fuel pressure guestion

[331 stang91]

So I run me fuel pressure at about 39 . When I'm under the hood and pull on the throttle allitle the pressure drops to about 34 or so . Is it normal for it to drop so much? Thanks

 

[DMAN302]

Pressure may go up..if vac line attached and given throttle, however pressure should NOT drop when throttle is applied. You need to look into the cause.

 

[HISSIN50]

Does the pressure snap right back up after a second? Initially there can be a lag (pressure dips then swings back up).

Good luck.

 

[331 stang91]

I'll check today, any suggestions as to why this may be happening? New 190 pump and 24 lb injectors?

 

[DMAN302]

Try fuel filter..could be clogged.

 

[331 stang91]

Filter is also new

At idle 39

- vac line 42 1/2

with throttle consistant throught all rpm's 32 1/2

I did upgrade my feed line to 3/8 and left the return line stock, but don't think that would be the problem?

Any suggestions?Thanks for the responses so far.

 

[331 stang91]

Anyone?

 

[Michael Yount]

Your pressure should be measured at warm idle with the vacuum line off the regulator and plugged; it should be 38-39psig under those conditions. WHen you plug the vacuum line back onto the reg at warm idle it should drop down into the 31-35 psig range (higher end if you have more cam less/vaccum; lower end if you have a milder cam/more vacuum).

 

[331 stang91]

thanks I always set the pressure with the line on!

 

[331 stang91]

but does anyone know why it drops when I give the car throttle? You saying cap of the top of the regulator?thanks

 

[HISSIN50]

You saying cap of the top of the regulator?thanks

Nope, he is saying to cap off the vac line which attaches to the top of the regulator.

 

[Michael Yount]

If you're running 39 with vacuum line on you're running too much pressure. Your technique for setting the pressure is incorrect.

 

[331 stang91]

I see thanks!