I have a B250 5.2L 318ci engine with throttle body fuel injection. I'm working some fuel issues (see other thread).

I realized nothing changes when I connect or disconnect the vacuum line on the fuel regulator. My fingers can't feel any vacuum anyhow. What is this line *supposed* to do? How can I test if it's working?

Two pictures attached, with the regulator in place and the regulator removed. Did I get the parts labeled properly?



Any information about the vacuum line behavior appreciated! Thank you.

 

Fuel pressure is supposed to be 'vacuum modulated'. I *think* it's 'ported vacuum', so, higher the flow thru the TB, the more vacuum you get. Try revving the engine a bit, and see if vacuum at that port changes.

 

HeyYou,

Okay. I see your words. But that doesn't mean anything to me. I don't know what is supposed to be happening or what it's suppose to do. Revving the engine or not, I cannot discern any vacuum on the line. I put a gauge on it. I put a moist figure over it. Nothing. I don't think it's pulling a vacuum at all, let alone modulating anything.

 

what year is it...i'll check the fsm.
surprised they use a vacuum fpr on a tbody injection.

 

Primem,

Thank you. It's a 1989 model. The Chilton manual identifies it as a vacuum connection. Sure ~looks~ like a vacuum connection (did you see the pictures above?) I'd be interested what you find.

 

I agree its a vacuum diaphragm... but tbody injection doesn't have to overcome changes in manifold pressure like a multipoint spraying into vacuum at idle and full atmospheric at wot... will look into it on Monday and report back.

 

It is referred to as a vent line in the 1990 parts manual.

 

SteveR,

Does it give any routing information or where it specifically vents to? If it vents to atmosphere, I would think it would not need a tube going anywhere - just open to the atmosphere. At least you're giving me confidence that it's not suppose to be sucking vacuum.

 

It may route under the air hat, so it draws filtered air, instead of whats hanging around in the engine compartment.

 

Well, I can see that the other end goes into the metal carburetor body, as show in the picture. From there, I don't know. That seems a fancy routing to just vent. Interested if anybody has more details.