Fuel Rail Regulator Question: Constant return flow with vacuum line disconnected?

[kanurys]

Hi guys,

 

I have a healthy 1999 Impreza EJ22 with about 180,000 miles running in my 1987 GL with a good aftermarket fuel pump. It's pumping a consistent 38 to 45 psi.

 

My questions is: When the vac line to the fuel regulator on the fuel rails is disconnected, is it still supposed to flow fuel back to the tank? I have a steady stream and pressure with it connected. When I disconnect it, the stream reduces very slightly but is still strong and the pressure rises a few psi. I'm trying to diagnose if it's not regulating properly - also temperature dependent... I'm having stalling issues when the car is hot and it doesn't throw any codes.

 

Thanks,

 

SK

Edited August 1, 2016 by kanurys

[Fairtax4me]

The fpr does not block the flow of fuel. There should always be fuel flowing back to the tank.

 

Normal pressure for an ej22 should be 25-30 at idle. Should jump up to 35-40ish under snap throttle or with the vacuum line removed

 

 

99 if it has the cone type idle valve, those are known to be problematic. Could try cleaning the IAC, but usually those just need to be replaced.

Edited August 1, 2016 by Fairtax4me

[kanurys]

Thanks, Fairtax4me. Can you be more specific about the "cone type idle valve" or it's variants? Thanks for the numbers and behavior description on fuel flow.

[AdventureSubaru]

Stalling issues with no codes can sometimes be a mass air flow or MAP sensor. Worth checking

[kanurys]

Stalling issues with no codes can sometimes be a mass air flow or MAP sensor. Worth checking

Signals look good form MAF. It's clean, too.

 

I just yanked the fuel pump and ran it in the engine bay with a little 1 gallon fuel can. The fuel pressure stayed way more consistent and under 40psi.

 

I think two things are happening:

1. The Walbro pump is a little too much pump for the rail regulator.

2. The hard fuel return line has too much restriction.

2.5. There may be some strange pressure/injector problems resulting from the over-pressure on the rail.

 

How do I regulate the rail pressure down to 30-35 psi on this engine?

 

Thanks

[Fairtax4me]

Your return line may be pinched or may be too small.

Remove the fuel return line from the regulator, stick a longer section on and stick that section in a gas can. Run it with the stock supply line and see where you pressure is with vacuum applied and removed from the regulator.

 

If the pressure is still high, try another regulator if you have a spare.

Edited August 3, 2016 by Fairtax4me

[kanurys]

Pressure is less in that scenario. I then put compressed air (about 90psi) on the return line. It builds pressure and is completely pinched or plugged. Any ideas on how to resolve that?

[Fairtax4me]

I would start at the pump housing since that's probably the most accessible.

Remove the line there and see if you can then blow air through it. If it flows freely after that its a blockage in the return pipe on the pump housing.

 

Where do the fuel lines run on those? Not familiar with those models. If they run under the floor pan of the car its possible one got pinched at some point while out driving. Or when a jack was put under the car If the lines are near the pinch rails.

 

Find where the lines run and inspect them closely.