Author Topic: fuel drain back issue  (Read 17335 times)

Offline screamin86

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fuel drain back issue
« on: September 29, 2010, 01:42:55 am »
been having a issue with all the gas draining back out of the fuel line/filter going to my 1406 edelbrock carb. i ran this exact carb on one of my trans ams and it sat once for a month before i noticed the fuel draining back to the tank. it wouldnt bother me so much but it makes for a pain when starting. the carb does need a rebuild i do know but i can fire it up and it with high idle for 2-3sec then die then  i have to crank it again for a few seconds until gas gets back to the carb. sometimes i have to crank it for awhile for it to even try to start. i have a new fuel pump and gasket thats maybe 2 months old then into a clear plastic filter that i got from federated autoparts then to a fuel pressure regulator mounted on the firewall then to the carb. ive got the rebulator on because i was getting around 6.5-7lbs of fuel presure with the replacement fuel pump. with winter coming up id like to get this issue kinda sorted out. i plan to rebuild the carb hopefully sometime in november (already have the kit and jet/rod kit) since thats when we will be in our new house and ill finaly have a garage :D.

here is a picture of how its ran and come to think of it i didnt start having this problem till i put the new heads/intake on which i was finishing in this picture.
86 k10 lwb 4x4:350 .040 214/224 444/466 112lsa performer rpm 1406 lt's summit racing th350 2800stall
03 yukon xl:tint debadge full boltons
86 ta:lm7 hot cam boltons

Offline Irish_Alley

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Re: fuel drain back issue
« Reply #1 on: September 29, 2010, 06:10:11 am »
i always thought it was from a leak somewhere maybe in the carb to see if its there get fuel back all the way to the carb and take the line off put a bolt in it and let it sit the same time it would normally take it to flow back and see what it does
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Offline Captkaos

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Re: fuel drain back issue
« Reply #2 on: September 29, 2010, 04:09:04 pm »
I would say you have a leak on the carb.  The bowls are becoming empty which is why you have to reprime it.
For a test, put some gas in the bowl and see if it starts back up.

Offline screamin86

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Re: fuel drain back issue
« Reply #3 on: September 29, 2010, 05:09:11 pm »
Ill see what I can do tomarrow hopefully. Its been sitting on a hill in the yard since sunday and been pouring down rain everyday :/ but it should be well and empty by now lol
86 k10 lwb 4x4:350 .040 214/224 444/466 112lsa performer rpm 1406 lt's summit racing th350 2800stall
03 yukon xl:tint debadge full boltons
86 ta:lm7 hot cam boltons

Offline Blazin

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Re: fuel drain back issue
« Reply #4 on: September 29, 2010, 08:56:27 pm »
Just make sure its not leaking into the engine. Eventually it will over fill your oil.
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Offline fred75

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Re: fuel drain back issue
« Reply #5 on: September 29, 2010, 09:01:46 pm »
  Fuel draining from the filter is normal. There should be enough fuel in the bowls for the truck to run long enough to fill the lines and bowls. I'd check the two float levels. This one drains all the fuel back from the filter pretty quick, especially when it's hot. But those bowls are plenty big enough to run the truck long enough to get fuel to em. Is the hard start hot, cold or both?
'82 C-10 305/TH350-TCC EDL PERF INT W/1406 AFB MSD-6A HDRS

Offline screamin86

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Re: fuel drain back issue
« Reply #6 on: September 29, 2010, 09:17:32 pm »
Mainly hard start when its cold sometimes when its hot but not very often. The plugs don't look bad no carbon deposits but dang does it smell strong of gas while running but no smoke.I run autolite 26 plugs gapped at .035 no carbon deposits have a good color on the plugs. I need to check my timming I set it up by ear and feel when I put the new heads on but I did tune the carb with a vac gauge pulling about 16 on the gauge. The carb has stock size jets and rods but I can't remember what spring I put in it I changed it once when I had that carb on my car but I will say if I back down into my moms yard which is on a small hill it will start to bog.
86 k10 lwb 4x4:350 .040 214/224 444/466 112lsa performer rpm 1406 lt's summit racing th350 2800stall
03 yukon xl:tint debadge full boltons
86 ta:lm7 hot cam boltons

Offline fred75

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Re: fuel drain back issue
« Reply #7 on: September 30, 2010, 08:08:32 pm »
  Hard start cold, assuming the electric choke is workin right; I'd definitely check the float level. Should be 7/16. I noticed you said earlier you had new needles and jets, which way you goin, richer or leaner? Smell strong gas while it's runnin, sounds like a fuel leak somewhere.
'82 C-10 305/TH350-TCC EDL PERF INT W/1406 AFB MSD-6A HDRS

Offline Swims350

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Re: fuel drain back issue
« Reply #8 on: September 30, 2010, 08:40:13 pm »
I had that happen before I just took the fuel tank return off the pump and plugged both ends with a bolt.

I'd check as they said bolt in the line and such to see if the line or anything else is leaking, if it leaks with the line off, I'd plug the return line and try again, if it doesn't leak with the line off, has to be the carb.
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Offline screamin86

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Re: fuel drain back issue
« Reply #9 on: September 30, 2010, 08:47:24 pm »
The kit I have is a generic performance kit for the 1406. Jets rods and springs.
86 k10 lwb 4x4:350 .040 214/224 444/466 112lsa performer rpm 1406 lt's summit racing th350 2800stall
03 yukon xl:tint debadge full boltons
86 ta:lm7 hot cam boltons

Offline fred75

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Re: fuel drain back issue
« Reply #10 on: October 01, 2010, 08:40:42 pm »
I had that happen before I just took the fuel tank return off the pump and plugged both ends with a bolt.

I'd check as they said bolt in the line and such to see if the line or anything else is leaking, if it leaks with the line off, I'd plug the return line and try again, if it doesn't leak with the line off, has to be the carb.

  Yup, those mechanical pumps are designed to drain back to the tank. Safety feature. Plug the return and I agree, should not drain back. Starts and dies, not enough fuel in the bowls, assuming the regulator is not restricting the flow. Those lines do add more distance for the fuel to travel, not sure if that's enough to make a difference? Also if the bowl vents or air bleeds were clogged, it would run rich. But you said the plug color was good. Just thinkin out loud about the fuel smell.
'82 C-10 305/TH350-TCC EDL PERF INT W/1406 AFB MSD-6A HDRS