GerritD

Hi 928 guys and girls,

After overhaul of 4.7 L Kjet 300Hp engine, almost impossible to start and when started very difficult to keep it running , also permanent blue-grey smoke from exhaust.
i followed the official WSM flowchart for troublesolving engine issues . All impedance and voltage measures of cables and electrical components were ok.
I checked WUR for debrie but filter ok, also Aux air valve is working .....help😜😢

could injection/air device be faulty because adjusting mixture and idle had no effect!
air plate is freely moving so plunger is not stuck. How to check this ?

strangely enough my engine worked fine for 2 days after the overhaul??? What could suddenly cause the excessive fuel and bad combustion? Compression on each cilinders is 11bar.

I am completely lost here...

GlenL

Year?

Randy V

I think you mean '928 guys, and Nicole'. She's pretty much the only 928 chick here on a regular basis.

michael j wright

Just throwing this out there. Normally, blue-grey smoke would be oil, black smoke fuel, white smoke water. Sounds to me that you have started burning oil for some reason, I would start by pulling plugs and seeing if they look oil soaked or smell of fuel. I could be wrong on this so I would ask others to join in and correct me if this is wrong. Just my .02
Mike

GerritD

Porsche 928S of 09/05/1980

GerritD

perhaps interesting : before I had another engine in my 928 : 4.5L 240hp type M28.01 which was not the original engine, therefore I overhauled a 4.7L 300hp.
Both engines are CIS kjet euro, same ecu, same WUR, same aux air valve, same connections.
Only distributor is different and there are 2 extra components :
- hotstart valve
- fuel pressure damper

Could the excessive unburnt fuel be related to one of both components that have become faulty?

SwedeInSiam

What engine do you have?
1980 RoW S don't have a ecu.

GerritD

with Ecu, I meant the control unit for the ignition pulse

GerritD

engine type M28.12 , 4.7 L 300hp

SwedeInSiam

Have you checked you checked the fuel pressures?
That's were I would start.

GerritD

same thought just crossed my mind. I suspect my fuel pressure has become ( it worked before though) too high.

SwedeInSiam

High control pressure will give a Lean mixture.
Low control pressure will give a Rich mixture.

Cold start valve could be stuck open either by a faulty valve or the wrong electric connector put on it.

GerritD

There is one item I perhaps have to check since exhaust is smoking alot : stuck fuel return line.

GerritD

I found my problem : the rotor in the distributor was misaligned ! When piston 1 is in top position, rotor should point to mark on the distribution at spark connection to cilinder 1.
Very strange as I am sure to have put it at the correct position


I now tried to start but no luck, no start at all, I even had backfire in exhaust and throttle house

GlenL

The important part is to have spark plug wire for #1 above the rotor when the cams are at their notches.

Then make sure the wires are in order. I traditionally mess up 5&6.