sick 928s

[bigcno1]

Hi folks my 1981 4.7 300hp 928s which is always garaged has been giving me a real hard time.
It was very hard to start spluttering and backfiring jumping off cylinders and just had enough power to drive outside,
I drained the fuel tank added new fuel and filter, new dizzy cap leads plugs no difference still sick,
I also checked the green wire to dizzy but it looks like new, checked for fuel leaks and all vaccum pipes are intact,
I removed fuel pump relay and jumped the connections so fuel pump runs constant after all this the car just
starts and dies immediately the fuel pump is very noisey and from what ive gathered this model does run at a much
higher pressure could the pump be faulty, is this engine fitted with a crank position sensor ?
There was a similar post a number off years ago but the owner didnt report on the outcome,

Any pointers would be appreciated Regards Cline.

Edited by bigcno1 on Sunday 15th July 16:12

Edited by bigcno1 on Sunday 15th July 18:50

[Cheburator mk2]

Your car is very sensitive to fuel pressure and fuel flow rates having a mechanical fuel injection K-Jet also known as CIS. Best thing to do is to take it to a fuel injection specialist who has the correct pressure gauges, which can be hooked to the metering head and thus they could check cold and hot control pressures. Your car does not have a crank sensor.

[cd1957]

Hi If car is running that bad,I would no longer run it.

I would check cambelt on both sides,and make sure dizzy is in line, when cam timing is on cylinder 1 and all marks also line up.

Chris

[LarJammer]

Do what they said. As an aside, i once had a non starting 928 in, good spark but very wet plugs. I found one of the fuel dampers had failed and filled the inlet manifold with fuel - and i mean filled. I drained about 1.5 litres of fuel out, damn lucky it didnt hydrolock or catch fire.
The moral is - get a specialist to look at it, they are not simple cars.

[bigcno1]

Hi Yes have checked the timing had new belt fitted 2 years ago , have double checked everything timing
is perfect its definately a fuel issue.
I live in N.Ireland and their just isnt anybody who knows these cars locally most are retired or dead,
without causing offence to any mechanics most off them i have asked ,
First question , A porsche 92 what???
Second question , Is that petrol or diesel ??
Yes i admit their a complicated car but ive owned her 12yrs without any problems i couldnt overcome,
I am going to replace fuel pump and fuel pump relay around £100,
Been quoted £55ph to look at it and i know more about the car than he does ,
Thanks for your pointers,,,

[cd1957]

Hi if the spark plugs are wet,I would go towards metering head over curling.

I would also take out cold start injector,see if it's stuck open.

I think anybody that has worked with K jetronic systems on other cars should be able fix.

[bigcno1]

Hi cd1957 yes i will have a look at those ive come across a company on the mainland
who can recondition the fuel injection system and there pretty reasonable .
She started today without all the bacfiring and got here back into my garage for now,
she definately suffering from fuel starvation.
Thanks for your help.

[cd1957]

Hi Bigcno1, the company i use for all my K jet repairs is, Ken Mills injection 01462 682432.

Best of luck.

Chris

[bigcno1]

Without removing the airbox assembly yet again is it true theres a small filter on the inlet to
the metorhead thats not really known about ?
Possibly causing fuel restriction ?

[bigcno1]

Finally got to the bottom off my troubles and cost me less than £25 and didnt need to go
to any specialist.
Removed and cleaned the injectors they were blocked with crude fitted new seals.
Theres a guy on youtube who demonstrates the procedure on the bosch injection system its simple
to follow , the fuel solidifies when not driven for while.