s2000Junky

Hey guys, to the point, i'm running a adjustable AEM fpr and aftermarket 340 fuel pump. I noticed on my fuel gauge today that the idle pressure has changed from my pressure setting to run proper afr and is now about 90psi and I cant lower the fuel pressure via the AEM fpr any lower then 60psi, which is where I use to have it set btw. The car seems to run ok although the afr does do some irregular things once in a wile and seems to be leaner then id like. I noticed the Philips screw on the oem fuel regulator/damper thingy is pushed out, I assume due to the high pressure now realized. I thought that was strange and screwed it back in and ended up breaking the screw, luckily I had a spare regulator to replace with and learned my lesson. I am a bit confused at whats going on here, why the pressure changed by itself and is so high, but fuel enrichment to the motor seems to be lacking. The only thing I can think of is I developed a blockage somewhere in the fuel system but I don't know how or where to look. I'm hoping one of you guys have had something similar happen, or and had some ideas as to troubleshooting this.

Thanks guys!

donaldmejr

I had the same thing happen to me (was seeing ~100psi) and it was a blockage at the AN fitting where it screws into the hose. The rubber inner hose of the braided line folded in when the fitting was installed.
I removed the fuel line coming off my FPR and bought about 10ft of fuel line from pepboys and a new AN fitting I hooked the pepboy line to the return fitting of my FPR and took it into a gas can. Cycled power to my pump and fuel pressure was at like 5psi (was 100psi with my return line going to tank). So I knew there was a blockage. I reset the fuel pressure to 60psi and started the car. and it held ~55psi as it should. Found blockage and issue fixed.

Remember a FPR just blocks the return of fuel to tank...hence when you screw in the adjustment screw fuel pressure increases. So if the return line is blocked the fuel pressure will go to max of the pump.

s2000Junky

Update: I removed the AEM adjustable FPR and installed the OEM one to see if the pressure would drop back to 43.5. It does not. Still idling at 90psi! With engine off, ignition on, the pressure holds at 80psi. With all off, the pressure in the rail holds at 70psi right now, but this seems to change whenever it wants. Ive looked at it later and its moved down to 60psi or so.

s2000Junky

Hey thanks for the input here, sounds like whats going on. I'll have to get under the car and start tracing out the lines for kinks it sounds like. Thanks

donaldmejr

I couldnt see my blockage but I had just had the line get a hole in it and had to redo the fitting so it made it alittle easier for me.

s2000Junky

I couldnt see my blockage but I had just had the line get a hole in it and had to redo the fitting so it made it alittle easier for me.
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Well Its really cumbersome trying to get under my car with my garage arrangement, I just hope its readily obvious to me like a kinked line within reach, that's my hope anyway, but if not your troubleshooting gave me something to think about with removing the line and priming the pump and checking pressure to see where in the system it may be blocked up. Something like that anyhow.

riceball777

sounds like a broken gauge

s2000Junky

Well I plan on performing the test procedure tonight with plugging the return line and running the other end into a gas can, I’ll let you guys know what I find.

soulicious

I had to swap to the large gold orifice on my AEM fpr to get my fuel pressure back to stock. Did you try that?

s2000Junky

No, are you talking about an optional size nipple to connect to the return hose? I put the stock fpr back on and it’s still at 90psi btw if that changes anything for what you’re thinking? With the aem fpr I could adjust it down to 60psi from the 90 but that’s it, would go no lower now. So seems like the return line somewhere is being pinched or blocked? That’s what I’m going to test tonight. This all seemed to transpire last night which is a few days after installing the 340 pump.

***Also I nearly ran out of gas yesterday because for some reason with this new pump, it shows one bar left on the gas gauge with no gas in the tank. Maybe because the pump is slightly longer and it’s put the sock lower in the tank but the float cant get to the bottom of the gauge register?? Is that possible? I know with some of the aftermarket socks/housing for these pumps it would run out with 2 bars showing but that’s because the sock wasn’t reaching the bottom of the tank I think, but I could be wrong, it might be the float position? Maybe I need to bend the float rod up a little to compensate?