fuel starvation? clogged fuel filter....

[737800FO]

Started out yesterday and as we cleared the no wake buoy I pushed up the power and within a minute or so my A-4 began to stall. I pulled the power back to idle and the engine continued to run smoothly, but only at idle. we returned immediately.

I just purchased the boat in april. the engine had not been run for about a year and a half, according to the previous owner. I drained the gas (it was amazingly clean) and added new gas and a fuel and carb cleaner (cant remember the brand).

I suspect the fuel filter is clogged (was going to change it, but didnt get around to it). It appears to be a Fram C-11 70PI, but I'm not sure about that. I cant really read the lettering. I'll probably just replace it with a Racor fuel filter.

Am I on the right track with this? Also, just thought of this, where is the oil filter on the A-4 or does it even have one?

Thanks,
Mark

 

[u079721]

The fuel filter would be my first guess too, given what you have described. But another thing you might want to check is whether there is any type of screen on the fuel pick up tube in the tank. On some boats there is a screen on the end of the fuel pick up tube that can get clogged with time, also limiting fuel flow. Cleaning that screen, or removing it altogether, can also help.

Good luck!

 

[robjpowell]

Many of us with old A4's have suffered similar problems. I would also suspect the filter but it could also be the manual fuel pump. It is well worthwhile installing a new electrical pump at the same time you replace the fuel filter. Moyers have one that has worked well for the last five years for me. Personally I have a large Racor as a primary and a smaller in line secondary. This combination seems to keep things happy. I replace both filters every 2 years irrespective of hours.

The A4 does not have an oil filter but Indigo Electronics sell one. I installed one as an upgrade prior to moving our 35-2 from Baltimore to Boston. I have been very happy with it.

Feel free to contact me if you have more questions.
Rob

 

[steven]

Wrestled with a similar sounding problem all last summer. Ran fine at idle, but stalled when fed power. I had a brand new filter, new fuel, points plugs. Tracked down the root cause this morning during my annual tune up - looks like a leaking (rusted through) exhaust manifold. So as well as checking fuel, you might want to check your exhaust system.

 

[Bill Sanborn]

It is possible to run the A4 by siphoning fuel directly to the carb from say a quart jar. This eliminates most of the fuel system as a problem source.

I have a small Racor filter installed between the fuel pump and the carb. The filter has a clear bowl so you can see if there is fuel flow, dirt, air bubbles etc. I can't remember the model but it uses an S2501 or S2502 element. This is in addition to the main Racor filter installed between the tank and fuel pump.

Will the engine ever run at high RPM even in neutral?? If not this might indicate a plugged exhaust.

 

[737800FO]

fuel filter, fuel starvation

OK guys,

I replaced the phram fuel filter with a Racor filter. I filled the fuel filter with gas, and tried to start the engine. After several cranks it did turnover. did this several times and was able to get it to run at approx 1500-2000 rpm for perhaps a minute or two and then it died (by the way the fuel that came out of the old filter was contaminated). I repeated this process numerous times thinking I needed to purge the air out of system. I had an appt so I was only able to do this about five times but all with the same result. Somebody had mentioned something about the fuel pickup screen, how do you clean this. I also found the fuel vent clogged and hopefully got it cleaned out.

The previous owner said that the engine hadnt been used for over a year. I drained the fuel but am wondering if I got all the sludge out. the fuel I removed was for the most part clean which surprised me. I am wondering if I need to rebuild the carb, but I am still leaning toward a fuel contamination problem. any thoughts.


Thanks
Mark


ps by the way this forum is fantastic and I really appreciate everyone's input

 

[jkenan]

A common cause of the problem you describe (on the A4's anyway) is a dirty main jet in carb, restricting gas flow when then engine is not in idle (there is an idle valve that provides gas to the engine at idle, which gets closed off once throttle is given and the main jet ttakes over supplying fuel - if the main jet is clogged, the engine will stall). It is not that big of deal to remove the carb and clean all components - I've done it at sea before when I experienced the same issue (just want to be careful not to spill any gasoline in the process). And you might as well clean all components anyway since you'realready disassembling it. Shouldn't take more than 20 minutes start-to-finish with a little practice. Of course, the dirt got in there somehow, so all the fuel filter suggestions here are completely valid.

Go to moyermarine.com and search their forum for 'loss of power in forward', 'engine power loss' or the like. You will find lots of goodinformation. Other things to check for low power in forward (not stalling) would be bad plugs, barnicles on the prop, timing, line wrapped around prop, and the like. Sounds like your main jet to me though, in this instance, since you're stalling...

Good luck.

 

[steven]

I have now completed replacement of my exhaust manifold - my A4 purrs at 2300rpmh and moves through power range smoothly in fwd and reverse. Been awhile since I could say that.

Nevertheless, agree with John that a common cause of symptoms is fuel jet and that is the main suspect - takes only a small spec of dirt to cause a problem.


--Steve