Fuel pressure questions

[97EagleTalon2nr]

Well my fuel pressure at idle is 53psi I read it should be 43-50psi -- I can only get about 73psi at 5lbs of boost. I'm running the Vortech FMU (I believe it to be a 12:1, although I haven't measured the disk.) with stock injectors and a 255lph HP pump. Also I am using Mike's FCD on a Hahn Stage 2 Kit. Key on, engine off, I'm making 18psi. With the engine on, at idle, it's 53psi. On Mike's FCD, he had two of the wires reversed, so I hooked them up to where voltage would raise when boost was applied, and I set it to 4.63V. At WOT it feels a little sluggish but at 3/4 throttle it pulls pretty hard. Should my idle FP be between 43-50 with the vaccum line unhooked or hooked up on the FMU?? TIA

 

[VelocitàPaola]

Also i am using mikes FCD all of this on a hahn stage 2.

First of all, get rid of that "FCD" and get a real FCD. Haha.

 

[97EagleTalon2nr]

Hey guys well i think ive come to the conclusion its my FMU cause i took the vac line off of the fmu and intake plugged the fmu side and put a pressure tester on the intake side and pumped it up and it held pressure just fine,but if i have it hooked up to the FMU then it loses 10psi in less than 2 seconds which is why i think im only getting about 65psi.Unless the fmu isnt supposed to hold boost which the way it works it should cause tahts how it raises fuel pressure.I guess ill take it apart and see whats the deal. TIA

 

[97EagleTalon2nr]

nevermind.

 

[VelocitàPaola]

I'd say the diaphragm/membrane inside the FMU is probably punctured. I don't know it you can replace it, but it wouldn't hurt to call Vortech and find out.

 

[97EagleTalon2nr]

The vaccum line had a tiny hole in it at the very end before where i had it clamped off i cut it off and put a zip tie on tehre nice and tight i couldnt find a small enough hose clamp. But this shouldnt affect my idle FP should it?

 

[totaleclipse_05]

Measure your disc also and see what it is. You can buy a recalibration kit from Vortech to make your FMU whatever ratio you want.

 

[97EagleTalon2nr]

Well i thought that would take care of my problem but i still only get about 73psi max so i jsut checked my FCD and it is at 4.57 i had it set to 4.63 would this affect my FP? im confused and i measured the disc and it was 2.7 inches. There was no spacer or w/e in the FMU just a piston, a disc, an o ring(which appeared to be to big. two blue gaskets one with an aluminum thing on it and that was it.The outside of the bigger blue gasket is tore a little bit but it isnt tore inside where it should affect anything.

 

[97EagleTalon2nr]

Its one thing after another i adjust my voltage down on my FCD to 4.59 thinking it might help now it throws a CEL 1297 I beleive.No change in map between start and run. WTF!is this FCD shot.Because isn't the voltage supposed to rise when you apply boost? cause it stays teh same but i can still adjust the voltage..

 

[VelocitàPaola]

The MAP sensor voltage should rise linearly from ~0.XXV to about 4.65V from full vacuum to 0psi. While under boost, the voltage should remain steadily at 4.65V.

It should be acting as a voltage clamp: the MAP is free to output whatever voltage it wants, unless it's higher than 4.65V. If your FCD isn't doing that, chuck it.

 

[97EagleTalon2nr]

I removed my FCD to see what it would do it throws a 108 map voltage to high but if its on there it shows no change in voltage so im thinking the FCD is shot but it reads 5.15V on the 2 power wires and .10 on the ground at idle with FCD unhooked.

With the FCD hooked up it threw a 1297(No change in map between start and run) and the voltage on the sensor wire was (4.63v) and source voltage (5.15v) on power wire someone tell me whats wrong. Sorry i cant remember wire colors

 

[totaleclipse_05]

You are blowing into the MAP sensor when adjusting the voltage right?

 

[97EagleTalon2nr]

no im using a coolant system pressure tester with a tip inserted into the map and pumping it up to 8psi but it doesnt matter if i blow into it with that or use a vaccum pump the voltage will not change. although it did when i installed it

 

[VelocitàPaola]

I'd say it's a bad, or improperly installed FCD then. The voltage should vary under vacuum, but stay constant under boost.

 

[97EagleTalon2nr]

Well heres my dillemma the yellow/black and green/yellow wire are both 5.15V with the engine on and hte FCD not installed the green/yellow wire should be at 2 somthing Volts right?well they are both at 5.15 and the car barely starts and idles i ahve to give it gas then it will idle and it hits rev limiter at 4k.

 

[97EagleTalon2nr]

Well i tested resistance from the map to the ecu and all the wires were good and not open or shorted.Im gonna get a map tommorrow but i dont think this will solve my FPs being so low under boost.Any ideas on that?

 

[97EagleTalon2nr]

Alright the pump is bad.I ran a wire from battery to the pump directly.Also grounded it to the body and it only got 80psi and then the pump failed it started whining and Fuel pressure would go from 60-20 20-60 over and over.I think the pumps trying to lock up so i shut it off i'm gonna order one from extremepsi.Voltage with stock wiring was 11.4V. Voltage with a direct wire from the battery and a chassis ground was 12.56 volts source voltage.Also i did all this with 8psi applied to the FMU through a coolant pressure tester.Although no one is keeping up with this thread it should help anyone else having similar problems.

 

[Shadow98]

I'm sure a lot of us are reading it, but not posting since we were trying to figure out to ourselfs what could be wrong.