Repairing my 911 1977 with 3.0 1983 engine

[Tal]

I need help from forum members understanding how to proceed in my repair.

I bought my 1977 911 (which has 3.0 engine from 1983) couple of month ago, and since then learning how to repair it myself. I went over the forum articles, and Bentley book (1978 - 1983).
It does not run well, like on cold start the RPM goes up and down like crazy and a lot of other problems.
I decided to start from testing the fuel delivery system (watched the video from Joe The Engineer, read the Bentley book etc), hooked up the fuel pressure gage between WUR to Fuel Distributor.
What I did so far:
1. Measured the system pressure - it is at 4.75 bar, which is well within the limit.
2. Then I wanted to measure the Cold control pressure, and I discovered that the Warm Up Regulator being original from 1977 (I read on WUR 0 458 140 033), not the expected one from 1981-1983 (which is 0 438 140 090).

I need forum members opinion on my following plan:
I came to conclusion that I need the right WUR and decided to replace it with the one that matches my engine 0 438 140 090. It seems to me that using wrong WUR is going to a problem for the proper operation of the engine.
So to buy used 0 438 140 090, and rebuilt it using 0438140004 Warm-Up Regulator Repair Kit (Non-Vacuum Type WUR) from K-Jet in Australia.
Assuming that I will be able to perform all the measurements for fuel delivery on rebuilt WUR (to test that I did it correctly) and electrical resistance for bi metallic strip, is rebuilding the 0 438 140 090 something that I should be able to accomplish on my own?

I worked on past on my own Jeep Wranglers, but they were much much simpler.

[boyt911sc]

You will need a good WUR-090 and OXS with ECU to get your lambda engine to run well. Rebuilding your WUR-090 is the easy part. Getting your lambda motor to operate well is your biggest challenge. Could you post a picture of your motor? Thanks.

Tony

[rwest]

Hi Tal,

Tony, above is an incredible wiz on CIS and will be able to help you through this if you follow his suggestions.

You may also want to read this thread as it has great info.

CIS Troubleshooting for Dummies

[Tal]

Rutager, Thanks for your feedback.
I went over the thread CIS Troubleshooting for Dummies, watched the videos in youtube, read the chapter in Bentley Manual, did all that.

Tony,
The status for Lambda:
1. The 02 sensor is not even connected to it's harness, but it is present.
2. The frequency valve is not connected to it's harness, but it is present.
3. The Lambda computer under the seat is present and hooked up to it's harness.
4. The fuel enrichment relay controller (the small box that comes attached to the Lambda computer) is missing. I bought https://www.ebay.com/itm/225920732147?mkevt=1&mkpid=0&emsid=e11412.m144671.l197928&mkcid=7&ch=osgood&euid=5f95a950520740429075e27e0d6564d5&bu=44399745761&osub=-1%7E1&crd=20251028152343&segname=11412 .
5. The plan is to connect the O2 sensor to the harness, the frequency valve to it's harness, install the fuel enrichment relay controller box, and then start measuring the O2 sensor and the dwell on the Frequency Valve through the test port in Lambda harness.

However, priority wise, it seems like it makes sense to deal with Lambda only after getting the system, cold control, warm control and residual pressure.

So far from the fuel pressures perspective, I have:
1. Year of engine - 1983
2. US or RoW (Rest of World) - USA
3. WUR model number - wrong WUR (from 1977), I will replace it with rebuilt correct PN 0 438 140 090
4. Ambient temperature at time of test (in degrees C): - NA, will be done with correct WUR.
5. WUR Resistance (in Ohms): - NA, will be done with correct WUR.
6. System Pressure (in bars): - 6.75 bar.
7. Cold Control Pressure (in bars): - NA, will be done with correct WUR.
8. Warm Control Pressure (in bars): NA, will be done with correct WUR.
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): NA, will be done with correct WUR.
10. Residual Pressure @ 5 min (in bars): - 1.5 Bar
11. Residual Pressure @ 15 min (in bars):
12. Residual Pressure @ 30 min (in bars): 0.2 Bar
13. Residual Pressure @ 60 min (in bars): ~0 Bar.


My understanding is that even with bad WUR, I should be able to see correct Residual Pressure.

[john walker's workshop]

A non lambda 78/79 fuel distributor and 045 WUR is a good swap. Saves a bunch of wiring and hassle.