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Old 09-13-2019, 08:01 PM
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Hard start won't idle disconnect fule pump idles great

I have a 350 SBC with a 671 blower. after sitting for about 1 year I went to start it last weekend and it wouldn't start. After several attempts, I believe I flooded it. So I took off the air cleaners and let it sit for a while and started checking some things out and discovered a few plug wires that were burnt from the exhaust. I changed those and gave it another try, I was able to get it to fire after several attempts and got it to run but was acting like it was getting way too much fuel wouldn't idle. Lots of black smoke out of the exhaust and it died again. I believe I flooded it again trying to get it started again, so I disconnected the fuel pump and attempted to start it again, it fired off and ran perfect as well as idled great until the fuel ran out. I did this twice. So if I have the electric fuel pump on it seemed as though it was getting too much fuel but once I disconnect the fuel pump it ran great. I have 7.5 PSI and has always ran perfect until now. Does anyone have any ideas what my problem is? Any help would be appreciated.

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Old 09-13-2019, 08:35 PM
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Floats are stuck
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Old 09-14-2019, 08:25 AM
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extra fuel

can u just try to tap the ea carb, say with the plastic end of good size screw driver. don't be gentle but don't break it either.
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Old 09-14-2019, 10:33 AM
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What carbs? If they're Carter AFB's or Edelbrock, they will only tolerate 5 psi max fuel pressure.
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Old 09-14-2019, 11:55 AM
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After sitting for a year the fuel dries out leaving behind sticky and in some cases gritty residue. This stuff if in the float valves of the carburetor or the float hinges or under the power valve seats of a Holley result in flooding the fuel bowl or leaks into the main metering circuit.


Even fuel saver additives don't help this over that much time.


7.5 psi is a lot for a carb they are happier at 5 to 6. For a blower motor using an electric pump there isn't a way to boost reference the pump as with a engine driven mechanical pump.


The way I do electric pumps is to use a high volume, high pressure pump that can at peak deliver more fuel that the blower at WOT can consume. Then use a bypass regulator or two as volume and pressure drops dictate to provide the flexibility of fuel volume needed between unboosted idle and full boosted WOT. Since carburetors are pressure sensitive the trick is to vary volume with varying pressure.


The bypass regulator provides this function by controlling the pressure at a steady state through bypassing the unused fuel portion based on engine consumption back to the fuel tank. Sp there is no need to run excess fuel pressure to cover the WOT boost condition.


One can use a self regulating pump, the problem with these is that the internal bypass keeps immediately rerouting the pump heated fuel back into the inlet side not giving it a chance to cool. At idle and cruise this can lead to some very hot fuel that will easily flash to vapor when the pressure is released such as passing through the inlet seat and valve of the carb.


Bogie
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Old 09-14-2019, 03:08 PM
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Yup, floats must have been stuck, a little tap on the sides of each carb did the trick and it is running great again. Thank you for the advice, I appreciate the help on this forum.
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Old 09-15-2019, 09:36 AM
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BogiesAnnex1

excellent recommendations !
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Old 09-18-2019, 01:10 PM
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Quote:
Originally Posted by BogiesAnnex1 View Post
After sitting for a year the fuel dries out ......


The way I do electric pumps is to use a high volume, high pressure pump that can at peak deliver more fuel that the blower at WOT can consume. Then use a bypass regulator or two as volume and pressure drops dictate to provide the flexibility of fuel volume needed between unboosted idle and full boosted WOT. Since carburetors are pressure sensitive the trick is to vary volume with varying pressure.....

Bogie
This paragraph should read:

The way I do electric pumps is to use a high volume, high pressure pump that can at peak deliver more fuel that the blower at WOT can consume. Then use a bypass regulator or two as volume and pressure drops dictate to provide the flexibility of fuel volume needed between unboosted idle and full boosted WOT. Since carburetors are pressure sensitive the trick is to vary volume without varying pressure.

Bogie
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Old 09-18-2019, 06:03 PM
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The carb(s) may need cleaning. If they had fuel in them while the car sitting up, it may have turned to goo and clogged up various passages. If the engine fires up and runs with the pump off, that suggests the pump pressure forces a very rich condition. You may need to replace the needles and seats, which might not be seating because of the varnish. Anyway, going thru your carb(s) is a good starting point. Good luck.
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