CIS and timing

jfd711 · 09-21-2011, 04:13 PM

Got a first time user here. Hope you can help?
I have a 75 911S with professionall rebuilt engine with all the Anderson recommended upgrades. The emission pump and reactors have been eliminated. The stock timing is 5 deg. ATDC. Should the timing be modified due to the loss of the emission setup? It seems to run better with some advance.
In NC we don't use CO as part of the inspection process. Since the spec for A/F is based on CO, is there another method to set the CIS.
The system and control pressure have been verified, but I still have allot of hesitation and bucking below 2k on warm-up and hot running. Looking at some of the other threads on CIS this seems common. I'm wondering if there is a relationship to the basic timing setup or not?
Any help will be appreciated. Thanks jfd711

ClickClickBoom · ClickClickBoom's Garage

Hey,
1975 911S Calif model, I did what you did, CIS is simple and tricky all at the same time. First check all your hoses and boots to eliminate vacuum leaks. make sure they are in the correct position. Second most likely no more than 30deg BTDC at 6000. Get a 3mm Allen and find out where to use it(this forum). I tuned my car and when I was done the CO meter arrived, I was just a tad lean. Believe it or not your seat of the pants and nose will get you real close. Check your distributor grab the rotor and pull as if you were trying to remove it, if you get any axial play get it rebuilt, you will get the tuning close but perfection will elude you, pcars like precise timing. Many rebuilders will go right past the dizzy and not touch it. My 2.7 runs like a top and gets 26 mpg, eat it Priuses! These cars respond well to fiddling and massaging, I have a hard time believing my car is 38.
eric

Flat6pac · 09-21-2011, 06:31 PM

Realize the vacuum on the distributor is a retard for emissions. Unplug it and you should be at about 5 degrees before TDC. Make sure the hose is vacuuming at idle. Put the hose on your tongue at idle, feel the vacuum. If you dont feel it the hose might be hooked incorrectly above the butterfly only giving you vacuum at high RPM.
Go for the 30 degree advance and let the idle set where it wants.
Bruce

RoninLB · 09-21-2011, 08:54 PM

In my CIS days I disconnected my dizzy retard permanently and set total timing at 35 BTDC and I believe idle timing wound up at 5 deg BTDC

fred cook · fred cook's Garage

Remove the distributor cap and try twisting the rotor. It should turn a few degrees and then snap back when released. If this does not happen, then you have frozen advance weights. This will keep the distributor from advancing as the engine revs go up. Good luck!

jfd711 · 09-29-2011, 03:43 AM

Thanks guys, these comments have been very helpful.
In reviewing specs, I found the WUR is supposed to have 18-22 ohms. Mine reads 36. Is that significant? And to what extent does the WUR affect normal driving after warm-up?
Any help is appreciated, Thanks jfd711

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by jfd711

Thanks guys, these comments have been very helpful.
In reviewing specs, I found the WUR is supposed to have 18-22 ohms. Mine reads 36. Is that significant? And to what extent does the WUR affect normal driving after warm-up?
Any help is appreciated, Thanks jfd711

JFD,

Do you know the number on the WUR? WUR (warm-up regulator) it is actually a control fuel pressure regulator that contributes to your fuel mixture from cold start to operating temperature. Keep us posted.

Tony

jfd711 · 09-29-2011, 03:24 PM

hi Tony
The Bosch no is..0438140009

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by jfd711

hi Tony
The Bosch no is..0438140009

jfd,

You have the correct WUR for '75. What's the cold control pressure you are getting? Test the WUR by running the fuel pump and record the control pressure versus time (every 30 sec.) until you get the max. control pressure (warm). Then check/test for vacuum/air leak. Finally, have the exhaust gas checked using a gas analyzer. Keep us posted.

Tony

jfd711 · 09-30-2011, 05:09 AM

Hi Tony
Thanks for responding.
The tests on fuel pressure were within spec, but I have not charted warm up temp vs time. In NC we don,t use CO for inspection, so there are not many machines around. I have estimated AFR as outlined in these threads. I have gone lean and then rich and now feel its very close. My problem is I still have a slight hesitation <2k. Since the WUR is showing 37 ohms which is greater than 18-22 spec, I'm wondering what affect the WUR has on warm/hot running. I have not taken the WUR apart yet and have not made the adjustable mod to it yet.
Any help is appreciated.
Thanks jfd711

Pillow · 09-30-2011, 06:22 AM

Quote:

I still have allot of hesitation and bucking below 2k on warm-up and hot running.

I hope you are not lugging your engine at these low RPMs? Unless you are sitting at idle under 2K is not good.

Scott R · Scott R's Garage

Quote:

Originally Posted by Pillow

I hope you are not lugging your engine at these low RPMs? Unless you are sitting at idle under 2K is not good.

I hate to say this, but in my "commute" this is unavoidable just due to traffic speeds. But when everything is "gelling" with CIS there is no issue doing this. My chief cause of the bucking, surging was a worn distributor.

T77911S · 09-30-2011, 10:31 AM

as long as your fuel pressures are correct cold and warm, i would not be too concerned about the resistance of the heater. with that said, it could be an indication that it is going bad.

you should still post the pressures.

make sure you dont have any air leaks.
make sure the ignition advavnce is working.
either do as Ronin said or make sure your vacuum advance/retard, (if you have vac advance) is connected to the proper port and is working.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by jfd711

Hi Tony
Thanks for responding.
The tests on fuel pressure were within spec, but I have not charted warm up temp vs time. In NC we don,t use CO for inspection, so there are not many machines around. I have estimated AFR as outlined in these threads. I have gone lean and then rich and now feel its very close. My problem is I still have a slight hesitation <2k. Since the WUR is showing 37 ohms which is greater than 18-22 spec, I'm wondering what affect the WUR has on warm/hot running. I have not taken the WUR apart yet and have not made the adjustable mod to it yet.
Any help is appreciated.
Thanks jfd711

jfd711,

We know that you have the correct WUR, could you give us the control fuel pressures (both cold & warm)? Where did you find/get the 18-22 Ohms spec for -009? Could you share with us? Thanks.

Tony

jfd711 · 10-01-2011, 03:43 PM

Hi Tony
The "spec" came from a Pelican "tech info center" article "911 Warm up regulator Adjustability" by Bob Tindel. I was not aware that it might be specific to year of car?

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by jfd711

Hi Tony
The "spec" came from a Pelican "tech info center" article "911 Warm up regulator Adjustability" by Bob Tindel. I was not aware that it might be specific to year of car?

jdf711,

Take a few minutes and re-read Bob Tindel's article. That's a good one. But it never said anything about 0-438-140-009 WUR. What it said was that the WUR had some what 18-22 Ohms resistance. And we don't know which WUR he was referring too. This is another myth that propagated when someone made a very informative illustration of an adjustable WUR that showed the value of the heating resistance of 18-22 Ohms. This is completely true for some models of Bosch WUR (0-438-140-xxx). But not all Bosch WUR's have the same amount of resistance (Ohms). It all depends on the model/ID number.

The later '81-'83 SC's use 0-438-140-090 WUR with approximately 10 Ohms resistance. The earlier SC's with -045 have around 24.5 Ohms. The -009's have about 32 Ohms and others have like 40, 50, etc. Ohms.

I have checked and re-checked the resistances of these WUR's and the good ones have different readings ranging from 10 to 67 Ohms. HTH.

If you expect that your WUR-009 to have 18-22 Ohms, I would consider that a bad one. It should have atleast 30 plus Ohms. HTH.

Tony

jfd711 · 10-02-2011, 05:11 AM

Hi Tony
Thanks for digging into the "variation of WUR ohms" (sounds like a spy thriller).

I am going to assume that the slight hesitation on low rpm acceleration is due more to a fuel issue. I think the AFR is about right. The cold and warm pressure and leak down are within spec. The fuel distributor and injectors may be suspect. Is there a technique for testing the injectors without blowing gas all over? How about tests for the fuel distrib? I have a spare fuel distrib. that I could test off the car. It sounds like rebuilding the FD is not a simple job due to resealing?

Anyway thanks for your help. If you, or anyone, is willing to comment on the fuel issues, it would be appreciated.

jfd711

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by jfd711

Hi Tony
Thanks for digging into the "variation of WUR ohms" (sounds like a spy thriller).

I am going to assume that the slight hesitation on low rpm acceleration is due more to a fuel issue. I think the AFR is about right. The cold and warm pressure and leak down are within spec. The fuel distributor and injectors may be suspect. Is there a technique for testing the injectors without blowing gas all over? How about tests for the fuel distrib? I have a spare fuel distrib. that I could test off the car. It sounds like rebuilding the FD is not a simple job due to resealing?

Anyway thanks for your help. If you, or anyone, is willing to comment on the fuel issues, it would be appreciated.

jfd711

jfd,

If you want this problem corrected soon, help us understand what's going on. It has been requested several times to post the fuel pressures readings. Some how you are withholding the information and like to depend 'on spec' terminology. The fact that you have been relying on a wrong spec makes the troubleshooting more difficult to tackle.

We need numbers, measurable data. Information that would lead us to the right direction. Knowing the fuel pressures will give you a better understanding about the WUR and FD. So what are the spec readings you are getting? Individual CIS components like WUR, AAR, TV, TTS. CSV, FD, DV, FV, auxiliary thermostat, etc. could be bench tested easily by DIY'ers like you or me.

What makes the troubleshooting difficult is that some people like to do guesswork instead of reducing or eliminating the variables to solve the problem/s. Test and verify the results. Thinking and assuming critical data won't help you/us find the problem/s. Keep us posted.

Tony

jfd711 · 10-03-2011, 08:15 AM

Hi Tony
Thanks for your comments.
By way of background, I do understand troubleshooting and the deductive process. The nearest CO machine to my garage is in another State about 70 miles away. The nearest Porsche dealership is 2.5 hrs away and they don't work much on 35 yr old cars. This is my first experience with a CIS system, that's why my first question was on the relationship between the WUR and timing. I was looking for the right "ballpark" to start. I got some suggestions on timing and by reviewing some other threads, it appears the WUR is not just for cold starts but warm running as well. "I think" the AFR is about right after following suggestions in other threads and when I get to a CO tester that will be verified.
The pressure testing was done by a local shop that works on Mercedes and BMW fuel injection systems. He has the gages and I don't. He indicated the cold pressure was "about 2 bar" on a 75deg day and the WUR did warm up in about 2 min to "about 3+ bar". The system pressure was 4.9 bar. And declared my system was "within spec". After your comment of measuring pressure over warm up time, I'm not sure how reliable my limited data is. I will try to acquire a gage set and redo these tests.
Thanks jfd711