completely stumped here fellas. My son and I have been banging our heads against a 1993 s10 blazer for a while now.

the fuel pump was replaced by a shop due to low fuel pressure, but that has not fixed the issues. key on pressure shows 52 while the pump is priming. as soon as the priming stops the pressure bleeds down to 38 and holds. This behavior occurs even with both the intake fuel hose and the returned are pinched off.

This lead me to believe it was a Fuel pressure regulator leak. We open up manifold and sure enough the left side was clean like gasoline was in there. We replaced the regulator and tested fuel pressure and the exact same thing happened.

not sure where to go from here. Any direction would be greatly appreciated.

 

To update I put the fuel pressure gauge on after the fuel filter and the same behavior occurred. This makes me think the fuel is going back into the tank through the fuel pump.

Could it be anything else?

 

To check the fuel pump itself you will have to make an adapter and test the pressure at the fuel filter. There are quite a few threads on here about that procedure and I think even a sticky.

 

ya that is what I did this morning. When I said I attached the gauge after the fuel filter I meant I attached it to the OUT port on the filter itself. Since it behaved the same I think the issue has to be at the fuel pump.

I am about to start the process of dropping the tank. Ill do some testing, but I think I will be replacing the fuel pump and the sending unit as well as the filter. If I do that the only things that aren't new in the fuel system will be the fuel lines and the CPI with the exfception of the regulator since I replaced that already. Which I believe was necessary.

 

ok dropped the tank and pulled the fuel pump/sending unit. I look inside the tank and this is what I see

http://imgur.com/a/5h8Vs

Now just to be clear I personally cleaned this tank spotless before we replaced the fuel pump the first time. That means all that corrosion must have come from the return line? Is that right?

How the heck do I make sure this doesn't happen when I replace the fuel pump THIS time(3rd time)?

 

Decided to go check the inside of the top of the tank and sure enough it is corroded. No signs on the outside. no leaks or pitting, but I can feel the corrosion on the inside when I put my hand inside.

I think this mean new tank, fuel pump, and sending unit. Sounds like a lot but 200 bucks should do it.