Fuel Regulator Problem (SX regulator)
 

I am having an issue with my car's fueling, Ive got her running !!! NICE!!! anywho, under boost it pulls fuel! all the way down to a damn 20psi even if I have the regulator cranked up to 85, The pump will put out 85 all day long with the motor off, like 65 with the motor on, probably more if I jack the regulator up more. but once I get on the gas we loose pressure like a ROCK. so I hooked up my trusty vac gauge and I think I might have found an issue, at WOT my vac on the regulator line drops to 0 PSI, is this normal??? Has anyone ever experienced these issues? If I leave the vacuum line off should it just maintain pressure? because even with the vac line off it drops pressure off.

Thanks!!

Sounds like something else. If you give WOT then there isn't really vacuum anymore which is why it would not recieve any. Vacuum should also lower the pressure since it closes the valve more in the regulator. Sounds about right. ANyone with better knowledge?

I thought it was rising rate? Maybe my pump isnt supplying enough but its a walbro 255 and I just rewired it ???!

also why would my pump flow 90 PSI fine but then shit the bed with load

Did you make sure you didnt get a knockoff Walbro? That would where I would start.

I baught it from someone on this forum (datan) and he said it was a good walbro 255, He used it in his car with no issues, I baught his entire fuel system - regulator.

Shot in the dark but you might want to replace the fuel filter. It might be restricting flow and causing the pressure drop. Also the regulator should raise pressure with boost. Jumper the fuel pump and add a compressed air source to the vac line and see if the fuel pressure goes up accordingly.

Again why would it fail under load but flow 90-psi without a problem???, Fuel filter is an inline 6an filter, said to be in good condition, I am not sure where to get a new filter :( Ill ask the local race-shop monday. I need to purchase a mighty-vac to check out the regulator, Applying vac = more pressure?

No, it should go up 1 psi for every 1 psi you put into it.

well when the injectors arent going, its much easier to hold 90 or 100 psi of line pressure. When they are spraying at close to 100% duty cycle, even with stock injectors you'll be spraying close to 2 liters/min. By spraying this much fuel, the pump can't keep up with the demand so the pressure drops. If its doing this just a little bit at the upper end (and all else is good with the setup), you should lower the pressure to a little below where it bleeds down to at high load. However, in your case it sounds like you either dont have enough pump capacity, the pump isnt getting the voltage/current it requires, or there is a restriction in the line getting to the rail such as a clogged fuel filter.

Make sure that the vac nipple you have it hooked to is actually a vacuum signal, not an air bleed for injectors or something. This may be why you arent seeing a pressure rise while in boost.

okay, Well I will pull the filter and check it out. I am running stock boost and stock primarys 720 secondarys on a walbro 255 I dont think im outflowing the pump capacity so I figure it should be the filter. I just rewired it as soon as I realized the issue so its a good 12-14v at the pump, direct feed from the battery using a relay :).

thanks so much everyone for your help, I truly appreciate it,

I cleaned my filter and it helped ALOT, but under boost we still go down to 20psi, I think it might be my fuel pump sock at this point even though its a relatively new walbro 255. Voltage at the pump is good. I am going to investigate this sock issue a bit later, Anyonr know anything else that could be the problem.

Again thanks so much for your help, I am so excited to have a almost running rx-7!!!

Did your test the FPR yet?

yes, My FPR isnt letting the fuel return or anything like that, I just have insufficient flow.

Buy a new walbro pump or better yet a bosch 044. It's better to spend a hundred or two now than a new motor later.

I am getting REALLY fucking frustrated, is their a way to test my pump? I cant believe im not getting full fucking fuel flow. I cleaned the sock, I replaced the in-tank lines and wiring and the fuel filter is good. I geuss it has to be the god damn fucking pump but I'm just frustrated and cant get a pump to get my car running tonight. FUCK!