Gas drains back

[Marlar]

After discarding a BG carb and replacing with an Edelbrock, the "65 327ci 365 hp(close) runs awesomely. However, after sitting for a day or so, I see that the gas has drained back beyond the glass fuel filter and is difficult to start. Do I have an air leak or something that allows the gas to drain back? There is no gas leak that I can see or smell.

 

[Marlar]

No suggestions? This is the fitst time one of my dumb questions has not gathered a definitive answer.

:confused

 

[Tom]

I am having the same problem with my 1965, 300/327. I haven't done anything with it yet. I am going to start with making sure all the fuel connections are tight. This just started a few weeks ago.

 

[Marlar]

I am having the same problem with my 1965, 300/327. I haven't done anything with it yet. I am going to start with making sure all the fuel connections are tight. This just started a few weeks ago.

Maybe someone will rescue us:eyerole

:W

 

[Viet Nam Vett]

Maybe someone will rescue us:eyerole

:W

Well..not an expert like John Z ...But ....The fuel should not drain back to the point where the line from the fuel pump to the carb is empty..as far as I know. There should be some fuel left in the line.

What comes to my mind based on your discription is a bad diaphram on the fuel pump. Now..I'm not trying to freak you out here...I'm only suggesting that you pull your oil check dipstick and smell check it for a gas smell.

It is possable that the diaphram is leaking and gas is leaking into the crankcase. If so.....Of course don't run the motor.

Disclaimer......There could be I'm sure other things causing this. Others will jump in here with more suggestions and things for you to check. So my suggestion is not necessarily Correct.

Be patient...sometimes it takes time for your post to be seen..

Good luck..

 

[John Mcgraw]

There is a check valve in the pump which keeps the fuel from draining back, but I do not think that that is the problem. The float bowls would still be full of fuel even if this line drained back, and the car should start up right away. This sounds like the float bowls are draining down into the engine after shutdown. This was a real problem with Q-jet carbs, since the plug in the metering well leaked on almost every Q-jet ever made. I do not know enough about the construction of the Edlebrock carb to offer the solution, but it is clear that the bowls are draining down. The bowls can not be sucked back down by a draining fuel line since the bowls fill from the top of the bowl.


Regards, John McGraw

 

[paul67]

You've really stumped me. On the Edelbrock the gas inlet is well above the bowls. I can't see how gas would drain back. As John mentions, Q-Jets are notorious for bowl leaks but I have never heard of that problem with Edelbrocks.

 

[Marlar]

Viet, John Mcgraw, paul67:

Thanks for your thoughtful replies. The new Holley fuel pump did not go on at the same time as the new Edelbrock carb. But it ,of course, could be faulty. I will check the oil for gas odor. If the check valve in the pump is faulty or has a bit of trash holding it open, the only way I see to check that is to pull it off, attempt to flush it and reinstall. It can be a bear to install, but possible. According to my local parts store, there is one company that actually makes an inline check valve. They are really proud of them at $70. If I go that route, I think the best place to install it would be as near to the fuel pump as possible. Agree?

;help

 

[Marlar]

Opps. I forgot to say that the carb has a mechanical choke which is not yet hooked up. I am using a repaired passenger side vent cable to hook it up. This should be done this weekend. This likely contributes some to the hard starting, but not all of it. I am of the mind that I can't see how the bowels can go dry because of the way the fuel is delivered (from the top).

:bang

 

[paul67]

I am beginning to wonder if you really have a problem. As my filter is metal, not glass, I cannot see inside to determine if it is full or empty after sitting for a day or so. But with the electric choke it starts right up after a couple of cranks. I tend to take the simplest and most inexpensive steps to repairs. In your case I would get the manual choke hooked up and go from there. That may solve the problem. I would imagine that even in a warm area such as GA some choke function, albeit it brief, is necessary for a cold engine start.

 

[Viet Nam Vett]

Viet, John Mcgraw, paul67:

Thanks for your thoughtful replies. The new Holley fuel pump did not go on at the same time as the new Edelbrock carb. But it ,of course, could be faulty. I will check the oil for gas odor. If the check valve in the pump is faulty or has a bit of trash holding it open, the only way I see to check that is to pull it off, attempt to flush it and reinstall. It can be a bear to install, but possible. According to my local parts store, there is one company that actually makes an inline check valve. They are really proud of them at $70. If I go that route, I think the best place to install it would be as near to the fuel pump as possible. Agree?

;help

Just to be sure it's not starting hard because of what you say is a lack of fuel... I would Pop the air cleaner and look down into the carb primaries..
and pump the throttle linkage.

It you see fuel squirt out from the accelerator pump into the carb venturi area...then I would say your fuel bowel has fuel and enough to start. Perhaps it's a choke problem..

 

[John Mcgraw]

I think that you are still chasing the wrong problem. You started out by saying that after sitting, you car was hard to start, and that you thought that the fuel was draining back down to the pump.

The car would not be hard to start even if the fuel line did drain back down. As long as the fuel bowls are full, the car should start right up, and should replace the fuel that drained down from the line almost instantly. If, however, the fuel bowls are empty, the car will fail to start until the engine has cranked enought to fill the bowls to sufficient level to feed the main jets.
The fuel draining down in the fuel line, WOULD NOT drain the float bowls. The bowls would only drain down if something was wrong with the carb, and it was allowing the gas from the float bowls to drain into the intake manifold on shutdown. Edelbrock may use the same crappy design that was used on the original Q jet, with the main metering wells being sealed off by a lead plug in the bottom of the well, but I do not know for sure, since I have never used one. The fact that the problem started when you put the carb on should be a clue.

You should be looking at the carb and not fixating on the fuel supply line from the pump. The fuel draining from the float bowls will cause dramatically increased wear due to oil washdown on the cylinder walls, and will end up in the crankcase diluting the oil. If the car is not starting because of empty float bowls, you need to fix this problem ASAP! You can put in an electric fuel pump, and it will mask the problem since it will refill the bowls as soon as you turn on the switch, but it will not fix the base problem. In any case, NEVER install an electric fuel pump where it is feeding a mechanical one, as this is a recipe for disaster. I am not saying that your line is not draining down, as it may be. What I am saying is that the symptoms you describe, would not be caused by the line draining down.

Regards, John McGraw

 

[Marlar]

Hopefully, I will get the manual choke hooked up tomorrow. In the meantime, I had rearranged the fuel line(a flex) and had the clear fuel filter horizontal. It had not drained this time and the engine cranked fairly quickly. Interesting. If this continues I will conclude "no problem" and quit trying to fix it. LOL.

All of your suggestions have helped me very much. Thank you.

 

[JohnZ]

Ditch the Bubba glass fuel filter with the rubber hoses and clamps - it's an engine compartment fire waiting to happen. :ugh

 

[Viet Nam Vett]

Ditch the Bubba glass fuel filter with the rubber hoses and clamps - it's an engine compartment fire waiting to happen. :ugh

Listen To What John Z says above. You can lose your Corvette in a HeartBeat to an engine fire..!!! Install the Factory type set up. You should be running a metal filter with steel lines from the pump. Ditch the hose clamps and use the flared lines with screw in fittings. Just my$.02 Worth

 

[Marlar]

Thanks for the suggestions, guys. I did get the manual choke hooked up (used the pasenger side vent cable that I repaired after relpacing it), adjusted the fast idle and it works well. The drain back problem has mysteriously disappeared. Mind you, I am not complaining, but that is odd. i looked into the fuel tank and it appears very clean and with no rust or other debris in the tank. The best I can come up with is that there was in fact something causing the fuel pump valve to stay open, like debris.

In any case, I am a happier camper now. Thanks again.

 

[paul67]

Glad you got things sorted. Now go have fun!

 

[Marlar]

Yesterday was a good day to 'drop the top', which is what I did. The car is way more fun to drive than my C6 because it is old(like me) and is surprisingly nimble(unlike me).