CIS Frustration!

Dave27S · 06-18-2009, 12:26 PM

Hi lads, im need of some CIS help! basically ive a stock 1976 2.7S. my original problem was the Fuel distributor was not giving out any fuel to #5 at idle. apart from that the car ran well from hot or cold, just a slight stumble on acceleration. I got a rebuilt unit but the car wouldnt start from cold. A pressure check showed that the cold pressure was 40 psi. i had previously checked my cold pressure with the previous FD and it was only 20 psi. the only thing i changed was the FD and the cold pressure went up to 40psi. tapping the plugs in the WUR did not make any difference to the high cold pressure. Then the new FD started to leak so i had to return it. The company fixed the leak and tested the FD again. the FD was returned to me again im getting the same problem.

so were i am now is with my old FD the cold pressure is 20 psi and the car starts fine. with the new FD installed and no other changes, the cold pressure is 40 psi and the car only splutters. i then sent my old FD to get rebuilt but was told that it couldnt be rebuilt so now ive only the new FD that my engine just doesnt seem to like!!!

i have opened and cleaned the the WUR and couldnt see and faults. the cold control pressure is even 40psi when i remove all the springs out of the WUR. ive also tried putting the output of the WUR into a container incase the return tot eh tank was blocked with no help.

From my understanding the FD didnt have any control over the cold control pressure. also my system pressure is at 65psi for either FD installed.

can anyone please suggest any help as with the shipping from Ireland to the US several times this problem has been going on for months and i cant enjoy my porsche. im at the point of considering a tbitz efi conversion to say goodbye to the CIS..............

Dave27S · 06-18-2009, 12:27 PM

oh yeah, ive also read all CIS posts on here and couldnt find anything similar.....cheers.

MotoSook · 06-18-2009, 12:58 PM

Do you have the P-v-T curve for your car handy?

Don't take this the wrong way, but you've started with the classic mistake of CIS troubleshooting (making adjustments without know why). You replaced the FD, then knocked in the pin in the WUR without really understanding what's going on.

If everything was working (AFR was off) when you installed the ned FD, and you then changed the WUR, you'll now have to pull the pin out of the WUR to where it was to get the cold pressure to within the P-v-T curve.

With a new FD (or rebuilt) the the flow through it may have changed compared to the old unit. Did you get the correct unit for your 2.7?

Instead of knocking the pin in on the WUR, you should have verified the desired pressure per the P-v-T curve, and if it was within the range needed, and the car still did not start, you should have adjusted fuel and air at idle to get it to idle and run until you reached operating temperature, then made the adjustments to tune it. DON'T DO THIS UNTIL YOU LEARN A LITTLE MORE ABOUT CIS.

It is likely that the bad FD you replaced has been bad for sometime and the CIS was adjusted to compensate allowing the car to run acceptably...then with the new and properly working FD, you then need to adjust thems back to pre-compensated adjustments.

So let's assume your WUR will provide a good range of cold and warm pressure. With the new FD installed, compare the pressure to the P-vpT curve. If the pressure is within range, you will likely need to richen with the mixture screw and reduce air with the throttle bypass screw. You do this in very small steps until the car will start and idle.

BUT! Don't do this until you fully understand what will happen and why. Will the car start with the new FD if you prime the engine with a squirt of fuel by lifting the air plate? How long will it stay running? If it runs can you increase throttle opening to get it to increase revs? Can you move the throttle place quickly or will it die unless you do it very slowly...

There are lots of questions you need to answer before anyone can help you....but you need to brush up a bit so you cna provide good feedback. It's tough enough to fix a sick CIS in person....but via the web and with limited feedback....good luck.

Paulporsche · 06-18-2009, 01:09 PM

What WUR do you have? What is the ambient temp when you are trying your cold starts? What warm cp are you getting?

Dave27S · 06-18-2009, 10:33 PM

Thanks lads. i have a 0 438 140 033 WUR. I do have the P V T diagram for my car and perhaps my original post wasnt too clear but i have spent a lot of time on this by now. testing yeterday at 12 degrees C my cold control pressure should have been between 20 - 24 psi. This is what i was getting with the old FD. when it warmed up with the old FD it went up to 40 psi with the vacuum disconnected as per the chart. My CO2 level was set to 3.5% and the car seemed to run well at this.
The new FD has cold control pressure at 40 psi and the car will only start breifly i assume on the CSV fuel, then die. If i prime by lifting the air flow plate it will run for a few more seconds but with the same issue. With the high cold pressure the air flow plate is not easy to lift. The PO had tapped the small plug in the WUR so i can move it up or down.

With the new FD installed the car will only start then stop after a second or so, no difference if i try to open the throttle slightly. I seem unable to lower the cold control pressure as if the fuel flow through the new FD is too hgih for the WUR to handle. My FD was a 0 438 100 006 and the new one is the same part number but is slightly different in that is has small adjusting screws under each outlet.

I am fully open to me making troubleshooting errors or errors in the sequence of my T/S so i appreciate any suggestions you have, thanks

mca · 06-19-2009, 05:00 AM

Have you tested fuel flow from the new FD to the injectors? Might as well eliminate that as a possible issue.

T77911S · 06-19-2009, 06:01 AM

very good advise from souk.

why mess with the pin in the WUR when it was working?
when you said this, "the cold control pressure is even 40psi when i remove all the springs out of the WUR", it really stood out to me. did you clean the little screen in the top of the WUR? if the PO had modded the WUR, it may be bad. i think paul has found out that if the WUR is bad, no amount of adjusting can help.

with the adjusting screws at each outlet, sounds like you have a newer FD, one that used the frequency valve. the CP was controlled in the FD by the FV.
i believe the FV lowers the CP by diverting fuel back to the fuel tank, so if it was not there, the CP would be high or higher. someone help me on this, not sure if this is right.
i have been curious as to how one would work without the FV. would you need to leave the FV in but unplugged? remove FV and plug lines? remove FV and put in a straight hose? why are we here, what is the meaning of life, is obama really lurch from the adams family?

Mysterytrain · 06-19-2009, 07:27 AM

Dave,
So from what I gather the rebuilt FD was returned because it leaked, repaired and then sent back so it is still the same item with the higher CCP. I would have requested another unit! Also, from what I understand if you re-install the original FD the CCP returns to a normal state? If all of this is correct then I would think the problem is with the rebuilt unit. The plunger might be a problem or there might be a clog in the FD at the Pressure Regulator valve. That valve controls the system pressure and also has an orfice that meters fuel returning to the fuel tank. It is my understanding that a restriction in the fuel return will give a high CCP. Since this problem only occurs with the rebuilt unit I'm guessing that the orfice might be blocked.

T77911S · 06-19-2009, 08:09 AM

yes, restriction in return line will cause it too.

Dave27S · 06-19-2009, 10:17 AM

thanks guys, so to answer some of the questions, the car ran with the old FD and the pressures were within the limits hot and cold. Changing only the FD puts the CCP up to 40psi and the car wont run at all, only starts then stops. reinstalling the old FD and everything back back to normal.
when i first got the new FD i had the same problem and wasnt happy with it so it went back adn apparently rebuilt and returned. i had the same problem but shorlty after installation it leaked so it went back. I requested a different unit but was told that they had no more of the same part number to rebuild. so i sent my original back to be rebuilt but was then told that it couldnt be rebuilt and they returned the same new FD to me. i now have the new FD that i cannot get to work on my engine and my original FD is now gone!
i was under the impression and told by the company supplying the rebuilt units that the control pressure were only controlled by the WUR and nothing to do with the FD and it must be something else wrong with the engine but it doesnt explain how the original FD worked fine - with the exception of the no fuel to #5 at idle.......

jrairplane · 06-19-2009, 10:37 AM

Dave, I have a 74 and went through the same frustration. I finally gave up a bought a used set of Zeniths. I have never been happier. The car starts, runs and sounds great.
I got the carbs for $400 and spent another $150 with MM (I know this was a gamble- but I had good results with them).

My $0.02 worth

jrairplane · 06-19-2009, 10:40 AM

Oh, I forgot to add I think they look pretty too.

Jim

Dave27S · 06-19-2009, 10:44 AM

Thanks Jr, im at a point that i dont want to spend any more cash or money on this if i think im not going to get anywhere. i might be just trying to convince myself to go carbs or EFI...

James Brown · James Brown's Garage

Hang in there dave, the CIS system is a very adjustable system IF you understand how to do it. You must learn and understand how all the components work togeather to get it right. There are very few CIS mechanics left on earth so YOU must do it. SOUK has great info and look at the TONS of posts on this subject (20-30% of all posts)! When you changed the FD that changes all the other settings, just small tweeks and she will be purring in no time! Might look into the electronic WUR from unwiredtools. expensive but might fix.

Paulporsche · 11:22 AM

Dave,

I went through a whole wack of CIS troubleshooting and finally got the car running great. One thing I noticed that may impact you, is that I couldn't get the ccps to change to the correct levels until I got the warm cp correct. It seems that it has to be done that way. I had to pull the cold cp plug way up so it had no impact on the cp. The I tested w/o starting the engine. I then got the wcp set corectly via the large dia plug. Only then could I go back and set the cold.

Once I found a WUR that had a bendable arm and was actually working, I found this was the only way to get both cps right.

Dave27S · 06-19-2009, 12:03 PM

Cheers Paul and James. ill try that and see how i get on. i had a look at the unwired WUR alright and it looks good but im not sure if i want to spend a fair bit of cash on this if i eventually go down a different route! ill keep tipping away at it for the moment.

James Brown · James Brown's Garage

i'm cracking the tillamar dew for you!

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Mysterytrain

Dave,
So from what I gather the rebuilt FD was returned because it leaked, repaired and then sent back so it is still the same item with the higher CCP. I would have requested another unit! Also, from what I understand if you re-install the original FD the CCP returns to a normal state? If all of this is correct then I would think the problem is with the rebuilt unit. The plunger might be a problem or there might be a clog in the FD at the Pressure Regulator valve. That valve controls the system pressure and also has an orfice that meters fuel returning to the fuel tank. It is my understanding that a restriction in the fuel return will give a high CCP. Since this problem only occurs with the rebuilt unit I'm guessing that the orfice might be blocked.

Dave,

One reason why your control pressure has increased from 20 to 40 psi is the effect of some sort of flow restriction at the banjo fitting area at the backside of the new FD for the return line to the gas tank. Before I suggest doing a pressure test, inspect the banjo fitting for the return line.

If the restriction is in the return line per se, both old and new FD will exhibit the same high control pressure. Since the build up only occurs with the new FD, I strongly believe the culprit is in the newly acquired FD. Keep us posted.

Tony

.

Dave27S · 06-20-2009, 10:51 AM

Hi guys, further troubleshooting today. gave it time to think over night and tried it for a start this morning.....no joy

so i open the WUR again and tapped both plugs up. put it back together to try set up the WCP first. by the way its reasonably difficult to blow through the WUR, even in the springs are removed. anyway no matter how i tried to set the pressures, starting with the large plug first, the CP wont go below 40psi. putting a separate return line from the outlet of the WUR into a can doesnt do anything. i didnt check on the last one but quite a bit of fuel returns to the tank - or at least tries to!!!

how do i know what WUR/FD combo should be on my enigne. do i have a mix of worng part numbers or am i looking at an FD that just doesnt suit my engine or is somehow different to the original one.......ah time for a beer.

Paulporsche · 06-20-2009, 11:11 AM

Both components have part numbers on them. Ordinarily, you can check them against the PET on this site, but if your car is a ROW they may be different from US models. You may be able to access the parts via the Porsche website or the Bosch site. Or if you post them or Google them someone may be able to confirm for you.

Is the bimetal arm in your WUR straight or bent (not counting the little "hook" @ the end)?

Also, did you try removing and/or cleaning that little screen on the top?

You may be able to get the ccp lower by shimming the arm down by inserting washers between the plug and arm.