Taphee6

iTrader: (2)

I have been having a fuel pressure issue for a few days and need a little help.

After installing a new torque converter my fuel pressure dropped from a constant 59#'s to 56#'s and would drop to 42#'s at WOT. I had the tank dropped and tightend the lines on the Walbro pump. Now pressure at idel is 59#'s but drops to 52#'s at WOT.

I pressureized the system by turning the ignition on and building pressue. The system goes to 59#'s immediatly, then drops to 46#'s and bleeds down almost 1.5# per 30 to 45 sec's.

I know that the fuel lines are not kinked or damaged. I just replaced the fuel filter. The injectors are not visually leaking.

Where do I go from here?

Thanks in advance

xssive

iTrader: (123)

Your intank hose is leaking/torn. The walbro intank pump has in internal check valve that maintains pressure after the initial buildup when you prime it. I had this problem 3 different times till I used braided line in the tank...

Taphee6

iTrader: (2)

It didnt look like there was any damage to the line. Is it possible the check valve is bad? making the pump bad?

highspeedspecialist

If check valve is bad then yes pressure will bleed back to tank. It doesn't have anything to do with your pump.

Taphee6

iTrader: (2)

Xsseive just stated the check valve was internal on the pump. Are you reffering to the Pressure Regulator?

highspeedspecialist

No there is a valve that is seprate from the pressure regulator^

stevieturbo

Does it maintain pressure when the engine is running ?

Taphee6

iTrader: (2)

After rechecking with a manual gauge, at idel the car maintains a constant 61#'s. Under heavy accerleration it drops to 52#'s. Also, the manual gauge shows a drop of 10#'s per hour when the system is presurized and not running.

I am not sure what the other valve is. I know there is the pulse dampner on the fuel rail, there is a vent by the rear brake assm., there is the pressure regulator, and the sending unit. Where is the other check valve?

stevieturbo

with engine running, and pump constantly running, it wouldnt matter if three was a check valve or not.

If the pressure is dropping, you either have a leak, or the pump cant cope for some reason. If its happening at idle or thereabouts, when there is virtually no load, or fuel needed, then you probably have a leak.

Taphee6

iTrader: (2)

After going throught the GM service manual, its either a bad fuel pressure regulator, bad fuel pump or broken or loose line in the tank. Either way I have to drop the tank again...I will post more when I inspect the guts of the tank. Does anyone know if GM sells just the fuel pressure regulator. I should just replace it while I am there...

onfire

iTrader: (17)

The GM regulator is just an orifice....be hard to hurt it with a hammer.

xssive

iTrader: (123)

Its a loose or torn intank hose. I went though this crap all three times, two of them the tear in the hose was barely visible. At wot my pressure would drop to around 54...


Use -6an braided hose in the tank with fuel line clamps, not worm drive clamps...

Taphee6

iTrader: (2)

I 'll try with replacing the hose first. Just to make sure I am clear, you are talking steel braided hose or the hose with the reinforced threads in them.

Taphee6

iTrader: (2)

Hose is fine. Replaced anyway still dropping pressure. Time for a new regulator...

99PontTA

the stock gm fuel pres regulator is a POS...upgrade it or at least replace it...i think its like 4 bucks from gm.......its insanely cheap...mine crapped out ....pres was very low......I would go with a external regulator in the return line

Taphee6

iTrader: (2)

You have to be kidding me. There is no way its $4.00. I researched this and GM lists the whole assembly for $450. According to GM it is the only way to get the pressure regulator. However thanks to one of the sponsors I found out the intank pressure regulator is the same as a 97 vette fuel rail regulator which GM sells seperatly. Cost $70. Please let me know if there is a better deal.

Thanks in advance

Taphee6

iTrader: (2)

Wow did one of the sponsors really give it to me in the ***. They charged me 63.55 + shipping for the regulator while SDPC sells it for $45.00. Someone is getting a call Wednesday.

99PontTA

h,mmm i had priced it at the local dealer for 3.95............i can check tomorrow with them if you like...........also another option would be to use the vette fuel filter...it has a built in regulator...but its prolly 50 or so...unfortuneatly plumbing in a external reg may be a problem because of the special tools required to properly shape the metal tubing ......brass compression fittings seem to leak fuel too easily at the pressures the fuel system runs at.I don't know what pressures standard flare fittings can handle.I've seen the tools needed @ around 250 dollars to make the oring type ends on the lines......then you would need the female threaded fitting to screw into the external regulator.I have a stock fuel pump-regulator *** ...i can look at it tomorrow and see what other options are possible

Taphee6

iTrader: (2)

If you can check that price I would appreciate it. Also a vette fuel filter with regulator would not work on a return line system from what I understand. The pressure would bleed out the retun side...

99PontTA

what year is your car?