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prkaye

Well Known Member
Can fuel be flushed through the primer lines with them not connected to the intake ports before first engine run, to flush out any residual debris in the lines and to check for leaks? Would this damage the fuel pump or primer solenoid?
 
I don't think it will hurt the pump. But i did it a different way. I flushed my primer lines out with Carb cleaner just before installing the lines from the gasolator to the primer solenoid and the lines to the cylinders. Mine worked fine for the first few hours, and then something plugged the primer line to the #4 cylinder (Have only two primer lines, #2 and #4 cyl). Had to remove it and flush it again. No issues for 56 hours so far.
 
I have a question regarding how much priming it takes using the solenoid valve primer and a facet pump. I am having a difficult time starting my carbureted o360 and wondered if perhaps I am not priming enough. I turn on the facet pump and watch the pressure build up. Then I hit the primer solenoid for about 4 seconds and then spin the engine. It takes a couple of these to get things going. Am I not priming enough? Does the carb have a booster pump that will squirt fuel if I pump it during the start attempt? I figure that it is better to not have too much fuel and risk fire...
 
Hi Don.......

.....We have the same primer/carb setup but what I've seen guys do is open the throttle too far. It barely needs to be cracked (Yes, it does have an accelerator pump....we give three strokes) so that the velocity of the up-flowing air is fast enough to carry fuel uphill to the cylinders. Try cracking the throttle no more than 1/8". This leaves a very small clearance between the butterfly and the venturi of the carb, making for fast airflow.

You can leave it in this position then walk around to the front with the mags off and pull the prop toward a compression stroke without going over top center and let it bounce backward. Do this two or three times and you should hear a "slurp...slurp" each time, near compression. This tells you that the throttle is open just right. If there's no "slurp...slurp", it's open too far.My late boss taught me this trick before I propped the Super Cub.

Regards,
 
Don, 4 seconds is not enough. If the engine is cold, 15 seconds does the trick for me. If it is warm, 5 - 10 seconds works. I don't like to use the Carb's accelerator pump because of fuel pooling in the airbox. But i know some who have no primer systems and have no problems.

Phil, I just went to Kragen Auto parts and bought CRC carb cleaner (spray can). Attached the
red tube and blew carb cleaner through the lines (off the airplane) through the nozzle side back. Then installed all the lines. After the first few flights, the airplane became hard to start even with 15+ seconds of priming. I removed both primer lines at the cylinders and pressure tested the system using the facet pump which is how i found out the #4 was plugged. I removed the #4 line and used the carb cleaner as I had during install and it cleared it. Never saw what was in the line.
 
Wow! 15 seconds...that seems like a long time which explains why mine must not be getting any fuel from only four seconds. Those tiny lines must not pass much fuel.
 
I agree, 15 seconds seems very long. I once primed mine for about 6 seconds and the engine acted as if it were flooded, coughed and sputtered. I now only prime for 4 seconds cold and not at all when warm. I have an O-320 with 3 primer lines and it seems to take quite a few blades before it fires up when cold. I sometimes pump the throttle once while cranking after about 4 seconds if it hasen't already fired, that usually does the trick.
 
I removed both primer lines at the cylinders and pressure tested the system using the facet pump which is how i found out the #4 was plugged.
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So, to do this you turned on the fuel pump, turned on the primer switch, and checked visually to see if fuel was coming out the nozzles? Or am i misunderstanding?
 
647jc said:
I agree, 15 seconds seems very long. I once primed mine for about 6 seconds and the engine acted as if it were flooded, coughed and sputtered. I now only prime for 4 seconds cold and not at all when warm. I have an O-320 with 3 primer lines and it seems to take quite a few blades before it fires up when cold. I sometimes pump the throttle once while cranking after about 4 seconds if it hasen't already fired, that usually does the trick.
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I only have two primer lines and they are on the same side. When cold, the engine fires immediately. Maybe I'm over priming but it works and the fuel is in the cylinders.
 
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