Fuel pressure

Matt_aka_Dale

SCCoA Member
At warmed up idle, fuel pressure is showing a steady 31psi. When key on, it shows max of roughly 28-29psi, but slowly drops to 11psi. The only leak I know about is the oring at the top of the sending unit. Fuel regulator is not leaking either. Do the readings I've found seem correct/incorrect?
 
At warmed up idle, fuel pressure is showing a steady 31psi. When key on, it shows max of roughly 28-29psi, but slowly drops to 11psi. The only leak I know about is the oring at the top of the sending unit. Fuel regulator is not leaking either. Do the readings I've found seem correct/incorrect?

Ideally, it should hold pressure for a long time. If there are no external leaks, then it must be leaking from an injector, the regulator, or the pump.

Mine used to hold pressure for days/weeks, but now it bleeds down slowly too. Not sure where from/to though.
 
To test the injectors, couldn't i just pull them out with them still on the rail and turn the key on to check? Or would there be enough pressure that they would just pop right out if i did that?
How can you test the pump to see if its bleeding off from there?
 
Fuel pressure should be 38-40 psi key on engine off. At idle it should be 35 psi and if you blip the throttle it should jump up to 50 for a second.
 
At idle it should be 35 psi and if you blip the throttle it should jump up to 50 for a second.

That statement is lacking in info, specifically manifold pressure. The fuel rail pressure should be 39.5 psi greater than the manifold pressure. In other words, if your engine is idling at 20 inHg, you should see ~29.7 psi at the fuel rail. If you're at 10 psi of boost, you should see ~49.5 psi at the rail.
 
I'm not sure what did it, but we have stable pressure once again. Checked to see if it was bleeding back through the pump, which held pressure. Checked in-line off the rail with a valve to cut pressure off before entering the rail to check the regulator. Checked on the in-car gauge to see if it was leaking out the injectors. Looks like that mystery is solved, gang.
 
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