911 SC Warm Up Regulator problem?

[lizhuo]

Hi - I would appreciate some maintenance and tool advice on backfire problems I'm having. Here are the details and symptoms:

1982 911 SC with 201,000
Valve job; oil & filter; air filter at 200K
Oxygen sensor at 156K
Fuel Filter - maybe at 171K

I just installed the pop-off valve this past Fall and immediately began experiencing backfires and hesitation whenever step on the accelerator after I start (cold or warm days). It does start immediately without trouble, but the idle is rough. It doesn't backfire until I step on the throttle. The car runs just fine and starts fine after warming up for about 5-10 minutes.

I received advice to check if the enrichment sensor (below the a/c compressor) had been disconnected. It was connected. Just to be sure, I disconnected; tightened the clip; and put a little dielectric on it.

I was advised that since the car starts without trouble - it probably was not the cold start switch. But that I might have a clogged Warm Up Regulator (WUR).

With the leads disconnected from the Warm Up Regulator (WUR). I measured the resistance across the terminals and got 36 ohms. Bob Tindel's guest article at Pelican gave some info on the WUR, but it also raised questions:

1) Do you think my backfire problem at starting is due to the WUR?
2) How do you remove the WUR to clean it? The Bentley doesn't seem to describe doing anything with the WUR.
3) What exact guage do you use to adjust the control pressure? Tindel's article calls it a CIS guage from JC Whitney. Is this the same as a "fuel pressure guage"? Where can I get one?
4) What are the correct pressures for the '82 911 SC?

As you can tell - lots of questions. I appreciate any suggestions and answers to questions that I don't know enough to ask.

[emcon5]

Originally posted by lizhuo
installed the pop-off valve this past Fall and immediately began experiencing backfires and hesitation whenever step on the accelerator after

Are you sure there are no vacuum leaks around the pop off valve? To me, running good before/bad after raises a big flag. It is possible that they are unrelated, but that is the first place I would look.

Tom.

[rfng]

Richen your mixture.

[Targa77]

I agree with the post about the pop-off valve. Check that it is sealing good around the edges.

[wckrause]

A vacuum leak as mentioned above seems like the first thing to look for, but here is the CIS pressure tester you'll need

CIS pressure tester

The WUR has a small metal disc diaphram that you can clean. You can turn it over so that you get a clean side against the fuel openings. I wouldn't do anything to the WUR until you get the pressure tester and verify that it is out of spec for both cold and warm control pressures.

The Bentley manual has a control pressure vs. temp. graph for your car. It may be in the archives of this board somewhere, or I can post it for you when you get your CIS tester.

[lizhuo]

I appreciate the advice received.

I've ordered the CIS fuel injection guage. I'll also double-check the seal around the pop-off valve. However, I put a lot of epoxy around it's edges when installing.

Another SC guy noted that he did not believe it to be a pop-off "air leak problem because it would run lean at warm idle and off idle." The vehicle runs just fine, once it warms up.

Som tips on how to richen the mixture and/or making the adjustments once I have the guage would be appreciated.

Thanks in advance.

[Jdub]

liz:

When you check your popoff, make sure there is epoxy all around that puppy. Pull the rubber o-ring inside and take a good look at it. Replace with a minimal amount of silicone grease or equiv. to help seal. See that the popoff snaps back nicely. Finally, put a dab of sealent at each end of the pin holding the cap to base. See that this pin is not off center, but centered with even amount of pin at each end.

Now check the airbox. See that you cannot get a fingernail under any of the screws at the floor of the airbox. If you can, the airbox is possibly blown.

John