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Gene · Posted: Tue Mar 13, 2012 8:18 am Post subject: '79 924 control pressure to high

Warm control pressure is 72lbs should be no higher than 55 lbs with valve open. System pressure is ok at 74 lbs. Car won't rev up past 4 1/2 grand but if I back off the gas pedal 1/3 it will climb up to 5 1/2 grand. Put a rebuilt wur in and no change, sent it back for another wur thinking it was bad and still have the sane readings. Did a gas volume test and its ok, and getting about .04 of an oz of fuel from each injector in 10 seconds. Before I pull apart the fuel distributor any one have an idea whats wrong ?

Joes924Racer · Posted: Tue Mar 13, 2012 9:22 am Post subject:

Hey never heard the pressure numbers before in lbs.

You know you can remove shims from the fuel diz. to lower pressure
right.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Gene · Posted: Wed Mar 14, 2012 3:10 am Post subject:

Well if you look in the Haynes or the Bentley manual they give the pressure readings in lbs and in bar, check it out.
Yes I know that I can adjust the system pressure but I said system pressure is correct, its the control pressure that is way to high at 72 lbs, should be 49 - 55 lbs range.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Seems like the metering head is likely at fault (or possibly a blocked or kinked return line), but how is the cold control pressure?

Also, adding the year and model of your car to your signature line can help get your questions answered accurately.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Gene · Posted: Wed Mar 14, 2012 3:47 am Post subject:

Cold or hot pressure is way to high, I agree, the fuel distributor must be at fault or I got 2 bad wur's in a row, not likely. Procrastinating about pulling apart the fuel distributor as I've never been inside one before, worried about getting replacement gaskets and o rings or losing plunger etc.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Before you do that I would pull the return line and check for obstructions. Maybe also blow out the passage where the return line bolts to the metering head with solvent and compressed air.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Gene · Posted: Wed Mar 14, 2012 3:51 am Post subject: '79 924 control pressure to high

Forgot to add that I checked out the fuel return line and it was ok.

Gene · Posted: Wed Mar 14, 2012 3:56 am Post subject:

Yes will have to do that also, but it did pass the fuel volume test ok so don't think there is an obstruction any wheres

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Volume would not be affected if the WUR return port were clogged.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

FYI, this thread has the complete set of diagnostic instructions for the CIS quoted directly from the Probst book, and should help you isolate exactly what the issue you is so you don't have to guess.
http://www.924board.org/viewtopic.php?t=35734

If it turns out your fuel distributor needs rebuilt, you might consider sending it out to a specialist for rebuilding given the need for proper sealing and the fairly precision o-rings required to do the job properly.

I believe Rasta has had reasonable success with Special-T (although I think they do not do the work in-house), and I've been very pleased with Jaytan Industries, who do the rebuilding in-house. They were courteous, knowledgeable, quick turn-around, and provided excellent warranty support on one unit that I had to return due to a malfunctioning port. (Apparently, one of the o-rings got pinched on re-assembly...so even the experts can muck it up!).
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erstwhile owner of just about every 924 variant ever made

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Gene · Posted: Thu Mar 15, 2012 3:58 am Post subject: '79 924 control pressure to high

Yes I'll have to check out the return port with solvent and compressed air, next will pull apart the fuel distributor and if I find no dirt or tore o ring etc will send it off. Took it for a test ride yesterday, top speed was 40 MPH and kept dropping speed till it quit on me after a mile. Started back up right away but kept dropping RPMs all the way home.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Heh, that brings back memories. . .I've limped aournd Fort Fun in a few POS cars in my day.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ptheskil · Joined: 03 Aug 2004 Posts: 128 Location: Essex, UK

Where did you get the rebuilt WURs from and can you be 100% sure of the quality. Sounds to me like a WUR or lines problem. There is no likely failure mode for the head which would result in higher hot and cold control pressures. Although there could be a problem if it was rebuilt incorrectly or mucked around with.
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1981 931 series2 Euro spec

Gene · Posted: Fri Mar 16, 2012 2:52 am Post subject: '79 924 control pressure to high

I got the rebuilt wur at Euro Port Parts, manufacturer was Python. When I put the first rebuilt unit in I had correct control pressure for a few minutes than went to high readings ,sent it back and with the second rebuilt wur it never showed the correct lower pressures, reads the same pressure as the first wur. Could be two in a row that are bad, but I put in a couple of wur's that I had in the car over the years that caused cold starting problems and I have the same high pressure readings from them and they always showed correct system and control pressure readings just cold start problems so this makes me think its not the rebuilt wur's. I'll pull off the lines and check them out. Car has only 88 K on it. Problem did start a few days or weeks after I replaced the fuel filter last year so dirt could have made its way into the distributor.