CIS Airflow Switch???

[patkeefe]

How does the wiring from terminal 85 of the fuel pump relay get back to the airflow switch? It doesn't seem to come through the 14 pin connector. I am guessing it is one of the connections in the two terminal "T" shaped block in the engine compartment, the other connection being terminal 15.
TIA
Pat

[cmonref]

The manual shows it from the relay via red/white to one T2, then brown/black to another T2, then brown/black to the contact switch. Looks like both T2's are near the regulator panel.

[Scott R]

Originally Posted by Brian K. Haggard

The manual shows it from the relay via red/white to one T2, then brown/black to another T2, then brown/black to the contact switch. Looks like both T2's are near the regulator panel.

Yup, it goes right to the rear electronics compartment, then to the front. Look dead center under the electric panel, you will see the red/white right there.

[patkeefe]

Thanks guys. I suspected that's where it is. My SC has been modded somewhere by the PO, such that my wiring was a mess. I just rewired the engine, the 14 pin connector, the 6 pin CDi connector, fabbed a new coax to the distributor, and need to build a new distributor coax. Maybe I can get my fuel pump relay to work again now.

My Bentley just shows generic wiring, no connectors, current flow or gauge sizes as the factory book would.
Pat

[sjf911]

Here are some photo's from my rewiring showing the sensor-plate connector in green and the T connector. The T connector is part of the CDI harness.

[RoninLB]

when i did my wiring over i installed a switch into the engine comp red relay wiring as a work on/off to the FP and a secret engine no start, or in my case not running for long. I used a Cole-Hersee marine. The toggle looks like the pic. I couldn't find a pn now.

[patkeefe]

Steve, Thanks for the pix

Ron...I'm currently running a toggle for FP on/off. We went to the same theft deterrent school
Pat

[patkeefe]

One further question:
How does the fuel pump relay actually work? Assuming I haven't turned the key to START yet, my perception is the small coil between 85-86 is powered with the ignition ON, which prevents the relay from making a circuit between 87a-30 and energizing the fuel pump. 85 is the ground. When the key is turned to START, does the contact make a circuit from 87-30, allowing the pump to run and temporarily bypass the 85-86 connection? Assuming the car now starts, 85 will ground through D-, and the coil will go open, and default the relay to the 87a-30 circuit.

Does the key have to go to the START position before the 87a-30 circuit will energize? In other words, if I simply turn the key to ON without going to START, should my lifting of the airflow plate in the fuel head bring the fuel pump on?

TIA
Pat

[1982911SCTarga]

In other words, if I simply turn the key to ON without going to START, should my lifting of the airflow plate in the fuel head bring the fuel pump on?

The way I understand it, yes. Lifting the airflow plate eliminates the wiring at the sensor going to ground. It thus breaks instead of makes.

Brian

[patkeefe]

OK, so here's the deal:
When I lift the airflow plate with the key on, no fuel pump. If I manually break the connection either via pulling the airflow switch 85 wire, or by pulling the plug on the switch, the fuel pump runs. However, checking voltage to the WUR with the fuel pump running only gives me 3.5 volts at the WUR. Pulling the plug off the AAR (another resistance device) still keeps 3.5 volts. Adding an extra ground to the WUR negative teminal (the ground for the WUR is actually at D- on the alternator) changes nothing. I am a bit perplexed as to where the voltage drop is.
Pat

Edit:
BTW, it appears the FP relay is working OK, as I have a known good one with the cover off, and I can watch the contacts. Also, I have no heater fan, or relay, as that was all removed. The 14 pin and 6 pin connectors are all rewired as per the wiring diagrams in my Bentley. I have continuity from 85 at the FP relay to the T connector in the engine compartment.

[1982911SCTarga]

If I manually break the connection either via pulling the airflow switch 85 wire, or by pulling the plug on the switch, the fuel pump runs.

This sounds correct, because you're breaking the continuity of that sensor switch circuit. This is a stupid question, but have you checked the "make-break" of the airflow sensor at the contacts on the mixture assembly switch with a test light or a multimeter and by lifting the airflow sensor? Maybe there's some dirt or improper insulation defeating things.

Brian

[911quest]

Guys lets take a step back and break this down first...

30 is battery voltage
87 energized
87a normally closed
86 supplied power to the coil (relay coil)
85 is switch ground (CIS plate sensor)

We know 30 is battery power and 87a is normally closed and it gets its voltage from Ign (15) so if you have the Ign switched to run the pump shouldn't run till terminal 85 shows a ground. as you crank the engine over 87 gets voltage from 50 (starter) the plate rises completeing the ground circuit energizing the relay allowing the fuel pump to run this is happening while you crank the motor over once you stop cranking the relay goes back to terminal 87a


here are some websites which might help
scroll down to page4
http://www.dlcparts.com/images/BoschGuide.pdf
Bosch terminal numbers
http://www.type2.com/library/identifi/bosterm.htm

[boyt911sc]

Originally Posted by 911quest

Guys lets take a step back and break this down first...

30 is battery voltage
87 energized
87a normally closed
86 supplied power to the coil (relay coil)
85 is switch ground (CIS plate sensor)

We know 30 is battery power and 87a is normally closed and it gets its voltage from Ign (15) so if you have the Ign switched to run the pump shouldn't run till terminal 85 shows a ground. as you crank the engine over 87 gets voltage from 50 (starter) the plate rises completeing the ground circuit energizing the relay allowing the fuel pump to run this is happening while you crank the motor over once you stop cranking the relay goes back to terminal 87a


here are some websites which might help
scroll down to page4
http://www.dlcparts.com/images/BoschGuide.pdf
Bosch terminal numbers
http://www.type2.com/library/identifi/bosterm.htm

Teminal #30 for the ignition switch is the battery power, terminal #15 is ON position, and terminal #50 is start. But the FP relay terminal #30 has no power until energized by 87a (relay). If terminal #30 of FP relay is 12 volts (battery voltage as claimed), then the pump will be running all the time. It does not make sense.

It is the reason why a jumper between 87a and 30 is needed to run the fuel pump because #30 has no power until energized by 87a (relay pulled out). Any thought about the discrepancy? Thanks.

Tony

[1982911SCTarga]

85 is switch ground (CIS plate sensor)

The CIS mixture plate sensor switch breaks the ground circuit when it rises. The ground circuit is complete when the plate is at rest.

Brian

[911quest]

If you trace 87 back to the Ignition switch you will see that it starts out as 30 battery voltage goes thry the swith to terminal 87 to the relay. but you have to have ground to keep the relay energized 85 is the ground. The airplate switch might not stay the ground it looks like D- off the alternator might become the relay ground once the car is running

when he dissconects it still runs cause the relay is going back to it's normally closed position so somehow voltage is coming from the 50 track.
this is why if yo jump voltage from battery to 87a the car will crank over.

[patkeefe]

So, I found this morning that the airflow switch doesn't open. I have continuity to ground whether I push up on the plate or not. It was working in the plastic airbox, but now it doesn't in the SS airbox. I can't figure why not, but I don't recall exactly how the contact was in the flap mechanism. And, there is zero chance I will be pulling the fuel distribution system apart to look it over.

Anyone got a picture of this mechanism so I can recall where the contacts are?

Still need to figure out the voltage drop at the WUR.

Pat

[patkeefe]

Wait...I had a picture!
I think the little tit contacts the adjustable screw, so when the plate lifts, the contact is broken, thus open circuit. That sound right?
Pat

[sjf911]

The air plate circuit is composed of the adjustable reed that you see on the left hand side of the base and a pin contact on the air plate itself. If you are getting a full time ground it implies that you have a short. The bridge piece is supposed to be electrically isolated from the base on both sides. I would check to see if the short is in the metering circuit or external. Have you unclipped the connector at the plate to see if you loose continuity? If it is internal, I would think that one of the two isolators is not working ( the rectangular insulators that cup the bridge on both ends).

[sjf911]

The two red circles are the insulators for the bridge piece. The red line is the external connector and the purple line is the reed. The yellow circle is the contact pin on the air plate. The external connector is bolted through the base to the bridge piece. Both of the bolts that hold the bridge piece are insulated. The connector side bolt is completely isolated from the base with an internal sleeve and the opposite side is insulated from the bridge with an insulated sleeve and washer.

[patkeefe]

Steve:
Thanks! You stated the operation more eloquently than "tit and adjustable screw", but have nonetheless confirmed what I thought. I need to see if something in the stainless steel airbox is touching the conductive side of the isolators.

I just put the engine back in, and I really don't want to drop it again, as most of the stuff is connected. I don't have the axles in yet, which makes dropping easier. I could probably lower the engine a bit to get at it.

Thanks again!
Pat