What does that vacuum line do?

[cardot33]

*02 Malibu 3.1L*
Hey all, I replaced the o-ring on my oil pump drive today and upon reassembly I broke the vacuum line that comes out of the harness and connects to the intake manifold near the fuel pressure regulator. Its not starting now, but I just don't want to jump to conclusions about this being the reason, but what does it do anyway?

[bszopi]

Got a pic? I can't think of which one that is... I doubt it would stop it from starting, though. I'd look for wires that you forgot to hook back up.

[60dgrzbelow0]

In very general terms, the FPR uses the partial vacuum condition inside the intake manifold caused by the draw of air in through the throttle body to fill the spaces in the cylinders during the downward suction caused by the descent of the pistons during the intake stroke. The tube you broke forms a path to the inner vacuum and causes a suction draw (like sucking on a straw forms a differential pressure that allows the outside air pressure to push down on the soda and up through the straw). In the case of your fuel system... the pressure remains constant from an electric fuel pump. The vacuum acts upon a fuel bladder diaphragm inside the Fuel Pressure Regulator enough to allow the fuel already pressurized to a maximum of 55 PSI the chance to enter the fuel rail for metered distribution to the fuel injectors... the greater the demand vacuum is...the more fuel is allowed to pass.

http://www.familycar.com/store/item/Chevrolet_Malibu_Standard_Fuel-Pressure-Regulator_2000_2003_SIPR234.html

[bszopi]

He's not asking about the EGR, but just a vacuum line near the FPR. Even so, with the vacuum line disconnected from the FPR, the car would still start and run.

[cardot33]

not the line to the FPR, I already know how that one works and where it goes to and such. the line I'm talking about hooks onto the intake manifold like an inch away from the fuel pressure regulator and then disappears into the wiring harness like a ninja so I can't tell where it goes. I'll have to take a picture of it tomorrow.

[bszopi]

Went out into the freezing cold just for you to look at how my Rendezvous is setup. Unfortunately, I just have a plug on that port, so I can't help you at all... My bet is still on a wire/plug somewhere.

[Azrael]

I've only seen that port used for the vacuum modulator on 4t60-e transmissions and/or vacuum tanks. Not something that'll keep the engine from starting though.

[pocket-rocket]

Since it vanishes into the harness, I wouldn't be shocked if it was for the HVAC controls. For sure that wouldn't keep the car from starting. Have you tried plugging the port on the manifold to try it out of curiosities sake?

Went out into the freezing cold just for you to look at how my Rendezvous is setup.

It was 10*F Tuesday, 20*yesterday and 24* today when I went to work around 4:00am Now when I see asterisks, I think snowflakes instead of degrees on this site...

[Jonpro03]

Found a picture of the motor. I believe that runs to the hvac. Plug the whole and then engine should be able to start. Or repair it (obviously).

[bszopi]

When I went to work at 7am yesterday, it was 5* with a windchill of -9*. It was supposed to be down near zero this morning, although I don't think it ever got there. Currently 37* with a wind chill of 29*.

[cardot33]

Thanks for getting the picture of it johnpro003. I plugged it but it still isn't starting so I'll have to work backwards and try to find what it is I intsalled wrong. I'll do that when I got more daylight, I put this together in the dark, taking it apart in the dark probably won't be very helpful.

[cardot33]

couldn't find anything out of place. pulled a plug and it was dry after all my trying so i'm wondering if i'm getting fuel. harness connector near alternator is plugged in, schrader valve spits fuel when i press it, fuel pump runs. what am I missing? turns over and sounds like it's going to start but then it just doesn't.

[bszopi]

All plugs for ICM are plugged in and tight? No blown fuses anywhere?

[cardot33]

yes all 3 connectors on the coil are tight and the plug wires are connected to the correct coil. sounds like its just about to start but it wont kinda weird.

[bszopi]

Did you check the second part of my post? Since you mentioned it doesn't look like you are getting fuse into the cylinders, but you have fuel at the rail (do you know the pressure?), there is a chance that the fuses for the injectors are bad. Slim chance, but its something easy to check.