I've been trying to check my fuel pressure seeing as I'm running rich and this would help me figure out which direction to go from here.


I have a full Snap-on Fuel pressure test kit and none of the adapters work for the schrader valve. I read that a Ford adapter for the would work but me and 2 others at the shop could not get it to fit.





I'm at a loss here. I cant get anything to stick on the valve to test pressure. I ran multiple scanners and none pick up a PID for fuel pressure.

Any ideas?

 

Put a tire pressure gauge on it. It is the same fitting. It might ruin the tire gauge??

bob

 

just more worried about getting a face/body full of gas........

 

What is the problem? Will it screw on, but it doesn't release the pressure so you read nothing? I had the same problem with two different adapters. It seems that this stuff is now so badly made (in China) that it doesn't work.

The adapter supplied with an Actron (a Bosch brand) gauge did work - once. Then the "depressor" pin fell out, rendering it useless. I e-mailed Bosch customer support, and they told me that the pin is considered a consumable and they sell them in packs of 5.

So here's what I did in the end : used a Schrader valve tool to unscrew the valve. No problems reading pressure without a valve.

 

The problem is that none of the fittings I can find will screw on to the valve. I can press them on but they are not threaded and not enough pressure to release valve.

If I unscrew the valve then I still have the problem of sealing the gauge around the valve as well as what happens when ignition is fired and 40psi of gas goes shooting through there?

 

My Harbor Freight test kit threads on but it takes a long time to get the gas out of it.

 

This is puzzling-

Are you certain you are on the fuel Schrader valve. It is a common valve and not at all unique.

You are not trying to go on the AC port by mistake, are you?
Vector

 

I was able to test it today with a regular gauge, a scanner and a few extra hands.
I'm sitting around 45-50 psi at idle.

The issue I am tracking is running rich. With scanner I am pulling about 10% trim, it is both banks so I'm looking for the "shared" parts. My O2 look similar on both sides but every 30 seconds or so the 2nd bank downstream goes wild for a second, then back to normal.

Already done plugs, air filter, MAF seems ok, so I was assuming a bad Fuel pressure regulator or clogged return line was problem. Theory is pressure would build up, then dump loose causing O2 to spike, then start cycle over again.

It seems fine at idle. I've got my scanner hooked up the next couple of days so I'll watch a few things and see what happens.

 

That sounds high. You should get 40 or so at idle, rising to 50 or so under full throttle.

Try taking the vacuum line off the fuel pressure regulator. It should go up by about 8 PSI.

The point of the vacuum connection is to increase fuel pressure as the throttle opens, and vacuum drops. If that isnt happening you have the full throttle fuel pressure, all the time.

 

My XK8 used to be 50 lbs with no ill effects. While on the computer at my local tech he reduced it to 40. I can't detect a difference in fuel trims or mileage.

 

Is that +10 LTFT?

If so, the sort of puts the fuel pressure out of the picture
because high fuel pressure would normally be causing the
LTFT to dip below zero in an effort to get around it.

 

Smoke test for vacuum leak.

 

-10%

Passenger valve cover was leaking oil. Fixed that, working on drivers side. small amount of oil on plugs. Coolant may be a bit low and air up in chargers. This could be reason for AIT2 going out and rich running (hot air instead of cool air into chamber)