vincematthews
Member
Just to say I've successfully managed to sort out one of the usual 924 problems (touch wood) by making up a test rig similar to the one in the Porsche Workshop Manual (also mentioned in Haynes). I'm not a big fan of the "replace the most likely part, and then another" approach so I thought I'd try the 'proper' way.
Before starting, the usual disclaimer, you are dealing with petrol that may be under pressure - take the necessary precautions . . .
My local branch of Stauff UK Ltd (hydraulic parts supplier) supplied the parts for about £50 inc VAT. This test rig can save you buying a lot of expensive and possibly unecessary new parts. Also I find that buying second hand may not save you money as most parts are now over 20 years old and are probably getting past their useful life.
Anyway the parts were:-
1. SPG 63mm 0-06 BAR/psi 1/4 BSP bottom entry gauge (0 to 6.5 BAR for hydrocarbons)
2. 1/4 BSP M/F gauge adaptor
3. KHR 1/4 ball valve
4. 1/4 BSP M/F/F tee
5. 1/4 RLT 300mm long f/w 6L female x male (2 off)
6. Dowty washers to suit (2 off)
To use this tester, undo the centre hose on the fuel meter head and attach it to one side of the test rig. Attach the other side of the test rig back onto the (now vacant) centre connection on the fuel meter head. All that's needed now is abit of logical deduction (and a glance at the workshop manual for the order in which to do things) and you should be able to work out which part(s) is faulty.
In my case it was the Control Pressure Regulator. I had checked it already and it had passed the electrical and basic function tests but this test rig was able to show that it was not holding system pressure for long enough to prevent the hot start problem.
BTW I took the old CPR apart and it is ever so simple inside. I think if you were to replace the internal o-ring (price about 20p) it may be possible to get it working again. Haven't tried it yet - anyone else had a go?
Let me know if you need more info.
Before starting, the usual disclaimer, you are dealing with petrol that may be under pressure - take the necessary precautions . . .
My local branch of Stauff UK Ltd (hydraulic parts supplier) supplied the parts for about £50 inc VAT. This test rig can save you buying a lot of expensive and possibly unecessary new parts. Also I find that buying second hand may not save you money as most parts are now over 20 years old and are probably getting past their useful life.
Anyway the parts were:-
1. SPG 63mm 0-06 BAR/psi 1/4 BSP bottom entry gauge (0 to 6.5 BAR for hydrocarbons)
2. 1/4 BSP M/F gauge adaptor
3. KHR 1/4 ball valve
4. 1/4 BSP M/F/F tee
5. 1/4 RLT 300mm long f/w 6L female x male (2 off)
6. Dowty washers to suit (2 off)
To use this tester, undo the centre hose on the fuel meter head and attach it to one side of the test rig. Attach the other side of the test rig back onto the (now vacant) centre connection on the fuel meter head. All that's needed now is abit of logical deduction (and a glance at the workshop manual for the order in which to do things) and you should be able to work out which part(s) is faulty.
In my case it was the Control Pressure Regulator. I had checked it already and it had passed the electrical and basic function tests but this test rig was able to show that it was not holding system pressure for long enough to prevent the hot start problem.
BTW I took the old CPR apart and it is ever so simple inside. I think if you were to replace the internal o-ring (price about 20p) it may be possible to get it working again. Haven't tried it yet - anyone else had a go?
Let me know if you need more info.
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