old mechanical carb

mkpj1

Petty Officer 2nd Class
Joined
Jul 11, 2006
Messages
108
Hello all,

I have an 1984 Mercruiser 140 181 serial 622xxx+. Started having some surging at cruising speed then stalling sometimes completely. Put together a testing rig per here and found air in the system to the point there was no gas at times in the clear tube. Double checked all connections from tank to pump to make sure they were tight. due to being a ways from the lake, on the muffs i took it to 1500 RPM and was stable at 1.6 hg. Pinched off the fuel line as described here and built little pressure after a minute~3hg. No more than that.

Here is my question: the pump is original. Took it apart cleaned it as I would a carb and put it back together tightening everything up. Vent to carb down where the spring is was completely clogged with gunk. Tightened everything up and put it back on. I also cleaned the pump filter as I would a K&N filter and blew it out with compressed air.

No air bubbles in the tubing for over five minutes on muffs. Took 1 minute to build over 6 hg of vacuum pinched off. Much much better than prior to cleaning. No way to test on the lake at WOT until next week. While I'm there for vacation.

Any thoughts on this? can I get away because it took quite a bit longer than 10 seconds to build 6hg of vacuum? No air bubbles at all for over five minutes idling and a short 1500RPM run.

Thanks in advance! Also, thanks for the troubleshooting sticky!
 

mkpj1

Petty Officer 2nd Class
Joined
Jul 11, 2006
Messages
108
Re: old mechanical carb

Max, thanks for the reply but the problem is the pump. It's old and weak and in the sticky for troubleshooting the guide states the pump should build up 6hg in 10 seconds. Mine took 45 seconds.

Sorry for the bad post, been awhile. Should be old mechanical fuel pump. Not carb. the old pumps can be broken down and cleaned. I did this and completed the pinch test before the vacuum gauge and it took 45 seconds to get to 6hg. there were no longer any bubbles or air in the clear tubing. Prior to cleaning it was almost ALL air.
 
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