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Old 12-15-2009, 11:02 AM
rrgrassi's Avatar
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Fuel return question

Last week I replaced the braided fuel return lines and plugged line.

It was time to do so as they were weeping and dripping a bit.

I was wondering, why does the car run rough, like fuel starved, when the return lines are no good?

I understand why it would run bad if the supply lines are compromised.

Oh, also, just about every line broke on the injector fitting, leaving some old line behind.

I did not attempt to cut them, as I know from reading this forum, that you can introduce new leak points cause by nicking the fitting.

What I used was curved needle nose pliers to remove the remnants.

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Old 12-15-2009, 11:06 AM
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I would think there is enough pressure for the engine to run just fine, the failing lines merely allow the excess fuel to flow via the path of least resistance.
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Old 12-15-2009, 11:07 AM
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I've wondered that too. The only thing I can come up with is that the hose shrinks with age and causes the return fuel to be restricted, which doesn't allow the fuel to flow properly.
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Old 12-15-2009, 02:43 PM
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I have had the Fuel Return Lines comming off of the Injectors leak many times on my Volvo and 2x on the Mercedes; to include having one come completely off of the Nipple on the Injector and it never had an effect on how the Engine ran.
The way I found they were leaking was either I smelled the Fuel or I saw the leak when I opened the hood.
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Last edited by Diesel911; 12-15-2009 at 02:48 PM.
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Old 12-15-2009, 02:54 PM
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If there was some way to completely block of the Fuel Returning to the Fuel Tank I suppose it would make it harder for the Pintel in the Injector to move up and Inject Fuel as it would cause a counter pressure.

There is also that littlie Pin Hole that is in the Secondary Fuel Filter Houseing. While I do not know how it is possible some say it can pull Air through that hole assuming Air is in the Retuning Fuel.

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