Typical Fuel Pressure?

[RustyRatRod]

Does anyone make an electric fuel gauge? I've never seen one. At least that way, you could route it to the inside of the car and get it out from under the hood. I think a high quality one (if made) might be a good alternative.

 

[340inabbody]

VERIFIED! Cold start came back to 6psi! The heat soak took the pressure down 60%. Pump is fine! FYI the rubber stopper never did ****. I guess PV does equal nrT…..but in this case something mechanical gives the reciprocal.

Charging system now works as well. Time to get her plates on….

 

[B3422w5]

I plan to check the gauge in the morning. Sounds like it’s more than possible ie probable when it gets warm it slumps 50-60% from what Ive read. Checking it right away will tell me for sure if thats the case. No sense throwing money at it if the whole thing is problematic…….

Will report back.

Just fixed my charging issue by bench testing my VR which wasn’t coming on/shorting at all. The new one trips at 14.5V …

Yea, I always check mine when the car/ under hood is cold, so heat doesn’t come into play.
If it’s hot under there, all bets are off regards accuracy.

 

[340inabbody]

Thank God, I have you guys to bounce the stuff off of if I didn’t I think I would go stark raving mad….
Thanks guys

 

[Ant]

So I am in the process of bringing my motor (340) up from a deep sleep after body restoration. I never had a fuel pressure gauge and decided to add one. I noticed at the start up cold the fuel pressure was initially 6 psi. After some minor changes in timing and idle and warm up it dropped to ~2.5 psi. From then on it stayed at ~2.5 psi regardless of idle/rpm.
It seemed to be running fine no stalling or anything. I’ll check the float heights when the motor cools down a bit….

I don’t know what caused the drop from about 5/6 psi down to 2.5?

Normal?
Oh and yes I am running a good pre-filter…

View attachment 1716275876

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Relocate that fuel filter, it should not be next to the exhaust unless you want the fuel to become vapor. Before you do anything, that's the fist thing you should fix.

 

[Dale Davies]

Those liquid filled gauges can lie to you when they get hot.

?? Used lots of liquid (glycol) filled gauges in the oil patch. The liquid lubricated the mechanism and helps settle vibration. Liquid filled gauges have a rubber plug on the top with a little nipple sticking up in the center. The top of that nipple is supposed to be cut off after installation. That is only about the top 1/32" to 1/16". This will leave a tiny vent hole so it reads accurately. These are generally a bunch more expensive than dry gauges.
That inaccuracy when hot could be the vent not open and the glycol expanding and exerting pressure on the Bourbon tube; a C shaped tube that straightens out as the interior has pressure applied.

 

[PRH]

That inaccuracy when hot could be the vent not open and the glycol expanding and exerting pressure on the Bourbon tube; a C shaped tube that straightens out as the interior has pressure applied.

That would be my take on it as well.

 

[340inabbody]

Those rubber caps are not airtight though. The whole in mine is quite large roughly an8 of an inch keeping it open without contaminants and crap to get in there not to mention possibly spill if the angle is right I appreciate the input I could try leaving it off, but if it’s not tight, I don’t see how that would pull up

 

[PRH]

When the gauge is all heated up and the reading is low, try pushing the cap to the side and letting it vent.
See if the needle moves.

Supposedly, a temp change of 30-35* can change the reading 1psi if it’s not vented.
I can see the under hood temps changing over 100* in the area where gauge is located.

 

[340inabbody]

When the gauge is all heated up and the reading is low, try pushing the cap to the side and letting it vent.
See if the needle moves.

Supposedly, a temp change of 30-35* can change the reading 1psi if it’s not vented.
I can see the under hood temps changing over 100* in the area where gauge is located.

Thanks I’ll give that a try when I get this thing running better. At least for now I know that an initial rating is probably good enough. But at some point, it would be nice to be able to see true pressure all the time.