Bleeding air in lines Perkins 4108

[sharkdiver84]

I've done a lot of research on here and other places and keep getting more confused. It seems to be getting more compicated than it should be, so i think i'm missing something.

All I did was disconnect the fuel line from the main fuel tank and add it onto a day tank i just acquired. The engine was obviously not running so i didn't expect much difficulty.

The Racor has it's own primer pump built in, and i thought that should handle it. But more research leads me to beleive I should also pump the lever on the fuel pump, and loosen that nut where the metal injector hose comes from.

Further reading makes me wonder whether i'll also have to bleed additional parts of the engine further down the line. I'm already in over my head with this much, and didn't think that would be necessary since the engine wasn't running. But i wonder if opening that nut to bleed while i pump the fuel pump will let air into that metal injector line as well?

Are Perkins 4108's really that complex to bleed every time you change a hose or filter? I'm stuck, afraid to proceed before I make the problem more complicated.

Is there any way to get the air out of the line and filter before it gets further into the engine? Any help is appreciated. Thanks.

[Emmalina]

Not complicated once you learn the order of bleeding the system.. One little bubble is enough to stop the engine.. Read the manual on priming the system. I always crack an injector and TWO till she starts....

[GrowleyMonster]

With an electric boost pump, it's pretty easy. I have the almost identical 4-107 and since adding an electric pump between tank and primary filter, all I have to do is crack a couple of injector lines unless I have just changed a filter or something. I keep a 5/8 wrench in a little scabbard in the engine compartment just for the purpose. If I change a filter or run the tank dry or something, yeah I have to run the whole system, but honestly, no biggie. The electric booster pump makes it simply a matter of following the fuel path, cracking connections, and tightening them back up when I see fuel coming out.

[akopac]

I have a Perkins 4108 and a cartridge less fuel polishing system between it and the tank. Well it’s got a racor, but I’ve never had to change it. I have an electric pump before the polishing system and just turn it on, start from the pump, and start cracking fittings till I finish with all the injectors
Takes a couple minutes. Makes doing filter changes and other maintenance much easier.

[Searles]

The 4108 in first light my sons old 1 tonner I ever only crack one injector half a turn ,spin her over until she fires ,close off bleed injector ,but I have also fitted a small solid state 12 volt lift pump .⚓️⛵️

[Bill O]

Originally Posted by Emmalina

Not complicated once you learn the order of bleeding the system.. One little bubble is enough to stop the engine.. Read the manual on priming the system. I always crack an injector and TWO till she starts....

Agree, the bleeding procedure is well documented in the workshop manual. Free copies of the workshop manual can be found online.

[skipperpete]

Originally Posted by sharkdiver84

I've done a lot of research on here and other places and keep getting more confused. It seems to be getting more compicated than it should be, so i think i'm missing something.



All I did was disconnect the fuel line from the main fuel tank and add it onto a day tank i just acquired. The engine was obviously not running so i didn't expect much difficulty.



The Racor has it's own primer pump built in, and i thought that should handle it. But more research leads me to beleive I should also pump the lever on the fuel pump, and loosen that nut where the metal injector hose comes from.



Further reading makes me wonder whether i'll also have to bleed additional parts of the engine further down the line. I'm already in over my head with this much, and didn't think that would be necessary since the engine wasn't running. But i wonder if opening that nut to bleed while i pump the fuel pump will let air into that metal injector line as well?



Are Perkins 4108's really that complex to bleed every time you change a hose or filter? I'm stuck, afraid to proceed before I make the problem more complicated.



Is there any way to get the air out of the line and filter before it gets further into the engine? Any help is appreciated. Thanks.

I’m curious about how you fill the day tank and how it’s connected to the engine, usually after the day tank is filled, the engine is then gravity fed and would rarely get an airlock.
Regarding your question, yes , Perkins fuel systems can be remarkably difficult to bleed...... under some circumstances. There are a few age related and fuel supply issues that can make any engine with a CAV DPA pump a real challenge to purge. The vane pump is one place where trouble arises as it wears and also the regulating valve in the pump cover, it has a tiny shuttle valve specifically for redirecting the priming flow around the vanes . Occasionally it’s necessary to open the case bleed screws and crank the engine to purge air as well as cracking the injector pipe nuts.

[c.K.]

Originally Posted by sharkdiver84

I've done a lot of research on here and other places and keep getting more confused. It seems to be getting more compicated than it should be, so i think i'm missing something.

All I did was disconnect the fuel line from the main fuel tank and add it onto a day tank i just acquired. The engine was obviously not running so i didn't expect much difficulty.

The Racor has it's own primer pump built in, and i thought that should handle it. But more research leads me to beleive I should also pump the lever on the fuel pump, and loosen that nut where the metal injector hose comes from.

Further reading makes me wonder whether i'll also have to bleed additional parts of the engine further down the line. I'm already in over my head with this much, and didn't think that would be necessary since the engine wasn't running. But i wonder if opening that nut to bleed while i pump the fuel pump will let air into that metal injector line as well?

Are Perkins 4108's really that complex to bleed every time you change a hose or filter? I'm stuck, afraid to proceed before I make the problem more complicated.

Is there any way to get the air out of the line and filter before it gets further into the engine? Any help is appreciated. Thanks.

Hey
I went through the same thing 2 years ago, even exchanged the prime pump thinking it was not working ( well it was as explained by the perkins maintenance in our area)
That aside I bled all connectors while priming the hand pump ( make sure it is not on the "cam")
Finally , 2 at the time, bled the nuts on the fuel injectors by shorting the starter (close when diesel comes out )
Did this twice runs perfect even wanted to go during the bleeding
Good luck