CIS to EFI (Megatune) conversion stalls

81-911sc · 09-25-2010, 10:57 AM

Hello,
My question deals with the aftermarket Megatune EFI system, BUT, directly shares the CIS wiring and sensors; mainly the fuel system, fuel pump disable (pink wire) and CIS flow/metering plate.
Problem- car starts and pump is pumping. Cat then stalls, pump not running. This happens over and over.
Where is the fuel metering plate switch and connector so I can test it? I can't find any images or location pictures.
I need to get this fixed as its my daily driver.

Thanks folks!

James Brown · James Brown's Garage

hummm, so the metering plate is used to shut off the fuel pump in the event the engine dies and the ignition is on? I would think you would not need that because the injectors are not receiving a signal when the engine dies and the ignition is on (reluctor wheel not turning). Just my guess, tell me more about the system or post a pic!

81-911sc · 09-25-2010, 01:40 PM

Thanks for the quick reply. I may not have been very clear on the initial post/question.

The manual says "You need to locate the wire that is connected to the rear of the fuel metering plate. It uses the same kind of connectors that are used on the fuel injectors. The way it works in the CIS system is once air stops flowing through to the engine (ie: engine stopped), the metering plate falls down, engaging a switch which turns off the fuel pump. We need to tap into this wire. There are two brown wires on this connector. On the 1978-1983 911SC the desired wire has a pink stripe on it."

I "miss-posted" that I'm still using the "CIS flow/metering plate."

I've "tapped" into this wire, which goes back to the Megatune EFI ECU. Where does the factory wire lead to? The wire I'm trying to follow is the one that went to the CIS flow/metering plate. Does it go to the Fuel Pump Relay?

I was later informed that a better place exists to tap into this fuel pump relay wire. A white plastic connector exists near the fuse box in the left hand side of the engine bay. It is at this location that the brown with pink stripe also exists. The later year vehicles have two spade connectors. In earlier years it was only a single spade connector.

I'm trying to get photos

James Brown · James Brown's Garage

Ok your on the right track. You understand that the manufacture is using Porsche's system to stop the fuel pump if the engine quits like in a accidents so fuel is not being pumped out a ruptured fuel line making a bad situation even worse with fire. All in all, a good idea. So any where you can splice into that system will be ok. Make sense?

81-911sc · 09-25-2010, 06:09 PM

I spliced into the wiring as told, and it worked fine for about 4 months, until 3 days ago. It will start, run for about 10 seconds, then stall (pump quits.) If I disconnect the wire going to the ECU from the old CIS wiring, it runs fine. But the pump will run forever as long as the key is in the on position. Other-wards, I've lost the "safety" aspect if involved in an accident. I was wondering if that wire was being shorted or something. Any suggestions? Is there a good wiring diagram for download?

Thanks so much

James Brown · James Brown's Garage

Sounds like corrosion in the splice, use a new splice and that should take care of that. Remember, rust never sleeps!