MonkeyMagic

I have been having trouble with getting fuel in my engine. I have fuel all the way up to the fpr. Now, I have the upper manifold taken off. Does the fpr need vaccum to open, or should it flow through even without the manifold on?

pfcmooney

which FPR do you have?

1987RX7guy

iTrader: (3)

I believe the FPR is pressure/vac sensative. But i'm not aware of it closing or not opening with lack of vacume. But it has the nipple for a reason.


BTW if you have pressure up until your FPR the injectors are seeing fuel. Your problem would probably be the injector drive system.

sc0rp7

iTrader: (3)

the FPR would still flow, the vac nipple is so it maintains relative pressure even though there is a negative pressure area inside the manifold where the fuel is going...

- chris

MonkeyMagic

alright, looks like I need a new fpr then.

thanks guys.

MonkeyMagic

oh yea, anyone know where to get a replacement, I found one on rx7.com, but it is for about $200 with adaptor kit.

1987RX7guy

iTrader: (3)

autoparts store.


BTW you might want to check your INJECTORS! If the FPR sees fuel then all of your injectors HAVE FUEL!

buttsjim

I think you need to think about this some more. A faulty fuel pressure regulator shouldn't prevent fuel from getting to your engine. If it closed completely, it would dead-head the pump, but your injectors are upstream of the regulator, and would still have fuel under pressure. I understand that the JDM spec is different, but what I just said is true for the American spec. Do you have your fuel line from the filter correctly plumbed into the primary rail?

The vacuum nipple just provides a means of reducing fuel pressure under light throttle loads. Your fuel pressure works against a spring-loaded diaphram to open a check valve to bypass into the return line. The vacuum pulls the diaphram from the opposite side, augmenting the pressure from the fuel. Under heavy throttle, the vacuum goes to zero, and it stops helping to open the check valve. So, now the fuel pressure has to open the valve all by itself, and the fuel pressure increases accordingly.

Rex4Life

How do you know it's bad?

Take the fuel line off from the fuel piping manifold by the oil filter. Put a gage on there and check the dead end fuel pump pressure--i.e. no flow. It should be like 70-90 psi on a gage--if it is the pump is good.

Then put a tee in that line and reconnect to the manifold. Run the pump and you should see about 43.5 psig without the car running (AFM fuel pump c/o jumpered). Make sure you have a good gas filter in place for this test.

If both tests are ok then it sounds like injectors or electrical to me.

HTH,

Scott

MonkeyMagic

I tested the injectors, they work. The injectors are getting signal from ecu.

The fuel pump is good, I installed it before I pulled my old engine, and it is working fine (brand new walbro 255 pump). The fuel is not even getting in the rail, it stops at that check valve or pressure regulator, whatever you want to call it. So that is where the problem is.

buttsjim

It sounds like you have the line from your filter going directly to the regulator. It should be going to the primary rail, so that the regulator is the last device fuel flows through before returning to the tank.

Edit: I didn't say it well, but I think your supply and return fuel lines are reversed.

HAILERS

********The fuel is not even getting in the rail, it stops at that check valve or pressure regulator, whatever you want to call it. So that is where the problem is.************8



The fuel goes from the flilter.........to the pulsation damper.........thru the primary rail......to the secondary rail..................to the Pressure regulator. So, from the above descripiton, you have the fuel lines backwards. Where? Got me. Sounds like the pressure and return lines are on backwards.

The fuel pressure regulator is the LAST thing in the system before the excess fuel goes back to the fuel tank return line.

1987RX7guy

iTrader: (3)

Sounds like a crossed line problem. I've seen it done by inexperienced mechanics.

the FPR should be hooked to the return side not the feed.

buttsjim

Well, the last 3 posts make it a consensus from Texas. It must be reversed fuel lines.

MonkeyMagic

The lines are not reversed, I thought the pulsation damper was the fpr. The primary rail is the smaller rail (on the bottom with pulsation damper on firewall side) and the secondary is the larger one (on top w/ fpr on firewall side). If this is correct, than I had my terms mixed up. So again, would I need manifold vacuum to allow fuel to pass thru the pulsation damper?

I have a workshop manual for this engine, so I am like 99% sure the lines are correct.

1987RX7guy

iTrader: (3)

FWIW the PD is supposed to be a shock absorber for high frequency pulses of pressure from the opening/closing of the injectors. I don't believe its capable of blocking fuel flow.


So my conclusion is that your lines are either blocked by something in them or you have crossed your lines.


It takes 5 minutes to check if they are crossed or not so stop waisting all this time and atleast eliminate that from the possabilities.



Santiago

buttsjim

Going back to your very first post and answering that question, NO you do not need manifold vacuum to allow fuel to pass through the FPR.

Now, as 1987RX7guy just said, the pulsation damper can NOT block fuel flow--fuel doesn't pass through it.

Finally, something is confusing. In your first post, you correctly said that your FPR had a vacuum fitting. In your last post, you said you confused the FPR with the pulsation damper. But, the PD doesn't have a vacuum fitting, so something sounds a little screwy here.

But just to be clear, manifold vacuum is NOT a player in blocking your fuel flow--it can only lower your fuel pressure when everything is in operation.

Edit: I mis-stated the bit about fuel flowing through the pulsation damper, somewhat--it does flow in through the banjo bolt, and out through the base of the damper.

buttsjim

Since you already have your upper intake off, maybe, as an experiment, you could just plumb your fuel supply from the filter directly into your secondary rail (at the end opposite the FPR), and temporarily eliminate the primary rail. See if the fuel passes through the FPR into the return line. If it doesn't, take the RETURN line off the FPR and blow through the line to the tank to ensure that it's not blocked. If the FPR is the problem, you can isolate it that way.

If you get flow with that test, re-plumb the lines correctly, and try again.

Rex4Life

I think I got it. The injectors don't get a signal from the ECU, basically once the ignition is on they see 12v power all the time, then the ECU supplies a ground to open the injector. You need to check the injector signal at the ECU and and see if they are getting grounded by the ECU.

How did you test the injectors? Tell me what you saw to say that they work.

If they are not getting grounded the wires will show 12v just sitting there waiting to be grounded. The only way you'll see the injectors working is when someone is cranking the engine (since yours won't run at all).

I bet hailers has a good way to check them--see if he pipes in.

Scott

Pinfield357

could always just get some noid lights

HAILERS

No you don't need vacuum. On a NORMAL RX-7, you can jumper the fuel pump check connector and then turn the key to ON. The pump should purrr and you should be able to hear the fuel running thru the fuel rails and returning to the tank.

A FPR that has been in a fire could cause the blockage. Been there, done that.

MonkeyMagic

For some reason, when I put the ignition on, the pump does not prime, but once I turn the key, it starts working.

As for the injectors, I don't have a noid light, so I used my multimeter to check it. At the injector, they were getting 6 amps and I believe it was 12v.

Before I took the manifold off, I did try to cross the lines, that still didn't work.

After taking the manifold off, I took off the rails and blew into each line. Air passed through the upper rail and out of the return line, and it also went through the in line, but I could not blow through the lower rail (smaller one), so I took an injector out, and air came out through the injector hole, but not at the other end, where the pulsation damper is. Do you guys understand what I am saying?

buttsjim

I understand what you're saying.

As I recall, the fuel should flow in through the banjo fitting and out the base of the damper into the fuel rail. Then it flows into the secondary. It sounds like you blew into the primary (lower) rail in the opposite direction of fuel flow, but it seems like it still should have been an open package.

If I'm reading correctly, it seems like the base of the damper is somehow clogged. Why don't you try blowing through it from the banjo fitting (with the rubber line to the secondary rail detached), and see if air passes. If not, you can unscrew the damper from the rail and inspect it. If it's blocked, it should be right there in the base where you can see it.

MonkeyMagic

Sounds like a good idea, I'll try taking it apart and inspecting it before I go out and buy a new one. I'll let you know how that goes.

MonkeyMagic

And I did blow in the opposite direction of fuel flow because before I took the manifold off, I tried blowing from the in side w/ the return line taken off, and it air didn't pass.