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Author Topic: Injector overflow piping....?  (Read 6117 times)

George A

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Injector overflow piping....?
« on: August 11, 2015, 09:46:00 PM »
I just finished running my Vidhata generator build and my new electric fan installation works beautifully. The air blown through the radiator is definitely warmer than the surrounding air, while the top hose is hot and the bottom hose is warm. From this I'm assuming that it's thermosiphoning correctly.

Only one thing left......when I installed my modified Indian fuel filter, I ran the line from the tank directly to the filter and ignored the injector overflow. Of course it drips slowly as the engine is running. If I remember correctly, the original setup had the overflow plumbed into the fuel line with a T, but I don't remember exactly where. Would it be alright to install a T right at the filter inlet and allow it to drain there, or will the height of the fuel tank above it cause it to back up into the injector?
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32 coupe

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Re: Injector overflow piping....?
« Reply #1 on: August 11, 2015, 09:59:43 PM »
Yes, the t before filter will be fine.
It's how I did mine.

G

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mike90045

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Re: Injector overflow piping....?
« Reply #2 on: August 11, 2015, 10:54:25 PM »
... and ignored the injector overflow. Of course it drips slowly as the engine is running.....

When I redid my plumbing, I just let the overflow line aim at my oil drip pan.   100+  hours and not a drop.   I suppose something is wrong, but what ?

32 coupe

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Re: Injector overflow piping....?
« Reply #3 on: August 11, 2015, 11:06:37 PM »
Mike,
I have seen injectors that have "spilled" excess fuel and others that "almost" run dry.

Of the three I've seen firsthand.



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dieselgman

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Re: Injector overflow piping....?
« Reply #4 on: August 11, 2015, 11:35:04 PM »
We much prefer seeing a good internal seal in the injector that precludes much leak-off going back through the line. Some of the early Dursley Lister designs used a very small drip-can actually mounted to the side of the cylinder so you can be sure that good tight original equipment will not pass very much fuel by the injector (by design). I think that the lapped surfaces between nozzle and body might be the culprits on a very leaky unit, but it generally does not seem to make much difference in the operation of the machine.

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George A

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Re: Injector overflow piping....?
« Reply #5 on: August 12, 2015, 02:27:26 AM »
Okay, so it looks like I'll be putting that T in tomorrow. Thanks everyone!
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Thob

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Re: Injector overflow piping....?
« Reply #6 on: August 12, 2015, 02:45:01 AM »
I know that a lot of people do quite well with a T back into the fuel line, but my recommendation is to take the injector overflow back to the tank.  That way if any small bubble of air works its way past the injector, it goes back into the tank and doesn't cause any bleed problems.  A lot of modern diesels are done that way.

dieselgman is correct, a new properly working injector should have very little leak off.  As they age, it gets to be more and more.

I've seen pictures of couple of Witte vertical diesels where the injector leak off was plumbed into the air intake just before it entered the head.  I didn't believe it on the first one I saw, but I saw another one a year or two later and it was done the same way.  Sounds to me like a good way to have the engine run away...
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carlb23

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Re: Injector overflow piping....?
« Reply #7 on: August 12, 2015, 12:10:10 PM »
I know that a lot of people do quite well with a T back into the fuel line, but my recommendation is to take the injector overflow back to the tank.  That way if any small bubble of air works its way past the injector, it goes back into the tank and doesn't cause any bleed problems.  A lot of modern diesels are done that way.

dieselgman is correct, a new properly working injector should have very little leak off.  As they age, it gets to be more and more.

I've seen pictures of couple of Witte vertical diesels where the injector leak off was plumbed into the air intake just before it entered the head.  I didn't believe it on the first one I saw, but I saw another one a year or two later and it was done the same way.  Sounds to me like a good way to have the engine run away...

Since its the leak off from the injector then there should be no way for a run away since the amount of fuel available to the injector is only what the pump can put out each time it sprays.  Any excess should easily be consumed via the intake without issue.

Carl

dieselgman

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Re: Injector overflow piping....?
« Reply #8 on: August 12, 2015, 04:37:46 PM »
It is worth mentioning here that all the modern equipment we work with, and that includes the majority of the Lister installations, use a leak-off return that goes back to the fuel tank under atmospheric pressure only. A number of issues can arise when plumbing the leak-off back into the supply side and it can confound the diagnosis process when air contamination rears its ugly head... simple is good, and a very clean fuel supply route with the minimum of connections is also good!

dieselgman
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Tom

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Re: Injector overflow piping....?
« Reply #9 on: August 12, 2015, 05:41:10 PM »
+1
Tom
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rmchambers

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Re: Injector overflow piping....?
« Reply #10 on: November 15, 2015, 10:13:38 PM »
I've always sent the return back to the tank if it's close by, if any air gets bled through that it won't get re-circulated into the pump and it will force the Diesel to go back through the filter so it keeps cleaning.  The output is often pretty warm too so it helps warm up the tank after a while.