New Denso Pump - Maxed out at 38 psi?
 

I just installed a new Denso fuel pump, fuel rail, 1600cc injectors and a fuel pressure regulator from the RX7 store and I am trying to set the fuel pressure. The problem I am having is that the fuel pressure will not rise above 38 psi even when I have the regulator cranked all the way up.

I can hear the pump working hard, but there is no more change in pressure once it hits 38 psi.

Just in case I am doing something wrong, I thought I should let you guys know exactly what I am doing....

With the ignition on and the engine off, I am jumpering the f/p terminal to the gnd to run the fuel pump. Next I am turning the nut on the regulator to increase the pressure. Nothing more, nothing less.

It does go up and down accordingly, however the pressure will not go above 38 psi. I thought I read that the base pressure, with the manifold at atmospheric pressure, I should be in the area of 43 psi. If anyone can shed some light on my issue it would be greatly appreciated.

What brand is the FPR? Maybe the spring inside is defective.

It is the SARD brand that came with my fuel upgrade kit from the RX7 store.

Please help. I am going to miss out on my chance to have my car tuned if I don't get it running by tomorrow.
Shouldn't I be able to turn the pressure up above 38 psi in this scenario?

How old is the fuel filter?

Brand spankin' new. I forgot to mention that.

I just went to the supply line coming off of the tank and hooked up a fuel pressure gauge and it was reading 40 psi, but that is as much pressure as it will make.

I think I got a POS fuel pump. What do you guys think?

Well, try pinching off the return line, or blocking it off. IF the pressure goes up, the FPR is to blame. If the pressure does not go up, the pump is to blame.

Are you absolutely sure you have the inlet/outlet on the FPR hooked up right? You'd likely have no pressure on the gauge if they were backwards, but it's just a shot in the dark.

I usually start off with 38psi base pressure at idle with adjustable FPR cars, but then I am no tuner either.

The last thing I did was dead head the pump directly into the gauge and it only made 40 PSI. If it won't make any more pressure than that coming directly off of the pump then I'm screwed!!

These high dollar supra, cosmo, aeromotive etc. pumps are all well and good, but for my money dual walbros will support anything you can do with a street driven 2 rotor, all for under 200 bucks. ;)

EDIT: plus, even if one were to fail, the other will still get you home. :D

My big problem now is that I bought the pump almost a year ago and I'm just now getting around to installing it. I'm sure the RX7 store will just tell me to bend over and take it up the a$$ cause there is nothing else I can do this far down the road, even though I'm just now installing it.

I don't know, Jason's a pretty good guy and you might want to call/pm/email him anyway. There might be something he can do for you and it can't hurt to ask.

Yeah, I know he's a pretty good guy. I'm gonna give him a call in a little while. I'm just pissed off that I bought a $200 dollar part that I'm probably not going to be able to get warrantied.

I've never heard of a supra pump failing, esp right out of the box......

Even if you put the gauge right after the pump and the FPR is in the the system. You are still reading what the FPR is holding pressure at. I would think that If you are able to make 40psi of pressure, the pump is still good.

Double check and make sure that you don't have anything wrong inside the tank. Did you reuse the o-ring on the pump out put nipple? How did you run the wiring? Know on a Walboro you have to splice the wires to hook it up. Do you have to do this with a Denso?

Also make sure you don't have any leaks in the system, this will bleed off pressure as well. Do you smell fuel from any ware? You changed the Filter, did you kink any of the lines on reinstalling it.

These are just some vague suggestions, hopefully they will lead you in the direction to solve the problem.

Brandon

I had it set up to "dead head" or pump directly into a pressure gauge with no other place to go and there was only 40 psi. I am going to try rewiring the pump right now to see if it makes a difference.
Thanks for your help so far guys.

Yeah, I was going to ask if you could confirm the voltage going to the pump, and maybe test the resistance of the motor coil.

Unfortunately I don't know what that resistance should be - perhaps a supra resource could help with that.

Dave

As much as this situation sucks for you, my question is, why have you had this pump for a year and wait until the day before your tuning session to try to get it working? You always have to leave room for error and issues when doing work on these kind of cars (or anything modified/custom for that matter) which is why I will generally not commit to any completion date on customers cars...it gets done when it gets done, and I don't usually send them out the door until I have gotten everything installed, running, and test driven for a short period. Then and only then will I call them and say "your car is ready tomorrow".

Don't forget to check the plumbing inside the tank, when you have it apart.

Deja Vu?

Is your pressure steady? Meaning does your needle bounce around or are you pretty stable? I had made about a 3-4 hour trip with no issues on my last pump. It literally died the day after when I took it out again. No warning at all. Granted it was a Walbro, but a pump is a pump and they fail...

It was a similar situation in that I couldn't get more than about 38psi out of the thing and I had cranked the FPR down.

I had a stock pump on another car wher a bit of plastic broken off the fuel sock stuck in the pump inlet partially blocking it. It had more or less the same effect, but was more like 30 PSI.

I would swicth the pump for a stock or other known good and try testing it again to verify that its not somthing other than the pump.