Fuel Pressure Q

[Jan Larsson]

So got all new injectors, brand new fuel regulator, clean install with new injector wire harness and a brand new fuel pressure gauge.

Problem before was it looked like a leaking injector and fuel pressure died as soon as I turned he ignition off. I was told fuel pressure should hold 1 - 2 mins after I turned the ignition off.

Right now the car runs but looking at the fuel pressure (I have 42 psi vac off while idle), when I turn the key off it's holding the pressure as long as the pump is running (for a number of secunds after the ignition is turned off) when the pump is turned off the fuel pressure starts to go down (slowly) so within another 10sec or so I have no fuel pressure. This is better than I had before swapping out my old injectors but it's not holding fuel pressure for the 1-2 min I was told.

Is there still something wrong or would this be normal? To be honest I don't see how it's possible to have fuel pressure for 1 -2 min after the pump been turned off as there is no drain back valves or similar.

 

[Razor]

Your fuel pressure regulator stops pressure from going down the return. Your pump has a built in check valve to stop it from bleeding down.

So if its not bleeding down the return, then the pump isnt holding pressure.

On a fuel injected car, you want to hold rail pressure for quick restarts.

If you plug your return.. or disconnect it there should nothing coming out, unless the regulator is whats bleeding.

HTH

 

[Jan Larsson]

Ok will do some more testing by pinching the feed or return line to see if it holds pressure.

 

[Jan Larsson]

So I pinched the feed line (rubber hose in engine compartment) when I had full pressure (engine not running) and it holds pressure until I remove the clamp I used to pinch the hose. So this means regulator and injectors are fine correct.

What is wrong with the pump then? Do I need a completly new pump, I got the Walbro 307 and it's about 3 years old max 4 years.

 

[Lee_Burough]

Jan,

I suggest you go to Steve Woods site, look under troubleshooting and then 'fuel pressure test'

You'll see some charts showing the procedures to isolate and test each component of your system. You'll get to the bottom of it I'm sure

lee

 

[Jan Larsson]

Thanks Lee, following the chart I end up at

Check For:
-Leaking Pump Coupling Hose
-Faulty in-tank pump


Question: what/where is the pump coupling hose?

When I installed the walbro pump I left the pulsator thing in there and never used the short hose with clamps that came with the pump as the instructions said use the pulsator, would that have anything to do with the problem outlined above?

 

[Razor]

Bad pump. Drop the tank and change out.

Piece of cake

 

[Jan Larsson]

Hmmm, not again Done that one but last time I had the complete rear axle removed so was not that bad .... well will order a new Walbro 340M pump then looks like ....