Porsche Bosch K-jetronic - 924 System Pressure + More 

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You didn't touch that the warm & cold control pressures as well as the A/F adjustment are also factors that impact fuel flow. Also there are O-Rings inside the metering head that can cause flow imbalance to each cylinder.

Hopefully you're reading this and can suggest some ideas as I'm tearing my hair on on a 924 Jet. Summary of symptoms: Car runs either way to rich but starts and runs okay when cold if control mixture set rich, or if I set the mixture so its has correct CO when warm, its coughs, splutters and barely runs when cold. So it must be the WUR then? This is what I've done so far to try and find the issue. Full system pressure check - all within Bosch spec when cold and warm, confirming WUR working. Rebuilt and cleaned WUR just to make sure. No difference. Swapped out WUR, no change. All new injectors. All new injector seals / screw in bosses. Flow check on all injectors - even and correct. Cold start injector, tested, functional and working - issue of poor cold running exists long after cold start injector fires either way. All new coil, distributor, plugs and leads. Swapped out ignition module, no change Stripped and rebuild metering head valve - new kit, fully ultrasonic clean etc, etc Cleaned out and checked all the injector lines. New fuel pump in tank and engine bay + filter Fresh clean fuel Inspected, cleaned and checked flow plate mechanism in metering head and test swapped ith a known working one, no change. Replaced inlet manifold gasket and resealed. New air filter. Smoke check for vacuum leaks, small one found and corrected. Timing checked and rechecked. New timing belt fitted and timing checked. Compression and leak down all within spec and even. When warm, car runs great but coughs, splutters and barely runs when cold. Make the mixture way to rich and car starts no issue, but then is poor when warm as too rich. Pressures and WUR checked, rechecked and different WUR swapped in to test, no different, All correct Porsche components fitted, nothing after market or high performance. Only other issue is that the auxiliary air valve didn’t appear to work very well,m i.e did not increase cold idle speed so had to modify this to give a 1,500 rpm fast idle which sovced that problem. Cold start mixture was same before or after so dont believe related. Lost as to what to do next?

Would you be able to service the K-jet metering head off my XR3i? Looks like you have a good setup there to test and work on them.

So if you increase system pressure, does it increase control pressure and scale the air meter up? Meaning do they stay in correct relation and the air valve will now require more air to move to, say, half fuel flow and it will be sending more fuel at half way?

Hello there, would the Porsche unit also work on a MK2, PL KE-Jet, or just on a KR K-Jet? What would you reckon you could get out of a PL Engine ?

What’s the merc injectors you’re speaking of, I’ve got a 924