Injector question

[icanfixall]

So the question was asked if when pop testing an injector does fuel come out the return area... Nope.. I have popped many injectors and never has any fuel returning. Never thought much about it till now. My feelings are we can't make enough fuel volume to create a fuel return. Remember these pumps can make 5400 lbs of pressure. Please don't hold me feet to the fire if its not that high. It might be 5000 lbs but its up there.

 

[riotwarrior]

I agree Gary I hqve not seen any fluid discharge from the injector return line holes whilst popping injectors.

I too never thought much about that lil tidbit.

 

[OLDBULL8]

Me neither. But there is a passage in the injector that will return any fluid leakage back to the return line.

Upon further investigation that is what I found out.

I previously stated that the fluid in the return line charges the injector with fluid, that is wrong.

Someone had a cutaway pic of an injector. Maybe on the TDC forum.

 

[Black dawg]

Injectors with little/no wear will take awhile to show any return fuel on a tester. Worn/very worn will start showing fuel much sooner.

 

[FarmerFrank]

I've seen it on a couple injectors but figured it was normal because it was excess fuel... Hope those weren't ones I put in
my truck!!

So if they won't return while pop testing, how is engine running any different? Just curious, if the pop tester won't show any return fuel how is the pump different? Is it a little fuel after it popped from the pump?


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[Agnem]

We do see a lot of fuel out of the returns when calibrating Moose Mates. This is because you do have to flow a good amount of fuel to fill the passageway and get fuel to the top to see it exit. They all emit fuel from the return by design. If they did not, there would be no cooling of the injector which is a desired effect.

 

[IDIoit]

We do see a lot of fuel out of the returns when calibrating Moose Mates. This is because you do have to flow a good amount of fuel to fill the passageway and get fuel to the top to see it exit. They all emit fuel from the return by design. If they did not, there would be no cooling of the injector which is a desired effect.

so, the excess fuel that flows out of the injector, and across from other injectors does assist in the cooling of the sticks?
we had a discussion about this a few days ago, and i was looking for more info about how the return lines do cool the injectors.
Mel, if possible do you have any more literature on the net that explains this?
id appreciate it!

 

[icanfixall]

Thanks for a better explanation about the return flow from injectors Mel. Now I realize why we do not see any fuel coming out the returns on an injector when we pop test them. Thanks..

 

[Agnem]

so, the excess fuel that flows out of the injector, and across from other injectors does assist in the cooling of the sticks?
we had a discussion about this a few days ago, and i was looking for more info about how the return lines do cool the injectors.
Mel, if possible do you have any more literature on the net that explains this?
id appreciate it!

Unfortunately, our technology pre-dates the computer era, so little or no information has been ported. Also, much of it is under wraps due to dealer agreements and so forth, so the best sources are library books on diesel technology. The cooling of injectors and fuel is a really big issue with common rail stuff, since the pressures in use superheat the fuel and could lead to undesired effects if not dealt with. A lot of common rail trucks actually have a radiator in the fuel return system to try and get the fuel cooled down before it gets back to the fuel tank. In our trucks the return lines don't actually cool the injectors, they just carry away the hotter fuel.