Having a bit of a mare' at the moment with my 72. Its a 1800 type 4 with 36 dells. It would seem that on tickover it doesnt fire on number 3, I have found this out by testing the temp of the exhaust as they come out of the head.It also pops back through the carb I can see the flames lol. I pulled the plugs and on 3 they are black indicating an extremely rich mixture, all the others were ok, so I changed plugs and leads to new (german) bosch ones. This made no difference to the tickover running, and giving it a test down the drive it bogs from tickover to full throttle when on the move resluting in me having to rev it out so to speak to clear its throat. I read through the trouble shooting pages of the dell bible and it was pointing at the idle circuit, and the idle jet in particular. I went and bought some compressed air in a can and blew out the jets popped them back in and it made no difference. I have tried to adjust the mixture but number 3 does not respond, all the others start to splutter when closed. 3 does F all. This also points to number 3 being the problem but I can't find the problem It is running at 3.5psi through a filter king. It has clean fuel. It has electronic ignition. It is timed to 28 BTDC The valves are checked. The carbs are sync'd The linkage is sync'd Number 3 has a spark as it kicks in later with the main jet. the dells are recently rebuilt from Eurocarb jetted correctly. Any other ideas welcome lol Matt
Stick the timing gun on no 3 ht lead to check if it is electrical, if its flashing at low revs you can then discount the electrical side. If its not flashing you have narrowed it down.
Not the same carbs but I have just had this problem with my type 1 engine and 34 ICT's also number 3 was not firing. i was dreading the worst as in low compression and a dropped cylinder. it turned out to be fuelling. Mine was sorted by adding a balance pipe between the manifolds. the symptoms were exactly the same as yours. not sure if you can add a balance pipe on the dell manifolds. also check the mixture needle is not bent on number 3. count the turns though so you can get it back to where it was. This can cause over fuelling. good luck mate.
Spark plug ll be black if not firing. Check compression ,plugs etc. There's summat peculiar about no 3 pot that I can't for the life of me recall. More pills nurse!
No 3 gets hotter than the rest, just the layout of the engine and has a stronger tendancy to burn valves. For god sake don't quote me. Excellent pils nurse!
Dells dont need balancing as essentially they are twin-twin carbs if that makes sense, one barrel is for one cylinder they share a butterfly linkage but all other adjustments are independant of each barrel.
To be honest and perhaps the part filling me with the most dread is this.... I think a compression test is on the cards as it can only be something like this
how are you sure number 3 is getting a spark on the main jet?? if it is getting spark then it must be pretty weak other wise it wouldnt be boggin down. Have you swapped the plugs to see if the problem moves with the plug??
The plugs, leads and cap are all new. The exhaust is getting hot on throttle just noticeably cooler on tickover...
As an experiment, I'd swap no 3 plug and lead. There's nothing special about no 3, BTW. It doesn't get hotter than the rest.
hmm I know what you mean now. I'd still swap the lead and plug as snotty said just to rule out ignition. if the problem doesnt follow it then it's down to fuel..... you might have a blockage before the idle jet... must be something relativley big though. does your mixture screw travel the same distance as the others?? do you have a filter before the carb? is there anything in there to point towards muck in the system? I'm not too familir with Dell's so I dont know how the idle circut works...
It was the case on early type 1 engines, where cooling air went over the oil cooler before cooling no 3 cylinder. Dog house type 1s and type 4s don't have a problem
You might want to check the idle jet on no 3 to check it's not blocked. Crud can fall down the hole where they live and bung the top of the jet up.
Leads have been swapped already and nothing changes. Same with the plugs. I will blow out the idle jet housing when i get home.
The screw winds in and out identically to the others, and i have a filter before the fuel pump as well as the one in the filter king regulator. From reading up the circuit is relatively simple, hence this frustration Filter.
