924Board.org

[Tiny]

Hi All,

Today my friend returned to the UK with my K-Jetronic Fuel Pressure Tester in his luggage!

can be seen here:

http://www.bmpdesign.com/product-exec/product_id/447/category_id/16/search_year/1980/search_model/12

The leaflet with it seems very brief, so I did a few searches on the board and googled to try and find a good write up on connection setup to test the cold/warm control pressure, and system pressure.

Does anyone know of a good write up/hyperlink for this online?

I'd like to take some pictures and create a post for the "How To" section on this board using this tester, as I feel that many could benefit.

Mike, if you're reading this, I'll gladly send this kit on down to you for a play afterwards.

Kind Regards,
Tiny
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*****1981 - 924 - Auto - London, UK******

[Smoothie]

I updated the pic links here -
http://www.924board.org/viewtopic.php?p=149394
(1 diagram + 3 pics there)
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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

[Smoothie]

Here they are again -

The diagram -
<click>


Pics of the gauge hooked-up - the last 2 show the hook-up, pic 2 in better detail (click for larger pics) -

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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

[Tiny]

Yay Superman Smoothie,

You were my next port of call, as I was just reading (that) your old post.... with those old yahoo links = ]

thanks so much man! Woohooo!

Tiny
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*****1981 - 924 - Auto - London, UK******

[Smoothie]

-a bit more info if you have the differing control line hookup at the fuel distributor - http://www.924board.org/viewtopic.php?t=21487&start=7
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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

[D Hook]

[Mike924]

[Tiny]

Hi all,

Following a control pressure test from cold engine switched off, I run the fuel pump and get a reading of 17psi.

However, this pressure does not hold when I shut the fuel pump off, the pressure slowly drops to 0 over about 20 seconds....and when the needle gets to 7psi I hear a high pitched noise coming from the fuel dizzy and then the needle quickly falls to 0 and the noise goes away.

Is this correct? or does my pressure regulating valve need attention/adjusting?

I did a system pressure test and it reads fine (65psi) when the pump is running, and it also seems to hold at 29 psi when the pump is switched off so I think the check valve and accumulator are OK.

I pulled the injectors and CSV no leaks or drips. Fuel Flow test looks fine.

When I start the car the control pressure does slowly start to rise from around 17 psi.

It's just that the car wont idle without feathering the gas when cold.

Once warm it's fine.

I am going to check the whole system for pressure leaks by warming the engine and shutting off monitoring the pressure drop over ten minute intervals, as stated on p77 of the haynes.

let me know what youg guys think on the pressure regulating valve?

thanks,
Tiny
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*****1981 - 924 - Auto - London, UK******

[Mike924]

Getting the hang of it then, Tiny?

Don't worry about the control pressure dropping when the pump is turned off. The pressure regulator valve is doing its job if your system pressure is 65 psi.

As for the check valve/accumulator, you need to check the pressure after 20 mins. I think the limit is 17 psi...?

There is a graph in the Haynes manual which shows how the control pressure should rise with temperature, but the important thing is that is settles at 55 psi (IIRC, the proper values are in the Haynes book) when the engine's warm.

If feathering the throttle improves the cold idle, then your Aux. Air Valve is either blocked or stuck (assuming, of course, no vacuum leaks!)
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[Smoothie]

Your symptoms, with the control pressure dropping to zero so fast, indicate a bad o-ring on the push-up valve (part of the fuel pressure regulator in the fuel distributor). This push-up valve is supposed to close the return from the WUR when you shut the engine off, to hold pressure in the system. If it's leaky, pressure in the whole system (fuel dist, injector lines, WUR and its' lines, and CSV line) is also dropping faster than it should after shutdown. -But that would only account for a hot start problem, not a cold start problem. For crappei cold idle, look to vacuum leaks, AAV opening wide enough, A:F mix, tune-up (wires, cap, rotor, and plugs).

<click> for larger..

The push-up valve is that cone-shaped part pointing to the left at the right side of the pressure regulator. The o-ring is at the narrow end of the cone.
_________________
"..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

[Tiny]

Hi Mike, I hope I am getting the hang of it!
I was wondering about that Smoothie, thanks.

Here are the findings of my warm up and then shut down system pressure test. p77 haynes

Car warmed to running temp / Fuel Pressure levelled at 51psi (CIS tester valve open)

Shut engine off and Fuel pressure psi went to to 33psi

Waited 10 minutes and needle slowly decresed to 27psi
(this is just within haynes spec of being between 27 and 29psi)

Waited a further 10 mins and needle was at 24psi
(haynes says should be no lower than 23psi)

But then...... during the 23rd minute of waiting....suddenly the needle fell much more rapidly from 20psi to 0 in (over about 20 seconds.)

Is this still symptomatic of the bad o-ring on the push up valve?
I do have the hot start prob btw.

thanks guys
Tiny
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*****1981 - 924 - Auto - London, UK******

[Mike924]

Two posssible explanations spring to mind:

1) the WUR resetting as the engine cools and dropping the pressure through the leaky O-ring as Smoothie says

2) the accumulator running out, having emptied itself through the leaky seal or via some other route...

Ozzie gets the prize for the best lateral approach to the hot start problem, Any leakage has to go via the fuel return line, he reasoned, so he just stuck a 25 psi regulator in the return.

Me? I forked out for a new accumulator. Sloved the hot start problem to the point where it's not a problem anymore, although it still could be better. I suspect I have a slightly leaky regulator O-ring, too...
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[Ozzie]

[Tiny]

I whipped out the pressure regulating valve from the fuel distributor, and saw the little o-ring on the tapered end. It looked like new so I just took of an put it on the other way round.

I noticed only one 1mm shim present, so I put another one in and now the system pressure has risen from 65 to 71psi which is still within acceptable range (haynes says 65-75psi).

re crappy cold idle
Checked the AAV and made sure it was fully wide open. As a test, I closed it off and replaced on the car to notice a much crappier cold idle. So I opened it up fully and things were noticably better but not good enough.

So now I wait patiently for a vacuum gauge....as I must be missing a vac leak somewhere.

more as i find out!
Tiny
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*****1981 - 924 - Auto - London, UK******