Can a weak fuel pump cause low idle problems?

[67Heaven]

Hello everyone! I have a 77 Johnson 35hp electric start long shaft. I can't seem to get enough air to the Carb with the cover on. Cover off I can adjust mixture accordingly and it runs great. Compression is good too. Can a weak fuel pump be at fault? I have also rebuilt the Carb. Any ideas? Many thanks!

 

[hidef]

Re: Can a weak fuel pump cause low idle problems?

Check the gasket around the base it might be leaking exhaust gases into the cowling which is why the engine runs better with the cowling off. The signs of a bad fuel pump is the primer bulb going soft and if you keep squeezing the bulb the engine stays running.

 

[67Heaven]

Re: Can a weak fuel pump cause low idle problems?

You really called it good hide. My base gasket has seen better days. Replacing that looks like one heck of a job. I was hoping to get thru this season without replacing it. I've also added a custom air scoop on the front to increase fresh air flow(had an extra cap). Bulb does get spongy but not enough to quit running. If there is anything else I can do I'm all ears?

 

[Daviet]

Re: Can a weak fuel pump cause low idle problems?

You can run it without the cowling on.

 

[67Heaven]

Re: Can a weak fuel pump cause low idle problems?

Yeh that thought has crossed my mind, I guess it's a case of having your cake and eating it too. I really wanted to keep it on for the good look & keep splashing off it. These motor are ugly without the cowling on them. Since this is an extra cover and I have a cool looking air scoop on the front I may open the back up where the handle is to let the "dirty" air pass thru. I'm being careful not to butch it up. If I took anything from this its the exhaust air that's creating the problem. Thanks guys, this site is awesome!

 

[Daviet]

Re: Can a weak fuel pump cause low idle problems?

You can double check it squirting some oil into the carb while it's running and see if you get smoke out between the powerhead and exhaust housing.

 

[boobie]

Re: Can a weak fuel pump cause low idle problems?

Put someting in the back of the hood also as this will give you good air flow. Did this with a lot of old 9.5 's that had the same prob.