I have a Marshall 0-15 lbs liquid filled fuel pressure gauge with a regulator in the line on a three deuce set-up. I had the fuel pressure gauge reading 3.5 lbs an constantly kept flooding the front carb, Changed needle and seat, lowered float, vented the liquid filled gauge, all the same kept flooding the front carb. Finally got out my old Kal-Instrument fuel pressure and vacuum gauge from days gone by, plugged it in the system and when the Marshall reads 3.5 the Kal Instrument reads 6.5lbs. Backed fuel pressure regulator off to red 3.5 on the portable gauge and problem solved. Question is, has anyone else found the Marshall Liquid filled gauges to be that far off calibration, did I purchase the wrong gauge, and if so what gauge has the tendency to be most accurate? Thanks
Gauges are most accurate in the middle of their range. I wish I knew who made a small pressure gauge that read from 0 to 4 or 5. That would be best for us guys with Strombergs.
Marshall is a good gage, i'm not a big fan of the liquid filled and when you say you vented the gage do you mean you lifted the little rubber plug and let a drop or two of liquid escape and relieve the internal pressure? When you reset the regulator, what did the marshall gage read? what regulater are you using - mfgr & part number. When the Kal instr read 6.5lbs why did just the one carb flood? what carbs? Nice truck.
Alchemy, I was in autozone the other day just looking around and they have a 0-7 range fuel pressure gauge. Not 0 to 4 or 5 but closer than 0-15. I ruin 7 to my Holleys but I am setting up some AFBs for my small block and they say that they use lower pressure so I am think that a 0-7 may do the job for me.
You made it out of the fuzzy dice and air freshener aisle? I may have to do the same next time I'm in there. Thanks.
I vented the gauge by putting a small hole in the top, .060, I read somewhere that this was a cure for liquid filled gauges that where somewhat inaccurate. I think only the front carb keep flooding because it was the first carb on the line and once the excessive pressure blew by the needle and seat on that carb it most likely relieved the pressure on the back carb. I could be wrong on this, just my theory.
I was in the floor mat and steering wheel cover isle, made it all the way to the end. I'm thinking about getting me a guns and roses steering wheel cover.
Marshall gauge would not move off the peg when the Kal Instrument was reading 3.5lbs. Engine runs fine, no leakage or flooding, Marshall reads 0.
I wonder if the hole for the fuel to pass into the guage was the same between the two ? Smaller hole equals more pressure.
Porknbeaner, thanks I will go to Autozone locally and see if they have one. Makes sense that the gauge may be more accurate if asked to operated in the middle. I want to run about 3.5 so 0-7 would be worth a try.
There should be no flow into the gauge, so I don't think this would be true. (???) Size of the hole might impact the speed of response but there is no line length to speak of here so I wouldn't expect any difference.
never heard of "venting" a liquid gauge. does this actually fix the gauge?how do you know how much to vent? i was thinking all the liquid did was to slow the movement so the display would be more stable. any info would be appreciated. thanks...jack
I have used several small in-line fuel pressure gauges over the years.......the only one that reads accurately is one made by VDO......all other "famous" makers were not even close.....most died after a few hours.......threw them in the trash can......
The gauge I have on my 3 duece setup reads 1 even sitting on the bench, I don't have alot of trust in it being acurate, but my carbs aren't flooding and the engine is running good= I'm happy.
This is the very best time to put your tools back in the tool box,wipe your hands and go for a ride. Frank
I hope I am wrong, but I believe the gauge you saw was 0-7 Bar, not lbs. I really do hope I am wrong because like you, I need a gauge with the small range to try to get the carbs dialed in. The only ones I can find with a very low range are the aircraft gauges and the price is a bit more than I wish to spend.
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