How To: Bypass WUR / CPR cold vacuum enrichment electronically

[FABombjoy]

You can bypass a defective enrichment diaphragm or add enrichment electronically. Volvo used to offer something similar as a retrofit kit but goooooood luck finding one. These parts duplicate that system using things you can readily purchase.

A negative switching relay with time-out function:
[Link To Phishing Virus Removed]

An adjustable vacuum switch, such as the Superior K058

A spare terminal that fits the Lambda controller box. I don't have a reference on hand.

-Adjust the screw on the vacuum switch to trigger at a at a slightly at a lesser vacuum level than idle. IIRC you can hear it in-hand when the contacts switch.
-Connect the vacuum line leading to the valley, normally connected to the T at the CPR, to the vacuum switch.
-Connect a ground wire to the switch common terminal
-Wire the relay power source 12v/gnd as indicated by instructions. Adjust time-out function to approx 8 seconds
-Connect a ground wire from the switch normally open to the trigger input on the time-out relay
-Connect the relay output to terminal 11 on the lambda controller.

Drivability adjustments. Might take a few cycles due to time-limited nature of cold engine adjustments:
-Vehicle immediately hesitates when cold - lower vacuum trigger threshold and/or verify that dwell shows 80+ reading when revving
-Excessive black smoke while accelerating - decrease relay time-out to shorten enrichment period
-Starts OK but then hesitates - increase time-out to lengthen enrichment period

[nkemp]

A negative switching relay with time-out function:
http://www.wolstentech.com/products/timedelayrelay/tdr-t.php

This site has gone the way of the Dodo bird.

I did find this image which is what I think you used and how you used it (Normally open switch, switched to ground).

70176

Is the above correct or can you verify or provide a circuit diagram of what you used? Knowing that I think a replacement could be found/made.

[FABombjoy]

No diagram but the idea is:

-Low load (low manifold pressure), terminal 11 not grounded
-High load (high manifold pressure), terminal 11 grounded

Timeout function mainly will prevent continuous enrichment once the vacuum valve switches over and manifold pressure is no longer at the vacuum switch. If the vacuum bleeds off while driving eventually it will trigger lambda enrichment nonstop.

Looks like there are a bunch of cheap programmable 12v time delay relay modules on amazon, ebay, etc. They can replace the TDR-T.
You can run 12v to the vacuum switch too if a negative switching module can't be found.

[Bitsyncmaster]

Warning. Don't try to open that link in the first thread. It results in one of those "Security Alerts" and locks up your browser.

[nkemp]

Warning. Don't try to open that link in the first thread. It results in one of those "Security Alerts" and locks up your browser.

I hate those. A PITA to get out of it and the last one played a loud sound constantly until I killed the tab. I know of one couple who paid the scammers a couple hundred dollars to resolve it and I don't think they ever knew it was a scam. My browser warned me before letting it play out. Hopefully the moderators can remove the link.

Looks like the ink was removed already. Good work.