Arrrrgh... help needed!
I have scoured the iBoats posts on QJ's and not seen my particular issue - poor running and power when the carb secondaries come into play.
Background: 5.0L OMC with a QJ 4MV model 17059286 on a 21' 1987 bayliner.
When I bought the boat (used) a few years ago it ran fine. While winterizing I thought I'd clean some debris off the carb exterior with cleaner, also sprayed into the vent holes. BAD IDEA.
Dried the upper gasket and next spring it kinda leaked and ran bad at lower rpms.
So I got a kit and did a rebuild, and now the idle and primaries run great - but the secondaries run like c**p. As soon as the secondaries start to open - the moment the air valve begins to open - it loses power, like bogging, and continues to do so as long as the secondaries are in operation to any degree. To me it seems like they are running lean. No black smoke or fuel smell when the secondaries are open.
I've checked everything I can think of - fuel flow into carb is fine (checked pump inlet vacuum and outlet pressure and flow, all is ok). Fuel filters are clean. Anti-siphon valve is ok. Fuel is clean, no water in it. Float is set plenty high and bowl is full. The secondary jets, fuel wells, and accelerating ports are clean and clear. The Secondary metering rods are installed correctly and move easily as the air valve opens. The air valve opens slowly and smoothly, about how I'd expect it should. I can see fuel going into the secondary bores as the air valve opens.
Timing is correct, firing order is correct, points are set correct. New carb-manifold gasket, which I also checked and is leak free.
I've taken the carb apart a few times to double check things, and put in another rebuild kit, all to no avail. I've scoured the net, read all the manuals and how-to guides, etc, to no avail.
The secondary circuit is pretty simple, I can't for the life of me figure out what is wrong, but something is. Any thoughts welcome. Maybe it isn't the carb, and other ideas welcome - but it sure seems like the carb to me.
Please, let's keep this thread to diagnosing this problem, I'd like to avoid thoughts on replacing with the venerable 1409, and/or the general merits of QJ v Edelbrock v Holley. I'd just like to figure out what the heck is wrong here...
Kurt
I have scoured the iBoats posts on QJ's and not seen my particular issue - poor running and power when the carb secondaries come into play.
Background: 5.0L OMC with a QJ 4MV model 17059286 on a 21' 1987 bayliner.
When I bought the boat (used) a few years ago it ran fine. While winterizing I thought I'd clean some debris off the carb exterior with cleaner, also sprayed into the vent holes. BAD IDEA.
Dried the upper gasket and next spring it kinda leaked and ran bad at lower rpms. So I got a kit and did a rebuild, and now the idle and primaries run great - but the secondaries run like c**p. As soon as the secondaries start to open - the moment the air valve begins to open - it loses power, like bogging, and continues to do so as long as the secondaries are in operation to any degree. To me it seems like they are running lean. No black smoke or fuel smell when the secondaries are open.
I've checked everything I can think of - fuel flow into carb is fine (checked pump inlet vacuum and outlet pressure and flow, all is ok). Fuel filters are clean. Anti-siphon valve is ok. Fuel is clean, no water in it. Float is set plenty high and bowl is full. The secondary jets, fuel wells, and accelerating ports are clean and clear. The Secondary metering rods are installed correctly and move easily as the air valve opens. The air valve opens slowly and smoothly, about how I'd expect it should. I can see fuel going into the secondary bores as the air valve opens.
Timing is correct, firing order is correct, points are set correct. New carb-manifold gasket, which I also checked and is leak free.
I've taken the carb apart a few times to double check things, and put in another rebuild kit, all to no avail. I've scoured the net, read all the manuals and how-to guides, etc, to no avail.
The secondary circuit is pretty simple, I can't for the life of me figure out what is wrong, but something is. Any thoughts welcome. Maybe it isn't the carb, and other ideas welcome - but it sure seems like the carb to me.
Please, let's keep this thread to diagnosing this problem, I'd like to avoid thoughts on replacing with the venerable 1409, and/or the general merits of QJ v Edelbrock v Holley. I'd just like to figure out what the heck is wrong here...
Kurt
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