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Old 11-23-2009, 11:56 AM   #1
branmcw
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Exclamation K-Jet POS!!!

81 245 K-Jet
starts hard and misses until it warms up then it runs fine any ideas what could be wrong?
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Old 11-23-2009, 12:08 PM   #2
tiredoldtommy
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Cold start injector or thermal timer? Or wiring to either or both.
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Old 11-23-2009, 12:38 PM   #3
branmcw
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ways to check?
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Old 11-23-2009, 01:11 PM   #4
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Do you have a manual? The Bentley manual is the best, but a Haynes would work too.

Also, the factory Volvo green books are available for download at K-jet.org. I think they have a troubleshooting file as well.
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Old 11-23-2009, 01:17 PM   #5
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Mine does the same think and in my case its the thermal timer.
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Old 11-24-2009, 02:56 AM   #6
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CPR is plugged and running either line pressure for control pressure, or it's running full control pressure when cold instead of dropping it. Check your control pressure cold and warm. It should be somewhere in the 35-ish psi range when cold, 55-ish psi range warm. If it's 65+ psi you're running at or near line pressure.
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Old 11-24-2009, 03:30 AM   #7
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CPR as above.

If I remember right the thermal only works while cranking and then does nothing over 80F or so, but you may want to check.
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Old 11-24-2009, 03:27 PM   #8
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There is the thermal time switch. It controls how long the cold start injector will spray while cranking. The cold start injector only sprays while cranking.

Then there is the thermal cutout switch which is used on the late model kjet and the kjet 240 turbos. This is an open/close contact switch at the rear of the left side of the block. It grounds out when the block temperature is below 60F IIRC. It is connected to the lambda ecu terminal 7 providing extra fuel for the engine while it's really cold. As the engine block temp goes above 60F the switch opens because that is a ton of fuel and isn't need as the engine gets warmer.

Lastly and very importantly above was mentioned the control pressure regulator. The control pressure is a feedback fuel pressure used against the plunger in the fuel distributor. In cold conditions the warmup regulator aka control pressure regulator lowers the fuel feedback pressure so the plunger will travel higher making the fuel mixture richer for warmup. As the temperature in the unit heats up with it's heater inside and the engine temp rises the control pressure is increased until the fuel feedback pressure is at a setting where it provides the warmed up engine fuel mixture.

You need to check the injector seals too. For checking the thermal time switch and thermal cut out switch you need a multi meter set for ohms and a cold engine to see if they are conducting. For the control pressure testing you need the kjet fuel pressure gauge setup which will let you test system presssure, control pressure, and rest pressure. Check out the Volvo manuals on k-jet.org. Download and readup how kjet warmup works and how to troubleshoot it.
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Old 11-24-2009, 04:13 PM   #9
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Read the sig.
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Old 11-24-2009, 04:26 PM   #10
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+1 for CPR. Did you check injector seals?
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Old 11-24-2009, 05:04 PM   #11
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The 1981 240 Turbos don't have the thermal cutoff switch, btw. But, I'm thinking it's probably the CPR, or it may be a gummed up fuel distributor, which is likely as well. Especially if the car has been sitting for a while.

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Old 11-24-2009, 05:48 PM   #12
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Yeah, I always forget that first year doesn't have that thermal cutout switch. I agree it's probably the control pressure regulator. When I bought my 82 turbo it had the same symptoms and it was a combination of bad injector seals and the control pressure regulator clogged.

It took about 8 tries before it would start and idle. Then after the injector seals but before the cpr it took about 4-5 tries. Then after the cpr was replaced it started easily and ran great.
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Old 11-24-2009, 06:08 PM   #13
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Fill the fuel filter with Seafoam and run it through the injectors slowly, a few minutes between pulses, with the fuel pumps bypassed and moving the air plate.
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