Ok so i resently changed my fuel pump. Bought a fuel presure tester. hooked it up and. When i turn the key on the fuel pump comes on and the presure shots to around 45psi then as soon as the pump turns off the presure goes to around 35psi and stays there...is this the presure regulator or something else...what other tests can be done and how much is a regulator?

Thanks in advance for the help guys

 

There are two things that hold the pressure on the system after the pump shuts off... the check valve in the pump (was your new pump a "stock" replacement?), and the diaphragm in the fuel pressure regulator. If you were losing pressure constantly, I would suspect one or the other, but the fact that is drops slightly and then "holds" for a long period of time would indicate that there isn't a problem with the check valve of the fuel pressure regulator.

What is the pressure with the engine idling - both with the vacuum line on the FPR, and with the vacuum line off the FPR? What is the fuel pressure at WOT, high RPM? That will tell you how the system is working.

 

at idel the presure is steady around 35-38. going now to check how it is at WOT..kinda hard cause i got a short line on the gauge.I got a stock replacement at pepboys but the plastic bucket thing it comes in has a crack in it...i have to keep the tank above 1/4 for it to run right. Going to buy a grantilli pump soon as i fell like take the tank out again.


Ok at WOT it stays just right at 40psi...but when i turn the key on it jumps to about 45 then as soon as the pump cuts out it drops to like 35 and jumps really fast from 35-37 like it is shaking (but no vibration)

 

ttt


anyone ?? before i spend 80 on a new regulator?

 

Start the engine. Pull the vacuum line off. Should be between 41-46psi. Put the vacuum line on, should pull the pressure down in proportion to engine vacuum.... typically in the 35-38psi range. When you go WOT, and vacuum all but disappears, the fuel pressure should return to the same pressure it was at idle (without the vacuum line) and hold there. Sounds like yours is mostly correct. Can't understand why it loses 10psi pressure when the fuel pump shuts off. Did you check the vacuum line for any signs of fuel, which might indicate the FPR diaphragm was leaking?