AEM regulator question

[GoatOfRafin]

Hi!

Yesterday, I installed a return fuel setup with an AEM regulator. My fuel pump is a Walbro 255lph hi-pressure model and I have 630cc Siemens Deka-IV fuel injectors.

For those of you who have an AEM fuel regulator, it comes with 3 diaphragm orifices (black-0.100", silver-0.150" and gold-0.200") which, from what I understand, regulate the sensitivity of the fuel regulator. When I had the silver orifice installed, the fuel pressure gauge needle was all over the place at idle so I decided to put the gold which is the largest one. By doing that, fuel pressure was stabilized at 3 bars approx.

I tightened the pressure screw and the most pressure I managed to get is 3.7 bars approximately. The thing is that I might need to raise my fuel pressure at 4 bars and I cannot do that right now.

Is this normal? Do you have any idea what might be wrong? Please note that I have not tested the black orifice and that the stock fuel regulator is NOT installed on the fuel pump.

[Smaay]

sorry cant help you. i use aeromotive regulators in my return systems

[GoatOfRafin]

Guyz, any info would be greatly appreciated. After a week or so, I realised that my fuel pressure is all over the place and the car stalls at idle. Please check this video out:

http://www.youtube.com/watch?v=OU6IRHiy7L4

For those of you familiar with the AEM FPR, I have installed the gold orifice. Moreover, fueling with my 630cc injectors is not sufficient anymore whereas with the stock returnless fuel system and FPR, everything was ok...

Please advise!

G.

[Batojiri]

keep it low, if you applied a vac line to it the boost pressure will hold the diaphram shut overcoming spring pressure and effectively raising your fuel pressure. average figure is for ever 1 PSI of boost pressure you get back an extra 1 PSI of fuel pressure. keep in mind if you have 30 PSI fuel pressure at idle its going to jump up to ~ 45 PSI at 0 PSI on your Boost gauge.

[Smaay]

you are supposed to remove the boost line from the regulator while you set the base pressure too.

[GoatOfRafin]

Thanks for the tips guys but how do these relate to the wild fuel pressure fluctuation seen at the video? Moreover, please notice that after the engine stalls, fuel pressure drops almost instantly to 0 bars. Is this normal? I thought that fuel pressure is supposed to remain more or less constant for at least 5 to 10 minutes after engine stops...

[Batojiri]

the AEM FPR isnt going to hold pressure after you take vaccum off it and turn off the fuel pump because its a spring adjustment type regulator with vac/boost port. this is normal and you should not worry about that. id worry about your injector sizing programming on whatever aftermarket fuel/spark controller you are using first, you will have to use a fuel pressure calculator to figure out how many cc/min your injectors are at your base idle fuel pressure otherwise that and the latency will make your engine run crappy and hence the weird idle and jumpy fuel pressure readings.

[GoatOfRafin]

Thanks for the tips... So, again, please notice that after the engine stalls, fuel pressure drops almost instantly to 0 bars. Is this normal? Note that the key is at the "ON" position so the fuel pump is supposed to be powered.

[lVlemphizStylez]

the AEM FPR isnt going to hold pressure after you take vaccum off it and turn off the fuel pump because its a spring adjustment type regulator with vac/boost port. this is normal and you should not worry about that. id worry about your injector sizing programming on whatever aftermarket fuel/spark controller you are using first, you will have to use a fuel pressure calculator to figure out how many cc/min your injectors are at your base idle fuel pressure otherwise that and the latency will make your engine run crappy and hence the weird idle and jumpy fuel pressure readings.

unscaled injectors don't cause your fuel pressure to fluctuate with an aftermarket FPR....Your car should hold some fuel pressure after you turn it off...If it's not there is an issue in the pump area or you have a leak in the system (probably by the pump or where the stock regulator used to be). I'm assuming since you have an aftermarket FPR that you've somehow blocked off the stock unit. This is where you might be having an issue. I'd check the pump and the how you've blocked off the stock FPR. I run an aeromotive which is a spring adjustment type regulator with a 1:1 port. I have for MANY years now...it holds plenty pressure after you turn off the car and my fuel pressure does NOT fluctuate

[Smaay]

^^^ that could be the case. did you put a block off piece where the stock regulator was? if its leaking then that might be your problem. or if you just removed it and didnt block it off. that might be exactly why you loose fuel pressure instantly

[GoatOfRafin]

Thanks guyz, I 'll check it with my mechanic next week since I am not inclined into doing such stuff... By the way, I have two more relevant questions:

- Do our cars have fuel filter?
- Does the Walbro have a fuel pump check valve?

Thanks again for your knowledgeable advices!

[Boosted2.0]

There is a fuel filter in the pump housing. Thats what that big white plastic thing the pump plugs into is.

Not sure if the Walboro has a check valve or not.

FWIW I set up an AEM on Mike Lu's car many years ago, and had no problems with it at all.

[lVlemphizStylez]

there is a valve in the walbro but it's a pressure relief valve...it opens I think after 85 or 90 psi of fuel pressure. It's the only valve I know of on the Walbro

[GoatOfRafin]

Thanks guyz, I just wanted to know if a defective fuel pump check valve could be the problem. Since the Walbro doesn't have any, it can't be a problem!

From what I can understand, something is done wrong at the installation of the return system, most possibly (as MemphizStylez and Smaay suggested) not blocking off adequately the hole of the stock regulator. I will keep you posted...

[GoatOfRafin]

Guyz, after all, my problem with the return system is solved. It seems that there was something wrong with the installation of the fuel pump, so nothing wrong with the fuel pump itself, regulator or fuel lines. Thanks for your help!