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AQ131A chokes up_next step advice needed

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film842

Contributing Member
AQ131A running fine in the San Juans, then began suddenly to choke up. Had to pump the throttle to keep it running and get home. Now at home, it starts but will not hold idlle or any rpms without violently pumping the throttle. Can rev it up to 3000 rpm but will not hold at any setting.

Here's what I've done so far. The motor was timed by a volvo tech two weeks ago and has been running fine. This motor has a rebuilt distributor, new plugs, points, wires, coil, dist cap etc. I checked the points and rotor and cap again, no problem. Pulled the fuel filter and found watery fuel so replaced the filter. Pulled that filter and it has clean fuel now. Also ran my kicker for awhile as it gets fuel from the same tank. No problem there. Checked the fuel tank vent and it is clear. Just to be double sure I'm siphoning the tank in order to replace it with clean gas and eliminate that problem. However, the fuel I'm getting out looks clean and doesn't separate when in a glass jar.

My question is what to do next? Should I just plan on rebuilding the carb or are there other checks I could make before I do that?

I'm feeling like it's a fuel delivery issue because when it does run, it doesn't stumble or miss. In fact, yesterday it would idle at 800 rpm's with no problem. Advance the throttle and she died.

Any thoughts?
 
I'm beginning to believe that the problem is fuel delivery at higher rpms. I can manually operate the throttle at the carb and see fuel squirting out into the barrel from the little bent pipe thing. Would that also explain why the engine idled yesterday without any problems but would die when the throttle was advanced? I'm going to try and test the pump by turning the engine over and trying to capture the fuel out of the fitting...and...not blow myself up.

So far, I have found that my tank does not have an anti-siphon valve. I assume that if there was one, it would be located on the tank hose fitting that supplies fuel to the engine.

So, my next step is to remove the only removable fitting on the fuel tank (it's where the sending gauge connection is located) and hope to find a fuel tank pick with a cleanable screen. I'm somewhat confused about this because the actual fuel fitting that delivers fuel from the tank is a simple welded connection with no removal or cleaning options. Oh well...will see what I find.
 
Mike, many of the dip tubes will be removeable. Take another look at it..... it may simply be that you are seeing the weld flange and confusing that with the removeable fitting that could contain the dip tube.

I'd not disturb your sending unit and gasket unit unless you must.

The fact that you can pump the throttle to keep it running, would somewhat indicate that the accelerator pump is suplimenting the main means of fuel delivery..... of which would be your low speed and/or main metering circuits.
This may mean that these circuits are NOT functioning correctly......... if this is indeed fuel related!

Question: What is a "rebuilt" distributor to you?
An electronic conversion kit installation.......... or a full shaft/bushing/advance mechanism/curve set/etc. complete over-haul, and THEN a conversion kit? The Pertronix conversion kit uses "Hall Effect" triggering.
If the magnet unit and pick-up are not aligned correctly..... or if you are experiencing a wobble at the original points cam (due to wear), then this will play some tricks on you.
 
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Rick...I had the distributor rebuilt by a well known downtown shop whose name I can't now recall...$135.00 total. They said they had done many many VP distributors over the years.
Three weeks ago Portland Sterndrives timed the engine and it ran great for two hours before suddenly developing this problem out on the water.

Yesterday, I removed the choke valve filter on the solex and cleaned it. Apparently you think I should hold off on removing the sending unit? Do you know if there is a cleanable screen in the tank that I can reach if I remove it? That's the only reason I was going to pull it.

This really has me stumped.
 
Also, I will have another look at the pickup tube connection on the fuel tank. It certainly looked like a welded on part to me.

Rick...if you have the patience here's a question. If I eliminate fuel supply as an issue, what would be the next diagnostic step realizing that I can't presently get the engine to run long enough to time it?
 
RicardoMarine said:
What suggestions are you getting from iBoats?
Click to expand...

I misquoted myself. This is the "other" forum I'm using besides BOC. A fellow on BOC just suggested that I have a fuel oversupply problem after reading my description of pumping fuel out of the little tube thing at the top of the carb. What I said was that when I disconnected the throttle lever at the carb and operated in manually, I would pump a small jet of fuel out of this pipe for every push on the throttle. He said that this little bent pipe is for fuel overflow, therefore the float must be stuck.

Also, I've had a couple of healthy backfires while trying to get started. Does any of this make sense to you?
 
film842 said:
I misquoted myself. This is the "other" forum I'm using besides BOC. A fellow on BOC just suggested that I have a fuel oversupply problem after reading my description of pumping fuel out of the little tube thing at the top of the carb. What I said was that when I disconnected the throttle lever at the carb and operated in manually, I would pump a small jet of fuel out of this pipe for every push on the throttle. He said that this little bent pipe is for fuel overflow, therefore the float must be stuck.
Click to expand...
That is incorrect! He may not be familiar with the Solex!

On some of these Solex Carburetors, there is a second little tube that is part of the metering circuit.
However, if you are seeing fuel spray from this tube (as the throttle shaft is moved from "closed" to "open"), it is the spray nozzle for the acellerator pump!
 
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RicardoMarine said:
That is incorrect! He may not be familiar with the Solex!

On some of these Solex Carburetors, there is a second little tube that is part of the metering circuit.
However, if you are seeing fuel spray from this tube (as the throttle shaft is moved from "closed" to "open"), it is the spray nozzle for the acellerator pump!
Click to expand...

Yes, that's the case.
 
I am not a expert on boats but sounds like a definate fuel delivery problem - like pumping the throttle you are helping the fuel pump - have you checked the fuel pump ?
 
harley2002 said:
I am not a expert on boats but sounds like a definate fuel delivery problem - like pumping the throttle you are helping the fuel pump - have you checked the fuel pump ?
Click to expand...

I do need to test it but am trying to figure out a test without blowing myself up. I could unconnect the fuel tube at the carb and turn the engine over and see what I get but it's a metal tube and somewhat clumsy. I think it will spray all over the place but maybe I can figure something out.

Is there any other way?
 
I've decided to order a new fuel pump and carb rebuild kit and then try the new fuel pump first. Then, if necessary, rebuild the carb.

So, I'll end this thread and start a new one about carb rebulding (which I've never done)

Thanks for everybody's input.
 
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