Hello guys, its finally time for me to post on here again after going through every trick I could pull out of my hat to figure out yet another problem with my 30+ year old engine. I hope you wizards are more perceptive than me, because I am beyond frustrated and defeated.
Here's the problem: BF30A idles rough, cuts out at low rpm, and sometimes is hard to start after dying at idle. Keep in mind, I have experienced no power loss whatsoever at low, medium, or high throttle. Just problems at idle.
Easy, right? Carbs, obviously. Time to clean them. Did that, no change. Must have missed something, let me do it again. No change. Ok, fine, I'll rebuild them. New o-rings, new jets, new fuel/air mixture screws, new float pins, completely and thoroughly cleaned this time, no orifice was left clogged. Check throttle plates, check choke, all good. Engine isn't hard to start anymore, but still dying at idle. Progress?
Next thought was fuel, tried replacing my fuel in case it was tainted, fuel can was clean, new fuel-water separator, cleaned and replaced all fuel lines, new fuel filter, fuel pump working well, everything fuel wise I double and triple checked. No change.
I noticed my fuel filter was dropping well below half-full the longer my engine idled, but the hesitation at idle and eventual dying will happen well before the fuel filter reaches this point. I tried continuously priming the priming bulb to maintain constant high fuel pressure, and there was no change.
Compression test time. Perfect readings across the board (120 psi if anyone wondered. And before anyone comments that that reading is low, 120 psi has been the steady compression reading across all cylinders for me since I bought this engine. And it has run perfectly for years at 120 psi).
Spark check, all good. New spark plugs anyway. No change
Drop coil test, no apparent issues, Replace coils anyway, no change.
Valves?? Went through the each cylinder at TDC and did valve clearances. All were good, except one, which I fixed. No change.
Vacuum leak? Tuned my carbs and didn't notice any signs of a vacuum leak, still sprayed carb cleaner around intake etc.. couldn't find one to speak of.
TIMING?! Yes, checked the timing, was good, but I still decided to take the belt off and go through the timing procedure again just to be thorough. No change.
Finally decided to do a leak-down test. Yes, I checked each cylinder at TDC of compression stroke. I have a cheap Amazon special leak-down tester, so I don't know if I trust the readings, but after calibrating it I got about 35% loss across all cylinders. Not terrible for an old engine. This is where it gets weird. For each cylinder, when I plugged the leak-down tester and compressed air shot in the cylinder, I could hear air blowing out inside my head. I took the valve cover off, and sure enough, I could FEEL air escaping from my intake valve on cylinder 3. Mind you, my tester was plugged into cylinder 1. Plugged it into cylinder 2, same story. Air seemingly leaking past the intake valve on cylinder 3. Plugged into cylinder 3, same story, BUT I got the same 35% loss in cylinder 3 that I did for cylinder 1 and 2.
So here's my question to all of you. How is it possible that I could have a leaking intake valve in cylinder 3, seemingly connected to cylinders 1 and 2, while still maintaining perfect compression across the board and having even and good leak-down test numbers? My first thought was a blown head gasket, but I would think if cylinders 1 and 2 were leaking into cylinder 3 to that extent, I would have massive power loss and misfiring, which I don't. Also, I would think that the compression readings would be significantly lower across the board, and especially in cylinder 3 where it seems I have a leaky valve. If I can HEAR air leaking past a valve, even when it is closed, compression should be wayyyy lower in that cylinder, and leak-down should show massive loss. And yet, compression is good across the board, leak-down is even and good across the board. How is this possible? Am I just stupid? Please someone help me. I'm out of ideas.
Also of note: I know water and steam coming out of the exhaust is normal, but sometimes it seems like an excessive amount of water and steam are coming out. Nothing crazy just...maybe slighly more than normal? Honesly I can't even tell, but maybe this also points to a head gasket leak. I would think if that were the case, though, I would have water in my oil.
Here's the problem: BF30A idles rough, cuts out at low rpm, and sometimes is hard to start after dying at idle. Keep in mind, I have experienced no power loss whatsoever at low, medium, or high throttle. Just problems at idle.
Easy, right? Carbs, obviously. Time to clean them. Did that, no change. Must have missed something, let me do it again. No change. Ok, fine, I'll rebuild them. New o-rings, new jets, new fuel/air mixture screws, new float pins, completely and thoroughly cleaned this time, no orifice was left clogged. Check throttle plates, check choke, all good. Engine isn't hard to start anymore, but still dying at idle. Progress?
Next thought was fuel, tried replacing my fuel in case it was tainted, fuel can was clean, new fuel-water separator, cleaned and replaced all fuel lines, new fuel filter, fuel pump working well, everything fuel wise I double and triple checked. No change.
I noticed my fuel filter was dropping well below half-full the longer my engine idled, but the hesitation at idle and eventual dying will happen well before the fuel filter reaches this point. I tried continuously priming the priming bulb to maintain constant high fuel pressure, and there was no change.
Compression test time. Perfect readings across the board (120 psi if anyone wondered. And before anyone comments that that reading is low, 120 psi has been the steady compression reading across all cylinders for me since I bought this engine. And it has run perfectly for years at 120 psi).
Spark check, all good. New spark plugs anyway. No change
Drop coil test, no apparent issues, Replace coils anyway, no change.
Valves?? Went through the each cylinder at TDC and did valve clearances. All were good, except one, which I fixed. No change.
Vacuum leak? Tuned my carbs and didn't notice any signs of a vacuum leak, still sprayed carb cleaner around intake etc.. couldn't find one to speak of.
TIMING?! Yes, checked the timing, was good, but I still decided to take the belt off and go through the timing procedure again just to be thorough. No change.
Finally decided to do a leak-down test. Yes, I checked each cylinder at TDC of compression stroke. I have a cheap Amazon special leak-down tester, so I don't know if I trust the readings, but after calibrating it I got about 35% loss across all cylinders. Not terrible for an old engine. This is where it gets weird. For each cylinder, when I plugged the leak-down tester and compressed air shot in the cylinder, I could hear air blowing out inside my head. I took the valve cover off, and sure enough, I could FEEL air escaping from my intake valve on cylinder 3. Mind you, my tester was plugged into cylinder 1. Plugged it into cylinder 2, same story. Air seemingly leaking past the intake valve on cylinder 3. Plugged into cylinder 3, same story, BUT I got the same 35% loss in cylinder 3 that I did for cylinder 1 and 2.
So here's my question to all of you. How is it possible that I could have a leaking intake valve in cylinder 3, seemingly connected to cylinders 1 and 2, while still maintaining perfect compression across the board and having even and good leak-down test numbers? My first thought was a blown head gasket, but I would think if cylinders 1 and 2 were leaking into cylinder 3 to that extent, I would have massive power loss and misfiring, which I don't. Also, I would think that the compression readings would be significantly lower across the board, and especially in cylinder 3 where it seems I have a leaky valve. If I can HEAR air leaking past a valve, even when it is closed, compression should be wayyyy lower in that cylinder, and leak-down should show massive loss. And yet, compression is good across the board, leak-down is even and good across the board. How is this possible? Am I just stupid? Please someone help me. I'm out of ideas.
Also of note: I know water and steam coming out of the exhaust is normal, but sometimes it seems like an excessive amount of water and steam are coming out. Nothing crazy just...maybe slighly more than normal? Honesly I can't even tell, but maybe this also points to a head gasket leak. I would think if that were the case, though, I would have water in my oil.