This has bugged me for awhile….my fuel pressure gauge doesn’t seem to work. First the details; 59a flathead with dual 97s, 5/16” fuel line routed as follows: from firewall to mechanical fuel pump, fuel pump out to firewall mounted Holley 12-804 regulator, regulator out to rear carb stromberg banjo fitting that has a Marshall brand (dry gauge, 0-15 psi) attached. Shouldn’t this arrangement work just fine? the fuel pressure gauge in this location has never read above 1.5 psi, best I can tell, despite adjusting regulator. So I decided to remove it and setup a bench top test of this gauge with a spare electronic fuel pump, spare regulator and 2 gas cans. In the test I have a Carter p90091 pump (4-5 psi) and a Redline regulator and the gauge is threaded into a 5/16” barb x 5/16” barb x 1/8” npt fitting. Plugged in fuel pump and let her go, adjusting regulator up and down, and gauge registers nothing, nada. Is it fair to say gauge is dead? mean while I’ve ordered a 1-10 psi Vintage Speed gauge to see if it will work. here are some pics , first of fuel line routing minus fuel gauge and second pic is bench test setup.
Instead of inline with the fuel bowl feed lines you can thread it into the unused outlet port of the Holley regulator using a pipe thread bushing adapter. I would be inclined to think your old gauge is no longer good since on the car and bench test showed no difference in operation when playing with the pressure settings. Also if your mech pump is rated for flat head use then a regulator is not required, you could just eliminate it all together.
The gauge is likely damaged. My experience with fuel pressure gauges when mounted on an engine is that a non-oil-filled gauge will have a short life. Engine vibrations will kill it. Hence the need to fill them with oil to dampen the harmful engine vibrations. I mount them outside the p***enger compartment but visible from the driver's seat so pressure can be monitored on high fuel demand WOT situations.
Those small fuel pressure gauges are often not useful. Price point tends to be low, meaning poor quality. If that cool little gauge is the same price as a set of dice valve stem doodads, you are not buying accuracy. Gauge range is often wider than needed. You want the expected operating pressure to be mid-swing, not the first ten percent. They are subject to internal (pressure pulses) and external (temp and vibration) forces that shorten life and accuracy. The smaller gauge means smaller, more delicate parts. Nobody wants a big 12 inch gauge sticking up, but the smaller size forces things to be less ideal. How a mechanical pressure gauge works. https://www.marshallinstruments.com/faqs/detail.cfm?id=22
that’s the plan, move gauge to unused port on the regulator once I get another one and test that it works. I ***ume moving it here there will be less vibration from engine? Or once I get pressure dialed in I’ll remove gauge. my mechanical fuel pump is rated as built and tested for 2.5 lbs but one of the carbs started seeping fuel. the guy who rebuilt carbs said to add regulator because sounds like pressure too high. So trying to get pressure verified with a gauge.
UPDATE: got the new Vintage Speed gauge and set it up in my bench test (see original post and pic) and it registers at a big fat 0 just like my original gauge. Not sure what the heck is going on. decided to mount the new gauge on the unused port on the firewall mounted Holley regulator. Removed pipe plug, added adapter and new gauge, fired up the engine to see what it reads….just under 2 psi…well that’s a something. Loosened lock nut on regulator and started adjusting fuel pressure up and down and fuel gauge never moved more than .5 psi….went fora drive and it’s at 1.5 psi. I friggin give up…ugh
If the pump output is 2.5 psi the lowest regulated pressure will only be ~2.0 psi because it takes some of that pressure to operate the regulator diaphragm.
@31 Coupe is correct. For the new 97's they state that supply pressure must not exceed 2.5 psi and I ***ume that is what the pressure from a standard fuel pump was/is and flatheads never had fuel regulators or fuel pressure gauges and they worked fine in all sorts of conditions. Therefore the 1.5 psi which you are seeing under driving conditions is a result of 2.5 psi pump pressure minus 1.0psi regulator loss. Are you able to increase the pressure at the gauge using the regulator or is the 2 psi you mentioned the maximum possible? Benchmark for 97's is 1.5 - 2.5 psi and I like to be in the middle and definitely not at the bottom. Re your test set-up what is to the right of your pressure gauge or is it just the 5/16 hose into the tank/container. If so there is no restriction in the line after the fuel leaves the regulator so your gauge reads zero. Have a look at the size of the hole in a needle/seat, That's a big restriction i.e pressure loss and the reason that you need 1.5 to 2 psi to get fuel into your carbs. Hope this helps.
No, not able to increase pressure using the regulator beyond 2 psi. Actually more like 1.75 was max. To the right of the gauge is just 5/16” hose into gas container. I ***ume I wouldn’t see a difference in fuel pressure reading if I moved gauge to rubber line between regulator and carbs? I may try temporarily byp***ing regulator using rubber hose with inline gauge to see what actually pressure is from mechanical pump. As said earlier, it was built and tested to be 2.5 psi.
Hmmm , Me 1st I would start with 3-4 gauges Test & calibrate Readings might take 10 . Then I would move to my Electric low pressure sensors like 5-10 psi max . This is just to get ideal on accurate reading of a gauge, There are big Diffrent between a $20 & $150 plus gauge . especially in the last 20 years. Off topic , people buy a can of Ac charge $60 How accurate do you think that gauge is that you throw in the trash? Back to Fuel pressure , Wants I have Know caliber gauge or gauge's , I move to next step. Looking @ what is shown Pic of engine You have so many size changes in fittings , hose , br*** , pump , filter ext . Yes I am being critical it all adds up ..Pressure & Flow all up & down , causing capitation . Fitting are all Not made equal.. Do not know how fair in testing you want to Go , you would need a Flow sensor in testing. Allso You Need to have 2 known accurate calibrated gauges in your test One @ first carb The 2nd @ second carb , Options Spring Popets , with bleed off Return .. There allso G force , weight of gas in line Pump trying to push fuel forward G Force pushing back to against pump, How is pump or outlet of fuel leaving tank , Gravity or ****ing ? Vent Hole size matters Vs diameter Of hose .. I also think Holley does or did make a 5psi max regulator. Just throwing this in , useing G Force & gravity is why Racers started moving fuel tank to front Killing to birds one stone .
Late to this party and as its not been mentioned but could well be a factor, the silicon gell / oil filled gauges can be required to be 'burped' perhaps a number of times before they begin to read anything like reliably. Apparently it's a common problem. I was told this a few years ago when I was having murder with a fuel issue on my new build. None of the starvation problems made sense and I was finding the gauge was reading zero when it shouldn't have been. Removed the rubber bung momentarily and gauge accuracy and reliability was restored. My problem turned out to be the byp*** regulator was shutting down because it was, for packaging and routing purposes, mounted inverted (but no mention of not doing that in the instructions!). Chris
Another update: pressure still reading just under 2 psi with gauge installed in pressure regulator so I feel good about that. It runs and drives great but idle seems a too rich because at 400 rpm the L100 cam has lost the great sounding “cadence”. This engine ran and idled great for the first 500 miles but something has changed in last 500. At idle, It sounds like it’s loading up and bumbles along for a few seconds and then clears up over and over. I’ve tried multiple times to tune and sync these carbs by disconnecting linkages, adjusting a/f screws and using a synchro meter. Can’t seem to get it dialed back in. I am sure it’s because I don’t have any experience doing so. I've also notice rear carb throttle shaft is sticking where the the idle lever won’t completely close against idle adjustment screw. The other issue I’ve had from early on and the reason I wanted to get the fuel pressure gauge working was that the carbs want to seep gas from a few places. The well respected Stromberg builder suggested that the fuel pressure maybe too high but I think not now that pressure gauge is working. what do I check next? Gas level in carb bowls? Vacuum leak on carbs or intake?
My self have experience with Multi carbs , Some here do not believe in modern tools or test equipment or its needed , But you need more then just One in test tool , you need multiples , & they need to be calibrated , Carb sync , best to use have one for each carb @ same time installed , all need to be calibrated so you can bounce /tune each carb , if not you will be chasing. This is required unless you want to be dealing what you doing now. O2 will held & tell you what's going on. Check you ****erflies to bore for sticking & not resting to idle adjustment Stop / screw .. Also just because carbs same Model / Brand does not mean that flow act same way @ different Rpms example @ 2,000 rpms One carb might flow 50 cfm 2nd carb might flow different cfm. So not balanced , so each cylinder not getting same Afr .. So how far do you want to tune / balance the same , Flow Jet Machine ? Seep gas ,,, small engines , gravity Fed tank supply even model A's all have Fuel shout off valve when not running . Fuel pressure I think you could use a old good Quality Low psi steam gauge just for testing purposes, Or test beak with ball ? Loading up , To low of Rpm's To cold of plug Wrong PV's Intake design Leak down test on all cylinder Not all pulling same amount of air @ same rpms , Most call it a engine , If more then "1" cylinder Each of the other's are there separate individual engines , separate valves Pistons ,cam lobes ext. Spark plug ,wires & So On . Engine simple but complicated Look @ your 5 finger if still have All 5 different length . So least you are NOT using 3 carbs, Even with "1" carb you can & most likely if Dig / Go deep enough you will see how all the cylinders are NOT equal, With out doing alot of research and development, it will make your head spin if you care about perfection
Your setup should work fine as described Gauge only reading 1.5 psi and showing nothing in bench test = likely faulty gauge If it doesn’t respond with a known 4-5 psi pump, it’s basically dead Good move ordering a new gauge to confi
I'd swap out the rear carb if your able. Your last post indicates it's not adjusting right and also the periodic fuel seepage is a red flag. If it were me I'd also feed both carbs simultaneously with a tee between them with the output of the regulator feeding the tee. Having dual carbs fed in series can give headaches when idling if the rear carb is flowing more than the front carb.
I don’t have a spare carb to swap in. Both carbs seep a little in various places.i think I might need to have on hand some rebuild kits. Where is a good place to get rebuild kits? I pulled the top off both carbs yesterday. Used paper towels to get gas out of the bowls so I could use electric fuel pump to fill the bowls and check level. Both measure a hair below 1/2”. Seem good to me. Can I unscrew and remove A/F mixture screws to check them for wear/ damage without any issue?
I usually get Stromberg parts from Summit Racing because it is easy to order. Uncle Max on here also sells parts and will give advice. John
I added my fuel PSI gauge [ use a 12 volt E-pump; 3 lbs ] so I have added to my homemade fuelrail { was a stainless SQ. 1in. X 1in. off junked lawnchair, next to 4x2s. Buffed it up like chrome.Gauge never worked well [ cheep little 5 lbs. PSI gauge],what works best> Is my fuel line,sem-clear red line= I can see fuel n bubbles moving to carbs 4x2,, The fun part is,like Christmas bubble lights,the clear carb main line shows bubbles< for as long as there is heat* in engine block,even when all if OFF.
here's a good place to start. Fuel seepage needs to stop either by rebuild kit, float level or fuel pressure adjustments. If not fuel gauge won't read right. Member ydopen gave you a contact for parts and advice. https://stromberg-97.com/how-to/how-to-install-9558k-float-hinge-pin/
uncle Max rebuilt these 97s for me and has advised regulator (done, psi @ 1.75) check fuel level (done, level @ 9/16”) and a fuel return line (not crazy about this idea as it adds ever more connections/fuel lines) to relieve residual fuel pressure. see above reply
return line regulators seem to work better and last longer. It's what factory fuel injected vehicles use. Speedway sells a Offenhauser Chrome Universal Adjust. Fuel Pressure Regulator, 1-6 PSI that has mixed reviews. Found this also, good detailed info: https://carbdoc.com/tech/articles/flathead-carbs/index.html#gsc.tab=0
The MAJOR reason for fuel seepage/leakage from a Stromberg EE-1 (Ford version 97), even if the carb is rebuilt, and a regulator and return line is added is airhorn warpage. Stromberg placed an airhorn screw in the center of the end of the bowl, but ignored the ends. The ends of the airhorn tend to warp upward with age, especially if someone overtightens the screws, or worse yet, installs two gaskets trying to stop the leakage. The castings must be returned to true using heat and pressure. Do not even think about the possibility of considering using either a file or a mill to make the castings flat !!!!! Ignore the preceding sentence, and start looking for replacement carburetors, as you will ruin the castings. The procedure is not difficult, although it may be time-consuming: (1) Remove all parts which heat might hurt (springs, neoprene, etc.) from both the bowl casting and the airhorn casting. (2) ***emble the two castings together with the original screws but without the gasket. Snug the screws, but do NOT tighten. (3) Measure, using a feeler gauge, the distance (warpage) between the airhorn and bowl castings at the ends of the airhorn casting where it meets the bowl cavity. (4) Acquire 2 c-clamps (or better yet, make a special jig if you do lots of carburetors). (5) Install the c-clamps removing 0.003 inches of the warpage (IMPORTANT - DO NOT TRY TO DO MORE THAN 0.003 AT ONE TIME). (6) Place the ***embly (2 castings with c-clamps in an ELECTRIC toaster oven, DO NOT USE A GAS OVEN), heat to 300 degrees, turn off the oven, and allow to cool naturally (DO NOT QUENCH). The c-clamps are probably loose at this time. (7) Repeat steps (3) through (6) until there is zero clearance between the castings. (8) Continue with your rebuild. Jon
That's pretty interesting, Carbking. It's a new tip to me, with much credence since it's coming from someone with tremendous carburetor experience.
Sounds like your gauge is kapoot. I install my gauges using the same regulator you have, and I install them on the second outlet of that regulator that you have plugged now. It gives the exact reading after it's regulated down.
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