MFI help!!

[BK911]

I just installed an MFI system on a 2.2S engine. The car wouldn't start until I hooked up the cold start circuit. Now the car starts, runs about 10 seconds, then dies. I have the correct fuel pump and I believe the MFI is timed correctly. I pulled an injector and it had gas in it. I turned over the car to see if gas would squirt out of the pulled injecter and nothing. I am thinking it is the MFI pump or clogged injectors. How can I tell?

Please advise!!

Thanks!
BK

[Early_S_Man]

I assume you are aware of Pelican's archive of MFI publications and information, but, if not, the URL is:
http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

First, remove all injectors, being careful not to lose the copper sealing rings, and soak overnight or longer in Berryman's B-12 Chemtool, preferably in a heated, ultrasonic cleaner at 120° F for 10 - 14 hours. If ultrasonic cleaning is done, but rust is not found in the solvent afterwards, consider tyourself lucky! If rust is found, you may not be out of the woods, yet! You should test the spray pattern for a uniform conical pattern. This can be done at a dealership or an auhorized Bosch service center.

Or, you could remove the lines to the injectors, and the injection pump from the engine ... put the lines back on the pump on the bench, attach all injectors to the lines and tighten, then turn over the cogged drive pulley, and hope for the characteristic audible 'CHIRP' and hopefully a conical spray pattern from each injector.

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[Oldporsche]

Pressurized kerosene as well as mineral spirits can be used to check the spray pattern of the nozzle. Put a pressure guage in line with the nozzle to determine the opening pressure and the closing pressure.

Good luck,
David Duffield

[BK911]

Gentlemen!

Thanks for the help! I have printed out most (if not all) of the info on the MFI url. However, I was unable to find reference to checking fuel pressure. I tried to "bench test" the injection pump while it was on the engine. I pulled an injector from the head and reattached it to the hard line. I cranked the engine a little and looked for fuel coming from the pulled injector. No luck! Now I would like to check the fuel pressure before and after the injection pump. Before the pump is easy. After is where I am running into problems. Is there a special Bosch pressure gage available? Or are there generic testers available?

Thanks again!
BK

[lsolon]

You have probably done this but, have you disconnected the fuel line before the fuel filter and cranked the engine to see if your getting any amount of fuel. I had this prob. where my car would start and idle for about 5 seconds then die. Drove me nuts for a week. Found it to be the fuel line that runs from the tank to the fuel pump. It was so old that when the pump was sucking fuel, it was also constricting the line.

------------------
72 911T.

[BK911]

Well, I haven't actually check that specific line. I have put in all new fuel lines but I guess that really doesn't mean they're right! At this point I am not going to rule out anything until it gets verified. I did install a clear tube in place of the MFI pump to see if there was flow, and there was. I am going to pull the line to the MFI pump and measure the flow rate. I was told about 24oz in 20 secs? Sound about right?

Thanks again!
BK

[Early_S_Man]

Well, actually the specified flow is 900 to 1000 cc in 30 sec. And, the pressure in the 'loop' from and to the injection pump is nominally 1 bar, 14-15 psi.

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[BK911]

Thanks for the quantification clarification! Any idea on how to check the injector line pressure? Money is no object, as long as it doesn't cost too much!

Thanks!
BK

[Early_S_Man]

Short of building a clone of the pressure tester shown in the 'blue book' (Check, Measure, Adjust)... take the injectors to a shop with Bosch certification for fuel injection testing and have them pressure and pattern test them.

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler