No vacuum at throttle body

[paddlenbike]

I was checking my fuel pressure and found that there was no vacuum to the fuel pressure regulator. I started poking around and found there is no vacuum to any of the locations marked here in red:

Of the two vacuum hardlines that run along the intake manifold, everything feeding off the larger one (lines in blue) had strong vacuum and all of the lines feeding off the smaller hardline (shown in red) had no vacuum.

I squirted some brake cleaner down the two hardlines directly behind the butterfly valve to make sure they weren't clogged and the engine instantly started sputtering, so the lines are open. Any idea what could cause this lack of vacuum? Am I wrong in thinking there should be strong vacuum at the two ports behind the butterfly valve?

FYI, my boost gauge shows 19 in/hg at idle.

 

[JonoTurbo]

Neither of those ports have vacuum at idle, test them with any amount of throttle and you should find they have vacuum.

 

[BoostFreak]

sorry off topic but are the two ports "behind the butterfly valve" on the TB a decent port to pull for the BOV because mine keeps fluttering and I'm afraid of compresser surge and I don't know if my BOV is getting enough vacume our not

 

[aljordan]

Wow... I JUUUSTTT put together that side of the motor.

He's there deal. The Fuel pressure-up VSV has 2 vac lines coming off it (L180 and L160). One of those lines tees off the big metal line that is connected to the intake manifold. The other vac line leads into the one of the metal lines that leads up to the FPR. You may want to by-pass the VSV and check your pressures again.

 

[Dirgle]

sorry off topic but are the two ports "behind the butterfly valve" on the TB a decent port to pull for the BOV because mine keeps fluttering and I'm afraid of compresser surge and I don't know if my BOV is getting enough vacume our not

No, there not a good source. You want the BOV to see vacuum when the throttle body closes, so that the BOV will open. What kind of BOV are you running? If it the BOSCH model then make sure you have it on the right way, it is very easy to get it backwards.

 

[NashMan]

you shoudl reall never use thou stuiped one there very week sorse for vac

 

[paddlenbike]

Wow... I JUUUSTTT put together that side of the motor.

He's there deal. The Fuel pressure-up VSV has 2 vac lines coming off it (L180 and L160). One of those lines tees off the big metal line that is connected to the intake manifold. The other vac line leads into the one of the metal lines that leads up to the FPR. You may want to by-pass the VSV and check your pressures again.

I had another FPU VSV laying around so I hooked it up...no change. There is strong vacuum going in and out of the FPU VSV because it's on the larger hardline. It's the small hardline (and all the vacuum lines in red) that have no vacuum.

Thanks for the help; keep 'em coming!

 

[lagged]

what exactly are you looking for? the TB ports wont have any vacuum with the throttle plate closed.

the BOV and FPR need a MANIFOLD vacuum source. the ports on the TB are NOT acceptable sources of vacuum for those items.

(they are only there for the EGR actuator and the charcoal canister coolant vacuum switch.)

 

[lagged]

I had another FPU VSV laying around so I hooked it up...no change. There is strong vacuum going in and out of the FPU VSV because it's on the larger hardline. It's the small hardline (and all the vacuum lines in red) that have no vacuum.

Thanks for the help; keep 'em coming!

the FPR VSV will let the FPR reference atmospheric pressure, not vacuum on an initial hot start for a certain amount of time. test the FPR vacuum line from the VSV again after driving the car for a little while.

 

[paddlenbike]

Thanks for the replies. The only thing I can imagine is the hardline between the FPU VSV and the bung where the stock FPR vac line attaches is somehow plugged. There is strong vaccum into and out of the FPU VSV, but not at the other end of the line at the FPR.

So what does the FPU VSV actually do? Does it shut off the vacuum source on a hot restart?