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Few months ago I bought a 1983 900. 8 valve 5 speed Kjet goodness. It's been.. alright, it's a nice car to drive but its needed a good amount of work. So far I've fixed all the engine oil leaks (power steering still drips..) and I got the AC blowing ice cold, along with a bunch of other little fixes. But there's a couple issues I haven't really been able to figure out.

The Kjet. It's got this weird surging/lack of power problem at low rpm. Most noticeable when the engine is cold, but it's always there. Gets worse the more throttle I give it but then it clears right up around 3000rpm and pulls nicely from there. I haven't done much because Kjet is scary and confusing, but what I did do is pull the distributor/air meter out of the car and get it all nice and clean. The control rod had some scuffing on it so I polished it up and put everything back together with a new fuel filter. No change. I also deleted the hot air emissions intake, which was stuck on hot intake. Not entirely sure where to go from here.

Then I've got an intermittent cooling fan problem. Seems to come and go on a daily basis. Basically sometimes it works fine, sometimes the fans will only turn on if the AC is on, otherwise the temp gauge will start creeping up in traffic or driving uphill. I really don't understand how the fan control circuit works in this car, but what I can say is that the problem definitely isn't the temp switch or the fans themselves. If I jump the switch on the left side of the radiator both fans spin up, but if I jump the switch in the upper rad hose nothing happens.




Thanks for any help you guys can give me.
 

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I will agree that kjet is a scary place, so someone else is gonna have to chime in there.

But the switch in the upper radiator hose has nothing to do with the fans. The only components are the switch in the radiator and the relay. If jumping the switch in the radiator turns the fans on reliably, probably that switch is bad. What you describe about intermittent function is consistent with fan thermoswitch failure.
 

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Discussion Starter #3
I will agree that kjet is a scary place, so someone else is gonna have to chime in there.

But the switch in the upper radiator hose has nothing to do with the fans. The only components are the switch in the radiator and the relay. If jumping the switch in the radiator turns the fans on reliably, probably that switch is bad. What you describe about intermittent function is consistent with fan thermoswitch failure.
Oh, I thought that was some sort of overheat protection switch cause when I jumped it the fans came on with the ignition off.
 

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If you haven't lost coolant it's not overheating. The gauge movement you describe is normal. Fans are triggered by A/C independently of the temperature.

I'm surprised you did no harm by taking apart the fuel distributor. It's not field serviceable. Don't take it apart.
You probably need to adjust the mixture. To do that, you need to read the Lambda pulse-relations using a specialized meter or a dwell meter (adjust to about 65%).
Open up the pressure impulse contact (the thing on the fuel filter) and throw away the spring inside to address your cold hesitation.
Any vacuum leaks make it run leaner, check everywher for them.
 

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Oh, I thought that was some sort of overheat protection switch cause when I jumped it the fans came on with the ignition off.
That's the opposite of what you said in the original post.

Jumping the switch in the upper radiator hose should ONLY turn off the AC when the car is running. If jumping that switch turns a fan on, you have a wiring problem. I would check the AC relay and the fuse box for shorts.
 

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Discussion Starter #6
If you haven't lost coolant it's not overheating. The gauge movement you describe is normal. Fans are triggered by A/C independently of the temperature.

I'm surprised you did no harm by taking apart the fuel distributor. It's not field serviceable. Don't take it apart.
You probably need to adjust the mixture. To do that, you need to read the Lambda pulse-relations using a specialized meter or a dwell meter (adjust to about 65%).
Open up the pressure impulse contact (the thing on the fuel filter) and throw away the spring inside to address your cold hesitation.
Any vacuum leaks make it run leaner, check everywher for them.
I never said it was overheating, but it sure got close. I'm no road going fighter jet expert, but I'm pretty sure the temp gauge sitting at 3/4 with the fans off isn't normal. So I got myself a new temp switch for the radiator, same temp as the old one, but unfortunately the plastic threads came out with the old one. I gobbed it up with teflon tape but I have my doubts that it'll hold pressure.

I wasn't aware of any mixture adjustment other than the idle screw right next to the fuel distributor. I adjusted that one to max vacuum and it idles pretty good. Warm starts are a little finnicky though. No clue what a pressure impulse contact is. And I've already done the vacuum leak routine, the car had a bunch when I got it. Previous owner seemed to think the 1600rpm idle was normal.
 

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Couple of experience observations. The Fuel metering gizmo is Fairly simple to Disassemble, Clean, Adjust. (Not rockit science.. just don't lose any springy bits and don't swap bores.:)
Despite Self Serving Bosh dogma claiming otherwise..
One can Easily set the fuel mixture.. Accurately!... using a Cheap *** Analog Voltmeter (if you can still find one.. I used to use a 5$ one). The needle vibrates with the system pulses and one only has to fiddle the Wee Allen screw until the Needle centres at 5.5 Volts. Easier done than explained.. try it :)
Also a Caution.. those Formerly White plastic now Brown injector lines are Brittle as Glass ! Seriously. Darker the brown the more fragile they are... bump one lightly accidentally . it will shatter like a piece of glass tubing in chem lab...Then you will need spend serious time trying to find a replacement (some volvos shared similar as an aid in the search ).
K Jet is a very simple contraption don't let the Myths get in your way.
 

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It seems that one could replace those plastic fuel lines with nylon hose or, probably, even fuel rated rubber hose. It's just a matter of the fittings at either end I suppose. Given the age, they are probably just basic flare or compression fittings. Probably most of the raw materials are available here -


AFAIK Cohline made the OE parts for the later cars. Certainly for VW versions of CIS.
 
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