Jim,

A couple of silly questions

1) Wouldn't I get zero pressure reading if the line between FD and WUR was plugged? That is where I have the guages currently connected, reading 68 psi. I may be missing something and please forgive my ignorance on CIS.

2) Can I perform this test by lifting the sensor plate and jumping the fuel pump at the relay socket? I would be very nervous doing this with the engine running... (unless I can get a friend with a fire extinguisher in hand I suppose).

I'm tempted to perform this test right now, but I also think I should do this in daylight. First thing in the morning.

Gotta find where that blockage is. Thanks a bunch for sticking with me on this problem

Tarek
'79 SC

Tarek,

For 1), It depends on how you have the pressure guage connected. You can hook the guage up in a couple of different ways. One is to take the normally connected fuel line between the FD and the WUR off at both ends and use the lines supplied with the guage to connect the FD and the WUR. The other is to leave the stock FD to WUR line connected at the FD, and connect the guage line to the other end of this line instead of the FD.

If you have the guage connected this latter way, and the FD to WUR line were blocked you would indeed read zero pressure. But since you don't read zero pressure, you don't have a blocked line here if you indeed have the guage hooked up like this. So that is not a silly question.

2) You can and should perform the test without the engine running. You can jumper the relay to do the test. I use a test wire with an alligator clip on one end and a banana plug on the other. I remove the fuel pump relay in the front trunk, insert the banana plug in pin 30 of the empty relay socket and connect the alligator clip to a normally "hot" fuse post on the relay panel. The pump will run as long as you have the jumper connected. Having the fuel pump running is all that's necessary to do the checks I mentioned.

To do a cold WUR pressure test, pull the 2- pin electrical plug to the WUR before you run the fuel pump. For the warm WUR test, just put the connector back in.

You don't raise the air flow sensor at all for these tests. Monkeying with the air flow sensor with the pump and not the engine running will dump raw gas into the cylinders, and if you do this long enough it can hydro-lock the engine.

Thanks Jim. Yes I had the guages connected at the WUR-FD without eliminating the line.

Update:

1) Fuel is flowing out of the WUR, as proven by the test you recommended.

2) Start up has improved dramatically, but I'm wondering if it's related only to warmer ambiant temperature

3) Still missing and backfiring during road test, but far less than before. Again, not sure how warmer temperatures have affected this. Running hotter though, which is not surprising, as the assumption is that it's running lean. Good thing I had a fan on the fender mounted oil cooler. Saved it from going all the way to red.

4) still no changes in pressure readings. warm or cold

Where does the line out of the WUR go to? It would save me a lot of time feeling my way behind the engine if I know where the other end is. Should I be under the car at the fuel tank at this point?

Thanks in advance
Tarek
'79 SC

ok another update:

I disconnected the return line to the fuel tank and plugged the tank side. I ran the pump without running the engine, and the return line did not seem plugged. Steady stream of return fuel came out of it. Meanwhile the guage still read 68 psi

What does it mean? is it proof enough that there is no blockage in the return track?

Thanks
Tarek
'79 SC

Try knocking the plug to lower the cold cp to the pressures quoted.

Tarek,

I have been thinking about the test I recommended. I neglected to mention a step in this test which only now occurred to me. There is a possible scenario that didn't occur to me to pass on until I read over your results. Did your control fuel pressure (with the valve open) remain high when you noted the fuel flow from cracking open the WUR return line? If it did, the fuel flow you noted could have been "backwash" from the fuel returning to the fuel tank consisting of the bypassed fuel from the regulator in the fuel distributor.

So the test I suggested would really only be definitive, if the return line from the WUR were blocked off so that the "backwash" from the return line didn't get mistaken for fuel coming through the WUR. Does this explanation make sense to you?

If you'll go to the CIS pages on my website, <http://members.rennlist.com/jimwms/CIS/CIShome.html>, and click on Basic Fuel Diagram, there is an early version of the CIS system. Your car won't have the Throttle CPR, and instead of the yellow return line from the WUR going directly to the fuel return back to the tank, it is routed through the FD before going back to the tank.

The line out of the WUR on your '79 should go back to the FD, where this return fuel gets dumped into the same passage that carries the return fuel from the FD back to the fuel tank. So there would probably be enough pressure at the place you opened the fuel line, for fuel to leak out *if* the WUR was blocked. I have a "tool" that I use to block off a banjo fitting, consisting of a hex bolt, two copper washers, and an acorn nut to fit the bolt. The Banjo fitting is sandwiched in between the two washers and the bolt passed through and secured with the acorn nut. then if you just tap the jumper to the Fuel pump, with a rag over the open WUR return, you can tell it if the fuel you are seeing is coming through the WUR.

Hope this helps some. Sorry for the delay in getting back to you.

Jim,

Thanks for the link and info. I repeated the test, this time with the banjo fitting plugged as you described. (Also still had the return line at the tank disconnected)

Fuel flowed out of the WUR, however, it wasn't like a fountain, as I would have expected. Pretty slow flow that did not go beyond 2 mm or so beyond the top. Enough to create a liquid layer and flow to the sides. Is this normal or is that a poor indicator on the health of the WUR?

Meanwhile, the return line at the tank flowed pretty strong.

Pressure reading WUR-FD is still the same

Thanks again for the help

Tarek

Thanks Paul for the advice. I like to believe I'm mechanically inclined, but must admit I'm shy about certain tasks or procedures. But since I'm getting to a point where I have less to lose, I'm building up the confidence to do this. I'm in research mode on doing this right now. I just hope I don't whack the thing too hard or create a new problem.

thanks again
Tarek

Scott,

The heating element looked good and clean with no visual indication to the contrary. If I take it apart again, I will make sure to re-measure.

Yes I might have to send it to these folks. Thanks for the info and recommendations

Tarek
'79SC

Tarek,

Based on your test, I'd have to say the WUR is the problem. You've taken the return line from the WUR out of the equation, and with system fuel pressure on the input side, and very little fuel out on the output side, it's obvioulsy plugged.

If you wanted to play around with the guage you have connected, and can find enough miscellaneous fittings to do the plumbing with, you could try the following:
take the WUR out of the circuit, and in it's place plumb in the guage. This would be: fuel line out of the FD to the gauge, and then on directly to the return line that was connected to the WUR. Now the valve on the guage is taking the place of the WUR, and in effect is an adjustable control pressure regulator. If you start with the valve closed, reading system pressure, and slowly open the valve until the guage reads the same as the cold control pressure, you could start the engine, and as it warms up, slowly close the valve until it reads the same as the warm control pressure. If the fuel mixture is anywhere close to where it should be with a properly working WUR, you could actaully drive the car, but not expect it to react properly during acceleration or WOT. If playing with the guage gives similar readings as what the WUR might give, this would be further confirmation of the suspected problem.

(Too cold to be in the garage tonight, and this is what happens when my mind starts wandering around while sitting here at the computer,)

Jim,

Unfortunately I couldn't get the required harware to plumb as described.... now I'm wondering if I should knock the plug or make the WUR adjustable. Problem is, I couldn't find any information on how to knock the plug. Should I just 'hit' it with soft blow hammer? sounds brute, but I'm wondering.

Thanks

Paul,

As you can see, I couldn't find info on how to knock the plug for some reason. Cou;d you please forward any information you may have?

thanks

Also, does anyone know if I can separate the inlet/outlet housing of the WUR from the WUR body? I'm wondering if taking that component apart and cleaning it will do.

Car running reallly really bad. max speed was 50 mph and sputtrting last night
thanks
Tarek
'79 SC

I made an adjustable WUR from the info published. It was handy in setting cold pressure. It was just a pain blipping the throttle to keep it running in that the car stayed rich all the time, thus I had to adjust the fuel distributor leaner to compensate. The fuel pressure never changed during the warmup phase. It was the heating element in the WUR.
I bought a WUR from Pelican and it starts perfectly from dead cold. Idles up a bit during the Aux air valve phase (2 min tops) then settles to a 900rpm for an added 5 min and then fully warm at 1000. I live with it.

Do the freezer test with the aux air valve. Take it off and put it int he freezer. Look through the hole after a few minutes. It should be open. Then hook up a 12 volt power source to the leads to watch it close.

If it's closed all the time then your car isn't getting that extra air into the starting phase.

I do think your WUR should change pressure during the warm up phase with your guages hooked up like the test procedure states.

Jim,

I was able to replace the WUR with the gauge. Set it to 30 psi and it started right up. Idle seemed a little high, around 1000 rpm. As it warmed up, I set the pressure to 50 psi and it's all good, except for idle being high, around 1000 or 1100 rpm. No sputtering or backfiring as I revved up. Now ready to go on a road test.

...I guess that confirmed yet again that the WUR is bad, didn't it?

Any sense in messing with the WUR to fix it, or should I just bite the bullet and buy a new or rebuilt one?
Thanks

Tarek
'79 SC

Good test, great idea. And yes that's a bad WUR. Once you get a good working WUR you will most likely need to have the mixture and idle speed set to get it right again.

Just got back from a short road test. Holy Crap the car is so much faster... I guess I had forgotten it was a Porsche ever since the symptoms of the WUR problems. Now restart is a bit tricky still. I kept it at 50 psi. Not ideal for cold start, but a lot better than before (which was 68 psi).

..Now for the longer road test

Tarek
'79 SC

Not to presume to answer for Paul, but check this Pelican link:
<http://www.pelicanparts.com/techarticles/911_warmup_reg/911_warmup_reg.htm>

I think there is more info posted on the PCA website if you are a PCA member.

Thanks Scott. I guess I'll be asking for help here for setting the mixture and idle speed correctly

Tarek
'79 SC

I always have to go to my p-car wrench, he charges me $21.00 for a mixture set. The reason being that I don't have three gas analyzer in my garage, and well he does. I just can't get it where I want it doing it by hand, I either get cold start hunting, or surging when warm. When my wrench sets it, its spot on perfect.