KJet fuelling problem solved.
Posted: 10 Oct 2015, 09:50
WARNING This is a long and boring post but I wanted to share my new found knowledge.
I have been trying to resurrect a KJet injection set-up for some while now. I have finally succeeded so thought I would share it with anyone that may be interested.
First, some background. I have a South African Microbus with the 2.5 litre 5 cylinder engine, fuelled by KJet petrol injection. Four years ago it was converted to run on LPG so the KJet fell into disuse. A couple of years ago I switched the KJet back on, just to make sure it still worked. It misfired like mad, not at all happy. I added injector cleaner to the tank but to no avail. I then removed all the injectors and sprayed brake cleaner through them. Problem solved.
Another 12 months down the line and I tried again. This time I got copious white smoke billowing out of the exhaust whilst driving, cutting out soon after stopping the car, and failing to restart. I then noticed neat petrol dripping out of the exhaust. Evidently running slightly rich.
Now began the fun. I stripped and cleaned every part of the fuel system, reasoning that the problem was petrol gum from our wonderful ethanol laced petrol these days. All injectors cleaned through and the metering head shuttle removed and cleaned. No change. When started it was very rich, white smoking and eventually fuel dripping from the exhaust. I removed the injectors and powered the fuel pump. Immediately they started spraying large quantities of fuel. Although it is a continuous injection system, it shouldn't inject on closed throttle. Now came many hours of trawling the net and posting on various forums to find someone with an answer. Volvo, Saab, Porsche, Mercedes even Ferrari who all use the same system but no joy. Plenty of comments of replace this bit or replace that bit but no reasoning behind it. Also comments of checking the operating pressures of the system, so out I go and buy a Bosch Pressure Test Kit. That confirms that all pressures are correct!
As you start to despair about fixing something, you start to lose focus and do silly things. Not good!
The lesson here is when your cylinders are full of petrol, make sure you disconnect the ignition system before spinning the engine with the spark plugs out.
I had just about given up any hopes of fixing the KJet system until I had a Eureka! moment lying in bed at 3am. Up early and out to try the idea out. It worked!
The metering head has a shuttle valve which in the case of my system is held in place by a slotted nut.
I had removed the slotted nut to be able to extricate and clean the actual valve. On re-assembly I had tightened and lightly nipped the nut. My Eureka! moment was realising that the nut shouldn't be tightened but was actually an adjuster. Winding it back flush with the hexagon nut stopped the continual spray from the injectors. Some more searching on the internet finally found an intial setting for that nut of 0.58mm below the hexagon.
All buttoned up again. All pressures checked and within tolerance. Out comes the Gunsons Exhaust Gas tester which shows 2.4% CO. Starts easily and runs smoothly. RESULT!
I have now dosed the petrol with "Ethomix" to prevent ethanol gumming and intend to do a monthly fire up on petrol to keep the system sweet.
So be warned all you dual fuel guys!
I have been trying to resurrect a KJet injection set-up for some while now. I have finally succeeded so thought I would share it with anyone that may be interested.
First, some background. I have a South African Microbus with the 2.5 litre 5 cylinder engine, fuelled by KJet petrol injection. Four years ago it was converted to run on LPG so the KJet fell into disuse. A couple of years ago I switched the KJet back on, just to make sure it still worked. It misfired like mad, not at all happy. I added injector cleaner to the tank but to no avail. I then removed all the injectors and sprayed brake cleaner through them. Problem solved.
Another 12 months down the line and I tried again. This time I got copious white smoke billowing out of the exhaust whilst driving, cutting out soon after stopping the car, and failing to restart. I then noticed neat petrol dripping out of the exhaust. Evidently running slightly rich.
Now began the fun. I stripped and cleaned every part of the fuel system, reasoning that the problem was petrol gum from our wonderful ethanol laced petrol these days. All injectors cleaned through and the metering head shuttle removed and cleaned. No change. When started it was very rich, white smoking and eventually fuel dripping from the exhaust. I removed the injectors and powered the fuel pump. Immediately they started spraying large quantities of fuel. Although it is a continuous injection system, it shouldn't inject on closed throttle. Now came many hours of trawling the net and posting on various forums to find someone with an answer. Volvo, Saab, Porsche, Mercedes even Ferrari who all use the same system but no joy. Plenty of comments of replace this bit or replace that bit but no reasoning behind it. Also comments of checking the operating pressures of the system, so out I go and buy a Bosch Pressure Test Kit. That confirms that all pressures are correct!
As you start to despair about fixing something, you start to lose focus and do silly things. Not good!
The lesson here is when your cylinders are full of petrol, make sure you disconnect the ignition system before spinning the engine with the spark plugs out.
I had just about given up any hopes of fixing the KJet system until I had a Eureka! moment lying in bed at 3am. Up early and out to try the idea out. It worked!
The metering head has a shuttle valve which in the case of my system is held in place by a slotted nut.
I had removed the slotted nut to be able to extricate and clean the actual valve. On re-assembly I had tightened and lightly nipped the nut. My Eureka! moment was realising that the nut shouldn't be tightened but was actually an adjuster. Winding it back flush with the hexagon nut stopped the continual spray from the injectors. Some more searching on the internet finally found an intial setting for that nut of 0.58mm below the hexagon.
All buttoned up again. All pressures checked and within tolerance. Out comes the Gunsons Exhaust Gas tester which shows 2.4% CO. Starts easily and runs smoothly. RESULT!
I have now dosed the petrol with "Ethomix" to prevent ethanol gumming and intend to do a monthly fire up on petrol to keep the system sweet.
So be warned all you dual fuel guys!