924Board.org

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

When pressurized the piston will have 30 to 40 psi pressing against it so yes there should be resistance. The warm up regulator (AKA control pressure regulator) is located behind the intake manifold.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

TajMan · Posted: Mon Jan 10, 2005 4:22 pm Post subject:

TajMan · Posted: Mon Jan 10, 2005 4:27 pm Post subject:

Smoothie · Posted: Tue Jan 11, 2005 4:11 am Post subject:

The WUR is well hidden. You can just barely see it here below-front of the coil as a flat piece of aluminum with two thin metal lines running over the left side of it - http://pg.photos.yahoo.com/ph/smoothies931pics/detail?.dir=bdb3&.dnm=d9f3.jpg&.src=ph

Yes - the CSV is attached to the rear of the submarine sandwich shaped part of the intake manifold. It's located dead-center in the above picture.

Yes - with fuel pressure in the system, the fuel distributors' piston should always be in contact with the air metering mechanism.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

Photos 1,2,3,6,8 & 10 have the Control Pressure Regulator (AKA the WUR) pointed out, in addition to a lot of other engine compartment components. Click the photo below to go to that photo gallery.

The piston should be in constant contact with the lever attached to the air metering plate. If you jumper your fuel relay and press the metering plate you should feel resistance from the start. But, unless the injectors are pulled (or lines disconnected), don't do this, as fuel will be injected into the head.
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'79 Eurospec 931

TajMan · Posted: Tue Jan 11, 2005 11:08 am Post subject:

My fuel distributor is off again soaking in a heavy duty carbuerator cleaner that the guy at NAPA recommended. I also got some seafoam I was gonna use when the car is running, is it strong enough to do anything if I let it soak in seafoam? I am 95% sure that the problem is still the fuel distributor with the way that piston slid out, it was in there pretty tight still, and I know that with fuel pressure from the pump it wasn't sticking out far enough to contact the arm of the metering plate when in the closed position. If it doesn't slide easier after soaking for a night then I'll look for a used/rebuilt fuel distributor.
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'87 924 S

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Just curious, does the piston look gummed up at all? I imagine it should have a noticeable discoloration from the dull brass color if it has enough deposite on it to be sticky. -Or else the deposite are in the fuel dizzy bore. As I recall, the pistons don't really "just fall out", I had to grab it with the tips of my fingers to pull it out. But it did come out smoothly.

I haven't been following this thread too closely, but if the piston is sticking then a simple test would be to turn the fuel pump on with the injectors in jars (to check the fuel output). With the engine off, the fuel pump on, and the metering plate in it's stationary position, I don't think you should see any fuel from the injectors at all. If you don't then deflect the metering plate fully then pull it back to rest. If the injectors are now spraying more than they were before when the plate was at rest then the piston is sticking. Fairly straightforward test of the piston.

Have you checked individual injector output? If one injector pumps out a lot of fuel and swapping injectors doesn't fix it, then the fuel dizzy is leaking internally.

ps- haven't used seafoam, but Chevron injection cleaner with techron is recommended by everyone I've ever talked to (although I don't know what exactly makes it so much better).

nick

TajMan · Posted: Tue Jan 11, 2005 3:23 pm Post subject:

When I pulled it out the first time there was actual dirt and deposits on it. I had to really grab it hard with pliers to get it out (I only grabbed the protruding tip so I didn't mess up the sides). After cleaning that off I thought it would be enought. I still had to use pliers to get it out the second time, I believe there is some varnish on the bore of the fuel distributor. I don't see any discoloration on the piston itself.

I never correctly tested all the injectors in jars, I just did that real quick to see if fuel was coming out of them at all before it started the first time. I did notice that around the same ammount leaked into each one when I did it, but after that I pressure cleaned the fuel injectors and some of them seemed to clear up a lot from how they were at first.

I'm trying to figure out a good place to use seafoam on this car. I usually do it in the brake booster line to the intake manifold.

I guess if I think the piston slides in the fuel distributor smoothly when I put it back together and the car doesn't run, I'll get that CIS tester or take the car somewhere that has one.
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'87 924 S

TajMan · Posted: Wed Jan 12, 2005 5:03 am Post subject:

IT RUNS!

After soaking in that cleaner the piston slid in extremel easily, I could hold the fuel distributor right side up and the piston would fall all the way out by itself! Put it all together and she started it right up, I knew I was right on the fuel distributor issue.

I gotta run to my new class I'm starting today but when I get home the first thing I'll do is change the oil.

One problem I noticed it still has is that after I made a run around the block and the car was idling, the tach would drop below ~500 rpm's and really shake / sound like the car was about to die for sure but then the they'd shoot back up to 1K. It would idle surge back and forth like this. Any ideas?
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'87 924 S

TajMan · Posted: Wed Jan 12, 2005 11:14 am Post subject:

I get home and try go bring it into the garage. The car started and ran for a second, but it did its idle surge thing and actually died this time. Wouldn't start again damnit! It is really cold and wet outside right now and it wasn't earlier, I don't know if that has anything to do with it. I guess I'll go at it again tomorrow....
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'87 924 S

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

I hate to keep re-hashing old ground, but you really do need to systematically approach this. This post has gotten so long I'm not going to go back and see exactly what has and has not been done, and in what sequence.

But, if you have not already...
Test the pump's throughput by measuring the return at the fuel distributor.
Test the injectors pattern and throughput by pulling all of them and putting them in small jars. Jumper the fuel pumps and depress the airflow plate a measured distance. Check each injector's pattern and measure the output of each injector over a given time. The volume should be very close to one another. I don't know what the tolerance is, but it probably should be within 5%, most-to-least. If the output isn't the same, swap injectors/lines and re-test. If the low volume follows the injector, then it's the injector that is the restriction. If not, it is either the line or the distributor itself.

Then, re-test at a greater measured airflow plate deflection for the same length of time. If it is deflected twice as far, you should be getting nearly twice as much (if not more) fuel.

If these test-out good, then I suggest you find someone who has a CIS gauge.

Your last post said that you initially found dirt in the bore of the distributor's plunger. If this is the case, I suspect that your distributor has internal corrosion and it will have to be rebuilt/replaced.

The Board is here to help, but you need to avoid "willy-nilly" fixing things, or taking a shotgun approach.

Here's the CIS troubleshooting page from the Factory Manual to help diagnose the system:

Click for full size image - caution, it's a large file to download
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'79 Eurospec 931

TajMan · Posted: Thu Jan 13, 2005 8:44 am Post subject:

I now know whenever the piston is sticking in my distributor because the metering plate won't have resistance right away with the key on (pressure in the fuel system).

Today I removed it one more time, messed with / cleaned it, and re-assembeled. Car started and ran / idled fine. I brought it into the garage and changed the oil. Good thing I did right away, cause my oil looked like it was 50% gas!!!

Car seemed to run fine and start every time I wanted it to.

Later, my little brother wanted a ride.

Of course as soon as he got in it wouldn't start this time.

Every time the car won't start its because the piston in the fuel distributor gets stuck up causing fuel to constantly pour out of my injectors whenever the key is on.

I know for sure my fuel distributor is the problem so you can all stop the suggestions about systematic testing and CIS pressure testers, etc.

I do want to thank you all very much for the help with the car though, I wouldn't have gotten it were it is without the help. I'm an active member of the 3SI.org (3000GT/Stealth) message board and know a lot about those cars, I'm often helping noobs with that platform through the same type of troubles, so I know what its like from both ends.

NAPA can get a new fuel distributor, guess how much, OVER $900!!! That blew my mind, I didn't think it would be that expensive from Porsche. I guess I need to look for a working used or rebuilt unit.

Anybody know the best place to get a fuel distributor???
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'87 924 S

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

It is an expensive part. You might luck out and find someone with a used one here on the Board, but buying a used one that has been sitting around is an "iffy" proposition. As has been said before, these fuel systems don't like to sit for long periods.

There is a guy outside of Dallas who has been supplying us with CIS parts ($370 for a 931 dist. head), though there have been a couple of reports that he is taking a while to get the core charges ($250) refunded. It would be up to you to ensure that communications are maintained, and that your funds don't fall through the crack. He rebuilt my unit and I've had several other transactions with him without any problems, but I am only one individual. Get the Bosch part number off the fuel distributor's data plate and check his web site. You may be hard pressed to find a better price. (standard disclaimers apply, I have no affiliation, etc, etc...)

John Hervey at http://www.specialtauto.com/porsche-parts/index.html
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'79 Eurospec 931

Paul · Posted: Thu Jan 13, 2005 11:27 am Post subject:

Let's see, you clean the fuel distributor and it runs, a little while later it's plugged up again.

Any chance your fuel system is still contaminated?

TajMan · Posted: Thu Jan 13, 2005 2:49 pm Post subject: