Still searching for my demons :reddevil I can't see what it would hurt but in checking all possibilities. My fuel pressure is 42LBS. Is that a problem? The list is long of post's made searching for a cure.
Thanks all.......... and no the service guy never showed, back to just me. :mad :seeya

 

If that is the value at idle with the vacuum line to the FPR disconnected it seems low to me.

Stock fuel pressure should be around 44psi; with my mods, I run 48psi.

 

Gotta re-check. I still had the vacuum line FPR hooked up, book didn't say to disconnect it :confused:


[Modified by PUREC4, 5:17 AM 4/24/2004]

 

Here's how it works, as I understand it.

Fuel pressure increases as engine vacuum decreases.

For every 2" of vacuum the engine pulls, fuel pressure decreases 1 psi.

So, for example if your engine pulls 16" of vacuum at idle (with a fuel pressure gauge reading is 42 psi) at wide open throttle, where this very little vacuum, your fuel pressure would have increased to about 50 psi.

Now, this is a rule of thumb as most engines aren't able to pull zero vacuum at WOT.

To keep from removing then having to re-install the vacuum hose to the fuel pressure gauge, I simply grab the hose with a pair of pliars and squeeze. This cuts off the vacuum to the regulator and my pressure gauge increases to what it "would be" at zero vacuum.

To answer you original question, though, NO, I don't believe a 42 psi reading is the problem. During close loop operation, the ECM will adjust the injector "on time" to compensate for different fuel pressure settings in response to 02 feed-back.

Assuming your fuel pressure is set correctly for your particular combination, if you raise the fuel pressure, the injectors will, as a result, flow more fuel for a given amount of "on" time. This will cause the 02 sensor to read a richer mixture and will signal that to the ECM. In attempting to maintain 14.7:1 A/F ratio, the ECM will then decrease injector "on time" to lean the mixture.

It's at WOT, when the ECM ignores input from the 02 sensor, that the higher fuel pressure pays off by allowing a richer mixture - assuming that the engine tune calls for a richer mixture.

Another added benefit of a higher fuel pressure is better atomization; better injector spray pattern. TPIS has documented several benefits from running higher fuel pressure.

Jake

 

Let's go back to square one and see if we can't solve this once and for all.

Okay, before you began changing parts, gaskets, etc., was the engine running well? If not, what was it doing?

I need a listing of all the settings you changed, parts you replaced, etc.

There are a lot of possibilities here, we just need to address them one at a time. Without a ScanTool, Diacom, AutoXRay or some other such program to get real-time numbers we won't be able to see what's going on, so all we can do is address each possible cause one at a time.

Once I get a baseline of what you've done and what the engine is doing, I can list the things that need to be checked. I'll have to leave it up to you, though, to do a thorough job of checking.

We can start with the basic things that are the easiest to verify BEFORE delving into open heart surgery.

Get back to me when you can.

Jake

 

You can email me directly at jakejr266@sbcglobal.net if you'd like.

Jake