Fuel Pressure Questions

[bones]

I have a 2003 Trilogized Marauder & under heavy acceleration it cuts out.
Fuel filter has been replaced. Checked fuel pressure at idle 28 to 30 PSI but if I snap the throttle fuel pressure drops to 10 psi & then shoots up
from 38 to 40 PSI. Any ideas what might be causing this problem. The car
has a Kenny Bell-BAP.

[Spectragod]

Bypass the Hobbs switch and measure the voltage output of the BAP, it should change when you adjust the rheostat. I would start there....

[Zack]

http://www.mercurymarauder.net/forums/showthread.php?t=27632

[bones]

I can't locate the Hobbs switch. Any ideas where it might be located?:eek:
I did check the voltage at the Boost A Pump. Idle = 12.00 to 12.50 volts
WOT = 14.26 volts
Ordered new gt-40 fuel pump.:bows:

[Zack]

I can't locate the Hobbs switch. Any ideas where it might be located?:eek:
I did check the voltage at the Boost A Pump. Idle = 12.00 to 12.50 volts
WOT = 14.26 volts
Ordered new gt-40 fuel pump.:bows:

Should be behind the boost gauge.

[bones]

Thats what I thought too. Gage is mounted on A-pillar & I thought
maybe they didn't have enough room for it. Looked in engine compartment
& no sign of it!! Voltage goes from 12.5 to 14.2 so it has to be there
somewhere right?

[Zack]

The BAP only turns on when the car is in boost (3psi or above)
It needs a vacuum source to operate.

[bones]

Hobbs switch located :banana:behind lower kick panel.
I will bypass & see what happens.

[Spectragod]

Hobbs switch located :banana:behind lower kick panel.
I will bypass & see what happens.


Where are you located in Ohio? Maybe we can find a member near you.

[bones]

I'm located in North Royalton Ohio. About 26 miles south of Cleveland.

[Spectragod]

I know that there are several members up in that end of the state, maybe they will jump in. Sometimes another set of eyes on a problem is a good thing.

Bypass the Hobbs, see if your voltage adjusts with the rheostat, and what the voltage is at the top of the scale.

[bones]

Bypassed hobbs. With rheostat at 10% 13+ Volts, 50% 17+ Volts.
Installed new GT-40 pump & checked fuel pressure. Strange things
happening when checking pressure at fuel rail. Pressure stays constant
at idle 30 or so then slowly drops to 20 PSI & ramps back up to 40 PSI.
I've never seen any car do this. Check engine light just started coming
on today. Car starts & drives but if you hit the gas heavily car stumbles
& then stalls. Pull over cycle key 2 times & starts right up. ( WTF ) :mad2:
IDLE = 30 PSI
WOT = 40+ to 60+ PSI
I have a friend coming over tonight with snap-on computer. Maybe he can figure out what is happening. Any suggestions?

[Zack]

What kinds of clamps did you use on the fuel pump? (in the tank)

Sounds like you will be pulling it back out!

Also, the check engine light came on due to the fuel rails being drained. Reset the light with a tuner and it wont come on again.

One more thing, it is important to have the orientation of the pump correct in the assembly, otherwise the fuel sock may hit the basket and starve the pump. (an extreme case)

[bones]

Zack:

Pump installation went fine. Secured with radiator style clamp on fuel line & zip tied basket to pump along with stock clamp & bolt.

I disconnected the fuel pressure sensor on the fuel rail & bypassed the hobbs. The fuel pressure stays steady around 44 PSI & goes up from there. Fuel pressure never drops off. Took for testdrive & car runs great????? Although that check engine light is still on. Maybe the fuel pressure sensor is bad????

[juno]

If you disconnected the FPS what is controlling your fuel pressure??? I do not know what your tune set it at, but stock it should be at about 39 psi. It should read it's setpoint minus any vacuum at idle/part throttle and plus any boost at WOT.

[bones]

Thanks for all the feedback guys I appreciate it. Problem is fixed.
The Mass Air Flow Sensor needed to be cleaned. Mass Air must have been causing fuel pressure problems all along.