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Old 02-21-2020, 08:51 PM   #1
hessam69
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Default k-jet B23E stalling when cold

Hi,

My 1984 240 starts up fine, idle goes low then stalls, then starts up and it's fine, if left for a few days sometimes it will stall twice before I can drive it. What are some items to check?

Thank you
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Old 02-21-2020, 09:57 PM   #2
John242Ti
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Maybe the auxiliary air valve isn't opening? I do know that the non-constant idle K-Jet engines, they did recommend holding the throttle open about 1/4 of the way when turning the key while the car is stone cold. As soon as it fires, you can release the throttle. That should let it idle at about 1300 rpm or so until it's warm enough that the aux. air valve will shut. I'd also check the hoses going to and from the valve. Even though it seems to idle fine once warm, they may be just worn enough to leak when the car's cold.
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Old 02-21-2020, 10:15 PM   #3
hiperfauto
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It could be vacuum leaks or incorrect cold fuel pressure. It could also be a failing accumulator since it gets worse over time. Check for vacuum leaks first and then check cold control pressure and rest pressure.
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Old 02-23-2020, 12:42 PM   #4
Victorrr
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I've had/still have (but I don't drive the car anymore) the same issue. From what I've found, its a big mix of a bad aux air valve, leaky injectors, bad WUR, bad fuel distributor, clogged PCV... K Jet is great and dead reliable when it's clean and in perfect working order. Otherwise you'll get weird things.

When dealing with a cold K Jet, try to start it without touching the throttle, but with the foot just above it in case it wants to stall right after starting up. Sometimes the plunger get stuck and the engine don't want to gain RPMs even with WOT, but then suddenly catches. It's really bad to deal with.
So yeah, try to start it normal the first time, having a healthy battery is important. Also bad fuel accumulator can get annoying too. If it doesn't catch on the first try, then try again but with the throttle partly depressed as stated above.

With bad K Jet, it's important to have a good ignition system. The 123 system I bought for mine helped a lot. I had really bad misfire and random stalling from time to time... Now its just running way too rich, killing plugs. Bad injectors too.

Is your idle high when warmed up ? Like 1100rpm idle when warm but barely above 600 when stone cold. It's so bad on mine that I have to sit in the car for 30s - a minute with the foot on the throttle to warm the **** up before going, or I risk stalling like a **** on the 1st few minutes of the run. I hate this feeling when the car bogs down... It should be high idle when cold and around 900 when hot. The opposite means the warming up systems aren't working and someone corrected by increasing the base idle via the screw. Not the right way to do it, but will get you there.

I'd say check the aux air valve, It's really really easy to check and It might be clogged. Also these rubber O rings around the injectors, with age they tend to leak.

If you can, get the special K Jet fuel pressure gauge. Stalling when cold can be the result of many things, the WUR is to consider... As said above, check the control pressure while the car warms up. Start it, ask for someone to held the throttle down or hold it yourself at the manifold. like 1500 rpm so it heats up. The control pressure should rise. Low control pressure = rich, high control pressure = normal. In theory. Mine is completely off. Too lean when cold and too rich when hot...

The aux air valve is heated and is opened when cold, then closes via it's heated element (or the engine's heat). They do fail/clog with time. Usually its not the only culprit.

If your K Jet is horrible when cold but fine while hot (but still drinks a lot without producing much power) then Its likely than it needs a good overall... I got tired of playing with it, let's go standalone !
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Old 06-16-2020, 02:16 AM   #5
hessam69
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Update:

It is confirmed, holding the throttle open during cranking on a cold start (about 20%) prevents stalling. Now, does this give any clues as to what the problem is? Am I correct in thinking it isn't as much of a fuel system issue than an airflow one? I had a look for the fuel pump check valve, but couldn't find one. Is it internal inside the pump or external much like LH 2.4 system? I tried changing the auxiliary air valve to a known working one, and found no difference. When hot, the engine also likes a bit of throttle to start. But sometimes not. Both fuel pumps work.
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Old 06-16-2020, 03:04 AM   #6
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You need to check the fuel pressure. I had the same issue which slowly got worse into the winter. I thought that it could be the idle valve and maybe it was gummed up and slow to adjust to the low cold idle. On a whim I finally checked the pressure and it was really high. Tried another WUR that I had and that fixed it.
I read here somewhere that some injection cleaner may help clean out the WUR. I would like to put it back on and run some cleaner through it.

High fuel pressure is leaner. The wur starts with a lower pressure and then as if warms up the pressures goes up.
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Old 06-16-2020, 02:12 PM   #7
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When I bought the 82 turbo it had the start then stall issue when cold. Sometimes would take five tries before it would idle. I ended up doing the full kjet service stuff like mentioned above. But the culprit was control pressure matched system pressure. A clogged control pressure regulator. This makes the engine way too lean when cold starting. When fully warmed up it would seem fine at idle but was down on power and not very responsive to the throttle.
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Last edited by dl242gt; 06-16-2020 at 02:12 PM.. Reason: add comment
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Old 06-16-2020, 06:52 PM   #8
hessam69
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So what did you do? Clean the regulator or did you replace or rebuild it?
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Old 06-16-2020, 08:05 PM   #9
dl242gt
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Quote:
Originally Posted by hessam69 View Post
So what did you do? Clean the regulator or did you replace or rebuild it?
I bought a rebuilt one. They were reasonable. I didn't try taking it apart but there are some good sites on rebuilding them and adjusting the pressure. You can even add a bolt to the bottom to adjust the pressure.
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