Cold weather drivability

[wolds]

Hello all, I have posted this question on the Rennlist site but the issue is not resolved and I thought I'd try here. I have a 1983 911SC ROW which I purchased in August of this year. The engine runs strong and up until the temps in central Ohio have fallen I didn't realize that the enrichment and elevated idle speed systems were not working. The car starts fine, but idle is low and sputters till it gets warmed up (usually within a few minutes). I have ordered a fuel pressure test gauge to access static, cold and operating temperature fuel pressures, but I thought I would post what I know so far and get your advise on how to proceed. First, I have confirmed that I have 12VDC at the WUR and at the AAR. I have also measured the resistance at both components. The WUR is 27ohms and the AAR is 21ohms. I pulled the AAR and observed that the valve is about 50% open when cold. I connected 12VDC to it an observed that it would fully close in approximately 2 minutes. I then put it in the freezer for 20 minutes to reset it back to its initial state. I have attached a picture of the WUR which I have a few questions about. First, I see a yellow electrical connector on the one fuel (return line?) coming off the WUR. Any idea what this is for and why it isn't connected to anything? Second, I ran accross a post from 05.15.2012 on this site from Vereeken in Belgium with a hand drawn picture of his enrichment circuit and see that there is a thermo valve in series from the WUR to the Decel valve. I don't have a thermo valve on my car, but I do have a tee coming off the decel valve with a 2nd piece of vacuum hose coming off it that is plugged at its end. If I had to take a guess I'm thinking that somewhere in the past the valve had been removed and the line plugged. Does this seem like a reasonable assumption? If so, do I need the valve and where does it mount? I'll have the fuel tester next Monday so I can speak about fuel pressures then. Any advise would be appreciated. Thanks, Warren

[boyt911sc]

Warren,

The extra fuel line attached to the return of your WUR is probably an electrical valve similar to your FV (frequency valve) and I've never seen one before until today. Secondly, I don't think you have the correct WUR for your car. It looks similar to a -034 WUR. Could you post the number stamped on it? When you get the chance to check your fuel pressures, post them so we could get a feel on what's going on with your engine.

Does the FV (frequency valve) vibrate when the FP is running? For your engine, you need both the fuel pressure gauge and dwell meter to effectively troubleshoot the problem/s. Keep us posted.

Tony

[wolds]

Tony,

My car does not have a CAT so I don't think I have a frequency valve. Regarding the WUR, I was going to pull it last night, but I couldn't get the large nut to crack loose on the WUR that holds the line coming off the center of the fuel distributor. I put some penetrating oil on it , but I didn't want to force it till I have the fuel pressure gauge. The vent tube on the bottom points right at the intake runner so there is no way that you could put a vacuum line on it even if you wanted to. I have a dwell meter, but the ignition is breakerless. Does it serve another purpose? I'll have my gauge Monday so I'll update the post when I have that data. Is the gauge setup as easy as just splicing it into the line from the distributor to the WUR using the adaptors that come with it? P.S., is there a service manual that would be better suited to working on a ROW car? Just an FYI, when I pulled the AAR the number on it was 0280140226. This number doesn't even show up when I run a part search. Warren

[Paulporsche]

You use the dwell meter on your car to set the duty cycle and (to a certain extent) the mixture.

In your case, it is obviously not for setting points.

As Tony said, pls post the pressure figures and let us know which WUR you have. I'm w/ him. I think your WUR shouldn't have any vac or atmo takeoff coming off the bottom as your O2/lambda system controls that.

As rule of thumb, always make sure all your ignition components--plugs, wires, rotor and cap are all up to scratch before you tackle the CIS.

[wolds]

Paul,

My car does not have a CAT, so I'm pretty sure I don't have a frequency valve, but I'll look. Can you clarify where it would be located if I did have one please? P.S., car has fresh plugs, cap and rotor and runs fine except for the cold weather warmup issue.

Thanks,
Warren

[Paulporsche]

I'm afraid Tony or others will have to help you re the frequency valve. As a ROW car do you have an O2 sensor and lambda control (under passenger seat)?

If not, then forget what I said about your WUR. The takeoff may indeed be correct. If you let us know the number, that will help.

Since ignition components are good, you should then check for vacuum leaks. Tony has several posts and threads on procedures and tools for this.

Finally, the control and fuel pressure figures are very important, as is the mixture %. It's very possible your control pressures are off, producing a lean condition in cooler weather, you have vac leaks, which will lean the mix and/or your mixture is simply set too lean. By knowing the figures and setting them right and making sure there are no leaks, you should be able to get your engine running correctly.

[wolds]

Thanks Paul,

Nothing under the seat other then the mounting points for a lambda control if it had been built for US market. I'll throw a vacuum gauge on it tonight to see what I'm getting. Old plugs looked good when I pulled them and gas mileage has been good also. Like I said, I'll have pressure data next week so that the issue can be addressed logically. Thanks for your help.

Warren

[Paulporsche]

Jim Williams' website on CIS:

http://www.google.ca/url?sa=t&rct=j&q=jim%20williams%20wur%20cis&source=web&cd=2&cad=rja&ved=0CDUQFjAB&url=http%3A%2F%2Fjimsbasementworkshop.com%2FCIS%2F&ei=0-V1UPSgCMPI0QGPh4GoBw&usg=AFQjCNG3OLbLw2WmW2a4YzdQ9ZEspp_OnQ

Also, you may not know this, but the "Search" fn on this site is amazing. Type in "CIS ROW" or " CIS WUR" or "CIS Test" and you'll get a huge amount of info on this. Every fall there seems to be quite a few owners w/ exactly your symptoms.

[wolds]

Paul,

Thanks for the link to Jim's basement, I see some good info in there.

Warren

[boyt911sc]

Warren,

If your car is without lambda, then it would be much easier to find the culprit/s. There are two (2) important criteria you have to verify:
1). Fuel pressures (control and system).
2). Fuel mixture. Aside from its setting, fuel pressure and unmetered air have considerable effect on the fuel mixture.

Since the engine is running, you have eliminated a couple of variables like ignition (sparks) and compression in the equation for solving your problem. Testing and verifying your results would lead you to better understanding of your problem if any.

When you get your fuel pressure tester, measure your control fuel pressure versus time. Just the FP running and battery fully charged. Example:
start.........? psi.
30 sec.
60 sec.
90 sec.
120 sec. and so on.
Up until the control fuel pressure stabilizes. No more than 5 mins. for the test. This would be your WUR profile. At the end of the test, close the valve and record the system fuel pressure. This simple test alone would give a good evaluation of your FP, WUR, and FD. Next step is vacuum/air leak test. Keep us posted.

Tony

[wolds]

Tony,

Thanks for the info. I'll be getting on this next Monday when the gauge comes in. Please clarify gauge install. I'm assuming that the test gauge simply takes the place of the line running from the fuel distributor to the WUR,is this correct?

Thanks,
Warren

[boyt911sc]

Originally Posted by wolds

Tony,

Thanks for the info. I'll be getting on this next Monday when the gauge comes in. Please clarify gauge install. I'm assuming that the test gauge simply takes the place of the line running from the fuel distributor to the WUR,is this correct?

Thanks,
Warren

Warren,

YES. I prefer to break the fitting at the WUR side instead at the FD side. Install the pressure gauge tester in series to the existing fuel line with shut-off valve by the WUR side so you could measure the system fuel or residual pressures. Some people do it by the FD. It is a matter of choice. Are you familiar how to manually run the FP by bridging terminals #87a-30 (FP relay socket) with the ignition @ ON position?

Could you find the number on your WUR? Thanks.

Tony

[wolds]

I can see where breaking the fitting at the FD would not be to easy. Hopefully I can break it at the WUR. I tried last night and the whole fitting wanted to turn. I put 2 wrench's on it, but couldn't get it to come free and I was a little concerned about putting too much torque on it and breaking it. Yes, I've read up on the fuel pump bypass. I'll be making a fused switch for it tomorrow. Are they typical 1/4" spade connectors or something else? Also, here's an observation I just made tonight. I pulled the electrical connections off the WUR and AAL, started the car and watched the rpm rise to 2K after a few minutes. I plugged the WUR connection back in and after a few minutes watched the rpm drop to about1800. Then, leaving that connection together I plugged in the AAL and after 2 minutes the rpm had settled down to 950 which is where I have it set warm. Car hadn't been run since last night and the garage was about 50 degrees F. Any thoughts? Warren

[javadog]

When you unplug those things, you eliminate the effect of the heating elements in each of them. For the WUR, that means the only heat that it gets is what comes from the engine, which won't be much at first. That keeps the fuel pressure low, which keeps your mixture rich. Killing the power to the AAR, you keep it from warming up so it stays open, thus bypassing more air into the motor. Voila, higher idle speed.

JR

[PrimeMvr]

Align your wrenches on the wur fitting so you can grab them both with one hand and squeeze. You can get a good amount of torque this way without spinning the insert out of the wur. If that doesn't work, squeeze them with a large channel lock pliers.

[wolds]

Thanks for the tip, I'll give it a try. One more thing that I observed was that when I pulled the vacuum hose off the WUR there appeared to be no vacuum signal at the open end. I didn't get a chance to trace the line back to its other end so I'm not sure where it was connected at this point. I'll look tomorrow night. Warren

[wolds]

Well, here's an update on my WUR. It is PN 0438140103. I'll reinstall it tonight and gather the pressure readings. I also found the connector for the thermo valve that had been deleted. First off, anyone know what year my WUR is supposed to be on? From what I gathered so far on this post is that my Euro spec should be running an 089. Also, do I need to have the thermo valve back in the car if I'm planning on cold weather driving?

[Scott R]

That WUR part number if for a Benz 110. Also sure it came from a Benz by looking at the WUR bypass kit that someone installed.




Like this ^^

Benz guys have this hooked to a box that bypasses the WUR under certain conditions. How it ended up in your car is probably a story only the PO can tell.

0-438-140-089
911 606 105 09

Is the correct WUR part numbers for your vehicle. Probably best to start by sourcing the correct WUR and start sorting out the other issues.

[boyt911sc]

Originally Posted by wolds

Well, here's an update on my WUR. It is PN 0438140103. I'll reinstall it tonight and gather the pressure readings. I also found the connector for the thermo valve that had been deleted. First off, anyone know what year my WUR is supposed to be on? From what I gathered so far on this post is that my Euro spec should be running an 089. Also, do I need to have the thermo valve back in the car if I'm planning on cold weather driving?

Warren,

WUR-103 was designated for Mercedes Benz 280 cars circa '76-'85. If you are familiar with the Bosch WUR's you could switch them but -103 is completely different from -089. I could lend you a thermotime valve and a -089 WUR. And try them on your car. I'll be on vacation starting tomorrow and will be back home after 2 weeks. For the meantime, pressure test your engine and verify that you don't have air leak/s. Let me know your plan.

Tony

[wolds]

Thanks Tony and Scott

Yes, I discovered just before reading both of your posts that my WUR was off of a Mercedes. I'm assuming that the WUR I have has a different "warm-up" curve? I am looking for a graph of one to see. I will take you up on your offer for the loaner parts and what you need for them. You can call me at 440-725-8751 if you have a chance. Will the mounting position of the thermo valve be obvious once it's in my hands? . When you get back from your vacation we can work out the details. I'm going to do a graph of my WUR to see how it compares to the 089. One other point, if I change out the WUR for the correct one will I have an issue with the tee'd fuel line coming off it. I'm assuming that the line coming off my incorrect WUR is not correct for my car. Warren