CIS Pressure part 2

[mike sampsel]

Okay, I have not tested pressures recently.

I let the car sit for 2 weeks without a start, and it would not start with a long crank. I primed to FP, jumper wire from 87 (the terminal on top of 30) to 30 to run the pump. then felt the lever to verify pressure. The car started but sputtered and had a little backfire/sputter for a while. After a long drive it settled out fine.

The next day (today), I started the car. Fired in 2 seconds, had the interesting results.

It cycled from 2000 rpm back to 1000 rpm ten times. This took approximately 5 seconds per cycle. After cycle number 10, then it cycled from 1400 rpm to 1000 rpm for 4 times then settled at about 1000 rpm. (did not touch the pedal).

So

1000 - 2000 rpm cycled 10 times
1000 - 1400 rpm cycled 4 times
steady at 1000 rpm

Ambient temp 55 deg F.

Is this normal, seems the AAR might be sticky?

Looking for some ideas.

[mike sampsel]

https://youtu.be/uHY12gz2m68

Video of the strange idle

[SkiVT]

You can remove the AAR and test it using a battery to heat the element for closing and a freezer for opening. Less work: while AAR still mounted to engine, pull hose and use a mirror to check if it’s open while engine is stone cold. Then do the same check, to see that it’s closed, after you have run the engine long enough to be fully warm. Based on the video and your description of it running great or settling out it seems unlikely the AAR is your issue.

The uneven idle and surging could be air leaks, to rich mixture, etc. if it’s mixture, the source could be pressures, the mixture screw, etc. need more testing to narrow it down.

[David Inc.]

I don't think an AAR fault would lead to a wandering idle like that. It's not opening and closing during operation just slowly going from open to close.

My first thought would be vacuum leak and/or mix like SkiVT says. How was it driving beforehand? And what happens if you play with the throttle during a cold start, and what happens after a hot start?

[mike sampsel]

Originally Posted by David Inc.

I don't think an AAR fault would lead to a wandering idle like that. It's not opening and closing during operation just slowly going from open to close.

My first thought would be vacuum leak and/or mix like SkiVT says. How was it driving beforehand? And what happens if you play with the throttle during a cold start, and what happens after a hot start?

Hot start: No issues

Driving fine when warm, acceleration is great

Maybe I need to look for a vacuum leak (smoke test when cold, 50 deg or so), found none last time I looked though, in July.

Mixture was fine last checked with AFR gauge (set warm though) 13.2 warm, toggled between 13.0 - 13.5 at start (checked last 10/11/2020)

[mike sampsel]

Interesting result on 12/16:
After sitting for 14 days, I expected difficulty in starting (long crank). Nope, fired in seconds, it was colder out than normal (about 35 F outside, 50 in garage). So it likes colder starts. Will test again in a while. The RPM went to 2K quickly then it back off to 1000 rpm. All good. No changes since the new fuel pump added.

The mystery continues. If it were a vacuum leak, issue, why would it only occur after a start when sitting for a week+. I.E. if vacuum leak related, why not occur after sitting for 2 days? And how might a leak relate to good cold starts?

[AndrewCologne]

Beside all that your suel pump sounds bad. And the sound comes up already when key is turned to pos 1. Whats the year of your CIS car? If its a newer/SC one the protection circuiut should make running the FP only possible when engine is turning.
https://nineelevenheaven-wordpress-com.translate.goog/die-schutzschaltung-der-benzinpumpe/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

[mike sampsel]

Andrew, Thanks for the link. CIS is ‘78, fuel pump was replaced in September, and it does not run with the key in on position (have jump from 30 to 87a). System pressure is a bit low and I plan to add a shim or two to raise it. Both this pump and the one I replaced are/were around 66 psi (the low end of in spec). I replaced the pump mainly to get a new check valve, although residual pressure was in spec too. New check valve and pump raised the residual pressure.

Still looking into why do some starts take long cranking time after a 2 week sit? Although the last one was start in 1-2 sec after sitting for two weeks

[SkiVT]

the video looks like air/fuel mix and amount being good, then not good, then good, etc. So fluctuating. Thinking of the air side first, could be leak(s). However, seems odd it goes away when hot. Leak could be in a spot that once warm, seals. This logic doesn't work with your recent cold temp no problem start. On the fuel side, could the plunger in the FD be sticking at startup, intermittently? Is the airflow sensor bouncing or loosing touch with the plunger letting more, then less air pass without a change in fuel with stuck or sticky plunger? Both resolve over the short warm up time period? I don't even know if that is possible. There is also the Primary Pressure valve on the FD and its gaskets(see link for one example). I thought those only impact warm start but maybe.

CIS Primary Fuel Pressure Regulator Assembly

Another test if you have the time: install your pressure gauge on cold engine. Start engine and video the pressure gauge watching the pressure build up to CCP and then watch it continue to climb toward WCP. Post the video. Basically watching for any sudden drops in pressure instead of a steady climb. Also watching for the TTV vacuum release pressure increase.

[mike sampsel]

Some good thoughts, not sure what I'll do next. But thoughts to chew on. Likely will get the SP a bit higher as the next step.

[mike sampsel]

Originally Posted by AndrewCologne

Beside all that your suel pump sounds bad. And the sound comes up already when key is turned to pos 1. Whats the year of your CIS car? If its a newer/SC one the protection circuiut should make running the FP only possible when engine is turning.
https://nineelevenheaven-wordpress-com.translate.goog/die-schutzschaltung-der-benzinpumpe/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

Oh, I remember now, I think I had the door open and the warning buzzer is buzzing, it's not the fuel pump.

[mike sampsel]

So yesterday 1/3/2023 (after sitting only 2 days since last start). I attached my PGauge and started the car. Started right up (it did so as well on 1/1 after sitting for 8 days).

Anyway after the start the surging of rpm was still present. The CP started at 22 psi and worked its way up smoothly to 47.5 psi in 2 minutes.
The control pressure was not swinging about to cause the surging idle. (Not a surprise though).

Summary with ambient temp approximately 60 F.

After I opened the line to attach the gauge:

Car starts in sec or two. Idle to 2 K, idle surges from 1.2 to 2 k some (could not watch it closely while videoing the CP).

CP goes from

22 psi to 47 psi in two minutes

Conclusion CP is all good.

[mike sampsel]

Here is the video


https://youtu.be/rD0SBq-WAFA