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Discussion Starter · #1 ·
I have a 1988 isuzu pickup, 2.3 liter, carbureted, 4ZD1 engine. Recently got this truck and was looking it over; found the mechanical fuel pump under the intake manifold, it was not easy to see but noticed one of the "outlets" on the pump is not connected to anything. No one seems to know what this is for, except to suggest it is some sort of vent. If it is supposed to be connected to something I would like to make sure I do that, so thought you folks might be able to help. Otherwise, truck runs great, gets 22 mpg city - don't know if that is good or bad for the model. So if anyone has any info. I would sure appreciate the help.
slmaxson
 

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That fitting often has a hose that runs down behind the motor mount on that side. Often the pump will start to leak oil out that vent, and the hose helps to keep oil off of things or ruining the mount. Other than that, it may just be a vent.

Dave.
 

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Discussion Starter · #3 ·
Thanks Dave-

I went ahead and bypassed the original fuel pump with an electric one and things have been going along great; I figured whatever that hose was, there should not be fuel coming out of it. Thanks for the reply.
slmaxson
 

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its a vent, but when the diaphram goes bad it starts to dump oil out of that hose. Its kinda like an earily warning device, i guess. The one thing with the electric fuel pump, your mechanical one is still being operated by the cam pin that pushes the fuel pump lever. You can still have the diaphram failure, so keep an eye on that hose
 

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Discussion Starter · #5 ·
Thanks for the tip about the vent tube, I believe it is losing oil through there. Guess I will have to resign myself to removing the mechanical fuel pump and finding a plate to cover the hole.

I read the forum everyday, and always learn something. Many thanks to you folks who contribute.
 
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