2G Adjusting AFPR with low vacuum?

[Cool Mr Steve]

I have about 14 in/hg of vacuum at the intake manifold at idle, and I was curious if that would throw my fuel pressure off. When I adjust the fuel pressure, I have the vacuum line off, but it still seems as though the fuel pressure doesn't stay constant at idle. I'll adjust it to 43 psi on one day, and the next day (or later that afternoon) I'll look at it and it will be 48 psi... Does the vacuum have anything to do with it, or do I have another problem mixed in there? BTW, I have no idea what is causing the low vacuum... I've posted it up here a few times and no one can give me any help on it. Cam timing marks line up, and I can't find any vacuum leaks.

 

[FORMONTOYA]

it is normal to have vac. at idle. mine runs about 17-18inm at idle. and you are correct, when you set the fpr you will disconnect the vac. line and then set it. once you hook the vac. line back up, the pressure should fall somewhat. if you have a quality fpr it should stay constant. what fpr? what size pump do you have? have you done the re-wire?

jim

 

[Cool Mr Steve]

I don't think the question is being understood properly... I know that I should have vacuum at idle, but MY vacuum is at around 14 in/hg, whereas it should be at least 17, indicating a vacuum leak or late valve timing. With this low vacuum, I want to know if it is possible to correctly calibrate my fuel pressure. If you have questions about my setup, please check out my profile.