Can you clarify; "verify fuel pressure increases to 38-44. The engine fails this test as the fuel pressure stays at 32 ( which is the same pressure as having the vacuum hose connected to fuel pressure regulator). This means the regulator is STUCK OPEN."?

 

Your fuel pressure regulator operates, approximately, in 3 different positions; fully closed, partly open, wide open (not exactly, but just want to provide a perspective).

1. When the engine is shut off, which results in the fuel pump stopping, the intake manifold vacuum level drops and the fuel pressure drops slightly from where it was when the engine was running, resulting in the fuel pressure regulator closing to try to maintain fuel pressure in a low to no intake manifold vacuum situation. In this case, the fuel pressure regulator will close completely.
2. When the engine is accelerating the vehicle and the intake manifold vacuum is low, similar to item 1 above, the fuel pressure regulator moves to a partly open position to raise upstream fuel pressure.
3. When the engine is idling or coasting, the intake manifold vacuum is high, causing the fuel pressure regulator to open up (let's just say to wide open) to reduce upstream fuel pressure.

If you cannot get your upstream fuel pressure to be in the 31-37 psi range, I would say that it seems like you fuel pressure regulator is not capable of opening up as far as it should to reduce upstream fuel pressure.

Just a silly thought. Why don't you remove the vacuum hose attached to the fuel pressure regulator, then attach a good working calibrated vacuum gauge to that hose. It will read zero when the engine is off. Start the engine and let it idle - what is the vacuum gauge reading for vacuum? Then using the throttle at the throttle body, rev the engine several times - does the vacuum gauge show the vacuum dropping momentarily than bouncing back to high vacuum? Might just be interesting to rule out vacuum delivery to the fuel pressure regulator as a possible source of your concern.

 

Echo- not sure how else to say it ( fuel pressure passes all tests except test for when disconnecting fuel pressure regulator vacuum hose, it fails that test because the fuel pressure doesn't rise) ( I assumed that means the regulator is STUCK OPEN)

93- on this engine when you turn the engine off the fuel pressure does not drop at all not even slightly
Upstream fuel pressure is fine in tolerance
The problem. Is the fuel pressure reading when vacuum hose is disconnected from fuel pressure regulator ( fuel reading is low) and the vacuum reading at fuel pressure regulator is 0 in hg ( whenever the rpm is increased , the vacuum reading stays at 0) I'm not sure but I think the fuel pressure regulator vacuum port goes to the bottom of the throttle body both before the plate (ported vacuum) and after the plate (manifold vacuum)


I made edit to post 1 with updated vacuum readings and 3 questions

 

Echo- not sure how else to say it ( fuel pressure passes all tests except test for when disconnecting fuel pressure regulator vacuum hose, it fails that test because the fuel pressure doesn't rise) ( I assumed that means the regulator is STUCK OPEN)

The way you put it got me confused until rereading it a few times:
You meant factory calls for pressure between 38-44 psi with vacuum hose off, and that your engine stayed at 32 psi, correct?
As mentioned in your other thread, pinch off the return line, if the pressure goes up, your regulator is stuck open. If the pressure stays low, your pump is not putting out enough pressure.

You also said 0 vacuum at the hose to the regulator, correct?
If the vacuum hose is good, you may have connected the hose to the wrong port; it should have full vaccum at idle and drops when the throttle opens.

 

2. Engine vacuum at fuel pressure regulator :
O inhg (I think this is ported vacuum? and so should be close to 0 inhg) . Also when increasing rpm the vacuum reading did not increase. Can someone verify the vacuum here should be 0 and why the vacuum reading did not increase when increasing rpm?

It sounds like you have a leaky or blocked vacuum hose to the regulator; zero vacuum there means it is seeing full atmospheric pressure, no vacuum at all so the regulator is not doing anything.

Or if it is a ported vacuum thru a solenoid valve, then that valve is stuck and not opening to expose the regulator to the intake vacuum.

 

2. Engine vacuum at fuel pressure regulator :
O inhg (I think this is ported vacuum? and so should be close to 0 inhg) . Also when increasing rpm the vacuum reading did not increase. Can someone verify the vacuum here should be 0 and why the vacuum reading did not increase when increasing rpm?

If you are not seeing -any- vacuum in the hose connected @ the FPR, at any time - agree w/ all above, there's the issue.

(I'd snake the vacuum hose & port @ the Intake Manifold w/ a piece of nylon string trimmer line to determine blockage, if here.)

 

I've seen old engines with intake manifolds that have never been cleaned have a vacuum nipple port capped on the intake manifold - removed the cap and there was no vacuum on the nipple. All the crude inside the intake manifold plugged the nipple. Had to go through the nipple with a small diameter wire to unplug it. Never know what you might find on these older engines that maybe hadn't received much if any maintenance in their lives.

 

Echo- I don't see how pinching off the return line could help diagnose ( the regulator is located before the return line)

93 - the fuel pressure regulator vacuum is connected to the throttle body by manifold vacuum and ported vacuum

Unfortunately I can't upload photo of vacuum diagram on hood

 

Have you try it?

What happens if you turn off the faucet to the sink? You get full pressure that the system is providing, since there is no where the water can go!
If the system pressure is 60 psi, you get 60 psi! By the same token, if you are only getting 40 psi while spec calls for 60 psi, it is telling you the system is not providing you with the needed pressure.
Same if you put a restriction after the faucet if it is stuck open, you have effectively taken the faucet out of the equation! If the faucet was stuck open you get low pressure; putting in restriction effectively give you system pressure!

Just saying!

 

Why can't you upload a photo of your vacuum hose diagram on the hood?

Can you get a length of vacuum hose from somewhere at temporary connect it between the fuel pressure regulator and the intake manifold to see what the results are? And, please tell us what your fuel pressure regulator vacuum hose "is" connected to. It is pretty important to know what yours is connected to, which allows us to help you.

Pinching off the fuel return line downstream of the fuel pressure regulator should cause an upstream fuel pressure increase. If it does, then this will tell you that your fuel system is "capable" of the higher fuel pressures that should be present when the fuel pressure regulator vacuum line is disconnected - indicating your problem is solely with the fuel pressure regulator.

 

Most of the pressure regulators I dealt with had manifold vacuum then it drops if you open the throttle and the pressure should go up.
Clamping off the return line overwhelms the regulator and you read fuel pump pressure. This also tells you if the pressure drops the regulator is bad.
It assumes the check valve from pump to regulator is working, or you can clamp off both supply and return lines to check regulator.

 

Daigram above shows mani vac to regulator

 

I guess y'all are suggesting I experiment with
1. Fuel pressure gauge hooked up and 2,3
2. Pinching return line
3. Running a vacuum hose bypassed from the regulator to manifold nipple

I can't upload photo because it's disabled on my Toyota nation menu ( I guess because my data limit was exceeded)

I just thought of temporarily connecting that vac hose to intake manifold right before you posted. The fuel pressure regulator vacuum hose runs from fuel pressure regulator to 2 ports in throttle body (one located between the throttle plate and air filter and one located between the throttle plate and intake manifold)

 

 

With the setup in the vacuum diagram, the fuel pressure regulator would work the opposite way, stays open at 0 vacuum. Gets vacuum when the throttle opens up and fuel pressure increases.
Should be easy to verify, connect a vacuum gauge to the vacuum hose to the regulator, crack the throttle. Then use a vacuum pump to check the regulator, see if fuel pressure increases when vacuum is applied!

Maybe another one of Toyota's mid-year transition change setup.

 

Here is a complete view of what you previously posted. The lines that are completely black are hoses. The lines with white space in the middle are metal tubes. I believe this to be true anyway. So when the engine is idling, and you put a vacuum gauge on the vacuum hose that was removed from the fuel pressure regulator, you get a reading of 0" Hg?

 

96 5sfe

I done the fsm test of disconnecting vacuum hose to fuel pressure regulator and verify fuel pressure increases to 38-44. The engine fails this test as the fuel pressure stays at 32 ( which is the same pressure as having the vacuum hose connected to fuel pressure regulator). This means the regulator is STUCK OPEN.

tmauldin, for the test right above, can you confirm you left the port on the fuel pressure regulator open to atmosphere and plugged the port on the side of the throttle body (or plugged the hose to the throttle body)? This test for the camry V6 is the same and includes this diagram:

Also, did you do the steps of the test as follows?

(l) Start the engine.
(m) Disconnect the vacuum sensing hose from the air intake chamber and plug the air intake chamber outlet.
(nn) Measure the fuel pressure at idle.
Fuel pressure: 38-44 psi


Do all three of your fuel pressure regulators fail this test?

 

Just to muddy the waters a little bit - the vacuum hose routing diagram below is from a 1995 Camry 5S-FE (with air conditioning). Notice the difference is how that fuel pressure regulator is sourced for vacuum. It just so happens, on my information, it says the 1996 Camry 5S-FE only has fuel pressure regulator part number 23280-74150. All others use part number 23280-74100. Also interesting in Toyota EPC, which says part number 23280-74100 supersedes part number 23280-74150. I wonder if that is in error - in that 23280-74150 was very different mostly because of where it sourced is vacuum.

tmauldin, what is the part number of your fuel pressure regulator? And, does your 1996 Camry not have air conditioning? If it does, your 1996 model must no longer use the idle-up VSV (and some also have an adjustable regulator for controlling the amount of air added when the air conditioner is engaged - this one seems to lake that regulator).

 

Just to muddy the waters a little bit - the vacuum hose routing diagram below is from a 1995 Camry 5S-FE (with air conditioning). Notice the difference is how that fuel pressure regulator is sourced for vacuum. It just so happens, on my information, it says the 1996 Camry 5S-FE only has fuel pressure regulator part number 23280-74150. All others use part number 23280-74100.

toyodiy.com shows this on one of its pages for the 1996 5SFE Camry:

23280 REGULATOR ASSY, FUEL PRESSURE
23280-74100 (09/1991 - 07/1995) 1 $152.06
23280-74150 (08/1995 - 06/1996) 1 $142.33

ToyoDIY.com

Consistent with 93celicaconv's post, Toyotapartsdeal.com says the 74100 replaced the 74150.

 

93- post 17- your right about the colors on vacuum diagram and yes the vacuum reading at regulator is 0 .
Post 19-92 thru 95 federal 5sfe uses a different vacuum diagram than 96 federal 5sfe. My new smp regulator is pr52 and my old stock fuel pressure regulator is 23280-74100. It has air conditioning and it idles up when turned on.

Elle- I did not plug the port going to throttle body. No, my test was different, the engine was idling then I pulled the vacuum hose and I did not plug the vacuum outlet. I have not tried all 3 regulators , just one.

 

Elle- I did not plug the port going to throttle body. No, my test was different, the engine was idling then I pulled the vacuum hose and I did not plug the vacuum outlet. I have not tried all 3 regulators , just one.

For this test, I wonder if not plugging the port going to the throttle body may be causing the MAP sensor to see a higher absolute pressure, causing the computer to increase the duration of the fuel injectors, reducing the fuel pressure.

I would do the test exactly as described in the service manual (as quoted in my last post), and see if the fuel pressure is now 38-44 psi.

 

I wonder!
0" vaccum all the time? Even when you open the throttle?
What is the manufacture date of the vehicle?

 

Standard Motor Products (SMP) PR52 interchanges with Toyota 23280-74100. And they both appear to operate the same in tmauldin's car. Would be nice to know if Toyota 23280-74150 is actually a bit different, even though Toyota says they are equal. It seems that Toyota 23280-74100 all have vacuum connections at the intake manifold, but 23280-74150 has it's vacuum connection in front of the throttle body (where I would think the vacuum level is considerably different, unless that nipple is ported to inside the throttle body). I think tmauldin should, at some point, tie the fuel pressure regulator vacuum hose connection to an open (not plugged, not plugged up) nipple available on the intake manifold and see what happens there with fuel pressure. At least before going down any rabbit hole.

 

Echo- if regulator stays open at 0 vacuum then why does the fuel pressure hold steady for 45 min after engine is shut off? When the throttle is open , the vacuum did not increase and the fuel pressure stayed constant. I will try what you said.
Post 23: yes 0 all the time, manufacturing date 5/96

 

I am wondering if that is a transitional setup; the 'regulator' is actually none functional, except as a damperl. Since Toyota moved the fuel pressure regulator to inside the fuel tank on 1997 models, and block that port on the fuel rail with a plate.
If that is the case, it would explain why the fuel pressure doesn't change regardless of what is done to the vacuum line, since the output pressure from the tank is already regulated down to 32 psi in the tank!
Just speculating here, haven't done any research for anything information!

 

93- that nipple is ported in the throttle body between the throttle plate and air filter. I will try that but instead of wasting my vacuum hose roll, I'm going to pull 17-22 in hg vacuum on regulator with vacuum pump after plugging port ( I have caps)

 

Elle- the fuel pressure did not change at all when I didn't plug the port.

I have an appointment friday, so I can hook the fuel pressure gauge back up for a few days, it's a pita . I thought about torqueing down the banjo scrader valve bolt and leaving it installed ( find a cap for it) , I guess it's a fire hazard though

 

tmauldin, no problem; I understand this is a lot of juggling and wrenching, with a lot of fuel leaking in the process. Skip the test. I just would not assume the regulator is bad based on the result you describe.

 

I'm going to pull a vacuum on the port that runs from regulator to throttle body and it should be zero. Then I'm going to pull a vacuum on the same port but with the throttle body hole plugged , it should have a reading that holds.

I smoked tested the intake last year and there were no leaks.

I think I should do the tests y'all described to maybe better understand this 96 5sfe federal AIR and FUEL