Air in system??

[Joew2604]

I have 2 4-154 perkins diesels in my gulfstar. Had. it for about 12 years and it started first time as soon as the keys were turned. About two months ago the port engine wouldn't start. I bled it and it fired up fine. I ran them both for the next couple of weeks then again the port engine wouldn't start. Bled it again and it ran fine. Started it a number of times then today it wouldn't start again. Seems like air is getting in the lines somewhere but where do I start, and how do I solve this problem. Any suggestions or advice would be well received. Thanks

 

[OldDan1943]

Joew2604, I would start at the fuel filters. Look for signs of fuel leakage. That could be point where the air leaks in and a little bit of fuel leaks out, when the engine is not running. Could be the primary filters or the secondary filter on the engine. Check for loose connections or o'ring seals on the filter housings. Next up the line, fuel pump. Save the fuel pump till last. Check the tightness all the fuel line connections.

 

[Ex Sailor]

I have 2 4-154 perkins diesels in my gulfstar. Had. it for about 12 years and it started first time as soon as the keys were turned. About two months ago the port engine wouldn't start. I bled it and it fired up fine. I ran them both for the next couple of weeks then again the port engine wouldn't start. Bled it again and it ran fine. Started it a number of times then today it wouldn't start again. Seems like air is getting in the lines somewhere but where do I start, and how do I solve this problem. Any suggestions or advice would be well received. Thanks

Following .....Thanks for this post. Got the same thing with my twin Cummins and port engine too ........On initial look before we put it away for the winter, the marina tech. thinks it's the lift pump. ............ fb

 

[C lectric]

Before the problem started was any work done on the fuel system? Filter changes?

Racors have a ball check whose seat can be reversed easily but it is important to ensure it goes in the correct way. It is marked but is easily missed with the result of similar problems.

Fuel pumps can develop leaks and suck air when the diaphram starts to fail. Sometimes the fuel will end up in the crankcase.

Any filter can leak air into the system if assembled improperly or not tightened properly. Sometimes a seal gets out of place during assembly.

Of course hoses can fail, clamps loosen, fittings loosen.

A VERY close examination of the entire system can sometimes find a fuel weep where it should not be. Use of a BLUE paper shop towel to wipe around fittings and hose connections may show a problem. The blue towels will show a distinct colour change where a white towel will not.

A clear vinyl hose used temporarily between the engine and the last filter, then the lift pump and the filter and so on may highlight where the problem lies. THere will be bubbles but once bled they should be gone. If the hose shows bubbles again then the item just before may be the offender. Move it to the other side of the expected offender and if no bubbles appear anymore then you have found the culprit.

No, I'm not the one who thought of or suggested the clear vinyl hose, just passing it on.

 

[FF]

A clear vinyl hose is fine for trouble shooting .

For a fixed installation a refrigeration armored sight glass is easy and cheap , in whatever size the fuel line is .

Male and female end fittings make the install a snap.

http://choose.danfoss.com/products/sight-glasses/

 

[jjorgenson3]

Had the same thing happen last year. Determined the port Primary Racor had a hairline crack in the bowl even though I could not see one. Basically a little air was being sucked in when the secondary filters and then when you called for more rpms it would burp into the injector pump causing a power down and sometimes a stall. Rebuilt the two primary racor’s And problem solved.

 

[Lepke]

If you can't find the leak, add a fitting that will allow you to apply air pressure. You only need a few pounds, a bicycle pump will do. You will either see fuel weeping or hear the hiss of air.
I chased an intermittent leak for months until I added air and found a place in the fuel line that rubbed a tiny hole.