this is kind of a dumb question, but when your reading your fuel pressure, should it be at 39 psi with the vacume line on or off? i looked in the haynes manual and searched here but no luck.
question about checking fuel pressure
- Thread starter 88_GT_5_oh
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To adjust fuel pressure..
Take vacume line off, plug with finger, and adjust to the # you want.. normally 38-42 psi with your set-up.. When you put the vacume back on, the pressure should go down about 6 psi.. this is because there is a lot of vacume at idle.. When you hit the throttle, the psi will go back up to about the point where you set it.. good luck..
Mike
Take vacume line off, plug with finger, and adjust to the # you want.. normally 38-42 psi with your set-up.. When you put the vacume back on, the pressure should go down about 6 psi.. this is because there is a lot of vacume at idle.. When you hit the throttle, the psi will go back up to about the point where you set it.. good luck..
Mike
so right now it's been around 39 psi with the vacume on..this is probably why it seems like its running rich
possibly.. while just driving aroung, it'll be ok, when you hit it, the pressure will jump up, to around 44-46 psi..
best thing you can do is to pay 75 bucks, hit up a dyno, and fine tune it..
i went to get dyno tuned, after just screwing with the fp and my timing, i bumped my rwhp up by 12..
Not too bad for under 100 bucks
Mike
best thing you can do is to pay 75 bucks, hit up a dyno, and fine tune it..
i went to get dyno tuned, after just screwing with the fp and my timing, i bumped my rwhp up by 12..
Not too bad for under 100 bucks
Mike
k thanks man... i'll play with it a bit cause winter is coming (suposed to get snow tonight, probably will melt by noon) i don't wanna pay for a tune right now cause i'm parking it for winter
giddyup306
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- Oct 22, 2002
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giddyup306
Founding Member
- Oct 22, 2002
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Don't get me wrong it will but with aftermarket AFPR's around you can have pressure as high as 120 PSI of fuel pressure. That's the exception I was talking about.
ok, i gotcha. - i think that might fall outside the adaptive strategy parameters. LOL.giddyup306 said:
i was thinking in terms of the numbers 88 GT 5 oh posted - he might be 5-6 psi high. i think we would both agree that the puter will adapt to that.
(you threw me for a loop with your post as it would pertain to this thead).
giddyup306
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HISSIN50 said:ok, i gotcha. - i think that might fall outside the adaptive strategy parameters. LOL.
i was thinking in terms of the numbers 88 GT 5 oh posted - he might be 5-6 psi high. i think we would both agree that the puter will adapt to that.
(you threw me for a loop with your post as it would pertain to this thead).
OIC. I thought you were asking a question. I thought you meant to type a ? instead of a . Sorry about the confusion. Carry on
Michael Yount
Mustang Master
It should be checked with the vacuum hose off and plugged, the engine idling and warm. It should be set to 38-40 psi under those conditions. Depending on how much vacuum your engine (cam) makes at idle, when you hook it back up, pressure at warm idle with the vacuum line on should drop to 32-36 psi. When you "hit" it, you kill the vacuum in the intake and it should jump back up to the "no vacuum line" set point - 38-40. It won't go any higher than the reading you had with the vacuum line disconnected.
It shouldn't matter whether you've got the hose plugged or not once you've got it off, should it?
Michael Yount
Mustang Master
Practically - it probably wouldn't make a big difference; but without it being plugged (just hold your thumb over it) you've got a pretty good vacuum leak which impacts idle speed - that impacts alternator output which might impact fuel pump performance; and reduced idle speed impacts how the engine's using fuel. How big will those impacts be? Probably not big - but why wouldn't you cover the vacuum line with your finger while you're taking the reading?
Cause I was using one hand to adjust the pressure and the other to hold up the hood (no prop rod).Michael Yount said:
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