What is fuel press. supposed to be at??

[SASHO91]

I searched, but got tired.....
i did find one thing though... that at idle the press. should be at 28-32psi.. or something like that...
anyways... mine is at 35psi at idle. then when i hit it, just for a 1/4 second it jumps to alittle above 40psi... but when im in a slower rev, it hits about 37 then starts dropping. cant rember were it drops to... i will go check again after this... but i wanted to find out what it is supposed to be at idle and WOT...
TIA

 

[yamahaSHO]

Disconnect the vacuum line completely, it should read somewhere between 38-42psi. This would simulate WOT.

 

[SASHO91]

vac line on the FPR? right...
also. how long can i leave the vac line open? i would assume that too long would result in just a rich condition....

 

[yamahaSHO]

Yes, the vaccum line on the FPR. That's what we're talking about, right?

As far as lean/rich... You're upping the pressure on the rail, but you're also letting in unmetered air. Leave the line off as long as you need to test. Another option is to jump the proper pins on the two test connectors on the passenger side firewall to run the pump. That will run the pump without running the motor... That will simulate WOT on the rail.

 

[SASHO91]

Thanks Jason.
i will try that.

but that test with jumping the pins.... were are they located..... exactly... or better yet (since you allready told me were their at...) what do they look like....


i will try that next... but in the mean time i'll go check that...

 

[SASHO91]

Pressure was at, 43-44psi. w/ FPR vac line disconected.
is that all the stock FPR will push.. 45psi or so... ???

 

[yamahaSHO]

What size pump are you running? If you're running a 190lph, you're fine. A 255lph is what will give you problems.

 

[SASHO91]

from what i know... its a stocker.....

i guess the stock FP would put out that much pressure either way right?
or do different LPH FP's give different readings....

i would think not, as they all have to go through the same FPR....

anyways....

 

[Rockledge]

Pressure was at, 43-44psi. w/ FPR vac line disconected.
is that all the stock FPR will push.. 45psi or so... ???

The fuel pressure is regulated to that level, pursuant to the needs of the stock SHO engine. So why would you want any more pressure than that (unless you are going with a blower, bigger injectors, upsized MAF, etc.)?

This article has instructions and a diagram describing how to ground the FP pin on the EEC test connector in order to run the pump:

http://www.superhighoutput.com/tech_view.php?id=5

 

[SASHO91]

no i was just curious on what the stock FPR did...

yeah i know, i am going to need an adjustable FPR..... and a bigger FP......
just not to THAT point yet.....

EDIT: thanks for that info....

 

[Rockledge]

FWIW, the '94 Ford Factory Manual says these are the specs for the 3.0L Yamaha:

KOER = 28-33 PSI (Idle)

KOEO = 30-45 PSI

As noted, at idle the pressure with the FPR vacuum hose pulled (i.e., simulated WOT) should be at the higher end of the KOEO specs.

 

[SASHO91]

this is weird....
i just got back from a 30 min drive, from home depot, and i noticed she wasnt running normal... which she dosent really during the day... feels like she is down 10hp or so...

so i get home, and pop the hood to check fuel pressure... and its down at 25psi...
now i know that isnt far off, but what i did next was even weirder.... i pulled the vac line to go to WOT, simulated, any it only jumped up to about 30 or so... i think...

i'll go check it again... but when i was priming the system, it would only go up to 30psi...
it sounds right, but i dont know...
i want to test her at night, when she "feels" stronger.... i know cold air has alot to do with it.... but this is different...
anyways.. i'll be back with results... she has been sitting for about 30min now...

 

[NotSoSlowSHO]

When my pump started to die, the output was very erratic.

Sometimes the pressure readings would be dead on par.
Other times, off the map.

 

[SASHO91]

new FP here i come......



might as well....