WOT fuel pressure?

[BuickMike]

I have my fuel pressure set to 44psi static (line disconnected). At WOT with 22psi I was showing 62psi. Is this too low? I was expecting 66psi. Maybe my guage is innacurate. The pressure was rock steady and did not drop. My fuel filter is a new AC Delco. I am running a little lean (750-760mv) and want to make sure everything else is fine before I have more fuel added to the chip.

So...what do you guys think?
Thanks.

 

[87GN_70GS]

Yes, it is too low. WOT FP should track with base+boost. Apply the boost pressure to the regulator via artificial means with the car idling in the driveway and see if it will track then. If so, you don't have enough pump at WOT. If not, your gauge may be wrong.

 

[BuickMike]

Cool, thanks for the suggestion. I'll try that tonight. I guess another way to test it is to add 2psi static and see if I get 2 more at WOT.

 

[BuickMike]

Alright, so I ran a T connector between my regulator, boost guage, and my air compressor. I regulated the pressure to 22psi per the boost guage and fired it up. My fuel pressure guage read 66psi. It is set to 44psi static so that makes sense. Looks like I need a fuel pump.

 

[Chuck Leeper]

And....

Unless that O2 reading is from a WB, I'd rely on another method to determine the correct A/F ratio....
1. EGT.
2. Wideband O2.

The OEM O2 sensor is not accurate at ranges above or below 14.7. It may not be the pump, but the reading you are getting....

If the gauge you are using is a mini on the rail, that too may well be the problem.. I've tested ALOT of them on my injector bench and have found most to be 2 to 5psi off.....

Look at the plugs too.. they are a good indicator of the mix you are running..

 

[87GN_70GS]

It may not be the pump, but the reading you are getting....

The pressure readings are what is showing a problem; FP doesn't track with base+boost.

If the gauge you are using is a mini on the rail,

Probably not, since he is monitoring pressure at WOT...unless he has a really long neck.

 

[BuickMike]

Well, I used 2 gauges last night just to be sure and got the same readings on both. The one that showed 62psi at WOT and 22psi of boost and 44psi static showed 66psi with 22psi of artificial boost at idle. I used another fuel guage and got the same readings. Both are quality guages, not the mini rail mount type.
I'm also going to check the voltage at the pump.

 

[MSDGN]

What fuel pump are you using?...how old is it?...could be the sock is full of a little crap...also could be one of the clamps for the little piece of rubber fuel line between the pump and hangar came loose...this is assuming you have an aftermarket pump and didn't reuse the pulsator...before getting another pump...drop the tank and take a look...

 

[BuickMike]

The pump has been in there since before I bought the car. It was supposedly purchased from Modern Musclecar. So, it's about 6 or 7 years old. A Walboro 340 is what, $140? It's probably not a bad idea for me to replace it and be safe. I'll pull the tank before replacing anything just to see if there are any other issues down there.

 

[BuickMike]

Guess what folks?

I dropped the tank and learned a couple of things. First off, the hose connecting my fuel pump to the solid line was deteriorated really bad and had to be leaking. The other thing I found out is that I've got a Red Armstrong XP pump. I'm just going to replace the hose with a fuel injection rated piece and throw it back together. This explains why the fuel rail wouldn't hold pressure for more than 10 seconds when I shut off the car.

 

[87GN_70GS]

A Walboro 340 is what, $140

No, it's about $108 from http://www.autoperformanceengineering.com