where should the fuel pressure be regulated at? i took off the hose at the end of the fuel rail and put a gauge on it. does anyone know what the fuel pressure should be at the end of the fuel rail? i think i have a fuel pressure problem the car has been unfloodable for the last week or so and i have around 90 psi of compression on the rear rotor. its an 87 tll. oh, one more thing does anyone know if a N/A regulator would work? thanks james

 

They method your using is measuring the output of the fuel pump.

To find out the regulated rail pressure, just TEE into the fuel feed line on the left side of the engine. The fuel has to be allowed to flow to read the regulated rail pressure.

The fuel pump should be putting out approx 71.1-92.4 psi and the rail pressure should be approx 34.1-39.8 if the engine is not running and approx 28.4 at idle.

That's for a turboii. The n/a is very similar. It's in the online manual.

 

If you tee into the fuel line with a tee-fitting, you can mesaure rail pressure, which is really what we care about. With the car off, you should see 39-42 psi. With the car running, you should see 30-34 psi of fuel pressure, depedning on your engine vacuum.

By simply taking a hose off and connecting the gauge to it, you are measuring the maximum fuel pressure your pump can generate and the pressure drops associated with the lines... this is useful in itself when testing and designing a very high-performance fuel system, and testing the stock pump for extreme wear, but next to useless for determining any problems realted to the vehicle running.

Max pressure on a stock style pump will vary... expect 80 psi or so.

 

I obviously have a quicker computer than the scathcart. humor

 

That or you think at a rate faster than a chimp...

OOH, burn!... wait... to myself... aww, dammit.

 

I tee into the line at the end of the fuel rail? where is the regulator at?i thought that the line on the front of the motor ran from primaries to secondaries. if so shouldnt that be regulated as well?i thought the regulator was before the fuel came into the rail.if not how does it work?

 

wait..."The fuel has to be allowed to flow to read the regulated rail pressure." can someone explain?

 

You have to use a TEE fitting before the fuel pressure regulator. between the rails is fine, as long as you are using a tee fitting. If you simply disconnect a fuel line, and connect it to your fuel pressure gauge, you will not be seeing the RAIL pressure, you will be seeing pump pressure. You have to tee into the line.

 

Just what it says. You measured the zero-flow pressure of the fuel pump, which is pretty meaningless since the fuel must be flowing when the engine is running. This reading will always be far higher than the readig you get by teeing into the fuel line after the fuel filter. This gives you the pressure the injectors see when the enigne's running, which is the only important reading.

 

Maybe this will help. The fuel pressure regulator dumps any pressure above what it is supposed to be regulating the pressure at, at a given moment in time.

It does that by bypassing the excess fuel back into the tank. There is fuel flow ALL the time thru the fuel rail, when the engine is running.

That's a slightly flawed description, but it's the best I can do right now

 

thanks guys. i thought about it for a little while after i posted and i figured it out.