1975 Westfalia - F.I. Fuel Pressure

[dingo]

This morning, without having run the motor, i cracked open the fuel pressure-guage nut and there was no pressure..zero. With guage on, i got her started with 8 or 9 cranks and at idle, the pressure read about 29/30 psi. After shutting down, the pressure dropped steadily...after 20 or 30 mins it was down to zero.

Should the system maintain some level of pressure when it is shut down ? and for how long ?

[Westy78]

Sounds like it's about where it should be at idle with the vacuum hose on the fuel pressure regulator connected. You should see some residual pressure after 20 min though. Over night it will slowly leak down to near zero. If your psi is within spec at idle with (26-30psi) and without (33-37psi) the vacuum hose connected on the regulator I wouldn't be to concerned.

[dingo]

Im trying to figure out why it takes like 10 cranks at least to start her when cold...when at one time it used to take only a crank or two. I thought maybe the 0 psi pressure had something to do with it. Other than that it runs just fine.

I found the Randy-in-Main write up on fuel pressure testing* on Samba. Very clear, concise and readable. It says that after 20 mins psi should not drop below 14. So my next move is to check for leaks at injectors, csvalve, check valve, regulator using the R-I-M technique.

* not sure if its available here on itinerant..if not search samba June 01 2006

[dingo]

System takes about 3 mins to go from 29 to 0 after shutoff. I tried clamping the fuel supply line as well as the one to the regulator...but neither one slowed or stopped the loss of pressure. Removed all injectors includig cs injector. I changed one that i thought might have been dribbling. I found it hard to tell whether injectors were leaking or not..didnt feel any wet fuel on my fingers. Replaced suspect injector, but no change. Not sure what next

[Amskeptic]

I tried clamping the fuel supply line as well as the one to the regulator...but neither one slowed or stopped the loss of pressure.

Clamp both simultaneously. Please have an easy fuel pump switch (I move the afm flap) and clamp return first. Move afm flap briefly as you watch the gauge get above 30, let go of the flap and clamp the fuel line just in front of #3. The rail must hold pressure in that circumstance if you have non-leaky injectors. My gauge had a leak once. . .
Colin

[vwlover77]

Sounds like the cold-start injector may not be working. Have you checked to be sure that it is energized when cranking the engine, or removed it so you can watch it spray?

[dingo]

Good diagnosis Tortus: i had heard the click of the CS solenoid so i had assumed it was working..but when i did a spray test..NO spray. Replaced with a spare from my 'Arctic emergency kit'...and i got immeadiate spray. Not only that, but i now have residual fuel pressure of 15 psi !!! and its holding !