver skewed and you may think you are making and adjustment and actually doing nothing, so don't know what you might have done. Was going to ask, ''did you try to make the adjustment when the car was running''. Bob

I'm kinda with you on this - one simply cannot "inadvertently" turn the main rack adjustment screw enough to make the car not run. I'm left wondering what really happened here.

[stownsen914]

The main rack detent might take one or two time adjust it to get the feel of it. But I'd have to agree that you really can't adjust it far enough to make the car not run at all.

[rowingone]

I would say John Eisenbud is one of the greats when it comes to MFI . . those in Denver know this . . . his opinion was just what I said . . the car runs perfectly after he worked his magic. And yes I watched John adjust the main rack while the car was running.