Fuel Pressure Regulator

My fuel pressure reading at idle is 45 psi. The factory manual and the Haynes manual both say I should be at 37 psi max at idle. They say that if it's higher than that, I have a bad fuel pressure regulator.

When I search online for replacement FPRs, they all say in the specs that they are 45 PSI. So that would be the same as what's in there, and 8 PSI (18%) over what the manuals call for.

Does this thing really need to be replaced?

I am willing to spend $$ on parts to increase MPGs, so if my higher than spec pressure is hurting fuel economy, I'd like to replace it.

 

When the engine is off, but fuel pump on, the pressure regulator may hold it at 45psi. It should be 38-44psi. So, the specs for new ones may be for when there is no vacuum applied.

First, check that at idle the vacuum sensing hose has vacuum and is not clogged. Second, apply vacuum directly to the fuel pressure regulator with a handheld vacuum pump and check that it holds vacuum. Third, you could plug the vacuum line at idle and apply vacuum directly to the regulator with the vacuum pump, then measure the fuel pressure.

 

With out trying to be arrogant, the FSM and Haynes are wrong.
Trace the supposed "vacuum" line from the FPR to it's source. If it is upstream from the throttle plate, then there is no vacuum modulation of the FPR and fuel pressure should remain constant when the engine is running. The pump does not run with just the key "on". The only 1st gen Tacos that do modulate the FPR are some of the early 3.4s despite what the FSM says.
45psi is just fine.

 

Thanks for keeping me from chasing my tail. I figured that might be the case.

 

To run the pump with the engine off but key on, the FSM says to attach the "Toyota hand-held tester". Before OBDII there were terminals in the check connector under the hood (Fp and +B) that would allow you to turn the fuel pump on manually. The sticker on the check connector still lists Fp and +B but the wires are not there!

You're right, at idle there should be little or no vacuum at idle in the "vacuum sensing hose", but under some load with the throttle plate open there may be some. I'll have to test this for myself when I get my engine up and running again.

 

Go ahead and check for your self, nothing wrong with that, it's what I did. Keep in mind that applying vacuum to the FPR will in fact reduce the pressure. The same FPR is used in that capacity in other applications, just not the vast majority of 1st gen Tacos. Also keep in mind less pressure is not what you want at higher loads.

 

This makes me think I should disconnect that vacuum line and cap it off on both ends.

 

While that "vacuum" line on your engine does not actually carry vacuum it does have a function. Should the FPR diaphragm leak, the fuel will travel along the hose into the main intake tube. This is much better than letting it dribble on a hot engine.
The little nipple should not be "capped". It needs to expose the "dry" or "atmospheric pressure" side of the FPR diaphragm to normal atmospheric pressure. Google "diaphragm pressure regulator" or "fuel pressure regulator" for drawings and explanations of how all that works.

 

I was doing a fuel pressure test on my 96 tacoma with a 2.4L engine, hooked up the fuel pressure gauge, turned on the switch, no pressure on gauge, started the engine, pressure was 48psi. I removed the vacuum hose from regulator and pressure did not move. I also accelerated the engine and pressure pressure went up a little. Should there be fuel pressure when ignition is on, engine off? What should be the fuel pressure at rest and idle?

 

Fuel Pressure Gauge by 96tacoma2wd posted Oct 5, 2016 at 9:16 PM[/GALLERY]

 

If I were to replace a regulator, how would I take off the hose with the clamps in the pic

 

Just use small needle nose pliers to squeeze the clamp then slide it down on the hose, then slide the hose off the regulator. You can see the little metal tabs extending from the clamp where you can grab and squeeze. Or are you asking about something else?

 

I don't have pliers, but even when I took off the clamps the hose looked like it was stuck to it

 

The rubber hardens and there is a raised ring on the fitting. Usually twisting it helps loosen it up, then you can gently wiggle/pull it off. Worst case you break it or it splits and you have to replace it.

 

Why don't you pop for a couple of bucks and get yourself a set of picks? Perfect for loosening rubber-to-steel connections!

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You can also use them to pick your teeth. Or your nose. Or whatever...