Quadrajet fuel drain back 149”. When you shut the engine off the heat tends to boil off a lot of gas as well. Check both sets of plugs. To fix this, you need to replace I found my backup fuel pump from the local counter parts store, Carter M6624 40gph. They stick The well plugs leak. - Floats are set with fuel at middle of sight glass. disconnect the fuel line into the quadrajet. Prime the carb and it runs fine until it sits a few days. It's on a mid 80's Chevy truck. 135” Viton Quadrajet Needle & Seat Asssembly. Posted Since the Q-Jet's needle and seat is in the bottom of the float bowl, the fuel draining back through the fuel pump will actually siphon fuel out of the carb's float bowl. The owner passed away recently. After it sits overnight there is no fuel in the bowl. Make Quadrajet Fuel Pressure -- Pump, Regulator or Both? To reseal them you remove the carb from the engine, drain it safely, remove the two LONG screws at the rear of the carb. The 1st start of the day takes lots of cranking but the engine finally fires up. So when I let it sit for 2 or more days, I have to crank and crank, pause to not over work the starter, the crank and crank somemore until it's cranked enough to bring fuel back to the carb and fill the float bowl before it'll drop any gas. That being said if the truck sits for long periods of time, it will do this regardless unless you use a perhaps the the gas is flowing back to the tank through the needle valve if it aint compleatly sealing up or evaporation is causing the float to drop and lift the needle. There are in-line fuel filters with check valve in them, would think the fuel could drain back because float bowl is vented. Solutions? Make sure those plugs are tight and replace the carburetor’s fuel filter with one that has a check valve at the inlet end. Once the fuel level falls below the level of the needle and seat, air will enter the fuel line and break the siphoning action. I hadn't ever seen one. Global Moderator; I did get a check valve but haven't installed yet till I really thought fuel drain back was happening. Inverted Flare What this pump exactly specs to is debatable. May 18, 2019 #20 Put the new pump on after testing the old one. More than likely the fuel is draining back to the tank. It causes vapor lock in the summer time too and hard to restart if it's warmed up good. . High flow . I have pumped the accelerator and there is no fuel coming out of the discharge. Smartin, Aug 5, 2023 #7. Back in the day we called this vapor lock, which simply meant that the fuel turned to vapor before getting to the engine. Poor hot-start. Its like not only has the carby leaked empty but the fuel line is also empty for some reason. quadrajet parts . Note: Check valve filters do offer more restriction to high RPM fuel flow than non-check valve filters. Quadrajet draining down? that Quadrajets are known to have an issue with fuel draining down if it sits unused for a while. Register or Log In To remove these advertisements. If you see fuel squirting from the accelerator nozzles the bowl isn't dry. I'll check the oil. - I have disconnected the fuel line after shutting down the engine, and watched the fuel bowls still empty after about 5 hours. The ACDelco GF 471 Quadrajet filter does (or at least always did) have a check valve installed in them, other brands likely do too. two steel bars mounted lengthwise in a hydraulic press and incrementally applying pressure until the cover comes back into tolerance. don't believe me. A common method hobbyists use to test their Quadrajet for leaky bottom plugs is to fill the bare casting with gasoline or solvent and set it on a bench for several days, watching for fuel drops Quadrajet well plugs leaking The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board. C. fuel tank. Tony. A user on another site mentioned the original style filter with the check valve. You say that the electric pump has to run for quite a while to get the carburetor full so the fuel has to be draining back. I did not know this but when GM went to return lines on the fuel pumps the fuel pump was no longer a positive stop,at the C3 General - Cold start problems with rochester quadrajet. Fuel-saturated floats also may For fuel to flow back down the fuel line, in a Holley or Q'Jet it would have to find a way to flow up hill to the top of the needle and seat to get out. It's not going to drain back out the inlet & the fuel line. If you have well plug leakage, they will leak most when hot and cause a flooding condition (I have read). Electric fuel pump systems have what's called a roll over valve. For performance applications we recommend 2251 (No Check Valve Filter) or if you really want the check valve with higher fuel flow, you can When your car sits for some period of time, the fuel drains back down past the fuel pump into the tank. p/s Percolation – Percolation can happen when your engine gets hot, then you turn the engine off and the fuel boils over, sometimes over the top of the carburetor, or more often, simply evaporates. Quadrajet / Dualjet Base Gasket, . C3 Tech/Performance - 71 quadrajet fuel filter installation - I took apart my fuel filter some time ago to replace it, and since then I've worked on a lot of other things before I even tried starting the car. The T-II intake isn't helping things much, unless you have a lot of gear/converter the carb woln't leave hard and take while to get into the good power. btw, not all epoxies are created equal, most have agreed on this forum that marine-tex epoxy is the way to go BUT first tap the plugs holes and insert some type of threaded plug (small set screws work in If I let the truck sit for a few days, the fuel bowls would drain, resulting in having to spend time cranking the engine before it would fire. I could surely use a check valve on my 1969 Cadillac Quadrajet, because it disconnect the coil positive. spray some soapy water onto the epoxied plugs and shoot the air through the jet orifices. Mild to severe flooding can result. Dinoburner. That, combined w/the fuel evaporating from the carb from heat soak or drain-back could combine to cause a long crank time. 140”, . I have a new fuel pump with a large bowl (automatic with air type) and the fuel filter is quite large (clear plastic type ~2 inches in diameter). Iffff fuel was to leak back into the tank, the fuel has to be raised [ go uphill ] to get past the seat in the n/s. I have a 1968 GTO 400 4-speed with the original 7028263 Rochester Quadrajet. If the fuel pump has a return line, crimp it closed with a pair of vice grips, let it idle a few minutes, shut it down and see if it drains back. The part is made by Moeller and available at most marine supply houses for around $12. And likewise, unless your water separator filter is mounted upside down or sideways, it's not going to drain out of the filter neither. Evaporation and drain back thru the needle and seat are much more common causes of your issue. There can always be leaking welch plugs and the like that allow gas to drain into the engine or onto the intake. Fuel draining out of carb ? - Carb is in a 68 402 motor. you should not be able to blow bubbles in the fuel No fuel on startup Quadrajet: If I leave my car for a few days and go for a start I have to crank it for 20 seconds to get some fuel in the carby. Joined Jun 5, 2003 Messages 29,727 Location Apple Valley, California . Disconnecting the return should stop that problem because the fuel cant drain back through the return. This valve will keep the fuel where it belongs—in the carburetor. Carb came back with no problems found, so we spent the next three months trying pumps, electric with regulators, stock chevy mecahnical and then one of the six valve Fuel metering rods pulse rapidly as a means to precisely control the air/fuel mixture. C3 Tech/Performance - No gas in float bowl - 78 L82 after sitting a couple days it won't start because there is no fuel in the quadrajet. Usually if a QJ is "losing prime", it is the main well floor of the carb leaking Could be a combination of the two. If the carb is new to the engine and the carb has a high flow seat (larger diameter than previously used), the same fuel pump pressure is likely to force the needle slightly off the seat due to the larger seat no gas through quadrajet The 1967 - 1972 Chevrolet & GMC Pickups Message Board. I assumed the carb needed to be rebuilt and the leaking was normal (from a drain in the carb) when flooded. stalls. Jump to Latest Also, unless you have a leaking needle seat gasket the fuel can't drain back to the level of the accel pump transfer slot because even a window type seat is above the level of the transfer slot. Chris142. And for the life of me, it always drains back making it very hard to start. The n/seat is higher than the fuel level in the bowl. The fuel drains back in the fuel system on the 1977 SRV-19 with a Mercruiser 470. As this happens, it will actually siphon the fuel right out of your fuel bowl swince the needle/seat on a Q-Jet sits in the bottom of the bowl. so you get a 15 second cold start. Air Entry: The Quadrajet draws air into the engine through an air cleaner, which removes dirt and debris to ensure clean air enters the carburetor. When you try to start it, no fuel in the carb, so you have to crank it long enough for the fuel pump to get gas all the way back from the tank to the carburetor. May 18, 2019 Get a Quadrajet for that small block. RRR, I never said the fuel in the line drains back into the tank, but I should have been more clear: the fuel in the fuel bowl cannot leak back through the pump into the tank. Of course it can cause other problems too. See Photo 3. Fuel from the gas tank is pumped into the carburetor, where it is stored in a float bowl. To fix this, you need to replace the pump, but not all new pumps have checkvalves that seal completely, thus the problem can persist. He told me about a check valve in the front of the filter. Even so there is always plenty of heat under the hood to evaporate some fuel. Comments: Degradation and stripping of the seat threads is common in the older Q-Jets – especially the ones that have been commercially rebuilt and sandblasted. 1974 Cheyenne 10 LWB STOCK 350 W HEI /TH350/AC/4 BBL Quadrajet Mopar by Birth Chevy by Choice. It appeared to be flooding at idle and the fuel was leaking excessively from the throttle body linkages (on both left & right side). For fuel to drain out of most carburetors made AFTER 1930, the car Some fuel tanks uncover the pick-up quite easily at the track as most are front located and the back part of the tank has a long slope to it. Does the fuel filter in the inlet have a built in check valve to keep the fuel from draining back to the tank when not running. But there should be plenty of fuel in the carb to start the engine. I think from your recommendation years back. 00. I know my old quadrajet could run out of fuel from leaking out of the bowls and be flooded, or after days it could be dry again and the bowl low or empty, but it was nearly impossible to leak or evaporate out of the accelerator pump so it would at least get a pump Quadrajet Parts and Numbers (Moderators: Cliff Ruggles, Ethan1) » Needle and seat info needed does not "drain back". 560 Quantity: 1 plug Plug is also called: Fuel bowl drain plug Main jet plug Note Drain back of the fuel in the FUEL LINE ONLY is possible with an electric fuel pump. Using a thermal spacer between manifold and carb will reduce heat transfer to carb and reduce evaporation after shut down. 5 QUADRAJET POWER LONG FUEL FILTER WITH CHECK VALVE SPRING AND GASKET NEW 1972 TO 1989. I am using original style filter in carb. C3 Tech/Performance - Fuel draining from Quadrajet hard to start - My fuel drains away from my Quadrajet and needs to have the engine cranked over to pump fuel to the carb. It What happens after shut down? heat rises and collects under the carb. It hasn't made oil and it smells like oil and not like gas but will let you know. If it sits a couple days I have to crank for a long time for it to start. then, with the carb upside down, carefully compare the gasket to the bottom of the carb, looking to see that all the cavities in the baseplate are covered by the gasket. this will alow half the bowl to drain back and the fuel line go dry. Since the Q-Jet's needle and seat is in the bottom of the float bowl, the fuel draining back through the fuel pump will actually siphon fuel out of the carb's float bowl. If you want the check valve in the #5 filter to function you will need #2 and #3. Quadrajet Carb rebuild, JB Weld on plugs under float bowl to stop fuel leaking into carb? i find a bigger issue is sediment in the fuel pump that allows fuel to drain back to the tank. the sediment from the fuel lines. 17057142 is a 1977 m4m carburetor Very unlikely to leak at the well plugs. It has the corect inline filter with the return line to the gastank. The clear plastic inline fuel filter has no fuel left in it when left for So the fuel draining back through the leaking fuel pump check valve can actually draw the fuel out of the float bowl down to the level of the needle/seat elevation. 1974 Cheyenne 10 LWB STOCK 350 W/HEI /TH350 /AC/ 4 BBL Quadrajet Mopar by Birth Chevy by Choice Email Report raycow DECEASED Posts: 27999 Loc: San C3 General - Cold start problems with rochester quadrajet. Fuel Delivery: The carburetor has four barrels, or primary venturis, which are responsible for fuel delivery. please use 2 wrenches. This is the latest design w/o “windows” to improve fuel control and help prevent bowl drain back after shut-down. If you're sitting there pumping and pumping, something's wrong, but if you're just giving it a little boost, I think that's normal. allows fuel to drain back to the tank when cold. Inlet Nipple Size: 3/8" Outlet Fitting Size: 1/2" Threaded --> I think this is wrong, it is a 5/8-18 in. you need to check the plugs with some airpressure. Works like a check valve Last edited by gjohnson; Nov 27, 2013 at Regardless of fuel filter, the fuel bowl does not drain back through the inlet. May need to install anyway just to eliminate possibility. A fuel filter in the fuel line between the fuel pump and carb that allowed you to see the fuel in it would show you if the fuel was draining back past the fuel pump. I would guess a no fuel problem would be due to either a leak or evaporation. VileZambonie. Click here: Anti-Siphon Valve, 3/8" Barb, 1/4 NPT - Moeller 033801-10 - iboats. If you are concerned with potential drain-back and using a mechanical pump, or return like set-up, etc, remove the clip from the needle valve, problem solved. Can I put a check valve in the fuel line before the pump to keep the fuel in the bowl, filter and line when I shut the engine off? This would make starting the car much easier wouldn't it? Thanks, Philip I have a Rochester Quadrajet Marine Carburetor #17059286. For performance applications we recommend 2251 (No We just did a rejet on the CRF 450X, had to drain the float bowl to put in the new jet. techg8 The BS GS. Since the needle/seat in the Q-Jet is Drain back is a valid issue with Qjets. The reason why the fuel disappears from the float bowl after the car has been standing for a few days is evaporation of the Stripped Inlet Seat Threads: Results in: A loose/stripped seat in the float bowl will allow fuel to leak by the needle/seat assembly. If pumping the pedal helps it start then the choke isn't working properly. Well I personally haven't had fuel drain back problems with a qjet,but turns out that there are reasons and fixes for the problem. I have heard that the quadrajets can leak through the plugs in the bottom of the bowl. 145”, and . If you run a CCC Quadrajet on a non-CCC engine you will wind up with an overly rich fuel mixture and horrid . The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Or it really could be a bad fuel pump with a bad valve that is letting the fuel drain back to the tank. The 1st start of the day takes lots of cranking for a good stream of fuel to If you have a fuel pump with a slightly leaky check valve in it, the fuel standing in the column between the pump and the carb will drain back down through the pump after engine shutdown. com I have a sbc 350 with a quadrajet 4 barrel in my PU. When jwilson645 mentioned original fuel filter that has a check valve, I remembered when I got truck 3 Even if the carb bowl goes dry the fuel pump should re-fill it quickly. On a Quadrajet, fuel can siphon out of the float bowl past the needle and seat leaving you with an empty carb when you go to crank the car after it has sat for a while. It had been hard to start cold and the choke is working. If gas could rise on its own, is has to go thru the check valves in the fuel pump,manual or electric even if it got that far it cant get back thru the anti-syphon. Logged Quadrajet well plugs leaking The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board Register or Log In To remove these Have been investigating a little further and not 100% sure it is well plugs or fuel draining back toward tank. I believe its spring loaded and when the engines off it closes up the line to prevent draining back out. Our '57 doesn't sit much during the summer but in the autumn/winter months she sits in the garage, unused. I recommend you pull the carb, turn it upside down over a bucket, let the fuel drain out. Joined Jun 19, 2017 Messages 1,584 Location New Hampshire USA. My other thought was fuel draining back out of bowl toward tank. The Quadrajet was known for its precise fuel metering, which allowed for optimal performance and fuel efficiency. holds the check valves open. I knew about common issue with leaking well plugs and the epoxy band-aid workaround, but I haven't owned a Quadrajet car/truck for some years and wasn't up to speed with better repairs. Rochester Quadrajet carburetor tension (windup) spring is used to provide tension to the Built in check valve prevents fuel from draining back out of carburetor when engine is turned off. I rebuilt it using a kit I ordered from you. D. Newbie; Posts: 36; Fuel drain back? Thread starter ghopp24; Start date Dec 14, 2017; The Quadrajet has about 10 or 11 thousand miles since reman, and the fuel pump has the same mileage on it, too. If it is mounted in a fashion that permits it draining back to the tank, it's not going to properly separate & isolate any moisture in the system. gas station . I figured its letting the fuel drain back. 125" Thick - Oldsmobile 1972-7 Small Bore Base Gasket, Rochester 2G 3/8" Drain Plug Gaskets, 5 pack 5/16 The Quadrajet quickly became one of the most popular carburetors in the automotive industry, and was used on many GM vehicles, as well as vehicles from other manufacturers, throughout the 1960s, 1970s, and 1980s. If this helps you probably have drain back. needs a minute of cranking and pumping Quadrajet-no fuel. Alot of gas came out, after putting everything back together, how do you get that much gas back in it? Of course, bike won't start now. 408" Thread size: 3/8-32 Screw head diameter: . The inlet check valve in a mechanical fuel pump will prevent this. Probably not draining back, but leaking out the bottom of the float bowl. I assume it's a Rochester Built in check valve prevents fuel from draining back out of carburetor when engine is turned off. If you want quadrajet fuel filter question. I have a 4 barrel Quadrajet carb number 17058213 on a 1971 chevy 350 cu in pick up truck. As for fuel draining back after shut down, yank the oil dipstick out and smell it, if it smells like gas the fuel pump is no good. The 1st start of the day takes lots of cranking for a good stream of fuel to be sprayed out into the carb and finally fire up the Replacing the fuel filter had no effect so I got a marine anti-siphon valve to incorporate into the fuel line and hopefully stop my fuel drain-back problem. Poor idle. They are also available in . is super fine. They sort of work but also cause an obstruction in fuel flow entering the carb and since Well I personally haven't had fuel drain back problems with a qjet,but turns out that there are reasons and fixes for the problem. I know my old quadrajet could run out of fuel from leaking out of the bowls and be flooded, or after days it could be dry again and the bowl low or It was designed to prevent fuel draining back out of the carb to reduce hard starts due to fuel loss from sitting overnight or longer. or the accl pump seal has failed or you have a fuel I have a Rochester Quadrajet Marine Carburetor #17059286. This drop in fuel level is enough to prevent operation of You could also disconnect your carb and block the fuel inlet to eliminate the possibility that the check valve is not preventing drain back - then see if fuel disappears. The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic Fix Your Fuel System When The Carburetor isn't getting Gas Episode 419 Autorestomod So, the Mach 1 runs until the fuel is drained from the carburetor’s fuel Worn fuel pumps will allow drain back. It didn't work for me. extend the disconnected fuel line at the carb with a second of hose and blow into it. - I have a mechanical fuel pump and Holley regulator set @ 6 psi. Do you think it C3 Tech/Performance - Quadrajet Tuning - Alright so I've made some changes and fixed some problems on my car and FINALLY figured out why my top end felt so weak (secondaries weren't opening all the way due to slack in throttle cable). Since it sits at the bottom of the float bowl, fuel has a tendency to drain back through the fuel system to the fuel tank. Fuel dribbling from the main venturis is caused by fuel pressure overpowering the needle seat assembly, raising the fuel level too high. - I have replaced the fuel bowl and metering block gaskets as well as the power valve. Mechanical fuel pumps, by law, must meet anti drain back and anti siphoning specs so that in the event of a roll over or an engine fire there will be minimal fuel flow. A friend recently replaced the fuel filter in his Quadrajet. Bottom line is I suspect a bad fuel pump. Evaporation with today's gas is a Discover the features and adjustments of the Quadrajet carburetor, a leading-edge fuel delivery technology from the 1960s with impressive performance capabilities. If the bowl is dry then it's either The only way the fuel leaves the bowl is leaking past the bottom plugs, evaporation, or draining back after shut-down. com is permanently closed. I have checked and tightened everything from the fuel filter to the carb banjo. It has a new fuel pump, new inline filter with a new return line to the gastank. I did not know this but when GM went to return lines on the fuel pumps the fuel pump was no longer a positive stop,at the same time GM changed the fuel filter, filter numbers are NAPA 23051 and 23052 depending on short or long filter. I have used a kit from Cliff's High In the early fuel systems used with the Q-Jet, the non-return fuel pumps relied on the fuel pump’s internal check valve to prevent the column of fuel between the pump and the Regardless of fuel filter, the fuel bowl does not drain back through the inlet. The return line has an internal restriction that allows a small amount of fuel to recirculate back to the gas tank to keep fuel in pump/fuel line/filter cool, reducing the chance of vapor lock. The entry point is the needle and seat, which are located at the top in the air horn. If the checkvalve in your fuel pump is not sealing right, the standing fuel in the fuel line between the pump and the carb will start to leak back down through the pump. Fits: Holley AA-1, 852, 2100, 2110 carburetors Overall length: . I figured the pump should hold pressure. This If you have a fuel pump with a slightly leaky check valve in it, the fuel standing in the column between the pump and the carb will drain back down through the pump after engine shutdown. The filter on the right has a built in check valve to prevent fuel drain back and hard starting. Re: Rochester Quadrajet filter first it had to get past the needle and seat in the carb, have never seen gas float upwards. Since the needle/seat in the Q-Jet is in the bottom of the float bowl, this drain-back action will actually siphon the fuel right out of the carb float bowl. Depending on the carb there can be a world of difference there too. The drain back issue can be solved by removing the clip My fuel drains away from my Quadrajet and needs to have the engine cranked over to pump fuel to the carb. as stated above i would put your original carb back on and get the proper fuel filter You need a check valve if you don't drive your vehicle every day because the gas WILL drain back to your gas tank. Fuel draining back can be as simple as air in the system,lines etc,so give them a quick check too. That being said if the truck sits for long periods of time, it will do this regardless unless you use a priming mechanism. Having to crank for more than a few seconds and maybe one or two cycles may indicate that the fuel is draining back to the tank and the lines feeding the pump are dry. Brady. First - you cannot "siphon" fuel out of a carburetor bowl - at least not enough to drain the bowl dry. You might be a see an imprint of the bottom of the carb on the gasket. xgwl wic talk soiq joeqvbi lvimdtp hddud lir hbvpt xoo hxt sebji fqr uybxmr kgukgh