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OK, got a weird problem that I can’t seem to diagnose.
Background: I did a full rebuild of the motor and it was running well with likely 6 hours on it. A little hard starting but ran well one started… and was on my list to diagnose later. The next trip up I discovered a coolant link due to an exhaust stud leak from the coolant size. The weird thing was that the motor wouldn’t start as well. So I got a new manifold from MMI swapped the old one out, then noticing that the core plugs on the manifold had slowly leaked on to the carb. So I figured that may be part of the problem with not starting.
So cleaned up the carb, but did not rebuild it, and when I tried to start the engine, no joy. After many attempts, I finally tried only closing the choke halfway and opening the throttle about half as well and could get the motor to fire a bit but then promptly died. A few more attempts and no real improvement. I then thought that “well everything else on the engine is new, I’ll buy a new carb from MMI” and then rebuild the old one at my leisure. So when I put on the new carb, main jet 1.5 turn out from seat… on an the engine ran a tiny bit better, but would now die in 12-15 secs or when I released the choke.
I then checked pretty much everything, fuel gauge at the carb show 3.5 PSI, the polishing filter is new, I triple checked the distributor wires, made sure the carb was lubed and the advance was not stuck. The spark plugs are wet and black t and looks like it’s running rich but the insulated tip it a decent shade of brown (not tan). I checked the cap and rotor, no carbon traces and yes, I have lots of spark. I zero timed the engine three times and finally, with my engine mojo confidence greatly diminished… I even re-watched Don’s video on timing the engine, just I case I had a mini-stroke or something similar.
On the 2.5 hour drive home I was puzzling through what I could have missed and the only hail-mary I could determine was there was air leak I introduced somewhere… but that was an afterthought.
One thing about the engine that is not stellar is the distributor has a lot of slop in linear (up-down) shaft. But when I looked that the cut of the gears and rotation of the shaft, I determined the an slop would get "pulled down". Plus it worked well for the first 5-6 hours.
Other ideas of things to try? This my 3rd A4 and the first two I got to purr… but this one is vexing. ☹
Background: I did a full rebuild of the motor and it was running well with likely 6 hours on it. A little hard starting but ran well one started… and was on my list to diagnose later. The next trip up I discovered a coolant link due to an exhaust stud leak from the coolant size. The weird thing was that the motor wouldn’t start as well. So I got a new manifold from MMI swapped the old one out, then noticing that the core plugs on the manifold had slowly leaked on to the carb. So I figured that may be part of the problem with not starting.
So cleaned up the carb, but did not rebuild it, and when I tried to start the engine, no joy. After many attempts, I finally tried only closing the choke halfway and opening the throttle about half as well and could get the motor to fire a bit but then promptly died. A few more attempts and no real improvement. I then thought that “well everything else on the engine is new, I’ll buy a new carb from MMI” and then rebuild the old one at my leisure. So when I put on the new carb, main jet 1.5 turn out from seat… on an the engine ran a tiny bit better, but would now die in 12-15 secs or when I released the choke.
I then checked pretty much everything, fuel gauge at the carb show 3.5 PSI, the polishing filter is new, I triple checked the distributor wires, made sure the carb was lubed and the advance was not stuck. The spark plugs are wet and black t and looks like it’s running rich but the insulated tip it a decent shade of brown (not tan). I checked the cap and rotor, no carbon traces and yes, I have lots of spark. I zero timed the engine three times and finally, with my engine mojo confidence greatly diminished… I even re-watched Don’s video on timing the engine, just I case I had a mini-stroke or something similar.
On the 2.5 hour drive home I was puzzling through what I could have missed and the only hail-mary I could determine was there was air leak I introduced somewhere… but that was an afterthought.
One thing about the engine that is not stellar is the distributor has a lot of slop in linear (up-down) shaft. But when I looked that the cut of the gears and rotation of the shaft, I determined the an slop would get "pulled down". Plus it worked well for the first 5-6 hours.
Other ideas of things to try? This my 3rd A4 and the first two I got to purr… but this one is vexing. ☹
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