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New problem - bad fuel pump?

AbramJ

AbramJ

1/2 ton status
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Location
Tempe, Arizona
First, thanks all who helped me with my other thread about the ticking noise (loose rockers). I've been driving the truck around the neighborhood the last couple weeks and then last week got a 30 day temp tag. I've driven the truck on the main roads now several times in the last week with no issues.

Yesterday my brother came over and we drove the truck around the block and just as we were pulling back up to the house it died like it wasn't getting any fuel. I jumped out (my brother had been driving) and watched as he turned the truck back on. I have one of those clear filters between the hard line from the tank and the fuel pump. Normally when the truck is running you can see the gas moving through the filter, but there was no movement and the gas level in the filter would drop when the truck shut off.

Last month we replaced the following with all new parts:
Fuel tank
Sending unit
Rubber fuel lines
Fuel pump
The clear view filter I mentioned above
Hardline between pump and carb
And I had the carb professionally rebuilt
We also blew out the fuel hard lines on the chassis a few times with compressed air before we installed any new parts

Engine is a carbureted 350sb. Is it possible the fuel pump went bad? Or is there something else I should look at? The truck was running the best it has in years up until yesterday, so I'm pretty frustrated that it's having issues, again.
 
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Welp, in my case the fuel gauge reads half a tank when it’s empty. Found that out the hard way... hahaha
Are you sure you have fuel in the tank, push the truck back and forth, listen for sloshing.
Fuel lines do have a return.
 
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Seems unlikely that you could be drawing air through your lines since you just replaced the rubber lines, possibly a small crack in the hard lines, I'd check the lines pretty close
 
1300obo said:
Seems unlikely that you could be drawing air through your lines since you just replaced the rubber lines, possibly a small crack in the hard lines, I'd check the lines pretty close
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I would double check the fuel lines too. Secondly it soounds like your pump is leaking off after shutdown which it shouldn't. You can also bypass the stock fuel system with a short piece of hose from the pump input to a can of gas. That will confirm the pump is working properly.
 
Start at the pump and work yourself back checking for any leaks or loose fittings. Do like what Skunked said with a hose and jerry can to rule out the fuel pump. I have had them go bad very very quickly before. Maybe the sending unit doesnt match the gauge? I know for temp gauges the resistance has to be same between the gauge and the sending unit. A 300 degree gauge has to have a 300 degree sending unit other wise it reads wrong.
Joel
Norcal
 
Thanks for all of the suggestions, it gives me something to do this weekend/next week.
 
Alright, I had time to check some things on the truck today. I filled up a Jerry can at the gas station and got some 3/8 and 1/4 fuel line and another Clearview filter.

I disconnected the rubber lines from the pump and attached my temp lines from the pump into the Jerry can. The truck fired up and gas was moving as you'd expect it to and the fuel filter was full. It looks like the pump is still good.

I reconnected the lines and moved to the middle of the truck where there are rubber lines between the two lengths of hardline. Disconnected the rubber lines (had to clamp the end of the supply line because gas kept pouring out, I'm guessing because there was enough siphon pressure still in the line to keep drawing fuel?) and hooked up my temp lines. Truck fired up as before, but I noticed this time the fuel filter at the Jerry can never got more than about half full, the fuel filter in the engine bay was similar situation.

Both times I pulled the return line out of the Jerry can enough to see the end and gas was coming out without issue.

I then reconnected everything and ran the truck, again fired up no issues. I decided to replace the fuel filter on the engine bay with the new one I was using for the test and went ahead and replaced the rubber supply line between it and the pump.

Later this evening I took the truck out and drove it the exact same way my brother had when it died last week. The first time I really got in the throttle it seemed to slug down and then backfired out of the carb and went back to normal. I drove it the exact same route around the block two more times with no issues.

I parked in front of the house to see if completely stopping and letting it idle would cause it to quit, but it kept running fine and I pulled it back into the garage with no issues. Although I did notice after I shut it off that it looked like something was smoking from the back of the passenger side valve cover, and out of the breather tube coming out the top of three cover that's normally attached to the air cleaner. I couldn't see any oil leaking so I'm not sure what that was about.

That was about 2 hours ago and looking at the Clearview filter in the engine bay I noticed it's only about 1/4 full again, when before it'd be pretty much full. I'm not exactly sure what to check now.

I know some of you mentioned an air leak, how do I test for that?

I'll try driving it tomorrow and see if the quitting issue happens. (I jokingly told my wife maybe the truck was suffering PTSD and having flashbacks to how poorly my brother treated it when he owned it so it was giving up to get him to stop driving it)
 
Normally an air leak would be from an old hose or split. Possibly you have a crack in a hard line. I would think it would damp when engine is running. Gonna say double check all the new rubber lines, and clamps.

The back fire symptom may be a low float level, or accelerator pump not moving enough fuel. Sounds like it went lean when you goosed it.
 
I took the truck for another drive just now (my preferred time to test as there's no traffic this early (230am)). I drove it for about 45 minutes with no issues. I made sure to do some stop and go at intersections, left/right turns, fast/slow.

I'm not sure my fuel gauge is reading correctly; I tested the gauge a couple weeks ago, though, and it seemed to be reading correctly then. Maybe the sending unit isn't sending the signal right? I don't know. At any rate I put about 18 gallons in even though the gauge was reading about 3/4 before I filled up (40 gallon tank). Now it reads full. Unfortunately I didn't think to test the new sending unit before we installed it and the new fuel tank.

I'm going to look over the fuel lines when it gets light out and see if I can find any issues. The hard lines were the only things I didn't replace, but now I'm thinking I should've bit the bullet and paid the oversize shipping to get new ones.
 
Like I stayed earlier, rock the truck and listen for sloshing in the tank and make sure you have fuel or enough fuel to get deeper slosh.

dont rely on the fuel gauge at this point.

check inline tube for the hard line.

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AbramJ said:
Thanks again, I'll look into that.

As an aside, took the truck through emissions today, passed, and finally got it re-registered after almost 7-8-ish years.
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You’re in Tempe? I’m over in Gilbert. Bring that truck by.. hahahah

We can let them idle in my driveway, making the neighbors crazy..
 
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