Fuel Pressure

kevsha

Registered User
Ok, so i got my SC back to gether. i installed a new adjustable fuel pressure regulator. my question is what kind of fuel pressure do i want to see. basically all i have done is a 10% pulley, screamin deamon coil pack and live wires and a k/n cone filter, and a magnuson rebuilt blower.

i have like 33-34 at idle and like 38-40 when i rev it up. i havent really been able to roadtest it as i just now got back from my insurance agent and put it back onto my policy.
 
pretty sure Ford's are 39psi relative, so at idle its usually around 20 inches, or about -10psi, so idle pressure will be 39+ (-10) = 29psi, get it?

With a better blower and OD pulley it will probably flow a bit better so your number's sound about right.
 
You need to set your base pressure at 39psi with the car running and the vac line off the regulator. Do you have a wideband o2 sensor? You really shouldn't need to adjust for those mods.
 
My fuel pressure is between 30 and 35 at idle and goes straight up to 50 when you rev the engine. I was just wondering if that was good or not.
 
Hook a fuel pressure gauge up to the car. turn the key halfway and jump the fuel pressure relay so the pump runs continuously with the key turned halfway and the engine off. You can jump the relay from actual relay in the trunk or from the eec-iv test port on the passenger side of you engine bay in front of the firewall. Pressure should stay at 39psi, if not you need to set it at that. If you set it with the engine off, you don't need to remove the vaccum line. This is the easiest way I know.

btw, if you are able to check you fuel pressure while driving you'll need to pay close attenetion to your boost gauge. Drive the car and give it just enough throttle to hold 0 vaccum and 0 boost on your gauge. At this point the car should make 39psi fuel pressure.
Chris
 
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Thanks everyone. i have it set to 39 PSI vac line off engine running... i haven't really been able to test it under load, or with boost as it seems as if the motor "breaks apart" as soon as you give it more than 1/4 throttle.... it has at least one dead miss and i can't figure out why... it seems like maybe and ignition problem....i don't know. it will run smooth when reving it up at idle, its just when i take it on the road that the problem is evident. i thought it wight be my incorrect fuel pressure... but the problem persists
 
its not your fuel pressure causing the problem, its called detonation. You intake temps are too high with the 10% pulley, unless you have upgraded the IC or added fan I recommend you do it now. At least drop your plugs down a heat range or two, an Autolite 764 or 103.
 
its not your fuel pressure causing the problem, its called detonation. You intake temps are too high with the 10% pulley, unless you have upgraded the IC or added fan I recommend you do it now. At least drop your plugs down a heat range or two, an Autolite 764 or 103.

intake temps too high at 1/4 throttle or less? i'm not even hitting 1lb of boost before it starts to fall apart and barely any load/RPM. i have dealt with detonation before but with high load, rpm, and boost.... i mean i'm shooting in the dark here and it definatly seems like an ignition problem... i installed the plugs from SCP:

http://supercoupeperformance.com/partBrowser.aspx?partId=80

and gapped them to +-.060" per instructions on this page

http://supercoupeperformance.com/partBrowser.aspx?partId=510

idk, i'm probably going to pull the plugs and look at them and maybe see about going a step cooler like you said...
 
are you running the Screamin Demon coil? There have been many reported issues with them.

well, i took it off a friend of mine's SC before he sold it.... he never had any problems with it, then again he ran stock wires and never changes the gap.... i wish i had my old coil pack to swap in....
 
Thanks everyone. i have it set to 39 PSI vac line off engine running... i haven't really been able to test it under load, or with boost as it seems as if the motor "breaks apart" as soon as you give it more than 1/4 throttle.... it has at least one dead miss and i can't figure out why... it seems like maybe and ignition problem....i don't know. it will run smooth when reving it up at idle, its just when i take it on the road that the problem is evident. i thought it wight be my incorrect fuel pressure... but the problem persists

I had that problem once it turned out to be a couple of spark plug wires switched. It ideled fine but under any load missed bad double check your spark plug wireing also I remember one of the manuals having the wrong diagram make sure you get a accurate diagram
 
I remember one of the manuals having the wrong diagram make sure you get a accurate diagram

it wasn't wrong on the ford manual was it.... because thats what i went off of, the ford 1990 workshop manual....that would suck it it was incorrect though it wouldn't supprise me... anyone have a pic of the coil and the firing order?
 
it wasn't wrong on the ford manual was it.... because thats what i went off of, the ford 1990 workshop manual....that would suck it it was incorrect though it wouldn't supprise me... anyone have a pic of the coil and the firing order?


PlugandWireLayout.jpg



David
 

thanks, yea i think thats what my ford manual says too... i'll double check when i get home from work. i have another set of wires to try and swap in.. i know the cyl 5 boot is ripped. i tried to correct it with electrical tape but its possible that wan't good enough, though i don't hear it arching anymore
 
got it figured out, cyl 5 plug wire boot was torn... put some shrink tubing around it and seems to be keeping it unsulated pretty well... figures, ii spend 110$ on these damn wites and i end up tearing a boot putting them on.... my luck
 
FYI, you can still get OEM motorcraft wires for around 60bux from the dealership.

Corey

indeed you can, and i can get them even cheaper as i used to me a mechnic at the delaer near me and they still give parts to me at cost. but i was going with an upgrade since i upgraded the coil.... and then i ripped the boot
 
I think a gap of .060 is way too much for a supercharged car, I would gap them closer to prevent spark blow out. Maybe someone else can chime in on this also, I forget the gap but I thought it should be like .045.


Mark
 
where did you get your fuel pressure regulator from? Why did you go with an adjustable one? I think mine may be going out, but not sure - I would like to have an idea where to get a FPR if I need one though, and what people recommend is best suited for our cars...
 
where did you get your fuel pressure regulator from? Why did you go with an adjustable one? I think mine may be going out, but not sure - I would like to have an idea where to get a FPR if I need one though, and what people recommend is best suited for our cars...

i needed a new one, and a friend of mine had bought a lot of like 10 of them for his Turbo Coupe because he found them cheap on e-bay and the early regulators are the same as on a fox body. so i used it because he gave it to me rather than purchacing a new one... its an Accel regulator. SCP sells adjustable regulators too...

3 hole http://supercoupeperformance.com/partBrowser.aspx?partId=118

2 hole http://supercoupeperformance.com/partBrowser.aspx?partId=119

I think a gap of .060 is way too much for a supercharged car, I would gap them closer to prevent spark blow out. Maybe someone else can chime in on this also, I forget the gap but I thought it should be like .045. ...

you are correct, that is alot... HOWEVER if you click on the link i put up the the Screamin deamon coil pack that i got from SCP it is recomended to open the gap up due to the fact that the new pack generates a stronger spark i gapped them to the bottom of the scale given on the page. and since i trust that Bill at SCP has a substantial amout more knowlage about these cars than me, i used his recomendation

The Screamin' Demon Coil is designed to produce a longer duration spark and allow plug gaps to be opened up to an astounding .060" - .065".

taken from

http://supercoupeperformance.com/partBrowser.aspx?partId=510
 
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