Hey guys,

Still having some issues with my carb and the fuel getting to the engine.

I've changed EVERYTHING now, blown out the lines, and still I have some issues.

Here are some pics so you can all see what's going on:


I've got everything assembled, and tight. Here's what it looks like (2 barrel Autolite 2100)


Fuel keeps coming up the line to the fuel filter (but it appears to be only air from the tank because it bubbles in the fuel filter then bubbles in the carb... The fuel then bubbles up out of the top of the throat of the carb and out of the two holes circled (because it's air)


The fuel then spills out over the EGR plate and the intake, creating a mess of the place...




Do I just not have enough fuel in my gas tank, or is there something really wrong with my fuel system?

I've got about 3 gallons of fuel in the tank, and I thought it would be enough... but maybe not...

 

If any fuel at all comes out of the two holes you've circled, then the float is not shutting off fuel flow. This is the only way this can happen. This can be caused by the float retainer not being installed, debris in the seat, or improperly set float height. Of course, the fuel pressure could be too high, but if you're running the stock mechanical fuel pump, it's a non-issue. One of the three aforementioned items will be the culprit.

 

Ahh... well, guess it's time to take the carb back off!

I have replaced the fuel pump with an OEM replacement, but there was something different about the pump that sort of didn't strike me as anything serious. The fuel inlet line and the outlet line were swapped on the new pump that I've installed. I was ensured that it was a 351W model fuel pump by NAPA.

I looked over both fuel pumps and they were IDENTICAL, except for the inlet and outlet locations being reversed on the pump itself (no big deal?)

I'll have to check the fuel bowl and make sure everything makes sense under there... I had it apart to see if anything looked wrong, and that was a big "no" from my part.

I'll have to get some pics up of what my float looks like so that someone can help me diagnose what's wrong if I can't find anything.

Guess we'll be back here in a few days if I don't find anything

 

I had the same issue several years ago with a 4 bbl, and found the float was bad. I replaced the float and made sure it was adjusted, and it ran perfect.

 

Just finished figuring out this same problem myself. Like Tees77150 said above it's probably your needle and float that need replaced almost garunteed. MAKE SURE your gas tank is vented that was my main problem. And fmc44 it is possible to have a mechanical pump and have fuel pushed past it if there is nough air pressure I learned this lesson all too well. My truck gave me nightmares for a month because of this issue. I didn't believe at first either.

 

Where was the air pressure coming from?

I thought maybe I didn't have my tank full enough and it's sucking air from the tank and sending it through the lines up to my carb cause the fuel filter looked like it was bubbling when I tried to start it (fuel wasn't coming, but air sure was!).

 

The air was coming from the gas tank not being vented. Find out if your gas tank is vented. You do this by seeing if you have a vented gas cap. It doesn't take much to vent a tank at all. That was where all the air pressure was coming from in my truck. Maybe you already know all of what I just said, but if you are only getting air and no fuel at all coming through the carb I don't know wat else it could be. Are you sure there is no fuel coming up? and have you taken the fuel line off the carb started the truck and checked to see if fuel pumps comes out?

Adam

 

Yes my gas tank is vented, and I just bought a new gas cap for it so that I was sure that it would be vented (locking vented gas cap from LMC).

I am getting fuel up to the carb (the fuel filter has fuel in it, and it's half full), but it seems that there is air coming through the line up to the carb somehow because the fuel filter keeps bubbling up with air inside it until I shut the engine off (or it runs out of fuel from me pouring it down the carb, whichever comes first).

No I have not taken the line off the carb to see if fuel comes out (when I start it). The fuel pump is new and I don't want to stand around watching my fuel pour out all over the place. However, that sounds like what I should be doing just to make sure that the fuel DOES come right up to the carb.

I'll see what I can do this weekend to get some more pics up and check the float/needle to see if it's shutting off the fuel or not.

Thanks for the suggestions guys. And on second thought, I wonder if I actually did toss that old gas cap out yet or not... wonder if my new LMC vented locking cap is on the filler neck... better double check that! lol

 

Get a "fuel pump and vacuum tester" and check fuel pressure, then put it in your tool cabinet or drawer and you'll find it useful in all kinds of ways.

K-D Tools KD 2521 Fuel Pump Vacuum and Pressure Tester

 

Looks like a neat tool, but i'm not even sure how to use it. It would require air and not fuel, so how do you keep the fuel from getting into the testing line?

 

Not specific to this brand, but useful information none the less.

http://www.actron.com/media/usermanu...it_MNL_Eng.pdf

 

Thanks very much for this on Vacuum testing!

I've got to go out and get myself a vacuum tester now... I never knew you could test so many things JUST with vacuum. Although some things can't be pin-pointed directly to the source, it's still good information!

 

So just an update with a few more issues to solve...

I got my truck running just fine, and yes it was the float. The float was not hooked up correctly, and thus it was staying wide open even with fuel in the fuel bowl.

Now I've got an issue of my truck dying after being started and running for around 10-12 seconds.

I'm guessing this is an idle/mixture issue that I have not yet had a chance to do on my carb. Currently, my carb is just freshly rebuilt and is not tuned (even though I give out that manual to everyone, I don't even have time to use it! haha).

Could my truck stalling/stopping after being started up be an EGR valve issue?

My EGR valve is not hooked up because I'm not entirely sure what to do with it at the moment. Since the engine is a 351W, and is an old one at that, it does not have a Ported Vacuum Switch on the intake or anywhere noticable.

I do have a vacuum reservior that's currently being used by nothing, but has 3 ports on it (in the shape of an upside-down triangle... two on the top, one on the bottom).

Also, after inspecting my EGR valve with a flashlight, I noticed that my transmission seems to have a vacuum line that's hooked up to nothing at all, just sitting behind my block... chilling out, doing nothing... (the unknown transmission line looks just like the fuel sending unit's metallic nipple that feeds into the rubber hose that goes up to the engine, but it's meant for a vacuum line... I know this because of its size... The hose meant for it is the exact same size hose that would fit on my carb)

Could my unknown transmission line that's hooked up to nothing be a big issue on this, or is it meant for a different discussion?

 

That "unknown" transmission vacuum line, goes to the modulator valve. It needs to be hooked to a manifold vacuum source, or the trans won't shift properly.
The only way an unhooked EGR valve will affect the engine at idle, is if the valve is stuck open. It's normally closed at idle, and only opens when the engine is under a load.

Having a bunch of unhooked vacuum lines can certainly cause idle issues, especially if they are letting the engine suck in air.

 

Modulator valve you say?

And do you mean intake manifold for the source that the tranmission needs to be hooked up to?

I don't have a PVS as I said a while back, so I'm unsure on how to get this line the vacuum it needs.