240 K-Jet Fuel Issues: Bad Distributor Or Multiple Issues?

Fuel issues continue to plague my 245 and its B21FT and hopefully you all can help. Not sure if it's just one thing that needs tweaking or multiple problems that need to be looked at.

In the last 12 months I've done the following:

• New Bosch fuel filter
• Dave Barton harness that I verified was all plugged in
• Cleaned distributor piston & replaced O-ring
• Drained and refilled tank with fresh 91 octane
• Changed all copper washers twice and 2x checked they were all torqued

There's probably more in my build thread.

But every time I turn the key, the following happens:

1.) I put it to ignition position 2 and let it build up fuel pressure. Car sounds fine.

2.) Clutch in and turn it to Engine ON, engine fires up and dies unless I pretty much keep it floored hard. Car will turn on and run bad. Tach needle bounces up to 2.5-3k but revs freely if I keep my foot down.

3.) Foot comes off accelerator. Car sounds fine and then promptly stalls with a metallic squelch.

4.) Under the car is a steady drip of fuel from the right-side where the distributor and airbox sit. The airbox lid will be drenched in fuel and I've seen the lines going to the injectors weep a bit, though I've mostly solved this with the second round of copper washers.





I've noticed that the hex-head fitting between the main supply line and the metal fuel line with the arrow pointing out seems to weep a bit, though I've yet to see anyone suggest turning it a bit.


4.1) Car will do warm starts. I'll give the banjos a good tighten and it pretty much repeats steps 2-4.)

For fun, I popped the boot off the air flow sensor and wiggled the plate up/down a bit. I could feel some engagement with the piston in the distributor, though it didn't feel linear. Unfortunately I have not gotten around to making the fuel pressure tester, but I will say that the lines all ejected pressurized gasoline into my face/a towel at a very forceful rate. The car also runs, which suggests it's getting some quantity of fuel, air, and spark, though it's unclear why it's not getting enough of the first two in a way that makes it happy.

Question to you all: I was wondering if this was a sign of a bad distributor, bad idle valve, or some combination of ungodly problems that come with pushing fuel at its designed pressures through the old K-Jet system? Any other paths worth exploring?


Thanks for humoring me.

The leakage is a concern. To me, it almost looks like it's weeping from between the two halves of the distributor. So, I'd probably go ahead and replace the assembly with one from a known running car. Ideally, try to get it with the lines and injectors. I think I'd go ahead and replace the lines as well. Then, if the runnability issues continue, start looking elsewhere.

The requirement to have the throttle wide open might be a flooding issue. I know that when swedishiron.com and I were trying to get my 245 running halfway decently after it began running very poorly on the way to his house, it finally got to the point where the engine wouldn't start. Only once I blocked the throttle open, did it begin to run. Do you have access to a digital multimeter with a dwell function? If yes, connect that to the red wire that's hanging loose near the battery (normally has a black plug on the end), and verify that the idle mixture is between 42 and 48 degrees dwell with the oxygen sensor disconnected, lowering to 41-44 degrees dwell with it connected. After adjusting, run the engine around 1500 rpm for a few seconds, then let it drop to idle and check the meter again. Repeat the process of adjusting if it's still not within spec.

With respect to the idle air valve, you can test that out, by disconnecting the two harness plugs, then jumpering terminals 1 and 4, as well as 2 and 5. Start the engine. It should run at about 3200 rpm. If you do this with it stone cold, it should act the same as if you stomped on the accelerator while cranking. So, same stumbling when first started, then finally running at a steady 3200. If it does so, then the idle air valve is fine.

For troublesome fuel fittings on kjet. You can use some thread sealant like the loctite 592. Put it on all contact surfaces. The fittings will seal easier so you don't have to overtighten the fittings to get them to seal.

dl242gt said:

For troublesome fuel fittings on kjet. You can use some thread sealant like the loctite 592. Put it on all contact surfaces. The fittings will seal easier so you don't have to overtighten the fittings to get them to seal.

Click to expand...

+1 for sealant
Broke two banjo bolts trying to get the washers to seal

Follow up: I tried a new distributor, one that doesn't seem to have a sticky plunger. It starts and runs stronger with each subsequent start, though I haven't bothered checking the idle at this stage.

For fun, I set up my camera over the distributor. It's a little hard to see but fuel gushes out of the frequency valve, specifically what looks like the hard line. You can't really see it from this angle, but there are indeed two copper washers on the fitting, plus a dab of sealant on the threads. I swear I heard the frequency valve buzz.

Attempt 1ff to about 16 seconds in)
https://youtu.be/FTMouW1mpH4

Attempt 2ff to about 30 seconds in)
https://youtu.be/Ug1J3mwBem4

Is the frequency valve busted or could there be another issue causing fuel to be pushed out? I'll be ordering a pressure gauge and I am curious as to what other, lesser-known causes would result in something like this happening.

If fuel is leaking from the frequency valve you need to replace the valve and lines to it. If you know how to work with the nylon fuel line then you could possibly repair it. But generally you replace the assembly, use new washers and that should fix that leak.

little hint here, locate a CIS-E fuel distributor and fuel lines with the ECU, ECU harness, and sensors from a VW Fox, VW Quantum, or Audi 4000S. Only 2 wires to connect to the ECU to make it work. You may need to adjust length of wires.

lummert said:

little hint here, locate a CIS-E fuel distributor and fuel lines with the ECU, ECU harness, and sensors from a VW Fox, VW Quantum, or Audi 4000S. Only 2 wires to connect to the ECU to make it work. You may need to adjust length of wires.

Click to expand...

Good to know, I'll keep an eye out for one hitting the scrapyards out here in SoCal. There's still a few of 'em on the roads.

For those of you watching at home, I tried the sealant trick and had a friend start the engine. The frequency valve's soft line proceeded to fail in a very entertaining manner, so hopefully 2manyturbo's replacement will help me get this thing on the road again!

Never consider a CIS E installation. It's the most over complicated version of kjet that there was. There is a sensor for all kinds of stuff and an ecu to control or monitor it. The system was used on Mercedes 190E cars here in the US besides the aforementioned VW and Audi cars.

If you need a fuel line the lines from a kjet CIS E car are nice to use but that is the only part to consider. The fuel distributor and airflow sensor parts on the engine are completely different.

dl242gt said:

Never consider a CIS E installation. It's the most over complicated version of kjet that there was. There is a sensor for all kinds of stuff and an ecu to control or monitor it. The system was used on Mercedes 190E cars here in the US besides the aforementioned VW and Audi cars.

If you need a fuel line the lines from a kjet CIS E car are nice to use but that is the only part to consider. The fuel distributor and airflow sensor parts on the engine are completely different.

Click to expand...

Other than the fact that they chafe on everything and #4 isn't long enough.

snailmale said:

Fuel issues continue to plague my 245 and its B21FT and hopefully you all can help. Not sure if it's just one thing that needs tweaking or multiple problems that need to be looked at.

In the last 12 months I've done the following:

• New Bosch fuel filter
• Dave Barton harness that I verified was all plugged in
• Cleaned distributor piston & replaced O-ring
• Drained and refilled tank with fresh 91 octane
• Changed all copper washers twice and 2x checked they were all torqued

There's probably more in my build thread.

But every time I turn the key, the following happens:

1.) I put it to ignition position 2 and let it build up fuel pressure. Car sounds fine.

2.) Clutch in and turn it to Engine ON, engine fires up and dies unless I pretty much keep it floored hard. Car will turn on and run bad. Tach needle bounces up to 2.5-3k but revs freely if I keep my foot down.

3.) Foot comes off accelerator. Car sounds fine and then promptly stalls with a metallic squelch.

4.) Under the car is a steady drip of fuel from the right-side where the distributor and airbox sit. The airbox lid will be drenched in fuel and I've seen the lines going to the injectors weep a bit, though I've mostly solved this with the second round of copper washers.

I've noticed that the hex-head fitting between the main supply line and the metal fuel line with the arrow pointing out seems to weep a bit, though I've yet to see anyone suggest turning it a bit.


4.1) Car will do warm starts. I'll give the banjos a good tighten and it pretty much repeats steps 2-4.)

For fun, I popped the boot off the air flow sensor and wiggled the plate up/down a bit. I could feel some engagement with the piston in the distributor, though it didn't feel linear. Unfortunately I have not gotten around to making the fuel pressure tester, but I will say that the lines all ejected pressurized gasoline into my face/a towel at a very forceful rate. The car also runs, which suggests it's getting some quantity of fuel, air, and spark, though it's unclear why it's not getting enough of the first two in a way that makes it happy.

Question to you all: I was wondering if this was a sign of a bad distributor, bad idle valve, or some combination of ungodly problems that come with pushing fuel at its designed pressures through the old K-Jet system? Any other paths worth exploring?


Thanks for humoring me.

Click to expand...

Cold start is the square warm up regulator,it's like a choke. It is quite easy to rebuild if you are careful and make notes.leaks tend to be old copper washers or grit,it must be very clean .I suggest taking out injectors cleaning with carb cleaner, do this to the square warm up regulator.found that in a car that was lethargic that taking off the injectors and cleaning them resulted in the car being very nippy and a torque monster.change the seals while there. Also note that kjet is ultra sensitive to vacuum leaks.it is a super precise reliable system if used with good fuel. If left for a long time it tends to gum up the WUR square thing. Hope this helps.