I set my Fuel pressure at 48 psi, i hooked up the vaccume hose and reved it and it would drop a few psi. Isnt it supposed to go up when revved? Confused, please help!

 

maybe your fuel pump is ****ting th ebed. how many miles are on it. have you changed your fuel filter yet. the gauge should go up to the pis you set it at when the vacuum line was off.

 

Just for kicks, pull the vacuum line off the regulator and see if
there is vacuum on it with the engine running.

 

hehehe, ported (EGR) vacumm off the TB to the FPR...you never know

As for the original question, i can't answer it directly since i have no idea what you are really seeing when you 'rev' it, or even what you mean by 'rev' it. Instead i'll simply explain how it is supposed to work and you can go from there.

The FPR is directly referenced to manifold pressure such that when the manifold is under vacuum, the FP will drop proportionally with the vacuum.

When you are at WOT, your manifold is at 0 vacuum so you will see your max FP. If your FP drops while at WOT that means your fuel system is not keeping up, whether it be a tired fuel pump of clogged fuel filter, etc.

If you are free revving it in neutral you will see the pressure go up for a second, depenmding on how far and long you are hitting the gas for (this is b/c the manifold vacuum drops, so pressure increases), then when you let off the gas and your engine is spinning back down, manifold vacuum will be even higher than a normal idle and thus your FP will read lower than at a normal idle.

All that you need to know is that FP should be it's highest at WOT and basically be it's lowest at idle (except as mentioned under decel). If your FP falls off at WOT you have delivery issues. If your FP is doing funny things like being peak at idle and WOT, but drop under part throttle and revving then there is a chance you hooked the vacuum feed for the EGR solenoid to the FPR. The FPR gets it's vacuum right off the plenum, not the bottom f the TB.

 

You never know.
I fixed that problem on a customer car before.

 

The only way your going to have more vacuum is when you down shift and put the motor under pressure. Just reving the motor and letting it drop wont give you and excessive vacuum. I'd put money on a fuel pump or filter...

 

Just once could you chime in with a coherent accurate answer. I've tried to ignore you as much as possible, but every thread you touch you come in and either completely mistate yourself, or you are flat out wrong.
A decelerating engine (such as one that was just revved up and now is spinning down with a closed throttle) will most certainly show more than idle vacuum.
And if your fuel pump/ filter can't keep up when free revving the engine, you probably wouldn't have the flow to even drive down the highway, and would most certainly fall flat on its face and die at WOT. Free revving doesn't use any significant amount of fuel compared to actually loading and driving the engine.

I'm sure you mean well, but please check your facts before confusing the readers of my board

 

No Joke, that should be at the top of every damn Board here.

 

Just once could you chime in with a coherent accurate answer. I've tried to ignore you as much as possible, but every thread you touch you come in and either completely mistate yourself, or you are flat out wrong.
A decelerating engine (such as one that was just revved up and now is spinning down with a closed throttle) will most certainly show more than idle vacuum

when in gear...

i watch a vacuum guage in my car everyday and under normal rev from idle when it comes back down to idle it returns to the normal vac no more above it...


hmm..well i had a fuel pump that couldnt keep up and went just fine on the freeway, so can you tell me more...

thanks for your concern though

 

What's your vacuum gauge reading Kdogg? I'm curious because I've only had mine on sitting in the driveway. Everytime I've revved the motor the vacuum would jump to slightly higher than idle vacuum on it's way back down. That's simple physics there, it has to. You don't have a vacuum leak in your gauge do you?