Attention: TDR Forum Junkies 
Long time lurker, but this problem has me a bit stumped. My fuel pump died a few weeks ago. After the original Carter pump lasted like 12 years, the "improved" FASS DRP managed a whopping 3 years. Ran 12V to it straight from the battery while troubleshooting and it didn't so much as make a noise. Just totally dead.
Not wanting to do this again, and at the same time wanting to make things a bit more robust, I embarked on a total fuel system update with a somewhat non-traditional approach. So after parts trickling in on a near daily basis over the past couple of weeks, I finally have the whole thing put together and ... it's not doing what I'd hoped. Bear in mind this is a completely stock 2001 HO engine. I'm mildly ashamed to admit that I haven't even been running a fuel pressure gauge until now. So, hand slaps aside, here's what I've got now, starting at the tank:
Tank -> Vulcan Drawstraw 1 -> 3/8" braided fuel line w/ AN fittings (all old lines removed - 3/8" everywhere now) -> 85 micron pre-filter -> Walbro GSL392 fuel pump -> FASS fuel pressure regulator -> stock fuel filter -> VP44 w/ gauge on the VP44 inlet port. VP44 outlet port teed in w/ outlet on back of head back to tank, separate return line from FPR back to tank. Fuel pump run off a relay now, pump and pre-filter mounted on frame, FPR mounted in the original lift pump location.
After much making of fuel lines and brackets and wiring and such, I finally had it all put back together. Jumpered the relay to run the pump first. Everything looked good, set the pressure to about 20psi as a starting point. The Walbro was pulling 6 amps, right what the spec charts say it should be doing. After doing that for a bit to take a first look for leaks, I put the relay back in and bumped the starter a few times and then tried starting. On the 3rd attempt, it fired right up and sounded good. Pressure still sitting at 20. Now here is where things start going downhill. Sitting in the driveway idling, if I bring the RPM up to say 1200 rpm and hold it, the pressure slowly drops. And keeps dropping. I didn't let it go all the way down to 0, but it never stopped going down. If I let off the gas and return to idle, the pressure comes back up. I didn't even drive it around the block.
I'm baffled as to what the cause of this could be. Basically the entire thing is new, save for the fuel filter, which I changed about 1000mi ago, and the little overflow valve / banjo bolt on the outlet of the VP44. I've seen enough threads that indicate the Walbro should be fine. Heck, sitting in the driveway idling, I'd think a Geo Metro fuel pump should just about keep up.
Thoughts? As much as I need to get the truck back on the road, I am also genuinely curious as to what the problem is. I didn't think I needed to run a line from the manifold to the fuel pressure regulator, but I must admit it does seem like that would improve things. But I never see anyone saying (at least on a stock truck) that they run the VP44 at 17psi ABOVE MANIFOLD PRESSURE. I'm used to seeing just plain old 17 psi. So I'm inclined to think that doing that would just mask whatever the real issue is.
Not wanting to do this again, and at the same time wanting to make things a bit more robust, I embarked on a total fuel system update with a somewhat non-traditional approach. So after parts trickling in on a near daily basis over the past couple of weeks, I finally have the whole thing put together and ... it's not doing what I'd hoped. Bear in mind this is a completely stock 2001 HO engine. I'm mildly ashamed to admit that I haven't even been running a fuel pressure gauge until now. So, hand slaps aside, here's what I've got now, starting at the tank:
Tank -> Vulcan Drawstraw 1 -> 3/8" braided fuel line w/ AN fittings (all old lines removed - 3/8" everywhere now) -> 85 micron pre-filter -> Walbro GSL392 fuel pump -> FASS fuel pressure regulator -> stock fuel filter -> VP44 w/ gauge on the VP44 inlet port. VP44 outlet port teed in w/ outlet on back of head back to tank, separate return line from FPR back to tank. Fuel pump run off a relay now, pump and pre-filter mounted on frame, FPR mounted in the original lift pump location.
After much making of fuel lines and brackets and wiring and such, I finally had it all put back together. Jumpered the relay to run the pump first. Everything looked good, set the pressure to about 20psi as a starting point. The Walbro was pulling 6 amps, right what the spec charts say it should be doing. After doing that for a bit to take a first look for leaks, I put the relay back in and bumped the starter a few times and then tried starting. On the 3rd attempt, it fired right up and sounded good. Pressure still sitting at 20. Now here is where things start going downhill. Sitting in the driveway idling, if I bring the RPM up to say 1200 rpm and hold it, the pressure slowly drops. And keeps dropping. I didn't let it go all the way down to 0, but it never stopped going down. If I let off the gas and return to idle, the pressure comes back up. I didn't even drive it around the block.
I'm baffled as to what the cause of this could be. Basically the entire thing is new, save for the fuel filter, which I changed about 1000mi ago, and the little overflow valve / banjo bolt on the outlet of the VP44. I've seen enough threads that indicate the Walbro should be fine. Heck, sitting in the driveway idling, I'd think a Geo Metro fuel pump should just about keep up.
Thoughts? As much as I need to get the truck back on the road, I am also genuinely curious as to what the problem is. I didn't think I needed to run a line from the manifold to the fuel pressure regulator, but I must admit it does seem like that would improve things. But I never see anyone saying (at least on a stock truck) that they run the VP44 at 17psi ABOVE MANIFOLD PRESSURE. I'm used to seeing just plain old 17 psi. So I'm inclined to think that doing that would just mask whatever the real issue is.
