Thinkin’ I need a Fuel pressure regulator?

I did a fuel pressure test & pressure at idle was 44.

Shut the truck off & pressure held at 40 for the 5 mins.

Hooked up a not so great vacuum pump loaner from autozone to the regulator & started the truck - pressure 44. The pump managed about 7inHG & held as long as I kept pulling the trigger. Pressure dropped to 40.

Put the regulator hose back - 44.

Took the regulator hose off, yup, 44.

One of the checks in my Haynes was to hook a vacuum gauge to the regulator vacuum hose. I did this & got nothing. If this happened I was then to check for a manifold leak. I went through the booster intake & all was good.

Oh, & I pinched off the fuel return line & the pressure rose quickly.

Am I missing anything? Or should I check anything else while I have the gauge hooked up? Or before I add fpr to my to do list?

 

Is your Fuel Pressure Regulator leaking Gas ??

 

What pressure is it supposed to be?

 

No

 

Pressure at idle is supposed to be 31-37

Pressure at idle with regulator hose detached is supposed to be 38-44

 

Explain how the Fuel Pressure Regulator works??

 

It controls the pressure of fuel before it hits the fuel rail. I believe it uses a diaphragm to regulate, based on demand, the amount of fuel that goes to the injectors, intake & combustion chamber.

 

at idle when there isnt that large of a demand for fuel there is vacuum on the diaphram and the pressure is less, as the throttle is open and manifold vacuum is reduced and there is a greater demand for more fuel, there is more fuel pressure.

http://www.enginebasics.com/Engine Basics Root Folder/Fuel Pressure Regulator.html

 

Good explanation. Thank you.

My idle pressure is actually higher than it’s supposed to be. Now of course one could question the calibration of a pressure gauge, especially a loaner, however my understanding is when I pull the hose from the fuel pressure regulator, pressure is supposed to go up. It did not.

Also, i just checked the pressure by opening the throttle & there was no change.

The only times I had any change was 1. when I applied vacuum to the fuel pressure regulator & it quickly rose, which my manual stated it was supposed to rise slowly
2. when I shut the truck off & it dropped to 42 & held there for at least the 5 mins. & then slowly dropped.

 

Your year wants to see the 38-44 thing all the time. There is no vacuum control. The FSM section on this is a misprint and has confused plenty of folks. The vacuum control was only found on some early years yet the FSM continued to talk about it till the end. In real life a stock engine and fuel management system can easily deal with pressures from 38-60. It's just not that critical on the V6.

If your "little hose" from the FPR is like the pics here, that is confirmation of no "FPR vacuum modulation". There is no functional vacuum present at the "resonator" box.
https://www.tacomaworld.com/threads/whats-this-hose.706522/#post-25074208

Judging on your results, the FPR is fine.

 

So opening the throttle should not change the pressure? Or are you simply stating that the fpr is not a problem. This was my Haynes manual, not the FSM. Just sayin'.... I use the FSM's for some things, however I find that my truck is often not covered by the '01 manual.

 

Correct, the fuel pump running wild and free delivers more pressure than the engine can use hence the need to "regulate" it down to a controlled number.
The pump itself has a relief/check valve that that allows some of the excess to bleed off before it ever gets near the engine. That also helps to maintain a certain amount of fuel flowing thru every nook and cranny of the pump to help keep it cool.

 

Ok. Well that sucks that these manuals are leading me astray. I guess I need to keep searching, although not really sure what to use if not my manual. I mean I know TW is a resource, but asking for walk thrus each time I check something is not the way I wanna go. & I'm pretty sure it would get old to members as well. Anyway, thank you....

 

Keep the faith, you got the attitude.

Be glad that your not a wide eyed kid learning on the job from two mechanics that serviced the Presidents plane when it had pistons.
"Hey kid, get me the relative bearing grease. It's on the shelf in back. And I want the stuff in the green can, not the red". They were perfectly happy to let me search for the fictitious stuff for hours. Proud of themselves at that.

 

I’m still a little confused by it all, however dirtypool has posts on here explaining that there is no vacuum. Just thought you might wanna check them out.