0-5 PSI fuel pressure gauge

[Hotrodvw]

"While ideally it should remain the same, as long is it remains within the acceptable range for your carbs you're okay.

You may need a long hill do drive up to check your fuel pressure at full throttle.

Scott Novak"


You said it yourself.......once it's set, no need to mess with it. Bottom line here is, mine is set, and works just fine from idle to full throttle. There's no need for more conversation here.

[david58]

"While ideally it should remain the same, as long is it remains within the acceptable range for your carbs you're okay.

You may need a long hill do drive up to check your fuel pressure at full throttle.

Scott Novak"


You said it yourself.......once it's set, no need to mess with it. Bottom line here is, mine is set, and works just fine from idle to full throttle. There's no need for more conversation here.

Does anyone else see a contradiction here?

That is not a contradiction the key words here are ideally and should

[Scott Novak]

There's no need for more conversation here.

Actually there is. Not only are you making false claims about what I said, you are spewing bad advice.

You said it yourself.......once it's set, no need to mess with it. Bottom line here is, mine is set, and works just fine from idle to full throttle.

I said nothing of the kind. What I said was:

Once you adjust the fuel pressure you need to check it at both idle and full throttle. While ideally it should remain the same, as long is it remains within the acceptable range for your carbs you're okay. Scott Novak

Unless you can read the fuel gauge on a dashboard, how much does it really do? You want to be able to monitor fuel pressure from idle to full throttle acceleration. How are you doing to do hat with the fuel gauge in the engine compartment? Scott Novak

Nowhere in either of these statements did I imply that you did not need to check the fuel pressure once it was set. In fact I stated that you needed to check/monitor the fuel pressure at idle and full throttle/full throttle acceleration. You can't do an acceleration test on a dynamometer, as it doesn't have the force of gravity working on the fuel.

Any number of things can affect the fuel pressure even with a pressure regulator. The most likely is a clogged fuel filter. Also possible is a fuel pump that doesn't work properly when it's hot or cold. Not to mention that the fuel pressure regulator itself can be bad. There is more than one type of fuel pressure regulator, and they don't all maintain their fuel pressure equally well.

You need to be able to monitor the fuel pressure while you are driving. A datalogger would be even better as you could look back over the entire drive to see if there were any fuel delivery problems.

Granted you car will run just fine without any fuel pressure gauge hooked up. But until you have measured the fuel pressure under all driving conditions, you don't know if your fuel delivery system is working properly.

Adding a fuel flow meter to each carb would be even better, as fuel pressure doesn't tell the entire story. Even if your fuel pressure was maintained, a clogged float valve could restrict the actual amount of fuel entering each carburetor.

Scott Novak

[david58]

To add to what Scott said it could also show you a pressure drop if you had a fuel leak in the lines which, can be the end of a good day. So there are very good reasons to know what your fuel pressure is at all times.

[Hotrodvw]

I still have my own view. I'm not here to bitch about it, apparently you guys are. You do it your way, I'll do it mine. When I have problems, I guess you can tell me you said so.

[raygreenwood]

Everyone is both slightly on and off the mark.
There are no fuel pumps that put out significant pressure ...per-se. Not even fuel injecetion pumps. They put out volume. Sustained volume agianst a calibrated restriction = pressure....period. It does not matter what you believe personally.

That being said...if you are going to run around quoting to pay attention to only the middle 1/3 of the gauge and 3-5 psi is your critical range...none of the gauges pictured here are worth anything. If you have a critical range of pressure (say 5 psi)...wherein any 1/2 psi of gain or loss (1/10th of the scale) is 10% ....get a real gauge.

the least gauge quality you should be using is a class A gauage. that is 1% tolerance of actual reading for the middle 1/3 of the scale and and +/- 2% for the rest of the sacle.
Ideally you should be using a class 1A guage minium. That is 1% variance to actual reading full scale.
In graduations from 3-5 psi...you really should have a class 2A guage....that is accurate to 0.5% full scale.

Now....there are no usable size guages....that you WANT to afford....that fit the bill of full time rigidly bolted to the fuel line in the engine compartment..........that are accurate to anything.....that are in class A, 1A or 2A. Thts because these classes of guages....without spending your left arm....cannot even hope to remain marginally accurate with vibration and heat of an engine compartment.

In fact...all guages have a specific heat range at which they are accurate....and none that you can afford work at a range from 120 -200 F.

I have class 2A guages for working on fuel injection. They stay in the padded box until they are used...cause otherwise...like all other guages of equal or lesser quality...they are useless when subjected to vibration and most especially...heat....liquid filled or not.

Kind of a moot argument considering the quality of gauges we are arguing about.

By the way...the problem with panel mount gauges are that there are pumping losses in long fuel lines...as well as temp issues. The only accurate ones use a fuel line mounted transducer and a shielded wire link to the dash.

Unless you have this stuff.....its not helping. Rigidly mounted engine compartment fuel guages are patently innacurate after not too many miles. Ray

[Scott Novak]

By the way...the problem with panel mount gauges are that there are pumping losses in long fuel lines...as well as temp issues. The only accurate ones use a fuel line mounted transducer and a shielded wire link to the dash.

Ray,

While I would never advocate running a fuel line up to a dashboard mounted mechanical fuel gauge, why would this affect the accuracy of the gauge? A long fuel line to the gauge, especially if it was a rubber fuel line that can flex, may reduce the response time of the gauge. It would also average out any pulses in fuel pressure. But as there is no continuous flow, how can there be any pressure losses that would affect the reading on the gauge?

As I hadn't actually stated this, I would only recommend using an electric fuel pressure gauge with a pressure sender at the carbs and the gauge mounted on the dashboard.

You don't need to have a super accurate fuel pressure gauge for driving. HOWEVER, and this is a BIG however, you do need to calibrate the electrical gauge against a known precision gauge. Then you will have a compensation factor to make relatively accurate readings.

Scott Novak

[Manny]

Sorry, guys, I did not mean to start a debate here. I found this at Grainger. It's P/N 2C641
It's not a panel instrument so mounting in a panel could be a challenge. Pricey too. Any comments? for or against.
Manny

[Hotrodvw]

You don't need to have a super accurate fuel pressure gauge for driving. HOWEVER, and this is a BIG however, you do need to calibrate the electrical gauge against a known precision gauge. Then you will have a compensation factor to make relatively accurate readings.

Scott Novak

Why do you need to calibrate or check a gauge against a known precision gauge that is accurate to +/- 1% of the middle third of the gauge? I would find it hard to believe that most shops actually do this. Is +/- 1% not good enough for the average joe? I think it is.

[Hotrodvw]

Well, then you suck as much as I do.

[bajaherbie]

my summit mechanical fuel pressure gauge is in the back of my baja

[Scott Novak]

You don't need to have a super accurate fuel pressure gauge for driving. HOWEVER, and this is a BIG however, you do need to calibrate the electrical gauge against a known precision gauge. Then you will have a compensation factor to make relatively accurate readings. Scott Novak

Why do you need to calibrate or check a gauge against a known precision gauge that is accurate to +/- 1% of the middle third of the gauge? I would find it hard to believe that most shops actually do this. Is +/- 1% not good enough for the average joe? I think it is.

Hotrodvw,

Pay a little more attention when you read. I said "You don't need to have a super accurate fuel pressure gauge for driving." Which means that the accruacy could be horrible. However, if that inaccurate gauge is calibrated against a known accurate gauge, you can make an error table. With that you can look at the readings on the inaccurate gauge and make your correction so you accurately know what your fuel pressure really is.

Scott Novak

[Scott Novak]

Sorry, guys, I did not mean to start a debate here. I found this at Grainger. It's P/N 2C641
It's not a panel instrument so mounting in a panel could be a challenge. Pricey too. Any comments? for or against.
Manny

Manny, that gauge would be great to use to calibrate a cheaper electrical dashboard gauge. But I wouldn't want to permanently connect it in an engine compartment.

Scott Novak

[Hotrodvw]

You don't need to have a super accurate fuel pressure gauge for driving. HOWEVER, and this is a BIG however, you do need to calibrate the electrical gauge against a known precision gauge. Then you will have a compensation factor to make relatively accurate readings. Scott Novak

Why do you need to calibrate or check a gauge against a known precision gauge that is accurate to +/- 1% of the middle third of the gauge? I would find it hard to believe that most shops actually do this. Is +/- 1% not good enough for the average joe? I think it is.

Hotrodvw,

Pay a little more attention when you read. I said "You don't need to have a super accurate fuel pressure gauge for driving." Which means that the accruacy could be horrible. However, if that inaccurate gauge is calibrated against a known accurate gauge, you can make an error table. With that you can look at the readings on the inaccurate gauge and make your correction so you accurately know what your fuel pressure really is.

Scott Novak

That's the dumbest damn thing I've ever read. I can read scott. Who keeps a gauge that they have to make an error table?????? Why not buy a quality gauge. You're not quite as smart as you think you are, but your fantastic ability to make others feel small to pump yourself up, is what you bull poop everyone with. That's been evident on the samba. Once again, you can go through the steps, I'll work with what I know and have................which again does work just peachy.

[Scott Novak]

You don't need to have a super accurate fuel pressure gauge for driving. HOWEVER, and this is a BIG however, you do need to calibrate the electrical gauge against a known precision gauge. Then you will have a compensation factor to make relatively accurate readings. Scott Novak

Why do you need to calibrate or check a gauge against a known precision gauge that is accurate to +/- 1% of the middle third of the gauge? I would find it hard to believe that most shops actually do this. Is +/- 1% not good enough for the average joe? I think it is.

Hotrodvw, Pay a little more attention when you read. I said "You don't need to have a super accurate fuel pressure gauge for driving." Which means that the accruacy could be horrible. However, if that inaccurate gauge is calibrated against a known accurate gauge, you can make an error table. With that you can look at the readings on the inaccurate gauge and make your correction so you accurately know what your fuel pressure really is. Scott Novak

That's the dumbest damn thing I've ever read. I can read scott. Who keeps a gauge that they have to make an error table?????? Why not buy a quality gauge. You're not quite as smart as you think you are, but your fantastic ability to make others feel small to pump yourself up, is what you bull poop everyone with. That's been evident on the samba. Once again, you can go through the steps, I'll work with what I know and have................which again does work just peachy.

Hotrodvw,

People frequently make their own error correction table for their speedometers and odometers when they use a non-stock size tires. Sometimes it amounts to using a marker to mark the speedometer with the corrections. Very few people actually have their speedometers adjusted to read accurately with a different size tire. Unless perhaps they have an electronic speedometer and odometer that allows for easy adjustment.

Error correction tables are made when calibrating dynamometers and a host of other measuring devices. In fact it's done in calibration labs across the country on a daily basis. My Fluke thermocouple meter comes with an error correction formula to correct the temperature readings when the meter is operated outside a specified ambient temperature range.

In an ideal world everyone would own perfectly accurate gauges. Not everybody can afford accurate gauges, nor do you need an accurate gauge, as long as you have calibrated that inaccurate gauge against an accurate one. What you need most inside a car is a rugged and reliable gauge.

Some people will even go to the trouble of making a new corrected scale for the gauge.

Making an error correction table is hardly a dumb idea, and many people around the world do it.

Not having gauges inside your car isn't going to stop it from running. But if you want a fuel pressure gauge to be useful, dashboard mounting it where you can read it while driving, or datalogging from a pressure sensor is the way to do it.

Permanently mounting a mechanical fuel gauge inside an engine compartment doesn't let you know anything about full throttle acceleration, and doesn't tell you much more than idle fuel pressure, unless you are running it on a dynamometer. The heat and vibration may affect the accuracy of the gauge. It's also one more unneeded device inside the engine compartment that could fail and cause a fuel leak. Oil pressure gauges aren't all that useful inside an engine compartment either. Better to mount it on the dashboard.

Scott Novak