Are tank selector valves known to block fuel flow?

[chevymotocross]

Hey guys, my 87 Chevy 305 TBI has low fuel pressure. I am only getting 8 psi at the TBI inlet. I recently bought an adjustable fuel regulator to pump up the pressure a bit for performance. I installed a gauge before installing to get a baseline reading. Only 8 psi. I then installed the adjustable regulator, hoping to bump it up, but with it cranked all the way, it is still at only 8 psi (factory should be 9-13).

I changed the fuel filter with no luck. I tested for a bad regulator by pinching off the return line and seeing if the pressure rises. It did not rise so the regulator is fine.

I don't see any leaks or kinks in the lines.

Bad fuel pump? Well I would say absolutely but the tank and pump are only 2 years old (Carter pump). My truck has dual tanks. The other tank leaks, so I don't use it. For testing purposes, I put some gas in it, selected that tank, but pressure is still only 8 psi. How is it possible that both pumps are putting out the same pressure?

The selector valve works, it switches between both tanks fine but is it possible that it might be partially blocking flow (due to age)?

What else should I do? Truck runs fine, and gets decent mileage (15mpg), but I feel there is something wrong with the below factory rated pressure. Plus, I paid $80 for an adjustable regulator!

[rfmaster]

Chevymotorcross

It depends on couple of things, but usually the in tank fuel pump is a culprit. More often it is the a small section of fuel line between Fuel Pump and feed through. It is common for that hose to leak, reducing available fuel pressure. It should SAE 30R10 rated fuel hose - fuel submersible ratted. Today's gas is one nasty mix of chemicals that will eat older fuel hoses and pumps! I suggest that you perform a 'deadhead' test on you fuel pump, by pinching off return fuel line. You should see at least 20PSI for a healthy TBI pump.

A common replacement fuel selector switch made by Polack (and others) has 9mm outlets (just under 3/8") - and it is not designed to be on pressure side of the fuel pump. According to instructions it is designed to be on 'sucking' end of the fuel pump. I do not know which fuel selector switch you have, but perhaps it is worth checking it for fuel flow to be certain.

I use adjustable FP regulator on my conversion - works great once I dialed in other parameters (I set my for 15psi).

//RF

[chevymotocross]

Bought a gauge adapter for the filter location. Napa actually sells one exactly for this purpose, it goes right in place of the fuel filter, pretty nice piece. Well, still, I'm only getting 7. 5 psi. The other tank is putting out 9. I think it is just a coincidence that the other tank is also putting out low numbers. I believe that pump is original as well as the tank (that tank rusted and leaks). But geeze, my other tank and pump are only 2 years old and I used a brand name Carter pump.

I guess I pretty much condemned the pump bad. Any brands to recommend? Anything else I can check for before replacing the pump? Should sending unit also be replaced? I will say that I forgot to mention, for some reason, only when entering highways, the truck will hiccup, almost like it is going to stall, but catches itself and continues on. I read somewhere that this is also an indication of a weak pump.

[87 STEPPER]

Before you buy another pump do this...........

Disconnect the pressure and return lines for the good tank at the selector vlv and place the pressure guage into them and run the pump and check the pressure if its anything above the 7.5 the selector vlv is stuck 1/2 way or has an obstruction.

[chevymotocross]

Originally Posted by 87 STEPPER

Before you buy another pump do this...........

Disconnect the pressure and return lines for the good tank at the selector vlv and place the pressure guage into them and run the pump and check the pressure if its anything above the 7.5 the selector vlv is stuck 1/2 way or has an obstruction.

I was looking at doing this, I had the selector shield cover off and looking at this. Problem is, there is barely any rubber hose to work with and not sure how I would connect those into the gauge adapter since the adapter has threaded female ends. Very little room unfortunately to tap in a gauge there. http://www.jegs.com/i/JEGS/555/15271/10002/-1 That may be exactly what I need but it still will be a very tight fit. I believe the truck uses 3/8'' Fuel hose at the selector valve?