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Isuzu Pickup Fuel Pump Leaking?

Q. Vincent, I have a 1988 Isuzu pickup, 2.3 liter engine, 2 barrel carburetor and 95,000 miles. Shortly after acquiring this truck I was checking it over and noticed that one of the outlets on the mechanical fuel pump was not connected to anything. It was chance because the fuel pump is under the intake manifold and not at all easy to see or get to.

Isuzu Pickup Fuel Pump Leaking?

There are three hoses on the other side of the pump, other side of the diaphragm(?), that are the "IN", "OUT" and "FUEL RETURN" that are all hooked up correctly. I asked at a local parts store and they suggested that I connect a hose to it and let the hose hang to the bottom of the truck b/se they thought this was an "emergency" outlet in case the diaphragm ruptured and that way fuel would not spill all over the engine.

I did this and have checked it while the engine is running and there does seem to be fuel coming out of this hose. So my question is: should this be teed into the fuel retun line, or is it indeed a safeguard and it is now telling me that my fuel pump is about to die because of the fuel leak?

Ordinarily I would just put on another pump but since I have to remove half the engine to get to it that is not practical and if it needs replacing I will opt for an electric pump and bypass the mechanical one. The truck runs fine at all speeds and gets 22 mpg in the city.

I have looked in my manual and it does not address the issue of fuel pump line routing. Any help you can give me would be greatly appreciated. I love your website it is a great resource for all of us "shadetrees".

Thank you...

A. I'm a little confused here. According to all the information I have, that has an electric fuel pump. I think what you are looking at is the fuel pressure regulator. That would have an "IN", "OUT" and "FUEL RETURN" and the fourth fitting is for a vacuum line.

Isuzu Pickup Fuel Pump Leaking?

Typical Fuel Pressure Regulator.

I'll bet the previous owner knew it was bad and disconnected the vacuum line. Not an uncommon thing to do on that engine to get a little more power out of it. However, if there is fuel coming out of that vacuum fitting,that means the vacuum is torn and the fuel pressure regulator needs to be replaced.

Look under the truck bed and I believe you will find the fuel pump.

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