hwyengr

That's only part of the test, though. If you've got leaking injectors the pressure will also drop off quickly. Clamp the supply and return lines to check that the injectors hold pressure, clamp the return line to test the check valve, and clamp the supply line to test the pressure regulator.

Ed Petry

Newbie shark owner here.

What is a Shark Tuner?

Thanks in advance.

John Speake

Hi Ed,
Info here:

http://www.jdsporsche.com/sharktuner.html

The Sharktuner can be used for remapping but is also a very useful diagnostic tool as it shown the operation of LH and EZK ECUs in real time.

kos_007

First of all please don't clamp nor kink the flexible OEM fuel lines - you will crack the hard plastic inner lining resulting in fuel leak and engine fire.
I had a similar problem with my 89 S4 and it was a sticky Idle Stabilizer Valve.
I replaced it with the one below and it's all good now. The intake manifold needs to come off for this - it is a perfect excuse to replace all the rubber hoses and seals WYAIT.
http://www.ebay.com/itm/261571886326?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

kos_007

Sorry - I just re-read your OP in which you state that the ISV was replaced also.
Leaky injector is a real suspect then.
Here is a good alternative replacement:
http://www.ebay.com/itm/Porsche-928-...oeaKcg&vxp=mtr

hwyengr

Clamping the hoses is a part of the factory test plan for diagnosing fuel system faults.

Ed Petry

Hi,
Thanks for the info. Will the tuner work on pre-85? Mine is an '81 NA 4.5L.

Thanks in advance.

davek9

No, needs to be an '85 or newer that uses the ECU's.

For your car it's DVM (digital Multi-meter) time and check all the values given in the shop manual under troubleshooting.

Chalkboss

Solved- got a set of four hole injectors and no more hot start issues. I had pulled all the plugs and found one pretty wet, but I never got around to putting a gauge on it.

Happy with the way it runs now. Porsche smooth.

StratfordShark

There is a service info note for (I think) MY91 onwards to say hoses now have polyamide inner and should not be clamped.

So what is correct procedure to clamp off these newer hoses?