Folks looking for more ideas. I’ve been chasing the tail on this one. 30 coup running stock tank, stock ball valve at bottom of tank and stock piping to stock full bowl. Alls been updated and restored. Stock hard line down past floor board the to rubber line to fuel pump. Rubber line out of pump to hard line on fire wall to regulator the two clear fuel filter to fuel rail. Car runs great gage reads 2 psi. Then shell starve for fuel. I get out as it’s running and gage reads 0 for a few then gos to 2psi and noticing very little fuel going through clear filter at fuel rails??? I’ve changed pump which did nothing. Played with regulator and at this time the adjustment is full open! So pump delivers 2psi which that’s max on these carbs. I’m running 3. I’ve got all new filters. You can here pump run. What do you all think. Kinda hard to roll out always wondering about fuel. Thanks all ideas welcome at this point! I must be missing something here. Good Day!!
Try without the filters. I've recently had 2 Napa gold filters that actually collapse when I turn the pump on.
I’ve got the fuel bowl filter it’s new bowls clean. Micron filter at pump which is large screen. Bowl always has fuel in these episodes? It runs well for longer drives but at some point will act up cold or hot..
Speedway's knock off of a Holley.....but then again the Holley's quality is starting to lag too (overseas). I'd sure look at that regulator though.
That really does sound like an unvented tank; ask me how I know. Try leaving the cap loose for a while and see if anything changes. If the vent is blocked you'll notice it more quickly when the tank is full than when it's low.
If using stock fuel tank in cowl Should Not need a fuel pump , Should have No issue Gravity feeding carburetors Unless there is a restriction 1 gal fuel weight 6 pounds ish , Experiment with a jet and fuel supply line so does not over come needle and seat when gravity feeding. I have been having issues with the Clear plastic fuel filers shown lately , Napa & Autozone . On 5-25 hp small engine's. Japan part's better Quality than cheap China, Aeromotive make's Quality fuel regulators and pumps
On my test run I used gravity feed. In was proven unstable to provide consistency on Tri-Power big 97s. It would allow max of 19/2000rpms. Then starve ? Firewalls to close for mechanical pump system. Thank you for the ideas.
My fuel cap sorta rattles if to full on roughy terrain it slops out. Venting not an issue. Thanks for the help.
Just received a new Hollie from S-way the mounting hole were not tapped?? Go figure. Three day out from test run I’d say.
Mark, I agree with you and your need for a fuel pump...that works. I lean towards the regulator as well but this is a shot gun approach... Zero pressure on the gauge should be a clue....but since it is on the outlet/regulated side you don't know if it is the regulator or the pump....if you had a gauge on the inlet to the pump, that might tell. I use a Holly 12-426 fuel pump to 2ea, 97 carbs on the 12V banger and it doesn't require a regulator. It has been good to me. The 6V banger has a Facet pump that has been problematic, you could hear it running but it didn't pump. I recall replacing it and it is now on it's third one in 15+ years I use a Malpassi fuel pressure regulator and I like it because it looks more era appropriate and it works flawlessly. https://www.heritagepartscentre.com...MIxvjBqqeajwMVY7IDAB2yWyyuEAQYASABEgLTvvD_BwE follow the link or queri under Malpassi fuel pressure regulator.... good luck
Is the tank clean? I had a piece of teflon tape floating around in a tank once. Everyone in a while it would get sucked up against the fuel line in the tank and block the fuel. When the suction stopped it would fall off and all was well again until next time.
I had a customer one time that had fuel starvation problems. Turned out that he had an unvented cap and the fuel leaving the tank eventually cause a vacuum and caused the starvation! He was pulling his hair out in frustration. We recommended a vented cap, and voila! Problem cured!
^ This reminds me of. In the early eighties Harley Davidson started using a smog cap on some FX and XL models. It was a vented cap, but it was controlled by a spring that would open at a certain vacuum, and pressure. Problem was the vent wouldn't always open to vent as it should. Get much above sea level and they would stay closed, causing the fuel to stop. It was a source of lots of confusion. The engine would act like it was out of fuel...the rider would open the tank to check...nope, plenty of fuel. In the process of checking the fuel the vacuum in the tank was relieved. The rider would fire up his scooter and ride off...only to have it happen again...and again...and again.
I’ve drove the car quite a bit when it was stock model A never had an issue till now so kinda raises your brow.. I’m going to take a look inside the tank. Thanks
If none of the above recommendations help, which I believe they will, perhaps consider whether the diameter of the stock lines ( I am not familiar with Model A) are possibly insufficient size for 750cfm carbs at 2lb pressure ?
@mark hogan I believe A tanks have a debris collecting Area right in side tank Outlet . I believe As where 3/8 I.D. Hole .maybe 7/16 ? Try borescope if you have. Some vent caps Vent to small ,Vacuum restriction , but sure you tried with out cap . There must be a restriction @ tank outlet, @ ball valve Feral , @ carbs inlets, ext. Typical F-H lucky if 100 hp , not that much fuel consumption. Facet Brand makes good low pressure fuel pumps . The / those small low pressure gauges below 10 psi , size of 50 Cent piece Are not accurate, The smaller the gauge the internals are just to small for the precise mechanism needed, I have called / email many top Manufacturers In Industrial & common gauge manufacturers Brands .USA & European.
Clem beat me to it ..... if the gravity feed volume straight to the carbs was insufficient maybe the supply line between the tank outlet and the pump inlet can't cope too and it's cavitating. Maybe experiment with a larger diameter hose going between the pump inlet and into the top of the tank filler neck ..... just to isolate that aspect of the problem. Good luck.
thanks @Budget36 , don’t think those pictures loaded when I initially read this thread - poor internet connection today !
it was a thought to me also at build time. Seems I’ve driven long distance 55 or so miles before taking a break with out a hiccup. Then when it starts it’s random. Soon I’ll have a new regulator on and inspect fuel tank from neck. So if lines work for a long Strech at Hwy speeds 2500-2900 Rpm I’m thinking my problem lies in the murks of the unknown !
I had that thought also? I’m running second Facet pump figured it was pump? Then opened the fuel regulator to max it read 2 1/2 -3 pounds psi. So I’ve ran the regulator wide open no restriction. It was so close to what I wanted. I’ve had zero seepage or flood issues.
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