Hoping to resolve running issues with Icts tomorrow, when first starting van has small backfires mainly on tickover. Has been happening since replaced fuel lines and back box, have checked for air leaks/exhaust leaks removed and cleaned idle jets, played with mixture and carb balancing, checked valves, timing, cleaned pod air filters, replaced fuel filter, new fuel. Only thing I noticed was the new silicon Ht leads no 1 plug the rubber cap came off the Ht, refitted but with rubber seal cant confirm it is 100%. Will try spare one first tomorrow. Engine has 34 icts, Sdva dizzy and JK stainless exhaust and ran Ok
If it's the exhaust then, perhaps stating the obvious, but there must be unburnt fuel mixture in the exhaust. Are you able to satisfy yourself the engine is firing on all four with correct timing, there's no misfire?
A healthy ignition system will still fire through a gap in the lead, but it does fire a bit weaker. I would also check the condition of things like points and gap, distributor cap, rotor arm, nose of coil looking for flashovers. Also loose spade connectors. Popping is fuel unburnt in the exhaust. A too lean mixture on one cylinder goes straight through and burns when it meets hot gas from another cylinder. A misfiring spark plug also does this. So its either a mixture thing or electrical. A badly worn points or worn out condenser might cause this, or a failing electronic unit. Or a dirty spark plug.. A recent chain of issues for my bus were fixed by re tightening or replacing female spade connectors on the electronic ignition module, changing the coil .. back to the dented and horrible looking one that came with the bus 10 years ago. and replacing the spark plugs, making sure the ends of the silicone leads had not slipped up under the shrouds.. Somewhere in all that, rough running and occasional cutting out at junctions were cured. With electrical spade connectors the simple test is to grab the wire and pull it moderately hard say about a pound or two or 10N ... If the connector comes off the spade or the connector comes off the wire...thats a problem you need to fix.
I had a cracked plug cap last year. Misfire but no popping or banging. 55 should be big enough. I'd be looking for a small air leak.
For now cured backfire, replaced Ht lead and base set mixture screws. Left carb was 3/4 turn richer than other . Will separate carbs and set up later. @zedders will double check idle jet size too. Sent from my SM-A405FN using Tapatalk
A leanish setup one side means that one cylinder gets really starved at idle because the firing order sucks mixture right-left-left-right 1-3-4-2 and with dual single barrel carbs that means one cylinder of the two gets more fuel. Also happens with centremount carbs..my progressive really shows it , one cylinder has black on piston on each side other one is clean. The solution is a pair of dual barrel carbs or fuel injection.
No point, you fixed it. 55 are fine, 58 are fine. Mine runs happy on 42, it just won't start from cold with those even in summer.
