Fueling problem

[ACLR8R]

Ok I have been trying to fix a fuel issue that I have had for about a month. My fuel pressure will drop over the course of driving. If I start out with good fuel pressure (around 40psi line off) I can drive the car a couple of miles and check it and it will be down to around 36psi line off, and it has gone down to as low as 26psi. So I started by taking off the reg. and cleaning it and putting back on. It starts over back at 40, then drops with time, so I replaced it but it did nothing.
Here is what I have done.
Replaced regulator
Cleaned injectors
New Racetronix Hotwire
New fuel Pump (Walbro 340)
Still does it every time. I am getting kind of frustrated.
Any suggestion would be greatly appreciated!
Thanks

 

[XLR8]

Clogged fuel filter? You are using a good FP guage and not one of those little gauges that stay attached to the fuel rail right?

 

[ACLR8R]

Oh ya I also replaced the fuel filter. I am using a rail mounted guage but even if the numbers are a little off, it should show the drop in pressure correctly right. Also when the fuel pressure is down the motor gets knock like it is down on fuel pressure. Also I forgot to mention that even when I adjust the pressure back up to 40psi through the regulator, it still gets knock like the volume isnt there.

 

[ACLR8R]

Any other ideas?

 

[SPOOLFOOL2]

Do your O2s on your scanmaster match the drop in your fuel pressure? My guess is that your gage is being affected by engine heat (the same heat that causes knock). I'm pretty sure this happend to me. good luck.

 

[ACLR8R]

yes the o2's drop, it is lacking fuel for sure. the gauge has been on for a while and has always been correct. It has got to be something else.

 

[BOOSTEDGNs]

check your hotwire power going in gooing out to the pump etc drop the tank again maybe defective pump, it happens

Alan

 

[bogie1]

I had a similar issue. Low 02's under boost , fp would not go over 55# no matter how much boost. I had a hot wire kit and a red's XP pump less than a year old.
The fix for mine was, the hose clamp on the FP had fallen down and was letting fuel escape under high pressue. I had to drop the tank to find it.
I tried everything else before I dropped the tank but in the end that's what fixed it.
Good luck

 

[ACLR8R]

I just put the pump in on saturday to try to fix it, and the hotwire last wed. neither fixed it, had probelem with old pump and wiring and still have problem with new pump and wiring.

 

[SPOOLFOOL2]

Did you do a good check on all the small vacume lines and fittings for leaks to make sure that the FP regulator is getting a good signal? Can you borrow a remote FP regulator to verify that your FP goes up 1 lb. for every lb. of boost? Make sure that your metal FP line that goes up the front of the block is'nt kinked or dented.

 

[Racetronix]

Are your fuel trims showing a drop in fuel delivery?
Are you 100% sure your gauge is accurate?

 

[ACLR8R]

Originally posted by Racetronix
Are your fuel trims showing a drop in fuel delivery?
Are you 100% sure your gauge is accurate?

Yes, I can tell as soon as it starts going down because it starts to get part throttle knock and I cant go over half throttle with out it pegging my knock gauge. I will check the gauge but from the looks of things it is accurate, I am just losing pressure.

 

[5ltretr]

I;m having the same problem pressure starts out normal , then dropps to 26PSI.

Any fix or ideas?

thanks

 

[ACLR8R]

I havent been able to work on for a little while, and unfortunatly it hasnt fixed itself. If you figure it out be sure to let me know!

 

[5ltretr]

going to drop the tank next.

 

[ACLR8R]

Well I tracked it down to vacuum on the reg., when I take the vacuum line off and plug it the pressure stays normal. I cant find a leak anywhere though

 

[ACLR8R]

anyone?

 

[Racetronix]

Defective regulator or you have the reference line plumbed into a bad spot.

 

[ACLR8R]

Originally posted by Racetronix
Defective regulator or you have the reference line plumbed into a bad spot.

What do you mean? the vacuum line not placed correctly?

 

[azgn]

bypass the steel tubing from the vacuum block and run a piece of vac line direct to the regulator......that thing has been known to leak