Mechanical fuel pressure gauge vs electric???

Okay guys and gals, I keep hearing that inline mechanical gauges are inconsistent. I need to put a fuel pressure gauge in my engine compartment and was curious if any one could substantiate these claims or not?

I would prefer to run a mechanical but I'm open to what ever.

Thanks

 

It seems that there are two basic options.....electric or mechanical. I do not understand how anyone can ever think that mechanical is unreliable. Have we become so attached to electronics...computers and so on...that we think ****og, mechanical, devices are not worthy of use?
Good Lord!!

 

Mechanical is the most accurate.

 

I've got a Holley Red pump and mech, regulator. No problems, and I've run it now for over two years, I keep it at 4 psi. I feel more confidant with mech. things, all my gauges are mechanical units also ( SW Wings ). I have to agree with Flatheadguy, I'm not against using electric gauges and regulators, I just prefer mechanical because I've never had an issue, at least not in the last 40 years.

 

The only way a mechanical gauge is going to be inconsistent is if its defective of of extremely low quality.

With a mechanical gauge, If you see pressure fluctuations or needle bounce its a good indication that the fuel pressure is actually varying.

An electronic gauge isn't fast enough to show that variation, yet if you do see fluctuations, the first thing you look for are bad connections, and then verify with a mechanical.

Not sure where you heard the info that confused you.

 

I've seen it. There are a handful of people I know that have the mechanical gauges that you would screw into a fuel block and they are terribly inconsistent.

So instead of making this a debate guys how about some one offer some suggestions of a gauge they have used And found it to work well.

That's more what I need.

 

1½" Shock Proof Gauges. FAQ.


My liquid filled gauge went from showing 6 PSI to 0 PSI, do I have a faulty gauge? The gauge is fine, you are most likely seeing the effect of temperature increase on the filled gauge offsetting real pressure.

All mechanical liquid filled gauge cases are sealed (to keep the liquid in) so as they heat up pressure will build up in the case (approx 1psi for every 30-40F temperature change). This case pressure exerts a force on the mechanical movement and offsets the actual process pressure. This effect is typically only noticable when measuring low pressures (i.e. on a 0-15 psi gauge).

For an accurate pressure reading on a liquid filled gauge you should vent the gauge at a specific temperature before taking a pressure reading. You should revent the gauge whenever the temperature of the gauge has changed significantly (either heated up or cooled down).

To vent the gauge, turn the gauge so that the air bubble is next to the fill plug and gently pull the vent plug to equalize the gauge case pressure with the atmosphere (reference pressure). Then carefully reinsert the fill plug so no liquid can leak out.

If you are taking readings on a frequent basis we recommend remote mounting the gauge with the plug in the upright position to make venting the gauge easy. You can even use a needle to put a very small hole in the plug to permanently vent the gauge. If you do this however, make sure the plug is in the upright position so no liquid fill leaks out.

That's from marshal, ( http://www.marshallinstruments.com/faqs/index.cfm ) I like their stuff. A liquid filled gauge is the best at tolerating vibrations, heat has some effect on the reading, as well as ambient temp such as summer vs winter. The do need to be zeroed when temp change . Also a 0-15 psi gauge is more apt to show variation than a 0-100 gauge.

Is it possible that is the inconsistent type of phenomena you are speaking of ?
Vent the gauge and it should be as accurate as any need could demand.

 

Have you examined those gauges for a country of origin? FWIW, the little mechanical fuel pressure gauges sold by most of our big speed equipment catalog retailers are chicom.

jack vines

 

Had the same problem with my mechanical liquid filled fuel pressure gauge on the engine. When engine got warm gauge read zero. Auto-Meter has a mechanical NON liquid filled fuel pressure gauge (JEGS) that now works perfect for me. It is not as cheap as some of the others, but is now very accurate for me.



Ago

 

They can be hard to read if you get a lot of vibration but a good mechanical is all I use and my engines seem to run fine.

If I was going to have it in the ****pit I would run an electric just because I don't like the idea of riding with a fuel line in my lap.

 

I dont know how it was done in "traditional" days, but now it is illegal in race cl***es to have a direct reading mechanical fuel pressure gauge in the p***enger area. Thats why you often see them mounted outside on the cowl.
To mount the gauge inside the car, you need to use an isolator which is mounted outside the pasenger compartment.

 

Thanks guys for providing me with an answer

In this case I will most likely look for a Stewart Warner mechanical non liquid filled gauge. I am thinking I would maybe run it off of a fuel block or maybe one of those mechanical single port blocks that you put in the middle of a hard line?

Anyways, thanks for the knowledge.

 

This subject has come up many times before. All you have to do is drain the fluid out of the liquid-filled gauge and it will perform as it should. Not sure when a liquid-filled fuel psi gauge is really needed, because normally they simply are not.