1972 S MFI suspect
 

The porsche sat in my garage while I worked on other projects for 1 year. Now it will not run. It will turn over and catch for a second or two (will not idle for long).
What I understand from reading this forum is the MFI has set up and possible cause of problem. I tried to push in the control rack with no detectable movement. I removed the side cover on the MFI and I can see where the pistons are moving up and down when engine turns over, I sprayed some seafoam on the springs and pistons. Can I use seafoam to lubricate the control rack shaft?
I removed two of the fuel lines that feed the right side of engine from the top of the MFI assembly and I'm not getting any gas out of the MFI.
Also, the small line that runs from the fuel filter to each velocity stack (lower portion of stack) is this the cold start system? and if so would that not bypass the MFI until it warms up.
As you can see I'm not exactly sure how the fuel system is suppose to work.
Any suggestions would be appreciated.

ps.. I drained the fuel tank and added 1 can of seafoam to two gallons of fresh high test gas. I also removed fuel line to right side of MFI and i have plenty of gas flow from pump and filter.

Lash L.

Do you have fuel pressure? The fuel pump is notorious to quit when the car sits.

Johan

When key is turned to the on position, do yo hear the pump whine, not the CDI, which causes the gas in the tank to burble?

I cannot tell you what the fuel pressure is but when the fuel supply line to the MFI is disconnected it will fill a quart jar quickly when fuel pump is energized.

Lash..

What puzzles me is the engine will idle for a second or two, so gas must be present in the combustion chamber to fire. I can repeat this action several times each time I turn the key to start the engine, it just will not continue to run..

i suspect that your cold start solenoid and cold start fuel squirters (tech term) are working well and providing enough fuel to start the engine, but your main fuel injection pump/system is not providing any fuel out to the injectors. The cold start solenoid will operate every time you turn on the ignition and provide a squirt of fuel to start the engine from cold, but then the main injector pump should take over, allowing it to continue to run. your injector pump is not doing that.

This could be an incoming fuel pressure issue. You have verified that your fuel pump is providing fuel, but not the pressure. Also, you have verified that you are not getting fuel out to the injectors. I would verify my incoming fuel pump pressure , just to be thorough, but that being said, I would concentrate on the injector pump. Note: Do this at your own risk, but I would remove the injector pump from the engine, and get it on the bench to concentrate on getting the rack to work. Do not force it! Shoot it with carb cleaner, etc, to remove varnish and crud. Then shoot it with penetrating oil, let it sit overnight...try, gently to move it....rinse and repeat, until it is free to move. If that does not work, I'd take it apart to see what the hang up is. If all of that is somewhat daunting, send it to Mark Jung (356RS) and he will rebuild it for you.

regards,
Al

PS: after all of that, you will still need to verify that your injectors are working.

OK.... I will have one of my friends assist me in checking Fuel pressure, what pressure reading should I expect to see? I initially had a fuel pump problem when I started the car after it sat for a year, it was not making its normal sound when the key was turned on. I removed the pump took it apart and reassembled and it worked.
Since the control rack won't budge I will follow your advice in using carb cleaner. Is there access to the front of the MFI where I can also squirt carb cleaner onto the control rack? I have removed the rubber cap over the rear access port of the MFI and shot some seafoam onto the control rack.
I will continue to apply cleaner to the control rack and give it time to work it's magic.
I also understand that if and when I sucessfully get the engine to run again I will need to change the engine oil to eliminate contamination from using a harsh cleaner.
I consider myself as a backyard mechanic having restored several cars (no Porsches) and think that if I need to I will drop the engine and pull the MFI. I have Wayne Dempsey book on rebuilding engines, is there a book on R&R the Bosch MFI?

Thanks Al for your advice.
Lash L.

The "book" is called CHECK MEASURE ADJUST
Search here for a copy
Follow CMA to the letter and you will sort out your MFI issues.