Hi experts,
I have a 4.2 rebuild engine with 2 strombergs and 123ignition. When I start the car cold it needs full choke and does not run on all cylinders. After slowly driving for a minute or so slowly all cylinders start running. Then after a few minutes more and pushing the choke back the engine backfires a few times and then runs like a charm.
What could this be.
Carbs have been rebuild and I suspect the ignition has to do with it. Changed the rotorcap once and did not do the backfiring for a month. Then it got back.
Have you checked cold valve clearances? Start with basics.
What do you mean with cold valve clearances. What should these be. So you mean lifting the valve covers and checking at TDC of the different cylinders
Sounds like fuel starvation to me!
1 Like
One thing you can try if you think it’s not hitting on all cylinders after start up from cold is to shoot the exhaust manifold with an IR gun as the engine warms up. Any cylinder that does not warm up as fast as the others is not firing for some reason.
The pattern (if there is one) may also suggest whether it is a fuel issue (e.g. front carb v rear carb) or ignition (just a random cylinder).
1 Like
As I recall the Stromberg choke system is really a fuel enrichment circuit. When activated, the two cables open fuel flow thru progressively larger holes. Your symptoms sound to me like only one cable is hooked up. Hence it starts on 3, warms up eventually to run on all 6.
As I said “I recall”. Which is where my theory might go off the rails. My Bentley shop manual doesn’t discuss Stroms.
Your Bentley doesn’t have Section Q? That’s where Strombergs are discussed - the Exhaust Emissions section (easy to miss).
And your memory is correct - a rotating disc that presents ever increasingly sized holes to enrich the mixture.
My PO installed it backwards so it presented ever decreasing sized holes - full choke when shut off moving to no choke as it was pulled. Don’t think that was easy to track down.
Float bowl needle sticking? Today’s gas gums up the rubber needles, and even Gross Jets are a problem over time. On my S.U.s, I can smack the top of the float bowl with a rubber hammer and it dislodges the needle. Of course, a rebuild is necessary to make it reliable.
Two things to watch out for when rebuilding or adjusting the float needle.
Make sure the needle makes a 90 degree contact with the float lever.
Make sure the float lever does not have a wear “dent” where it rubs on the needle.
I have been able to remove wear dents with a hammer and anvil where I hammer from the backside to flatten the dent against something hard and flat.