240 240 K-jet no fuel adjustment screw

Matt1275sMatt @Matt1275s Northern Territory

Hi, before I start I'll give a quick introduction. New to the forum I recently acquired a 1979 242gt after many years of dreaming. I will give a more formal intro once I have got things a bit more underway and have the car properly settled into its new home.

When I bought the vehicle it was majorly overfueling. I suspected a stuck fuel metering rod in the k-jet fuel distributor. This ended up being the case however it was so jammed with old fuel I had to open the distributor up to free the rod.

The result was I got it running roughly but must have messed up the o-rings inside as two of the injectors started delivering way more fuel than the others to the point of flooding only those cylinders.

Rather than continuing to mess around with the fuel distributor I opened and messed up I bought a rebuilt exchange unit. The current result is the exact opposite I now get no fuel through the injectors at all. Fuel pump is delivering fuel, I suspect the issue to be the allen key adjustment screw in the air flow meter.

My reason for this suspicion is that the screw seems to be completely missing. So I guess my question is does this look right in the pictures and could this be the reason no fuel comes through the injectors?

The black line on the allen key is how deep it goes down the adjustment hole (55mm). I used a 3mm and 2.5mm allen key. Neither feel like they engage any form of allen screw in the hole.

I am yet to get to the point of lifting the air flow plate by hand while someone turns it over to see if this lets fuel through to the injectors as I'm waiting on a second set of hands.

«1

Comments

  • Who did you source the rebuilt exchange unit from?

    I've seen them fitted with plugs before to stop people from adjusting them.

    Have you been able to check the fuel /control pressure?

    Kjet systems that have been sitting with stale fuel are a nightmare to sort out

  • Matt1275sMatt @Matt1275s Northern Territory

    Fuel distributor was from 'k-jet specialists.' The air flow meter is still the original one from when I bought the car I have only swapped out the fuel dist. Previous owner had a new/recod warm up reg fitted.

    Haven't checked the control pressure yet was hoping I could get some life into it first before I needed to look that far into it and do the finer tuning.

  • How old is the fuel filter?

    The Ozvolvo archive ozvolvo.org/archive may be a helpful resource on your 242 resurrection journey.

    I found this article that could be a good place to start. ozvolvo.org/archive/?download=Vm9sdm8vay1qZXQub3JnLzE5ODgxMElTX0tKZXRyaWNrczIucGRm

  • If you look into the chamber from the inlet side you should be able to see the grub screw on the arm to verify.

  • It doesn't take two people to test the injection whilst the pumps are on


    In theory there should be no injection with a closed metering plate (as long as the piston inside the distributor isn't seizing) so jump the fuel pump terminals at the fusebox so you hear the pumps running, then lift the metering plate enough so that you hear the injectors singing

  • I had a look on kjet specialists website and they list adjustable and non adjustable fuel distributors. Perhaps they sent you a non adjustable one?

  • Matt1275sMatt @Matt1275s Northern Territory

    Thanks Essbos that document was a good read.

    I hadn't got round to bridging the fuel pump yet as I haven't had a good look at where to bypass the wiring system but if it can be done from the fuse box I will give that a try. I have just been doing it while cranking the car over with the key.

    I did try to have a look through each side of the airflow meter for the grub screw while it was off but couldn't see anything obvious? That's why I was wondering if the allen key should go that deep down the adjuster hole?

    Before I changed the fuel distributor out for the new one, on the injectors that weren't flooding I was getting a good spray pattern and volume while cranking the car over, enough to have the engine running on just the good injectors with the other 2 removed.

    Now with the new fuel dist I get no spray from any injectors while cranking it over. Going to test the return volume and see if with the fuel pump running and lifting the AFM plate I get some fuel spraying through.

  • Matt1275sMatt @Matt1275s Northern Territory

    I put a screwdriver shaft between the AFM plate and AFM body to keep it held open by about 5-10mm, turned the car over and it starts up straight away and sits idling with no issues. Checked the injector spray in this state and they all spray a good amount to sustain the idle.

    I put the allen key back down the adjuster hole and turned it clockwise, I did notice the plate slightly lifting each turn so kept turning it to get the plate up higher to the point the allen key felt resistance.

    This still was not high enough to allow any fuel to spray through with the pumps running, and with the rubber intake joiner back between the AFM and throttle body the car would only fire briefly after the first crank die and then I would not get anything.

    Good to see the car is capable of running, pretty sure my problem lies with the fuel rod in the fuel distributor not being high enough at its resting point, governed by the AFM arm/flap, to allow fuel to spray through on start up however I don't seem to be able to adjust it any higher.

  • Casting my mind back, there is a metering pin and a cage in the distributor. The cage is locked at a specific depth with a folded locking washer. It that cage has been set too deep, you would need to push the pin in further to have fuel flow. Fine tuning is then completed with the grub screw.

    VolDan
  • carnut222Greg S @carnut222 Daylesford VIC

    IIRC lifting the flap with the adjustment screw will actually LEAN out the mixture...so maybe you need to go the other way? Think about it - if you raise the flap using the adjuster screw, it’s basically allowing more air in before the flap starts lifting the piston in the fuel distributor. I could be wrong as it’s been a long time since I dealt with a K-jet car (and I swore them off back then LOL!)

    The rest position of the flap has a spec...can’t recall what it is but there was a basic dimension somewhere in the K-jet manual showing where the flap should sit at rest.

  • carnut222Greg S @carnut222 Daylesford VIC
    edited May 13

    This may be of use too:

    I may have been a bit off on my comments above. Looks like the screw should not alter the flap position, only the relative position between the flap arm and the distributor plunger.

    VolDan
  • The airflow is controlled by the butterfly. Lifting the plate increases the fuel supply (aka rich).

  • Matt1275sMatt @Matt1275s Northern Territory

    Yeah your right the screw doesn't alter the flap it looked to be moving when I turned the allen key but it was just the pressure of me touching the allen key making it look like it was moving.

    I did cut off a tab on the lock washer that was folded over the bottom of the fuel rod, hoping that wasnt it? I thought it was just a tab to stop the pin dropping out before install as the old one didnt have it.

  • carnut222Greg S @carnut222 Daylesford VIC

    Sorry Ian. I meant in the static adjustment case, not during operation...yeah, I know lifting the plate up causes the piston to lift and increases fuel flow...I was just thinking what happens if you were to alter the static (rest) position of the plate and/or the relative position of the plate arm to the piston.

    VolDan
  • jamesincJames @jamesinc Oz Volvo Ice Fortress

    Clockwise richens the mixture. Turning the screw doesn't raise the air metering flap, it raises the fuel metering needle relative to the air flap. The end of the adjustment screw rests on the air metering lever arm. See pic:


    VolDanbgpzfm142Dauntless
  • Have you got the green book on this?

  • Matt1275sMatt @Matt1275s Northern Territory

    Only thing I have to refer to is a haynes manual which is very vague when it comes to the k-jet system.

    The documents that have been posted up on here from the archive have been very useful though.

    The car has had to sit on hold for a bit again. I don't live where the car is currently located and only get to work on it when I occasionally fly in for visits.

    Still trying to work out how to adjust the fuel metering rod higher. I'm on the look out for another K-jet air flow meter to play around with while I'm away from the car to hopefully setup in the meantime if anyone knows of one for sale and able to post?


  • We all do, sorta. TP30454 is in the Oz Volvo Technical Archive.

  • edited May 14

    Tech archive is here

    https://ozvolvo.org/archive

  • If the plate mixture screw is there, then there's two other culprits in the mix. The first is the control pressure regulator (referred to as the warm up regulator) and the line pressure regulator in the fuel distribution block itself. The one in the distribution block is to be set at 490 kPa/70psi. The CPR/WUR maxes out at 370 kPa/53 psi when hot.

    The CPR/WUR controls the fuel pressure on top of the plunger and is easy to block up with varnish/detritus.

    As the green book states "Should the control pressure regulator become clogged, there will still be line pressure in the control circuit. The control plunger is then unable to go up high enough. The air-fuel mixture becomes too lean"

Sign In or Register to comment.