MFI thermostat problems
 

Hi all,

I'm new here!

I have the following problem:

911E 2.4 1973 with MFI

engine is completely rebuild

When I started on the car before the rebuild the hose of the MFI thermostat was off and the car was running fine exept some oilburning and idle a little rough.

After the rebuild I mounted the Thermostat hose and expected the car to run even better as before,BUT when reaching 180 degrees the engine starts to pop and backfire.

When cold everything works fine.

I took the hose off again and it runs ok, only little rough on idle.

Because of the temperature in the enginecompartiment the thermostat still heats up but not as much as when the hose is connected.

So it seems my pump runs too lean ( already checked the rod 114 mm)

Anyone suggestions??

Thanks
Huugster

I had some similar issues on my 1970. In my case I had some issues with the micro switch and the thermostat itself was pretty dirty. I don't have the link to the picture handy but I am sure you can search it. The thermostat is a long set of metal washers that expand. I took mine apart and cleaned it which helped. Be careful the washers are on in a specific orientation so you need to make sure they go back the same way. Other then that I would suggest the tried and true CMA as making any random adjustments can just make things worse.

MFI is a black art, before you do anything with the pump, make sure the car is in perfect tune with the right plugs, timed correctly, etc.. After that, then start with the stacks, pump, etc..
http://forums.pelicanparts.com/porsche-911-technical-forum/473179-new-mfi-information-index.html
Goos luck and read like crazy.

That is a typical thermostat failure, more than likely the previous owner adjusted it without the thermostat or just hoped it was close with the hose off.
My first suggestion is that you send your pump and injectors off to Pacific Injection to set back up at spec , that way at least you know where you are starting from and not chasing your tail.
Other alternative is to do as above, take it apart clean and check for any obvious problems with the washers. You MUST be certain to place the washers back exactly as you found them.
Of course as tobluforo says your plugs, points , timing must be perfect before attempting adjustments.

Just send your pump to Mark Jung (356 RS) -- keep the work in the Pelican Family.

Vr,

Thanks for the answers.

Before I send the pump for repair I need to know for sure that its is the pump.

The engine is completely rebuild and everything is properly synchronized.

However when checking the microswitch and coldstart, I discovered some very weird electrical connections.

I.e. on the 14 pin connector the black/purple wire comming from the speedswitch relais is connected to the gray cable of the backup light.
There are more wires connected incorrectly but when changing them according to the electrical diagram it only gets worse.

Everything looks pretty original,but according to the wiring diagram the connections in the connector on the pannel in the rear are changed, the connector comming from the engine is ok.

But I can't see that there are made some changes in the past.

Does anyone has a wiring diagram for a 73 911e because I can only find 72 diagrams and maybe somthing changed in 73

Huugster

It appears that your thermostat is disguising the pumps lean running condition. After the thermostat leans out at 180 deg you have a lean running condition.

Eliminate the stop solenoid at the pump. Just unplug it. that may be defective, shorting out or not releasing because of the wiring issue.
You can run a test wire to the stop solenoid and hear a click to see if the solenoid rod is moving.