WUR wiring single ended? 73.5 CIS

[maze]

Hi Pelicans,
I have a 73.5 911 with CIS and the wire running to the WUR is a single wire (red w/ white stripe) and has a large 90 degree connector termination. The connector makes contact with both terminals of the coil connector. Seems to me it should have two wires, one for each end of the coil. I looked but didnt see any other wires in the vicinity.
Any idea whats going on here? It fires on the cold start value but dies out. After a bunch of tries it will gradually run longer and longer until its finally happy again.

I have the WUR taken apart for cleaning and will blow out the line to the fuel distributor also. The car sat for many years and the fuel distributor center valve was stuck. I freed it up per instructions in this forum.

Thanks much
Maze

[timmy2]

you have the wrong WUR for the 73.5.
It should only have one terminal that gets connected. Original would have been grounded through the WUR body.

You could install a later 2 wire timer jr. connector with a ground wire to try to get that WUR to work, but I doubt it is correct for your engine.

Your engine is running once warm due to heat soak in the WUR.

[john walker's workshop]

Or find a late style 2 terminal wire plug and run one wire to ground, like at the wur hold down bolt.

[maze]

Yup, that all makes sense. Thanks so much for your quick replies.
Ill try to make an adapter to ground one side of the coil.
As I understand the WUR function, when the coil gets power it tends to lean the mixture by increasing the pressure to the fuel distributor valve. So with lower output pressure the distributor valve rises thereby enriching the mixture. Is that correct? The coil on this is inactive so it should be running rich but actually seems to be running lean until the heat soak occurs.
Are there differences in the orifice sizes in the various WUR's that would affect the cold enrichment?

[timmy2]

All of the different WURs were designed for each years system. They all have different calibration curves.

Maybe Tony, (boyt911sc) has the correct WUR available.

[boyt911sc]

Originally Posted by maze

Hi Pelicans,
I have a 73.5 911 with CIS and the wire running to the WUR is a single wire (red w/ white stripe) and has a large 90 degree connector termination. The connector makes contact with both terminals of the coil connector. Seems to me it should have two wires, one for each end of the coil. I looked but didnt see any other wires in the vicinity.
Any idea whats going on here? It fires on the cold start value but dies out. After a bunch of tries it will gradually run longer and longer until its finally happy again.

I have the WUR taken apart for cleaning and will blow out the line to the fuel distributor also. The car sat for many years and the fuel distributor center valve was stuck. I freed it up per instructions in this forum.

Thanks much
Maze

Maze,

Look on top of the WUR for the Bosch ID #. Right behind the post (see above pic) are the numbers 0 438 140 xxx the last 3 digits identify a particular WUR. Please post the last 3 digits. Thanks.

Tony

[HarryD]

FWIW, here is the wiring diagram for the 1973.5 CIS update.

[maze]

Thanks so much for all the responses to my post. I really appreciate it, and the wiring diagram is a great help also.

The last three digits on the WUR p/n are 009

[E Sully]

The 73.5 original 0438 140 001, is not repairable from what I have read. The recommended replacement is 0 438 140 129, which is a 2 wire unit.

[RarlyL8]

-129 is the factory replacement for the -009. Either can be used to replace the more primitive TPS activated OEM unit. Wire it correctly and all should be good.

[timmy2]

Maze,
I made this up tonight for you with a used spare connector and some new parts.
It is a plug and play solution.
Ground the brown wire to a WUR mounting bolt and connect the original angled connector to the red/white wire.

Send me your mailing address via a PM and I’ll send this to you. (USA only)
Merry Christmas

[donlan]

Hello, All sounds like good advice (as it was for me when I was getting "the 20 year sleep going again") which it is But still not on the road.Regards,Michael.