JAKE

I decided to post this in a separate, ah, post, so that it would be available to the most CF members.

A couple of days ago I decided to check my FPR, not because I was having any problem or Service Engine Soon code, but just so I'd KNOW.

I attached a fuel pressure gauge to the engine and fired it up and the reading was 48 psi. So far so good.

I forgot to check the pressue rise with the vacuum hose DISCONNECTED, so yesterday I reconnected the gauge and used a pair of pliars to cut off the vacuum to the FPR with the engine idling.

Low and behold, the gauge didn't move a single psi. So now I know there's a FPR problem. FP should increase as engine vacuum lowers; mine didn't.

So I went to O'Reilly's and ordered a Borg and Warner adjustable FPR, part # 23064; $99.xx It came in this morning and I just finished installing it.

Upon firing the engine, pressure gauge read the same as before, 48 psi. When I did the ole' pliars trick again, pressure increased to 57 psi, just as it was supposed to do.

Moral, even though you "think" your FPR is good to go, it's a good idea to check it, just to be sure. This could also help those who have engines running lean at or near WOT.

Hope this helps.

Sorry, title should read FPR, not AFR
Jake

billybonesmusic

awesome info, simple test. LOL i thought i was looking at AFR dyno #'s but that's ok, we all know tony's AFR heads are the S@$%!

tequilaboy

I wouldn't trust the pliers trick.

The reason for disconnecting the vacuum line is to reference the regulator to atmospheric pressure.

By squeezing of the vacuum line, who know's what pressure is now in the regulator and line down stream of the pliers.

JAKE

Works exactly the same as removing the vacuum hose from the FPR and blocking the open ends.

Try it and you'll see; I have. Easier too, like many other "work-arounds"

Jake

tequilaboy

With the engine idling, you have vacuum or low pressure in the manifold and regulator relative to atmospheric pressure. The injector nozzles are exposed to the same pressure.

Squeezing off the line should result in the same low pressure being trapped in the regulator assuming there is no leakage, unless you're getting some pressure rise due to the sqeezing due to volume reduction.

With this procedure, there is no expected increase in pressure on the regulator. Therefore the fuel pressure relative to atmosphere should not increase.

If it does increase, than you're getting some leakage that allows atmospheric pressure to enter the regulator, or you've somehow increased the pressure due to the squeezing.

It may have shown the desired effect, but I woudn't consider this a conclusive test unless you know the level of the trapped pressure in the regulator.

JAKE

I can't understand why it is that something so simple tends to generate such responses.

Keep to the point. If the pressure doesn't increase when the hose is clamped on one FPR, yet it does increase when a new one is installed the picture is clear. Something's amiss.

GEZZZZZZZZZ! My point is simply: Check Your Fuel Pressure Regulator. I don't care how you go about it. Remove the hose and block it, clamp the hose, whatever. Just check it, that's the point of all this.

Jake

STL94LT1

So why is your fuel pressure set do high!! Just kidding, been reading your thread on the Camaro forum.

BTW: My fuel pressure is set as high as my AFPR will go without a fuel or tuning problem. I'm still running the stock injectors on my 375 rwhp engine.

JAKE

Hey, you should read my last two posts on this issue.

Amazing, all I'm trying to do is pass on a little information that may help others, potentially, discover a fuel problem.

What do I get for my effort . . . .

Maybe in the future I'll just keep anything new I discover to myself so I don't have to endure this abuse. What was it Richard Dryfuss said in "JAWS": "I'm not gonna take this abuse much longer!" LOL

Jake

Road Agent

48 psi sounds a little high and 57

JAKE

No another one! Please, please skip any consideration of the fuel pressure number. In other words, forget fuel pressure number I included in my initial post.

I'm not asking for tuning advice, recommendation or opinion. I'm not interested in whether others think my fuel pressure setting is too high, too low or just right. That is not the intent of my post; that's NOT why I posted.

Also, I don't want this to turn into a survey on what fuel pressure I should run. Let's keep to the point; The intent of the post.

Instead, look at the intent of the post, the intent being to have folks check for the proper operation of their FPR. Nothing more.

Rather than take my word for it, or anyone else's for that matter, (as to whether clamping off the vacuum hose actually works) do your own test. That's what I did. If you want to see who's correct and who's incorrect, do your own test. Simple, right?

This is not some macho thing where "I'm smarter than you" or my swansh is longer than yours. It's just a simple thing.

Here's the deal: With the engine idling and a fuel pressure gauge installed, the pressure will read the same when:

1. You use a pair of pliars to squeeze the vacuum line feeding the regulator to cut off (eliminate) the vacuum to the regulator (pressure will increase) or

2. You physically remove the vacuum line feeding vacuum to the regulator and block the supply port on the intake (pressure will increase a like amount.)

Either way, the increase in fuel pressure will be the same. It's just easier to use the pliars to eliminate vacuum to the regulator than to remove/disconnect the vacuum hose and plug it and its vacuum source.

Long posts justifying the reasoning doesn't serve to replace actual hands-on testing. I'm not guessing here. I've tried it both ways more than one time and on different engines, both L98 and LT1. It doesn't matter which way you choose to go, it's just that the 'pliars way' is quicker and easier.

But I don't want to get bogged down debating one method of testing Vs another. The point is, check your FPR. Stay focused; check you FPR.

Jake

Lichen

Thanks for the post, Jake. I checked mine yesterday and it was 41 psi with the vacume on or off. When I shut down the engine, it slowly dropped to 38 psi. I checked it about 20 minutes later and it had risen to 40 psi. Sound like a bad AFPR to you?

JAKE

The engine was idling when you made the test, right?

Jake

Lichen

Yes

JAKE

Where'd you mount the fuel pressure guage, on the schrader valve port with the schrader valve removed?

Is the vacuum hose solid, with no crack?

Did the fuel pressure increase by 7 psi or more immediately when you shut down the engine?

Jake

JAKE

Here's how I do mine:

I get a terry cloth towel and place it near the schrader valve location to catch the gas that'll spray out.

I open the gas tank cap to release the pressure from the tank

I use the little special tool to unscrew and remove the schrader valve.

Once all the gas has vented to the towel, I remove the towel and the little schrader valve - Be sure not to drop it.

I install the pressure gauge then turn the ignition key to "On" but I don't start the engine.

I check for any leak from the gauge connection.

If none, I turn the key off, way ten seconds or so and turn it back to "On". I look at the gauge to see if the pressure is registering and still no leak..

If everything checks okay, I fire the engine and let it idle.

I then use a pair of pliars and clamp off the vacuum hose leading to the FPR and monitor the pressure gauge for any increase in pressure. Pressure should increase about half of what the engine vacuum is.

So if the engine pulls, say, 18" of vacuum, pressure should increase by 9 psi.

With the engine still running I then remove the vacuum hose from the intake/plenum and put my finger over the hose bib.

I check the pressure gauge again and the pressure should have increased to the same amount as it did when clamped with the pliars.

Since the pressure didn't increase, I replaced the regulator with a Borg-Warner adjustable model.

With the new regulator installed, I did the same procedure as above. This time, pressure increased the same amount no matter which method I used - pliars or hose removal pressure increased the same amount.

Since my engine with a 230/236 cam, pulls 14" of vacuum, my pressure increased by 7 psi.

Hope this helps.

Jake

Lichen

I'll check it again tonight. But why remove the schraeder valve? My gauge just screws onto the valve.

conv90

Sorry JAKE, You know how GOOD I consider you , but I think Tequila is right.
You say: " removing the vacuum hose from the FPR and blocking the open ends"
If the open ends is the end of the FPR, I think you are wrong, Or I think that "your" way is not 100%sure.
The correct way in which i'm more confident , is to remove the hose from the regulator, then block the end of the hose to avoid an intake leak. the end of the FPR, IMO, should be left unblocked (it need to be in contact with atmosferic pressure).
BTW, you suggested a good advice. Checking the fuel pressure not only with the vacuum connected can let you know if you have a good regulator.
-Beppe-

rick lambert

Good post Jake that particular test has been used for years.
BTW, I'm just guessing here, but I assume (I know..bad word) that you remove the valve just to eliminate the possiblity of a valve malfunction...is that correct?

Lichen

Vacuum hose is new, FP did not increase after shutdown. In the photo, the two vacuum lines are disconnected just so I could screw onto the schrader valve. Now it's down to 39 psi with or without vacuum.

JAKE

As I've said before, don't just take my word for it, go out and do it yourself. That's EXACTLY what I've done. If I hadn't done it myself I would never have posted the way I have.

Ask anyone who disagrees if they have actually checked it themself, rather than just posting their theory or what they "think". I have physically done it!

Please, don't take sides based on what you've read here, check it both ways for yourself. That'll remove all doubt. What one "thinks" isn't always what actually "is". What he posted may sound reasonable and logical, but it just isn't so.

Here it is again: The pressure reading will be the SAME in either of the following events; engine idling:

With the hose still connected to the FPR Squeeze the vacuum hose shut with pliars OR

Remove the vacuum hose and block the port/bib on the intake OR

Remove the hose at the intake/plenum and block BOTH the intake/plenum ports/bibs AND the open end of the hose.

Doesn't matter which one you choose, the fuel pressure reading with increase and be the same psi.

Now, I don't want to have to keep beating on this. I've actually, physically done this. I suggest everyone who has doubts do the same.

Jake