Fuel seems to drain out of the line?

[Jerblazer72]

Hi everyone,
I have finished (mostly) the frame off restoration of my 72 GMC and abm a bit perplexed with the fuel getting to the carb. Here is the set up: Blazer tank relocated to the underside of the truck bed. Filler door modififcation to be behind the rear marker light. Vent line attached and run to above the filler so that fuel will go into the tank easily. Truck was set up at the dealer with auxillary tanks. Not back in yet, but using the original tank selector switch (mechanical). Edelbrick mechanical fuel pump, new flexible fuel line from pump to the carb. The truck runs fine once I crank on it for 10 seconds till the fuel gets to the carb. If it sits more than a day its at least 10 seconds of cranking on it till it gets fuel up there to run. Once its there it runs no problems. What do I need to do to prevent the fuel from draining out of the line when it sits? Thanks.

[cleszkie]

Are you sure that fuel is draining out of the line? Sounds like the fuel may be draining out of your float bowls. Even if all fuel drains out of your fuel line, there should be enough fuel left in the float bowls to start the truck and get the mechanical pump working to fill the line before the bowls empty. I don't know what carb you run, but it is not uncommon for this to happen on q-jets. a simple rebuild fixes the problem. Good luck.

[cdowns]

no spacer allows carb to heat up after turning engine off and fuel evaporates due to heat transfer

[j ripper]

If you have a q jet I would pull the carb apart and seal off the 2 plug holes on the bottom of your bowl. I just did this with some J B. Tap and thread plug would be the smartest way to go about it. Here is a pic. It's the 2 in the center also the 2 to the left in the pic. I would use arrows but I'm not that advanced!!


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[harrdawg54]

I have an Edelbrock 1406 and am having the same issue. I don't know what model you are running but I have to keep a small can of gas in the bed of my truck so I can get it to start if I let it sit for more than a couple of days. A fix would be nice.

[rsavage]

If you are running an airstone type filter in the carb, replace it with a paper type filter as they have a little rubber flap that acts as a check valve preventing the gas from draining back towards the pump. Worked for me.

[Jerblazer72]

Sorry for not getting back to this sooner, business trip got in the way. I am running edelbrock 1406 and has been completely rebuilt.

I do not have a spacer on it so that may be the issue, it has been running a bit hot 220 degrees. (I think i need a new radiator) did the electric fan upgrade and its not cooling enought. Thats for another thread.

rsavage: the filter in the carb is just a fine mesh cylinder type that fits into a space just inside where the fuel line connects. Not sure what an airstone type filter is.

Perhaps I will add a spacer to the intake manifold and see if that solves the problem. Thanks for the comments. Will keep you posted if the spacer fixes it. Any ideas how thick I should go on the spacer?

[rsavage]

Take the carb filter to your local NAPA or auto parts and get a paper type filter the same length. There should be a spring in the filter housing. Look in at the inlet end of the paper filter and you will see a rubber flap that will prevent drain back to the fuel pump. The spacer gasket is about 3/8" thick as a guess without going out to the garage to measure one.

[bubba353z]

You could put a check valve in the fuel line between the tank and the pump to prevent gravity from draining the line - or go to an electric fuel pump.

[GuyO]

Hi guys, I am having a very similar situation with my Edelbrock 1406 (which is new) but only after the engine is warm. First I replaced the fuel filter, that didn't work. Then I replaced the fuel pump because when the engine is idling I had little fuel in the glass filter and 0 -1 psi at the fuel pressure guage with engine warm and idling. Eventually, like CDowns said I bought the 1" phenolic spacer to reduce heat sink evaporating gas from the bowls but I still have the same problem but only when the engine is warm! I have excellent pressure when cold, I don't get it?? It must be the plunger rod that activates the pump gets hung up when the engine heats. It drives fine, can drive for hours but at idle the fuel "dissapears" or is very low in the filter and pressure drops. Thoughts? G.

[1972RedNeck]

Mine does the same thing. I just crank on it.

[GuyO]

Well, it appears that a mechanical needs to be primed. I did not know this and swear I never have done it before. However, after 2 new mechanical pumps I bought a electric pump for a 72 Blazer and plumbed it in series. Meaning that I have it pumping to and through the mechanical pump. It pulled from the poly tank, through 2 filters the mechanical pump and loaded the floats of the Edelbrock 1406 and my engine fired. Because I need to adjust my lifters and have my covers off, I did not start the engine and hooked up my under hood starter. While cranking the engine I noticed my fuel pressure gauge jump up to 7-8 lbs WITHOUT the electric pump! I let it rest a while and did some other tasks, came back and the pressure gauge dropped to 0, so I squeezed the remote starter trigger and the engine cranked, and the fuel pressure gauge jumped right back up to 7+ lbs!!!! Why would a mechanical pump need to be primed? Also, as I had sucked gas up through the line from 2 different sources to check for flow the mechanical pump did not build pressure. Wouldn't this have primed the mechanical pump?Anyone have any input?? This was very frustrating!! Guy