No fuel to carb

[Lu Blunt]

I’ve been driving my 79’ Chevy k30 350sbc without any engine trouble the last 5 years. When I first got the truck I swapped a Holley carb in place of the leaky quadrajet. Today the truck seemed to sputter on n off at anything above 3k rpm. It kept getting worse till the truck wouldn’t run at all and I was stuck on the side of the road. I added 5 gallons of gas to the tank which already had gas in it, I replaced the fuel pump with a new one. The fuel filter is new. I cranked the engine till the battery died then cranked till the jump box died. Motor never tried to start just turned over. When I actuate the carb the jets don’t spray any fuel. Any ideas??

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[Dmack]

Strainer sock on the pickup tube could be clogged, or the tank switching valve could be stuck between ports. I would bypass the valve and plumb straight from the tank to the pump and see if fuel flows.

 

[Bextreme04]

a cracked or loose line between the pump and tank could also be the issue

 

[Big Chip]

Or collapsed fuel line. You could also try some compressed air blowing back towards the tanks to see if there’s something stuck in there.

 

[Lu Blunt]

I’m headed back down to the truck this morning. I’ll bring a gas can and rubber fuel hose and plumb the pump straight into the gas can. If that doesn’t work I’ll double check the new fuel pump

 

[Lu Blunt]

Ran a hose from the fuel pump to a gas can and cranked n cranked n cranked then it finally started and drove the short trip home. I’ll inspect the fuel line to the tank and check the fuel pick up in the tank. Been planning a big block swap with an efi tank maybe it’s the time to start

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[Lu Blunt]

Only one tank has worked since I got the truck so I plumbed the good tank straight into the hard line. Also I’m going to replace the rubber hose with new and add a filter between the tank and pump.

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[Lu Blunt]

Got the fuel lines cleaned up and truck seemed to be running like normal. I drove 50 miles to town without any trouble. On the way home the truck struggled to hold 65mph. It wasn’t running rough just seemed down on power. I pulled over about half way home n checked things over but nothing looked wrong and engine temp was ok. When I pulled over the truck idled fine. Let it sit there n idle for like 5 minutes then back on the interstate. Seemed alittle better but not for long. Could barely hold 75mph then 70 then 60. At 50mph I down shifted to second and screamed off the exit ramp. Power seems ok in 1st n 2nd but a complete dog in 3rd. I’m not sure if it’s getting enough fuel. I bought an electric fuel pump to put between the tank and the mechanical pump. A couple of my other old trucks have helper style electric pumps and they seemed to run well. Been driving the 79’ k30 for 5 years and never had engine problems untill now

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[Lu Blunt]

I installed the electric pump and spent a while test driving the truck. Seems like the engine doesn’t like the electric pump on when you’re going real slow in granny or reverse. It’ll just die instead of lugging the motor. So I drove for while with the electric pump off. After the motor was warmed up sometimes it will sputter trying to maintain speed or if under load so I turned on the electric pump and it seemed to help it run better. Not necessarily more power but kept it from struggling as much. Might try to bypass the mechanical fuel pump n run the electric pump full time. I’ll test drive some more tomorrow

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[bedwards]

Looks like your running two fuel filters under the truck and if you have a quad there is a third one there in the inlet on it. Might be too much restriction.

 

[Madhorn]

Some holey carbs have a bronze filter just inside the fuel line input port on the forward bowl, sometimes they get plugged up.

 

[Ricko1966]

Okay I'm having trouble with that pic.Inlet of the electric pump should be lower than the fuel level.Outlet of the electric pump should be slightly higher than the inlet height.Last fuel delivery issue I had with my truck was the fuel pump lobe on the cam was wearing off a brand new pump fixed it temporarily but as the lobe continued to wear. I still wasn't getting enough fuel. It was a head scratcher for a minute until I held the Push rod in place with 1 finger, and cranked it with a remote starter button.Bedwards has a good point maybe your original fuel filter in the inlet of the Qjet is plugged up.I had to go to an electric pump but that's a whole nother night mere.I don't know how you wired that pump, the way I would is use a cheapy accessorie relay, fuse terminal 30 run it to battery + , run 87 to your pump + , ground the other pump wire, run 85 to the alternator exciter wire ground 86 that way your pump will only run if the engine is running.

 

[Lu Blunt]

There’s a filter on the inlet of the electric pump and edelbrock recommends a filter between the pump n the carb so I have an inline filter right after the electric pump. I checked flow where the lines meet the mechanical pump and seems to push gas no problem. so I don’t think the inline filter is restrictive. No filter between mechanical pump and carb

I replaced the original qjet with a Holley when I bought the truck. I will check for a bronze filter.

the electric pump is level with the fuel lines on the frame rail. Not as low as the bottom of the fuel tank but close enough to test. Instructions didn’t say to mount the outlet higher than the inlet.
https://static.summitracing.com/global/images/instructions/EDL-17301_17302_17303-Micro_fuel_Pumps.pdf

I haven’t considered cam lobe wear. But that seems possible. Motor has unknown mileage, there has been a ticking from the motor that comes n goes, can almost hear it in the exhaust. I’ll check closer to see if the mechanical fuel pump is making the noise. I’m going to test bypassing the mechanical pump before I buy a block off plate. I wired the electric pump according to the instructions.

I had the electric fuel pump wired to the ignition so my plan yesterday was to run the electric pump full time and drive like normal untill something happened. I creeped the truck around the yard n loaded it with scrape for a trip to town. Drove down the mountain 15 miles to get gas n drove another 40 miles to town. Truck never skipped a beat untill I got off the interstate. It would idle fine but if I let off the clutch it would die. I unplugged the electric fuel pump and truck drove great around town. Getting back on the interstate the truck immediately struggled to maintain 50mph. I pulled over and plugged the electric pump back in and the truck drove home no problem.

 

[Lu Blunt]

Maybe these will help

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[Bextreme04]

Have you checked to see what kind of junk you might have in the tank? If you have a bunch of junk floating around in the tank it could easily be causing all of your problems. I'd also look at the sending units to make sure you were getting a good vent to the tank.