I used information from the last few months of posts on the Brickboard to put together What I hope is complete tune up sequence for my 1977 B21E K-Jet.

So far the Head has been rebuilt, including cam shims, and the cam timing is correct. I have a rebuilt fuel distributor.

I know these bits are good. The idle is all over the place, the injectors probably need replacing and I think most of the vac lines leak. It is running very rich, It fires on all four, but eventually chokes itself up with too much fuel. I have already ruined two sets of plugs from fouling, and that's just running it in the garage.

Here is my plan to tune up the motor

B21E Tune Up Sequence

1. Check muffler, do you have one? If not, get one. Fix leaks in exhaust with muffler bandage.

2. Prime for start up. Remove cold start injector and confirm that it sprays fuel into bottle. Put it back.

3. Clean flame trap.

4. Find every vacuum line attached to the throttle body. Confirm that we do indeed have a sealed system. Any tuning is meaningless with vacuum leaks. Reassemble the system including pollution system and air filter.

5. Confirm that the throttle is fully closed with foot off gas, and fully open with foot to the floor. Fix free play in throttle cable.

6. Once nothing can leak air, run it to operating temp, then take the valve cover off to re-torque the head bolts.

7. Now that the motor is hot, remove cold start injector and run into bottle. Plug it's hole and restart engine. Confirm that no fuel is delivered

8. Start it up and wind the idle back to 900 RPM hot. If it chokes up too much from the excess fuel to attain a steady idle, wind the air fuel mix back a fraction using a 3mm Allen key, but we are not tuning the fuel at this stage. 1/5 to 1/4 of a turn anticlockwise significantly evens out that fuel curve according to Rhys. Just tweak it so it doesn’t choke itself up. 900 RPM hot is the aiming point.


9. Now that we know the idle is set up right as far as air goes, let’s get to work on the fuel flow. Unplug the return line to the tank and prime the fuel pump to run continuously. Once running it should circulate at least half a litre of fuel every minute. If not, it will not be delivering sufficient pressure.


10. Confirm ohmic resistance on control pressure regulator is correct. I’ve given up on actually figuring out what the various pressures should be. If the CPR appears to be OK electrically then it should be working well enough to tune around. If we are getting half a litre back with the ignition on run, then we can assume it works.


11. Pull the rubber hat off the top of the airflow sensor. Check it’s positioning is Ok using three strips of typing paper and a magnet. Realign as necessary.(ugh looks fiddly, hope I don't have to)

12. Next thing to do is to once more prime the fuel system to run then check the flow from the injectors. When the airflow plate is closed, the injectors may deliver a trickle but they should not be spraying. Put a Magnet on the bolt and raise it up and down. The injectors should all be delivering the same amount of fuel at each position, and it should be an even spray. Replace the injectors if needed. Test the new ones. You know they should be getting even pressure from the distributor: you just had the thing rebuilt.

13. Ok, plug the injectors back in and put the rubber hat back on. Start it up. Should run very rich. Keep winding the idle screw back until it begins to starve the engine. It should run a fraction rich, but as lean as you can make it and still manage step 14.

14. Test the mix by pumping the brake pedal. The extra air flow should raise the revs to about 1000. Rev it up to the redline and quickly take your foot off the gas. You should hear three pops from the exhaust, but that is all. Again, you are looking for the absolute minimum control plunger setting to achieve this result.

15. It is now time to tune the ignition. There are no breaker points to set. The control unit is a matter of faith, but I am assured that they rarely fail, and if you have spark that means it’s working.

16. Now that we’ve cleaned up the combustion it should stop fouling plugs, So time to change them.

17. Using 22mm (7/8") socket on crank pulley bolt, turn engine (CW, viewed from the front) to 0 degrees Top Dead Centre on #1 cylinder (per timing mark on crank pulley). Cam mark should also align at this time.

18. Remove dist, cap, rotor, and plastic dust shield (if present). Loosen dist. hold-down bolt. Put rotor back on and, leaning over to look straight down, see if centreline of rotor points to the groove/notch mark on dist. body, which will be about centred in the front-right quadrant of body

19. If necessary, rotate distributor till rotor and marks align. The turn it a bit more so the rotor is about 1/4" PAST the mark. This will put the timing about 10 degrees advanced. (The engine is at 0, the rotor was there 10 degrees ago). Final timing to be done with engine running, using a timing light. I don’t own a timing light, is there some way around this?

Thankyou so much for reading the whole thing.

Thanks to Bruce “Lucid” Young of New York for distributor details. Thanks to “Rhys”, sorry, couldn’t find your profile, for excellent information on the fuel system, and to an unknown Volvo enthusiast I met at the wreakers who told me how to listen for a correct fuel mix.
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Drive it like you hate it