CIS help

[IDrabble]

I have just removed my fuel tank from my 1982 911sc to repair it, now that it is back in the car will not run and is back-firing badly.Have I done something wrong? It looks like there are flames coming out frome the throttle butterfly area when it back-fires, any and all help will be much appreciated

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82sc

[island911]

I'm no expert on this but check the system pressure. (run the fuel pump w/o the engine running) If for some reason the fuel cannot return to the tank the fuel pump will over pressurize the system.
. . .and then figure out why it's not returning.

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'81 Platinum Metalic SC Coupe

[GIBSON]

I like the pressure idea, I'm also wondering if there is a procedure to bleed the system of air? It's a closed system as all modern fuel systems are, maybe there is back pressure from a blocked return line? Just guessing. We've got some good CIS guys out there, let's hear from you.

Bruce Herrmann
73911S

[wckrause]

You can bleed the air out of the system by turning the ignition to the ON position, and lifting the sensor plate inside the airbox. You should hear the fuel pump run, and as system pressure builds up, you will feel some backpressure on the sensor plate. You should also hear the injectors whine.

Let it sit for a little while before you start it after bleeding the air out. Anytime you open the fuel lines, you should bleed the air out.



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Bill Krause
'79 911SC Euro

[island911]

I believe the purpose of the fuel pump relay is to turn on the fuel pump ONLY when the distributor is firing. Meaning, the system pressure will go to zero w/o the pump running, (while lifting the flow sensor plate.)
You can jumper the fuel pump relay, terminals 30 &87a. Then the FP will run when the ign is on, but the engine is not running.

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'81 Platinum Metalic SC Coupe

[wckrause]

island911 -- on an SC, the fuel pump will run when the sensor plate is lifted. There is a contact switch within the airbox that causes this. It has nothing to do with the distributor. I've done this many times, and it is the recommended procedure described in my Bosch FI book.

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Bill Krause
'79 911SC Euro

[island911]

Thanks for the correction, Bill. Fortunately, I havn't needed to get in to the 911's CIS. From what I've seen it's the same system, in principle, as the VW's of the that era. . . .Except the fuel switching. Anything else?

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'81 Platinum Metalic SC Coupe