That's the fuel temperature sensor. When the fuel hits xxx-degrees (157ºF I think...not sure) the sensor opens up and vents vacuum to atmosphere, thus increasing fuel pressure. This is to help during hard starts when vapor lock or fuel percolation might be an issue.

If the regulator sees higher vacuum, fuel pressure is decreased. If it sees lower (or zero) vacuum, fuel pressure is increased. Typically, higher pressure would worsen a rich running condition. If the pressure is significantly too high then it can actually cause a rich running condition.

I'm not sure where you 'covered the pipe'---before or after the fuel temp switch.

A fuel pressure test is the best way to check the regulator. One visual test, though, is to pull the vacuum hose off of the regulator nipple and see if any gasoline dribbles out. If it does, that's a bad regulator for sure. Not, though, that lack of dribbling gasoline does not prove that the regulator is good.

Cheers
DD

 

If you mean the pump runs whenever the key is turned 'on' then, no, that is not normal. If it does then somebody has monkeyed around with the circuit.

However, the pump should run with the key to 'start' and it should be running whenever the engine is running.

It's not like the pumps on some older carbureted cars where you hear the pump pumping...and then not pumping....and then running again....in response to fuel pressure.

Cheers
DD

 

It's the primary player, yes.

(Well, actually, the ECU controls mixture, primarily in response to AFM readings)

Faults can occur, however, which cause over-fueling, that the AFM cannot do anything about.

Cheers
DD

 

Yes thats normal.

 

the fuel pumps as soon as the key is turned and remains on all the time the engines running would that cause over fuelling? also theres no valve on the fuel rail to check pressure. is there another way to check pressure?

 

Not intended operation. There's a fault in the circuit, or someone has modified the circuit





That's OK



No, would not cause over fueling. It's a safety issue....but it won't cause any running problems


Locate the hose to the cold start injector and disconnect it from the fuel rail. Now use that nipple for your fuel pressure gauge

Cheers
DD