79 SC - location of air flow sensor?

[LIRS6]

Does anyone have a photo handy which clearly shows the location of the air flow sensor ('79 911SC)? I want to disconnect it to run the fuel pump (for testing purposes).

TIA

Jason

[john walker's workshop]

The contact switch plug is green and located in the front of the AFM where you can't see it. Reach around the left side of the engine and you can feel it. Not to be confused with the cold start plug somewhat below it.

[LIRS6]

Thanks.

Would this be the location (circled) ?




Jason

[gomezoneill]

No, it's just below and to the right it's a blue plug. When you disconnect it the fuel pump relay closes and the pump runs.

[ossiblue]

There should be a connector from the engine harness that you can disconnect without trying to unplug the sensor from the intake. Look by the 14-pin connection in the engine compartment where the engine harness plugs in. Follow the large harness loom back toward the engine and you should see a single connector/wire emerge from the harness--I believe the color is brown/red. That is the wire from the sensor. Separate the single connector, and the sensor is isolated and the fuel pump will run with the key in the ON position.

Edit: I just realized you posted a picture with engine is out so if that's your engine, you can ignore my post. The sensor is clearly seen in your picture, just where gomezoneill said--a bit lower and to the right--in the metal collar of the intake.

[timmy2]

On the 78 - 83 models the brown/Red wire from the safety air flow switch at the fuse panel location is in a 2 pole T connector near the 6 pin CDI.
Unfortunately it is also the CDI switched power in that connector, so you would need to disassemble the connector removing the brown/Red and reconnecting the red so the car would run.
Or install a short red wire jumper with both male and female .250 connectors to bridge the gap so your CDI will run.

“Easier” to reach behind the metering body and unplug the connector unless you make up a jumper.

[LIRS6]

Originally Posted by gomezoneill

No, it's just below and to the right it's a blue plug. When you disconnect it the fuel pump relay closes and the pump runs.

Thanks to all replies - would that be this plug circled in this photo?




Jason

[Flat6pac]

Pull the red relay in the front board.
Jump 30 and 87a, with key on, the pump will run
Bruce

[proporsche]

Hi Jason..or use a little jumper wire with crocodily end connector.Bridge fuse no.6 and 3-5 the pump will run...do not do it for too long.
Ivan

[pmax]

Originally Posted by LIRS6

Does anyone have a photo handy which clearly shows the location of the air flow sensor ('79 911SC)? I want to disconnect it to run the fuel pump (for testing purposes).

TIA

Jason

The AFS (green connector) in my 80 as seen inside the engine compartment. I discovered it was left unconnected by the last mechanic for some reason which he never explained when I asked him about it.

[boyt911sc]

Originally Posted by LIRS6

Does anyone have a photo handy which clearly shows the location of the air flow sensor ('79 911SC)? I want to disconnect it to run the fuel pump (for testing purposes).

TIA

Jason

Jason,

If you are able to remove the AFS plug with the spring lock, your plug is already defective. You should not be able to pull the electrical plug unless it is no longer locking. If you want to test run the fuel pump, use the FP relay socket.

Remove the FP relay and jumper terminals 87a & 30 (relay socket) using a suitable jumper wire with inline fuse and switch and ignition switch @ RUN position. You need this jumper wire set-up for your fuel pressure reading tests. I just don’t understand why people want to ruin a good AFS plug by yanking it out to do a simple test.

This is like pulling your pants down with your leather belt on. Unless you are a contortionist and could shrink your waist line a lot smaller than your belt size you may do so.

Tony

[proporsche]

Hi Pmax..the reason mechanic disconnect the plug for this safety cut out is simple.If this plug gets bad and it is grounded it will stop the fuel pump from running.Cannot start the car problems.
So they just disconnect it.
This way anytime you put your key on, the fuel pump is already running before going to start over the ignition spring.
It is also possible the owner sometimes does not want to spend the money on repairing and replacing this bosch plug.

Ivan

[pmax]

Hi Ivan, Thanks. I will test the AFS and attempt to reconnect the switch. Sean

[LIRS6]

Originally Posted by boyt911sc

Jason,

If you are able to remove the AFS plug with the spring lock, your plug is already defective. You should not be able to pull the electrical plug unless it is no longer locking. If you want to test run the fuel pump, use the FP relay socket.

Remove the FP relay and jumper terminals 87a & 30 (relay socket) using a suitable jumper wire with inline fuse and switch and ignition switch @ RUN position. You need this jumper wire set-up for your fuel pressure reading tests. I just don’t understand why people want to ruin a good AFS plug by yanking it out to do a simple test.

This is like pulling your pants down with your leather belt on. Unless you are a contortionist and could shrink your waist line a lot smaller than your belt size you may do so.

Tony

LOL thanks Tony.

I presume that the fuse should be rated at 25 amps

Jason

[boyt911sc]

Originally Posted by LIRS6

LOL thanks Tony.

I presume that the fuse should be rated at 25 amps

Jason

Jason,

I use 15 or 20 amps fuses for my jumpers. Actually, I prefer the lower value 15 amps for my bench tester and I run my FP’s for hours. The 25 amps is the recommended fuse in the fuel pump circuit but have no problem using 15 amps in my set ups.

Your engine wire harness has the two-wire white electrical connector as mentioned by Dennis. One wire goes to the CDI and the other brown/red wire goes to AFS switch (Or Terminal #85 @ FP relay socket). This is where you do your testing for troubleshooting your FP, AAR, WUR, TV, and AFS switch).

Search for DKLever48’s post regarding FP relay testing and you will have a broader understanding how the electrical circuit works. Be an educated troubleshooter and share your experiences.

Tony

[LIRS6]

I'll use 30 & 87A for testing, thanks

Jason

[timmy2]

I like using the jumper on the Red CDI Power wire at the CDI T plug location as you can do it without running to the front of the car to mess around with the relay.
No fuse needed.