Fuel Pressure Regulator test?
 

Hi All,

Wanted to know about this unit...

Car is a 93 Lumina Euro with the older 3.1 (pre map, better intake gasket design, etc)

Fuel Pressure Regulator has a little vaccum hose on it, but the easy thing for me to do, is to connect a fuel pressure tester to the rail (has a port for this) and then I can check it to see if it's working, correct?

I'm assuming that I'd have less pressure at idle than I would at 2000 RPM, etc, correct, or no?

Does anyone off hand know what the readings should be at the rail for these?

Thanks

The pressure should be less at idle. To PROPERLY test the regulator you must remove the vac line. The pressure should go up at least 10 psi. The pressure at 2000 rpm will be exactly the same because there is no load on the engine so vac will be the same. Initially when you rev it vac will decrease for about 1 second so pressure will go up but you may not even see it on your gauge. You could power brake the car to 2000 rpm to load it but that is still not the correct way. If you can not get the line off the regulator directly you need to find the other end. By the t-body there is a plastic connector that has I believe 3 vac lines in it one of those is the regulator.






PURPOSE:
The function of the regulator is to maintain a constant pressure differential across the injectors at all times.

OPERATION:
The pressure regulator compensates for engine load by increasing fuel pressure as engine vacuum drops. The pressure regulator is mounted at the end of the fuel rail, and is serviced as a complete assembly.

The system operates in an acceptable pressure range of 284-325 kPa (41.0-47.0 psi) with the engine running. If the pressure is too low, poor performance and a Code 44 could result. If the pressure is too high, excessive odor and a Code 45 could result. CHART A-7 has information on diagnosing fuel pressure conditions.

CONSTRUCTION:
The fuel pressure regulator assembly is a diaphragm-operated relief valve with fuel pump pressure on one side, and regulator spring pressure and intake manifold vacuum on the other.

FUEL PRESSURE:



Ignition "ON" Engine "OFF" 40.5 to 47.0 psi

With Regulator Vacuum Applied [1] ..... 3.0 to 10.0 psi Less than Ignition "ON" Engine "OFF"

REMARKS:

[1] May be checked with either of the following methods.



With Pressure Regulator Vacuum Line Attached at normal idle speed.
Ignition "ON" Engine "OFF" with 10 Inches Of Vacuum Applied To The Pressure Regulator

how can I apply vacuum to that line? - I see the 3 you are talking about - wish I knew where each went to, from left to right... but at least I know where to start looking.

very helpful so far... so, it sounds like what I need to do, is KOEO, check the fuel pressure... then also check it when applying vacuum to that line, and it should drop, correct (key on engine off still)

so, if the number on the gauge doesn't move, it's a bad regulator, correct?

do they sell/rent hand held vacuum pumps or something? - I'm new at testing vacuum :-)

I have a new one already, which I can return if it's not the problem - how hard is it to change? - how does one relieve the pressure in the system first, which I'm assuming you must do?

I'm more interested in testing it first, to rule it out, etc...

how can I check the codes on an OBD I car? I only have an OBD II scanner... I read about some paper clip trick... does that work?

Thanks

There is vac on that line when the engine is running. However if the line is broken under the intake it will not matter. Yes they do see hand held vac pumps (try autozone).