Cold Start on 82 RoW SC

[WillJ]

Hi Pelicans, looking for some help with a minor cold start issue on my 82 RoW SC. I’m new to CIS and have had the car since Nov last year. The engine fires on the first crank but it sometimes dies immediately. Then on the second crank it starts but is definitely missing on some cylinders before ‘waking up’ after a few seconds. RPM then rises and falls a couple of times before sitting at 1400rpm and then dropping back to 900 after maybe a minute. This dying and needing a second crank only started recently and after replacing the FA which had a leaky diaphragm. I’ve done a pressure test, details below:

1982
RoW
Some unknowns on the motor, engine number matches the expected sequence (63CXXXX) but was rebuilt in the 90s and I have a California Bureau of Automotive Repair sticker on the door jamb indicating 3.2L. I have no history on the rebuild.
WUR 089
Temp 66f 19C
WUR resistance, 27 ohms

System pressure 4.8 (in line)

Cold control 1bar no vacuum
Cold control 1.7bar with vacuum (1.6 to 2.0 range from chart)

Warm control 2.85 bar - got there at 4mins, no vacuum (range should be 2.7-3.1 without vacuum)

Off
Drops to 2.5bar
5min 2.2bar
10min 2bar
20 min 1.9bar

For RoW cars with no lambda/o2 sensor should the cold control pressure chart be read with a vacuum applied? I was concerned the 1bar was too low but saw good readings when applying vacuum, and if that’s right then these pressures are all within spec.

Hot start is immediate (since I replaced the fuel accumulator). The only other item I’ve noticed is it sometimes it seems like it is hunting a bit when idling, there are barely visible fluctuations on the tach and a good ear can hear it. Other than that it runs great.

Idle drops when removing oil cap so no major air leaks but I have not fully tested for air leaks with a smoke machine or by spraying solvents around the engine bay. Pop off valve is installed in the airbox. Cat and air pump are in place.

What’s next to check? Could it be taking a second or two for the vacuum to be applied to the WUR? My inkling was mixture being too rich given the idle surging at startup. That could obviously be from many areas and I’ve not touched the adjuster in the FD. I wondered if the PO had adjusted it to account for the leaky FA and now it’s not leaking it needs to be tweaked back.

Looking forward to hearing from you all!
Will

[SkiVT]

The wur chart is w/vacuum which typically is .6 bar higher than no vacuum. I would smoke test for air leaks. Also confirm your vacuum lines are run correctly (see pic in link). Also confirm you have the ttv number 4 in this pic as it impact cold starts. It holds off vacuum for bit allowing a rich startup, which is a good thing. Your idle going to 1400 then back to 900 is also good but this shouldn’t be jumping around but rather mostly smooth up and back down. Troubleshoot one possibility at a time.

https://jimsbasementworkshop.com/CIS/pages/air_vaclines.html

[WillJ]

Thanks for the advice. Here’s a video of a cold start showing the symptoms.

https://youtu.be/Zmr8OSKab6w

I don’t have access to a smoke machine so I crudely tested for air leaks using liberal amounts of brake cleaner and listening for changes in rpm but there were none.

I checked the vacuum connections matched the chart you provided. WUR (5) connects to the Thermo valve (4). Then the Thermo valve (4) connects to the throttle housing (1) but the T connection to the vacuum control (9) is plugged. The operational bypass from 9 to 1 is also not connected. The only connection to the vacuum control (9) is the green manifold bypass line.

I tested the thermo valve, it works as expected - blocking vacuum when cold and opening up when plugged in and the heating element does it’s thing.

I also checked timing at idle and it’s sitting at 5’ BTDC as it should.

Interestingly it started perfectly yesterday from cold after I had performed a cold pressure test.

[boyt911sc]

Originally Posted by WillJ

Thanks for the advice. Here’s a video of a cold start showing the symptoms.

https://youtu.be/Zmr8OSKab6w

I don’t have access to a smoke machine so I crudely tested for air leaks using liberal amounts of brake cleaner and listening for changes in rpm but there were none.

I checked the vacuum connections matched the chart you provided. WUR (5) connects to the Thermo valve (4). Then the Thermo valve (4) connects to the throttle housing (1) but the T connection to the vacuum control (9) is plugged. The operational bypass from 9 to 1 is also not connected. The only connection to the vacuum control (9) is the green manifold bypass line.

I tested the thermo valve, it works as expected - blocking vacuum when cold and opening up when plugged in and the heating element does it’s thing.

I also checked timing at idle and it’s sitting at 5’ BTDC as it should.

Interestingly it started perfectly yesterday from cold after I had performed a cold pressure test.

Will,

Could you do this cold start test for me? Allow the motor to sit over night and perform a cold start. But before cranking the motor, test run the FP for 5~10 sec. and switch off the FP. Install the red FP relay back and start the car by just turning the ignition switch. No need to go in and seat inside the car. I like to find out if it would start in the first attempt after priming the system. Keep us posted. Thanks.

Tony

[WillJ]

Of course.

Here's a video of a cold start with the fuel pump primed first. Slightly different behaviour, started on first turn of the key, though reluctantly. A little bit of fluctuation before settling in and then dropping to normal idle.

https://youtu.be/gw1DteLz00o

Does this test confirm any of your suspicions?

And for good measure a hot start afterwards showing no issues.

https://youtu.be/RKv9wplnpUI

Separately, I've been trying to test the cold start valve resistance but it's a pain with the air pump in place. Might remove and test that later if I can.

[SkiVT]

Did you test your AAR, number 3 in that diagram, which provides extra air at cold start? Needs to be fully open at start. Don’t divert from Tony’s guidance but it’s fairly easy to see the opening in place and not that difficult to pull and test in the freezer.

Watch this video for more CIS

https://youtu.be/slCzVrrST2Q

[WillJ]

Thanks for the suggestion. AAR tested and is good. Open when cold, closed when warm, has voltage when engine running. Idle drops as expected after plugging in.

TTS - tested resistances hot & cold (G to ground, W to ground, G to W) and all are in spec.

[boyt911sc]

Will,

Sent you a PM with the new test procedure for manipulating the cold control pressure and with my phone #. Did you receive the message?

Tony

[WillJ]

Thanks for the message Tony.

For those following along, I thought that the cold pressure was in line as it mapped correctly to the chart with vacuum applied. Tony advised that it was too low and gave me an additional test. I increased the cold pressure by partially closing the valve on the pressure gauge then replaced the relay and started the car.

It started on the first click from cold, but pre-pressurized from the cold pressure test. It initially idled near 400 and then climbed to 1000. I also plugged in the WUR after a few minutes just to observe the pressure and idle changes and get to know CIS a little bit better.

Here’s the video for those interested. Will repeat later or tomorrow once pressures are down to zero and everything is cool. Suspect a rebuilt WUR may be in my near future.

https://youtu.be/cxaeqawlBeI

p.s. That air pump squeak is new and will be getting the WD40 treatment shortly.

[boyt911sc]

Will,

Ignore the instruction I recently sent to you via email about repeating the test with the WUR plug connected. You had done it already according to your above post. Your WUR is working except it is out of calibration.

If I were you, I would consider activating the decel and thermotime valve’s configuration into your system. If you like to send the decel valve to me, I could test and recalibrate it for FREE. Just mail it to me with a return shipping label.
Good job.

Tony

[WillJ]

Thanks Tony, email with you.

I repeated the same test but from zero pressure. Started nicely, WUR is definitely out of spec.
https://youtu.be/fYQdNjeaa80