Need Fuel Pump Relay GuRu - 78 SC

[Kevin Taylor]

1978 911 SC
Someone has butchered the wiring harness and added an
aftermarket fuel pump relay.
It’s only working some of the time but not all of the time.
This small black relay has no name
on it.
Only the NBR: C9406 it is five spade – 30 – 85 – 86 – 87 and 87a.
Eventually I want to go back to the stock one when I find someone
parting out a 78 911 SC.
In the mean time I would like to get a replacement rely for the C9406
so I can move the vehicle around.
Any ideas where I might find one or somehow identify who makes this
one or what German vehicles it fits?
I tried the local auto parts store and had no luck.

Thanks in advance.
K.T.
1973 911 E 2.4 MFI
1983 911 SC
1978 911 SC
1965 Devin "D" / 1967 912 Power Plant
YOUR CLASSIC RIDE – KCMO CAR CLUB - MEMBER
1998 GMC Serra 4X4 Z71
John Deere LT166
Money Can Buy Happiness........Buy A Porsche......

[Gunter]

I see you have a '83 SC.
Go under the passenger seat and carefully pull out the relay for the Lambda brain.

It might have the right pin configuration and rating.
These are Bosch relays and for the pump you want a 30A rating; a VW dealer might sell these.
Let me know if that works out.

[psalt]

Hello Kevin,

What do you mean, it only works part of the time ? The terminal numbers 30 (main power in), 85 (coil negative) 86 (coil positive), 87 (load out, energized), 87a (load out, not energized) are standard for all Bosch relays. The fuel pump circuit uses both load outs for safety reasons and my advice would be to trace the wires and understand the circuit before replacing the relay. Does it look like this :

Parts-Express.com:*12 VDC Tyco 5-Pin Relay SPDT 20/30A (Formerly Bosch) | spdt relay spdt sound security relays relay plastic mounting DC boss bosch relay 330-070 automotive relay automotive 12v bosch

[sixbanger]

That's what it looks like. But why would someone remove the factory setup and install this setup?

[psalt]

All the reasons I can think of are bad. That's why you should trace the wires, particularly the air flow sensor switch contacts. The fuel pump should not run with the key in the ON position unless the engine is running.

[Kevin Taylor]

Dr. Gunter - I see you have a '83 SC.
Go under the passenger seat and carefully pull out the relay for the Lambda brain.

Thanks Dr. I will check that when this snow storm lets up.
My truck doors were frozen shut this morning.
The 83 is covered with ice and snow.


Yes Psalt. Thanks. That is the little bugger. We will do some more investigating and
trace the wires back to the engine compartment. Thanks again. I appreciate it.

It is really nice to here it run again............been a while.




K.T.
1973 911 E 2.4 MFI
1983 911 SC
1978 911 SC
1965 Devin "D" / 1967 912 Power Plant
YOUR CLASSIC RIDE – KCMO CAR CLUB - MEMBER
1998 GMC Serra 4X4 Z71
John Deere LT166
Money Can Buy Happiness........Buy A Porsche......a

[boyt911sc]

Kevin,

Right now, I'm finishing a project installing a motor into a '78SC roller for friend. The main fuse panel in the trunk and in the engine compartment were both replaced. Contact me at atd911@hotmail.com while they are still fresh in my mind. The diagnostic tests for the wirings are very simple. A multi-tester for continuity test will be a great help. Having digital camera is a plus for communications. Good luck.

Tony

[Gunter]

Originally Posted by sixbanger

That's what it looks like. But why would someone remove the factory setup and install this setup?

Generic relays are a lot cheaper than the red OEM pump relay but whenever someone changes a stock set-up it's harder to trouble-shoot. A 30A generic relay can do the work provided it has the same configuration as the OEM relay.

Who knows what else was changed? Like psalts says, check the wiring and understand how the pump is normally controlled and why it shouldn't run just with ignition ON.

[Gunter]

Originally Posted by Kevin Taylor

Dr. Gunter - I see you have a '83 SC.
Go under the passenger seat and carefully pull out the relay for the Lambda brain.

Thanks Dr. I will check that when this snow storm lets up.
My truck doors were frozen shut this morning.
The 83 is covered with ice and snow.

Brrrr........ that sounds familiar. Minus 15 C right now here.

I have an unheated garage but the inside of the 911 is never below 0 because of this:
Passenger seat all the way back and a 150 watt bulb on a special little stand positioned on the passenger floor pointing up about 30 degrees towards the dash driver's side.

The stand is easy to make by using a regular connection box, a bulb socket with a short pigtail 3-prong cable all mounted on a small piece of plywood.

A 150 watt bulb gets pretty hot and the stand prevents it from touching anything. I run an extension cord through a partially closed passenger door. PLUS, cover the car with 2-3 old comforters.

Have done this now for several years and it works pretty good with the temps staying well above 0.