kdf1986

If my 75 vette sits for more than 1 day, it takes a long time to get it started. I have to pump the gas pedal to get enough gas to get it to turn over. After it runs, I can start and stop it all day without a problem. The problem seems to be that the gas leaks out of the carb, and there is not enough to get it started.

I researched the forum and the archives. One of the items that was mentioned was leaking fuel plugs, and to epoxy them with JB weld. In the photo below, are these the fuel plugs?

kdf

noonie

Here is a link to a post with pics to fix the wells.

http://forums.corvetteforum.com/show...8&postcount=21

I think the rest of the thread gives other causes and remedies of your symptoms.

kdf1986

Thank you for the post. I think the photos will help me with the rebuild. I am waiting for the 16th to get to this. I am getting all the parts I need together for working on it all at one time.

kdf

7T1vette

It won't hurt to add the JB Weld..if you do the job properly. But don't be surprised if the carb doesn't work any differently when you do. It could also be that the choke plate is not adjusted properly or the accel pump piston in the carb is not functioning properly. You should also make sure those are correct while you have the carb off the car.

7t3shark

The Q-jets had a notorious leak problem where two formed metal plugs are pressed into the body. There was an aftermarket kit that consisted of two machined aluminum plugs with o-rings that went into the holes after you remove the original plugs. You can just JB Weld the original plugs in. It's been awhile but I think they were in the center of the carb. The ones in your pic are not the ones I'm talking about.

chevygod

There are the main jet well plugs shown in your pic, JB Weld those, and then there are the secondary jet wells which are under the throttle plate assembly (aluminum base) roughly in the area of the glare-washout in your pic. JB Weld those as well. Make sure everything is clean before epoxying these so they will stay sealed.

I have had the same thing happen (no start after a few days) and it was due to a dryed out tip seal on the inlet needle valve. As fuel evap'ep from the float bowl, fuel level would drop lowering the float, opening the needle valve and fuel would go away, maybe back down the return line? Don't know how it was happening, but after sealing everything else didn't make it right, just replacing the needle valve did. Just a thought to check if your carb has some miles since a rebuild.

Best regards,
Tom

...Roger...

These plugs are soft and the factory did not use epoxy.You can re-swell and reseal these plugs by lightly tapping on them.By using a very tiny hammer and lots of taps they will mushroom inside their bore and stop the fuel at the end intended instead of catching the fuel on its way out in an epoxy "baggy".

lars

It's rare that the plugs leak. In the 700 carbs I've checked for leaks, I've had 2 that have had leaky plugs, and one of those was a leaky fuel inlet plug - not a well plug.

Before you start epoxying plugs and thinking this will fix the problem, just do a leak check on the carb: Fill the float bowl with fuel through the vent tube (it will take about 2 oz). Then, set the carb on some sockets on your workbench so it's raised off the surface. Simply observe the carb and see if anything drips out the bottom. If it drips, locate the source (i.e. primary well plugs or seecondary well plugs). I'll bet beer that it won't leak...

More common on the fuel disappearance problem is that the checkvalve in your fuel pump is leaking. When this happens, since the needle/seat in a Q-Jet is in the bottom of the bowl, the fuel in the carb will be siphoned out of the carb from the fuel draining back through the pump.
Lars

SteveG75

Thanks Lars.

You have me thinking that I need to replace my fuel pump since I have exactly the same problem. Fortunately, NAPA has them for just $35.

Now, I just have to get the car back from the body shop. Got rearended yesterday. $900 worth of damage to the bumper cover. Fortunately, that is all.

kdf1986

Lars, thank you for the response. I read in several of the responses that the problem may not be the well plugs, and did see in your previous postings that it is a rare occurence.

If the problem is in the fuel pump, would that also account for the heavy gas smell that happens when the car is garaged after a run.

I would rather replace the fuel pump first, rather than just start epoxying parts of my Q-Jet if it did not need it.

kdf

vettfixr

Good info. I have an Edelbrock Thunder Series 650 CFM on my 74 and if I let it sit for a couple weeks it too runs dry and it doesn't have well plugs. I'm wondering if the fuel pump issue is to blame in my case too. I think the Edelbrock has the fuel inlet at the top of the bowl but I could be wrong.

jotto

What carb gasket are you running? If its not the stock gasket, about 3/8 thick fibre type perhaps manifold heat is boiling off the fuel causing the smell? Just a thought....

lars

The pump can't siphon fuel out of that carb. In your case, it's a simple matter of having a vented float bowl with modern fuels. The ethanol additives cause the fuel to evaporate pretty easily, and the fuel will disappear out of a vented bowl when allowed to sit for a few weeks. The fuel level doesn't need to drop too far to cause a hard start problem - it only has to drop far enough so that fuel does not spill over the accel pump fill slot. That happens easily with the ethanol fuel evaporation problem (common issue on Q-Jets, too).

...Roger...

Lars isnt that what the check valve in the filter in the carb is for? The check valve in the pump isnt a very good valve for returning fuel,its ok as a check when pumping fuel.A brand new one will not hold vacumm on the pump inlet.And what about that.070 hole for the return line,there is no check valve on it.
kdf1986 I would try a fuel filter with check valve first.

kdf1986

Hello,
I am using the 3/8 thick gasket. When I took the carb off, that is the only gasket that was used. This is the photo of gaskets I have available. I am only using the one at the TOP LEFT in the photo.


Here is the side view comparison of what I am using on the left, and what the automotive parts store sold me on the right. I decided to only replace this with the original one I took off.



Is there supposed to be 3 gaskets used. Or a stainless steel heat shield sandwiched between 2 gaskets.

kdf

lars

It depends on what intake manifold you have. If you have the manifold with the "smiley-face" exhaust crossover groove that runs from side-to-side forward of the primary throttle bores, you need the 3-piece gasket with the stainless shield. All other intakes use the 3/8" gasket and nothing else.

jotto

Lars, just as a matter of interest what years were the 'smiley faced' intakes standard on and do you or anyone else here have a picture of said intake. KDF, what intake have you got and can you post a pic of it?

TIA.

kdf1986

I may have to wait until next week to get a photo of the intake manifold. This is on my 75 vette with a L82 engine. I am now working on my 72 vette in my garage. I have to wait until next week when I can rotate them around to get to the 75 again.

kdf

...Roger...

kdf did you have the check valve in the carb filter? I dont think what Lars said about the fuel pump was correct unless you have a non-stock type pump.Does your fuel pump have the return line?If so look in the bottom of this pic-the hole at the very bottom goes to the carb-the tube with the tiny hole is the return to the tank-it is open back to the tank and it has no check valve-in short the pump can not stop the flow back to the tank.

kdf1986

I know that the fuel pump has 3 connections on it.
One is to the carb, one is the input/fuel line, and the other should be the return line. I had a leak in the line from the supply to the fuel pump, so that is why I remember the connections.


I put in a new carb filter. Fram CG 11 or CG 12. I am not sure which one now. I dont remember seeing any type of check valve on it.
Here is a photo of my 73 Q-Jet filter. It looks just like this type.



kdf