i installed an AEM 1:1 Fuel Pressure Regulator. It had a pot to screw in an electronic fuel pressure gauge. So I installed everything, and the car is showing 0 PSI. This is impossible, car starts up and idles fine. I screw the pressure set screw in and it still reads 0 psi. Any ideas? Bad FPR or bad gauge?

 

I would suspect the gauge/switch. Is it getting a good ground?

 

most likely a bad gague, but possibly a problame with where the gague attaches to the fpr. you usre the gague was attached properly?

kind of off topic, but where did you mount the FPR (did it attach right to the rails), and how difficult was the install?

 

the FPR i got comes with a mounting bracket, i bought it from josh (excelerate). if you pop open the left vent under the windshield there is a hole inside to put a bolt through. you can follow comptech's FPR install directions for the blower unit.

the fpr has 2 inlets, 1 outlet, and 1 gauge port. keep in mind the FPR is mounted horizontally.

the small brass looking line coming directly at you in the picture is the inlet. the reason it is smaller is because it has to use the stock hose. the stock hose attaches to a hard line fuel pipe so it would be hard to increase the hose size. so i got a small fitting. the blue fitting to the right is the outlet line going to the fuel block/rails. underneath is the fuel gauge sensor (sending unit). it screws in to the FPR so i'm not sure how i could have screwed that up.


here is where we meet up with the fuel block and rails. as you can see this is a nice big hose pumping fuel in. believe it or not, this was the hardest fitting to get. i could have ordered the fitting, but i got my favorite local hose/fitting store to cut off the threaded piece of the original FPR, and braze it to a fitting for me. cost me $5, considerably cheaper than buying a fitting.


here are my temporary gauge wiring connections. i wanted the gauge in the engine bay so i could easily adjust the fpr, so as you can see. both the 12v constant and 12v ignition wires are going directly to the battery, and grounded to the battery. perhaps i fried the gauge since i did not install a fuse? as soon as i plug the gauge in it lights up. the first startup, the gauge went to about 15 psi. so when i adjusted the FPR to increase pressure, the gauge DROPPED. now it reads 0.


this is the pressure adjustment screw. clockwise increases pressure. so as you can see there is not much adjustment left. this frp goes from 20-150psi, so its not like i am too far out on the screw.

 

you said that it worked at first, but when you adjusted it stopped working. if you turn it back down does it start working again?

 

i tried decreasing the pressure while everything was running and nothing happened. i almost feel like the hoses are in the FPR incorrectly, but that still doesn't explain why i am not seeing anything on the gauge (i think).

anyone know what would happen if the inlet/out on the FPR got reversed?

 

What gauge are you using?

 

autometer sport-comp II fuel pressure gauge part #: 3663 (electric full sweep)

 

i found a thread where scalbert says an FPR on n/a application would be pointless...

https://acurazine.com/forums/showthread.php?t=43287

summary:
Scalbert: "Not to rain on your parade, but the feel is in your head. The Short Term Fuel Trim will of cut out any adjustments you have made within a minute or two. And then along comes the Long Term Fuel Trim to permantly negate any changes."

 

I read scalbert's posts in that thread and he is (obviously) correct. Your car isn't going to use more fuel than your car thinks it needs. Adding a new FPR isn't going to up the amount of fuel flowing through the injectors as long as you stay naturally aspirated.

And honestly... I still really think your car is running fine. If you were running too lean you would know it because your dash would be lighting up and you'd be experiencing detonation.

 

As for the gauge you could also test the voltage to ensure it's working properly. Although if you are running the gauge under the hood I would have gone with a mechanical gauge such as this one. http://www.jegs.com/webapp/wcs/store...1_745219_11903

 

only reason i had the gauge under the hood was for immediate tuning of the FPR so as to dial it in, then i ran the wires inside the cabin.

i'm an asshole. the second i was reading 0 psi i thought to myself maybe i put the hoses in wrong. but i never switched them. switch them up and its running fine now. i had switched back in the stock pump for now but may go back with a walboro.

steve - i would have to agree. only reason i am doing this is to play around on a dyno to see if adjusting the FPR really does anything. not saying i am looking for gains, but i'm worried that 2 dynos in a row showing considerably lean compared to what it's supposed to be.

i'm also curious to see the drop in fuel pressure when in vtec. my engine was rebuilt and basically redesigned to be 3.5L, granted only .3L more than stock, but i probably should have taken direct caution during the build just to make sure everything was running ok, but i figured everything would be fine.

 

maybe i'm crazy, but i feel like my low end has been restored. one of 2 things i guess, the walbro pump could have been bad? i've heard of them failing out of the box. fpr was maxing out? helms says should be 40-46, i have it dialed in at 49psi at idle right now. time for some more dyno testing.

 

is it one of those universal FPR's? or is it a "honda/acura" fpr?

 

It's universal

 

yes, i got the one that goes from 20-150psi. just make sure it is an inline one and not fuel rail mount. and also 1:1 unless you plan on boosting.

 

but isn't the comptech fpr 1:1?

 

If you squeeze this hose, I bet it's firm which indicates fuel pressure. This is the spot most people put their sensor too if I recall.

 

no, comptech is a raising rate because it is intended for boosted applications.

remember, fpr works with vacuum, boosted applications have a lot different vacuum than n/a.

 

yup, you can get a block that will allow a sensor to screw in and then the fitting on top, but my AEM FPR has a convenient port for a fuel pressure gauge.

 

That is incorrect. I've installed an aftermarket fuel pump and my fuel pressure went up and my air/fuel ratio went down, indicating more fuel was being injected to my motor. I've been running this way for weeks and my car has not adversely adjusted since. My fuel pressure is still lower than stock and I want to fix it using the same FPR as clean. I has been low ever since I blew my motor and converted to 3.5L. I'm not sure if the lowered FP is due to my Zex nitrous setup damaging the FPR, Fuel pulse dampener or the 3.5L upgrade or my custom fitting used to create a tap for my FP gauge.

I'll keep you guys updated.

 

this makes very little sense to me. an aftermarket fuel pump alone should not alter the fuel pressure since the FPR will dictate what that pressure will be. if your fuel pressure and afr gauge is operating correctly, that means your FPR is very weak at the moment. i'm running the stock pump w/ the AEM FPR and i was able to push my static pressure at idle to 60 psi, i backed it down to 49 for the time being, but i'm suprised the stock pump could do that. as far as the pressure at WOT... that will have to wait till tonight because i haven't gotten a chance to wire the gauge in cabin yet... i will let you know how much the stock pump handles.

obviously scalbert's posts are right... but i still think that i was running lean for whatever reason. i was riding 13.5-14s, when i should have been well under 13 according to most dynos for our cars. this means my car needed fuel. i'm curious as to what the next dyno will bring and if indeed the fpr is able to lower my AFR.

 

Serious? Shit, I'll get on installing my FPR ASAP. Anybody know if I should change out my fuel pulse dampener as well?

 

Serious? Shit if so, I'll get on installing my FPR ASAP. Anybody know if I should change out my fuel pulse dampener as well? Keep us posted after you install your pump. I'm curious to see if I'm way off base here and have faulty fuel delivery equiptment.

 

As CleanCL stated what you posted is what's incorrect.

A higher flow fuel pump isn't going to flow more fuel just because you installed a fuel pump with the capacity to flow at a higher rate. It's only going to flow at that rate if the FPR is telling it to flow at a higher rate.

If your high flow pump was always flowing more fuel than the stock pump you'd be stalling at idle, throwing CELs, and potentially causing hydro-lock from an abundant excess of fuel within the cylinders at such a low rpm.

 

FYI the supercharged guys run static fuel pressure around 65-70psi and 37–40 PSI with 20 Inch HG vacuum

 

So that being said, the most likely malfunctioning part left in my setup would be my FPR? I'll be swapping that out next week so I guess we'll see.

 

i can't really see you damaging too much fuel related parts from a blown motor. as i recall, your motor still ran somewhat, so that means it was surely getting fuel. i would just go with an FPR, that's the real bottleneck on the fuel line imo. contact josh for the correct FPR if you aren't sure. he had it shipped out the same or next day i ordered.

off topic: i have been using the guys at oemacuraparts.com (lance and lee), they have been absolutely terrific, thanks so much for that tip.

 

with static pressure set to 49 psi, WOT pegs to 59psi with no signs of dropping. other than wearing down the stock fuel pump, i feel like i could increase pressure even more. good thing i have a walboro sitting around. pressure is very solid and steady while cruising and WOT.

anyone know the injector limits off the top of their head?

 

You do realize that you can increase static pressure through the roof if you wanted to but the short term fuel trim is going to reduce the pulse width accordingly so that you are sending the same amount of fuel that you would at a lower pressure... the injectors are just opening for a shorter period of time.

 

yes, i know the fuel trims will even it all out, but for some reason i was still running lean according to the afr readings on the dyno. not sure why short of replacing injectors. figured maybe it had something to do with the FPR, so now i know it is pushing plenty of fuel to do what it wants with, if it was receiving low pressure, it would be running lean and it would pull timing to keep injectors open longer to dump fuel in, no?

 

If it were running so significantly lean that it needed to pull timing you'd feel it.

Increasing your static pressure has done nothing but add stress on your fuel system. Your injectors are now flowing the same amount of fuel just in a quicker pulse.

Do you have an on board wideband O2 sensor and gauge?

 

ill drop pressure back down to stock level.

no wideband o2 yet, need to get a bung welded in the downpipe.

 

Which setup did you choose? AEM, PLX, Techedge?

 

i'm getting a little confused. according to all logic, nothing but emanage would help to increase hp by adjusting fuel points because emanage is the only thing to do be capable of adjusting injector pulse.

https://acurazine.com/forums/ramblings-12/2003-m-benz-sl500-184430/

so how did he gain 11 whp and 24 ft-lb of torque?

 

You can back off the fuel trim but you can't adjust injector pulse width.

 

Also, his car was wacked before his tune. He states his AFR was 11.0:1. Well no wonder he picked up so much power by leaning out the fuel trim. Also his IMRC wasn't working so that too will result in over-inflated gains.

 

i've heard nothing but good things about zeitronix.

 

I've heard good things too. What's the cost?

 

expensive. lol. i'll have to look around for some more affordable widebands, i just liked the idea of logging capabilities.