Poor running K Jet

[Clan]

Originally Posted by Joe of Loath

Not sure on the plugs, will check tomorrow. They're gapped properly but have white deposits on them.

Crap on the metering plate like say, some oil that leaked into the intake and soaked everything?

That is just oil condensation from the breather hose which discharges a bit further upstream and gets drawn into the engine .

[Laird Scooby]

Sounds like it's running lean Joe! Very lean!

If the oil is sitting on the air metering flap then it could potentially cause this as it will weigh it down - it's very finely balanced to give the correct mixture throughout the rev range. It is only lifted by the passing of wind (not yours! ) through the fuel distributor and as it lifts it alters the fuel injection pressure.
As the injection is constant ("K"onstant in German, hence K-Jetronic), the only way to alter the mixture is by altering the pressure. If the pressure can't be altered because something is sitting on the flap and weighing it down it will run lean.

There are of course little touches to add the finesse needed such as idle mixture control which in simple terms is a pre-load spring on the flap to alter the mixture at idle and therefore across the rev range, also cold start enrichment by means of a warm-up timer (mind just went blank, can't remember how that works) but if there's enough oil on the flap that might well do it!

[aardvarkash10]

I was thinking more in the fuel circuit itself. The metering valve is incredibly fine - a few microns-width of crap is enough to make it misbehave.

A couple of years of MkI - III Golf GTI's taught me to avoid K-Jet like the plague...

[Joe of Loath]

It ingested and burned a lot of oil - about three to four litres probably. I'd plumbed the valve cover straight into the intake to relieve some pressure, forgetting that it's full of vapourised oil. Hence it condensed in weird places. All fixed now with a temporary catch can.

I'll take the K-jet thing off and clean as much as I can with clean rags and carb cleaner without taking it apart (unless it's safe to disassemble?), then see how it runs. It has to come off anyway to get to the (clogged) oil separator box.

I drove it back from Exeter or so with these symptoms, so if it's been running lean I hope I've not damaged anything...

[Laird Scooby]

There's a lot of "factory set" stuff in the K-Jet fuel distributor Joe and centralising the air-flap is very tricky!

I think what i'd try first is to remove the hose from the air cleaner underneath and the rubber "sock" between the inlet manifold and fuel distributor and then spray carb cleaner on top of the flap to clean it and let the resultant goo run out below, perhaps onto one of those rags

[Clan]

Originally Posted by aardvarkash10

I was thinking more in the fuel circuit itself. The metering valve is incredibly fine - a few microns-width of crap is enough to make it misbehave.

A couple of years of MkI - III Golf GTI's taught me to avoid K-Jet like the plague...

I always found the K jetronic utterly reliable on the volvos from 1974 to 1989 when they were current and for the years afterwards until they disappeared from the roads . I saw many daily for routine serving etc for that period and beyond .. The only small problem was the fuel pump control relay of course , but a re solder every 10 years keep them going I don't think the oily dirt is going to make any difference unless it is causing the plate to stick .
The system needs diagnosing with the special fuel pressure gauge , The control pressure could be out which is controlled by the Control pressure regulator with the two fuel pipes and an electrical connection , it starts at about 1.5 bar when cold and increases to about 3.5 bar when the engine is warmed up . The main fuel pressure is about 5 bar and stays the same all the time ..

[Joe of Loath]

I have a local Volvo specialist who seems to know K-jet, if I can't figure this out I'll take it to them. They have one or two guys still there who remember the K-jet days and didn't seem phased when mine failed MOT on emissions (just went under the bonnet and tweaked things until it passed).

One of the problems I "fixed" on my drive home was a broken rubber mount on the front of the unit, I held it up with some string off the bottom of the intake manifold for the time being. Could the sag/vibration have caused any issues?

[Clan]

Originally Posted by Joe of Loath

I have a local Volvo specialist who seems to know K-jet, if I can't figure this out I'll take it to them. They have one or two guys still there who remember the K-jet days and didn't seem phased when mine failed MOT on emissions (just went under the bonnet and tweaked things until it passed).

One of the problems I "fixed" on my drive home was a broken rubber mount on the front of the unit, I held it up with some string off the bottom of the intake manifold for the time being. Could the sag/vibration have caused any issues?

they should have the correct gauge i would think , No , the broken rubber bobbin won't affect anything , the plate is robust it doesn't wobble around .

[Joe of Loath]

Update:

After a couple of weeks at the new job and not feeling up to tackling the task, I grabbed a can of "Intake, EGR and Turbo" cleaner and set to work. I pulled off the air intake hose from the K-jet unit, started the engine, and sprayed about 3/4 of a can through at varying revs. Then I pulled the vacuum line for the engine management box under the dashboard (what does it do on K-jet? Who knows!) and sprayed it through there for a bit (serendipity - the nozzle fits perfectly and is sucked down by the engine vacuum just right). Let it idle for a bit, and took it for an Italian tune up.

Wow. Not only is it back to normal, it's better than it was. I actually scared myself giving it the beans round a couple of roundabouts. Thankfully it handles nicely now it's had an alignment and two new tyres so I didn't get any tyre squeal (would be super bait, lots of coppers out tonight), but wow.

Still going to treat it to a service I think, my new job pays significantly more than my last one did so I can splash out now...

[Laird Scooby]

Originally Posted by Joe of Loath

Then I pulled the vacuum line for the engine management box under the dashboard (what does it do on K-jet? Who knows!) and sprayed it through there for a bit (serendipity - the nozzle fits perfectly and is sucked down by the engine vacuum just right). Let it idle for a bit, and took it for an Italian tune up.

Wow. Not only is it back to normal, it's better than it was. I actually scared myself giving it the beans round a couple of roundabouts.

That there vacuum line is your ignition advance hose Joe! It tells the EZK unit (think it's EZK) how much vacuum the engine is pulling so it can work out how much advance to throw at the distributor.

I suspect the bulk of the effect was from squirting that foam or whatever it is through the fuel distributor.

The K-Jet B230E is quite a lively beast when everything is working correctly but you know that now and so does your underwear after the roundabouts!