odd cold-start issue

[Bob Kontak]

Originally Posted by wolds

Hey Tony,
When are you coming to Ohio?

Tony come to Ohio - HA.

[wolds]

He's going to have to if his son and daughter-in-law are moving here.

[wolds]

OK, so I checked the cold start switch and it is functioning. I see about 26ohms across it cold with the wires pulled off it, did not check it warm though. I measured (briefly) 12volts as I hit the starter at the yellow wire and again on the other terminal post so I'm good there. I was looking at a post Vereeken had on AAR's and read that they should be wide open at 0 degrees C. I'll need to check that. I do know that at 16 degrees C it was about half way open and it does close after a couple of minutes with 21 ohms of resistance measured at the bi-metal. So assuming that the system checks out and that the AAR needs to be letting more air through to lean out the mixture so that the cold run rpm would be closer to 1800, how would I go about that? PS, my CCP was 1.3bar @ 14.2 degrees C which is within spec for the WUR.

Warren

[boyt911sc]

Originally Posted by wolds

OK, so I checked the cold start switch and it is functioning. I see about 26ohms across it cold with the wires pulled off it, did not check it warm though. I measured (briefly) 12volts as I hit the starter at the yellow wire and again on the other terminal post so I'm good there. I was looking at a post Vereeken had on AAR's and read that they should be wide open at 0 degrees C. I'll need to check that. I do know that at 16 degrees C it was about half way open and it does close after a couple of minutes with 21 ohms of resistance measured at the bi-metal. So assuming that the system checks out and that the AAR needs to be letting more air through to lean out the mixture so that the cold run rpm would be closer to 1800, how would I go about that? PS, my CCP was 1.3bar @ 14.2 degrees C which is within spec for the WUR.

Warren

Warren,

This is how I test the AAR. First measure the heating resistance (Ohms).
1). Place it in an oven @ 300°F for 15 - 20 mins. and observe if the valve has closed up. If it has fully closed, then it passed the oven-test.
2). Cool the AAR to room temperature and place it in the freezer for 30 mins. Observe that it has partially opened. If it has partially open (50%-60%), then it passed the freezer-test.
3). Allow the AAR to cool to RT (room temp.) and compare the aperture opening at freezing and RT. Insignificant difference. Apply 12-volt to the heater's terminals. Record the time (mins.) for the aperture to close. What I found out from numerous tests is that on the average, a good AAR would start to close approximately close to 4 mins. Some would take longer like 5 minutes.

The objective of the above tests is to determine if the AAR is opening or closing with thermal application and applying 12 volts to the heater. The actual time it would take for the AAR to close when installed on the engine is less than the bench test time. What is critical is the time it would take to close the aperture during cold start.

BTW, the AAR's do not open fully and never seen one that is fully open since I started investigating them more than 15 years ago. I have boxes of these AAR's that I have tested and used in the experiment. My data point is not based on a couple of AAR's but boxes of them. And still doing the tests as of this writing.

Keep us posted with your test results.

Tony

[wolds]

Tony,

I ran the AAR test when my problems first arose back in October the way you described above and the AAR checked out good. So at this point the only adjustment I'm going to make is to lean out the WUR just a little and see what happens. I'll do that tonight after work. I will also check throttle plate rest position and make sure that is correct.

Warren

[T77911S]

the AAR has NOTHING to do with mixture. it does not lean it out, it only raises the idle when cold.
many people seem to have this misconception.

if you notice, both sides of the AAR are connected AFTER the AFM, so the air it bypasses around the TB has already been metered, or measured.

[Vereeken]

Originally Posted by T77911S

the AAR has NOTHING to do with mixture. it does not lean it out, it only raises the idle when cold.
many people seem to have this misconception.

if you notice, both sides of the AAR are connected AFTER the AFM, so the air it bypasses around the TB has already been metered, or measured.

Very true. But very counter intuitive. Took me a while before my penny dropped!

[wolds]

Got it. The AAR is bypassing metered air that has already been accounted for. So I will lean out the WUR CCP a little and confirm the throttle plate rest position. Good news I already know what was too lean because that's what the old incorrect WUR was doing and I have the CCP data from that valve.

Thanks

[T77911S]

how was the mixture set when you put the new WUR on

[wolds]

As I recall CCP was 1.3bars @14.2C. WCP was 3.5bars. I have not checked mixture. As I said above the car aside from this issue is running well. If I don't get the desired results from adjusting CCP then when I have access to a CO tester I'll be able to confirm mixture.

[Vereeken]

I am assuming your Thermal valve still works and is holding off vacuum to the WUR for about 30-45 seconds?

If that is the case and you do not mind resetting the CCP set it to 2 bar at that temp (I would even go as far as 2.5).

I know it is out of spec but I can only tell you by experience that it works on a 83 SC with a ROW engine and a 089 WUR. And I am not concerned about running too lean at that CCP since I have a AFM hooked up constantly.

Perhaps it says something about my engine but I do not know what as everything else checks out.

Michel

[T77911S]

if your pressures are within spec, you may just need to lean it out a tad.

i dont know if tony modded your WUR so that it is adjustable or not, but you might go an 1/8 to 1/4 turn lean first.

[wolds]

V,

Thermal valve is working (got it with the WUR from Tony as it was missing from the car) and does hold off vacuum for 30 seconds. Set CCP last night to 1.6bar with vac on @ 13 degrees C. According to 089 graph I'm at the high edge of the range for that ambient temp. I let the car sit over night and started this morning b4 work. Started resonably well so I think I'm pretty close. Going to see Shank Racing tomorrow with the MOPCA so I'll get a chance to drive it with the new settings.

Warren

[Vereeken]

Originally Posted by wolds

V,

Thermal valve is working (got it with the WUR from Tony as it was missing from the car) and does hold off vacuum for 30 seconds. Set CCP last night to 1.6bar with vac on @ 13 degrees C. According to 089 graph I'm at the high edge of the range for that ambient temp. I let the car sit over night and started this morning b4 work. Started resonably well so I think I'm pretty close. Going to see Shank Racing tomorrow with the MOPCA so I'll get a chance to drive it with the new settings.

Warren

Ok Was that 1.6 with the vac applied or with the vac held off. I am willing to bet that with a CCP of 2 your car would start very well. I know it is against the graph, but it works for me....same car same temps, same WUR...

Michel

[wolds]

V,

I got 1.6bar with the vac on and 1.1bar with the vac off. I'll post a follow-up on this after I drive the car which is the true test afterall. I think though if I am any leaner I will start having issues with hesitation and backfiring through the intake (which I want to avoid for obvious reasons).

Warren

Warren

[boyt911sc]

Originally Posted by wolds

V,

I got 1.6bar with the vac on and 1.1bar with the vac off. I'll post a follow-up on this after I drive the car which is the true test afterall. I think though if I am any leaner I will start having issues with hesitation and backfiring through the intake (which I want to avoid for obvious reasons).

Warren

Warren

Warren,

When you get a chance, could you check if the idle speed drops down when you remove the oil filler cap off with the engine fully warmed up? Or pressure test for vacuum leak/s.

Tony

[wolds]

Tony,

Yes, rpm drops when I remove the oil cap. I've had a vacuum gauge on the system at idle and I get a nice steady 12-13" of vacuum at idle. Just out of curiosity, I left the guages on the system overnight and did notice that system pressure had dropped to zero when I checked it this morning. I had run the car last night around 9:00pm and have done a residual pressure test which was OK. Is it normal that the system would eventually drop to zero after an extended period of time?

Warren

[Vereeken]

Originally Posted by wolds

V,

I got 1.6bar with the vac on and 1.1bar with the vac off. I'll post a follow-up on this after I drive the car which is the true test afterall. I think though if I am any leaner I will start having issues with hesitation and backfiring through the intake (which I want to avoid for obvious reasons).

Warren

Warren

I do not think that is a risk. The CCP is out of the equation after 3 to 4 minutes anyway. And at that bar setting I do not think you would be lean. Perhaps if the CSV would not work, maybe....but I let Tony comment on that.

I believe that the driveability of the car is linked with the WCP. I have mine also at 3.5 and I feel this is better then the 3.8 I had before....

[boyt911sc]

Originally Posted by wolds

Tony,

Yes, rpm drops when I remove the oil cap. I've had a vacuum gauge on the system at idle and I get a nice steady 12-13" of vacuum at idle. Just out of curiosity, I left the guages on the system overnight and did notice that system pressure had dropped to zero when I checked it this morning. I had run the car last night around 9:00pm and have done a residual pressure test which was OK. Is it normal that the system would eventually drop to zero after an extended period of time?

Warren

Warren,

Yes. The residual pressure test determines the rate by which the fuel pressure deteriorates over time. As long as residual pressure stays up on the gauge for 20 - 30 mins. you'll be OK. After several hours (??), it would drop to ZERO. This is normal.

Tony

[wolds]

Thanks Tony and Vereeken. RP is good. As I recall last night, I finished testing and went in to watch TV for awhile. I came back out probably an hour and a half later and I think I still had better then 1 bar in the system.