Running rich

[tthurlow]

I've got my 44 running better following issues with the vacuum system (see dafcars.proboards.com/thread/4036/help)
Now i have an issue with it running very rich (i think). The car will start and tick over fine. I've done the timing and checked the points gap-it seems to run better set slightly wider than the manual suggests). I have adjusted the volume control screw until it ticks over sweetly-it has a type 40 solex). The plugs are black as is the exhaust pipe. The car doesn't smoke though. My local garage put the probe up the exhaust and said there seemed to be a lot of unburnt fuel coming out the exhaust.

Although the car ticks overfine it will sometimes really struggle under acceleration, bogging down and spluttering until eventfully the revs build and off it goes. It makes driving a bit hazardous, especially when pulling out of junctions. It doesn't look like the car has any mixture adjustment on it. Any ideas? Thanks, Tom

[andrew]

The carburettor has two adjustments the owner can make, and they're the idle speed and the volume. The volume screw is at the rear of the carburettor and one screws it in (clockwise) to make the mixture weaker and out (anti-clockwise) to make the mixture richer. The idle speed is at the front of the carburettor and one screws this one clockwise to increase the tick-over speed and vice versa

To start the procedure, assuming the timing and ignition are in good order and correctly set, ENSURE THE CAR IS IN NEUTRAL and then start the engine, allowing it to warm up. Once it's warm, s-l-o-w-l-y screw the mixture screw IN until it can go no further (DON'T over tighten it) and then wind it OUT about 2 1/2 turns. In doing this the engine may stall, so start it again and allow it to idle. Now, by s-l-o-w-l-y turning the mixture screw out and in a quarter turn at a time you'll find the point at which the engine revs increase and the engine sounds smooth. This usually occurs when UNSCREWING the mixture. Once you're happy the engine's running smoothly, use the idle screw to reduce the idle to the point at which the clutch is disengaged from the flywheel. You can confirm this is the case by changing gear from forwards to reverse without hearing a "crunch". Next, depress the brake pedal; the revs should rise, albeit only slightly. The engine should NOT stall. If it does, the mixture's still too weak and needs to be a little richer. This adjustment should be done a quarter of a turn at a time-it's a finely tuned adjustment.

In addition to these adjustments, it's possible that the choke mechanism isn't functioning correctly. This can be checked by removing the air filter and confirming that when the choke control is fully pushed IN the choke butterfly in the carburettor throat is in the vertical position. If it isn't, then the choke cable needs adjustment. The ideal arrangement is to set the choke control a few millimetres away from the stop and then adjust the cable at the carburettor, so that the choke butterfly IS indeed, vertical.

Any more questions? Just ask! We're here to help!

[bobdisk]

andrew, Kermit is on the road!! I have fitted the engine out of the blue 33. It goes well, after it has warmed up, which takes 2.5 to 3miles. It was difficault to get the idle mixture and speed correct but once it is hot, it is ok. If it is a bit too rich, the engine shakes violently. If weak enough to get a smooth idle, the brakes/switch will stall it. I have left the vacuum solenoid disconnected because at whatever setting, using the brakes will stall it, and make it difficult to get going again. The exhaust connection to the inlet manifold hot spot broke off, so I blanked the hole. Does it matter that it is not connected?

[dafdaffer]

check the anti run valve on the carburettor that its operational, tight or that there is no gunk behind it, I've seen cars that have been adjusted to compensate it not working by adjusting the mixture screw, when you press the brake pedal the revs should increase by around 100 rpm. that should give you a good indication.

[bobdisk]

The carburetor solenoid works ok. Disconnect while the engine is running and it stops, which is what I would expect. Tap the connection, and you can hear it click. Its clean inside, and in tight.

[andrew]

Jul 20, 2023 6:16:21 GMT bobdisk said:

andrew, Kermit is on the road!! I have fitted the engine out of the blue 33. It goes well, after it has warmed up, which takes 2.5 to 3miles. It was difficault to get the idle mixture and speed correct but once it is hot, it is ok. If it is a bit too rich, the engine shakes violently. If weak enough to get a smooth idle, the brakes/switch will stall it. I have left the vacuum solenoid disconnected because at whatever setting, using the brakes will stall it, and make it difficult to get going again. The exhaust connection to the inlet manifold hot spot broke off, so I blanked the hole. Does it matter that it is not connected?

Bob, long time no speak! Reading through your post I can offer the following thoughts, but not in the order you raised them1

1/ The hotspot connection was designed to warm up the carburettor and in doing so assist vaporisation of the petrol/air mixture, particularly in cold weather. Unleaded petrol vaporises more easily than leaded fuel anyway, so this is not as vital as it perhaps once was. As long as the exhaust is not blowing I shouldn't worry too much about it, unless you plan to go driving in snowy conditions in the middle of winter!

2/ If the car's stalling when you apply the brakes are applied then the mixture is too weak, so instinct would suggest enriching it. You should check the solenoid cut-off is working correctly, which is easily done, by switching the ignition on & pulling the wire away from the solenoid and then touching it to the terminal; one should hear a "click" was the solenoid engages. If it doesn't, you've probably found your problem. Remove the solenoid and clean it, which might help. I've a spare on if you can't fix it.

3/ Disconnecting the vacuum solenoid is NOT a good thing to do, since it reduces the car's braking and more importantly, the car will more than likely be in the wrong ratio as it moves away, with concomitant "noises aft" as the transmission attempts to adjust itself when you drive off again, as you seem to be noticing!

I hope this helps! I also know I owe you a visit in my Daf, in order to assist you in your endeavours to perfect yours! I can only apologise for my non-attendance in your area, and blame my grandchildren! I WILL make it over to you sooner rather than later!

[bobdisk]

The carb. solenoid is working ok, see previous post. I will be seeing about some new seat belts this afternoon, journey about 9 miles, so when it gets hot, I will reconnect the vacuum solenoid, and see what happens. It seems ok without the solenoid, and takes off from stanstill without complaining.

[bobdisk]

A visit to Brooklands yesterday, a good run, apart from lots of road works, and waiting at their traffic lights!! Those waits helped it get hot! In the first couple of miles, the inlet manifold is cold. Whe we go to Brooklands, it was hot to touch. I think thats got something to do with it. When its hot, it idles nicely, and with the solenoid connected the idling speed does not change. It is a better start from standstill. Still think it needs an expert eye to get it exact!, yours andrew !