It appears that heat is definitely a component. I fired up the vette and moved it to the street. It started hard (as usual).

Tonight, I fired it up to take it for a drive, and it fired up fast and easy ... no problems.

The suggests that it needs to the heat to push the fuel somewhere else, as it was essentially cold but sitting for 8 hours and it wasn't a problem. The only other thing slightly different it was parked on a slight downward slope.

So, does this new information clear the fuel pump (for now) and re-direct the suspicion at the carb? Or are there other possibilities?

Brian.

 

Well, then ...I'll just stop by my local NAPA on the way home tomorrow and pick one up and see if that helps the situation at all.

Thanks.

 

I'm sorry guys but a fuel pump cannot siphon fuel from the carb. First, in order for this to happen the fuel pump would have to have a ruptured valve on the output side. If it was then the car wouldn't run since the pump wouldn't be able to push fuel into the carb. Second, if I was wrong on the first, the diaphram would have to be ruptured and the fuel would be draining into the oil pan and you would have alot of fuel in the oil. Ruptured diaphrams do happen but the symptons are gas smell and fuel being pumped out the vent when running not from gas siphoning after setting from some time. At some time almost everyone has had a fuel pump leak and this is when and where they they leak. Third, the fuel couldn't be siphoned below the needle and seat which is a few 32nds below fuel level. Not low enough to cause a starting problem.
The well plugs leaked just as bad on '85 carbs as the older ones. They are just plugs pressed into the housing without any kind of seal. Heat has nothing to do with it. Time does. Replacement plugs used an Oring to seal. The plugs sit below the main jets which are the lowest part of the fuel bowl. The longer the car sits the more fuel leaks into the intake. Eventually it will drain the carb completely requiring longer cranking time. You will also have 1 shot of fuel left in the accelerator pump chamber. It will not leak down because of the check ball in the pump feed circuit. After that shot is gone you have to keep cranking until the chamber refills. Since the chamber level is the same as the fuel level you have to wait until the fuel bowl is completely filled before you get a good shot from the pump.
Most people use JBWeld on the well plugs if they have time. The good stuff requires 24 hrs to dry so you can't do a rebuild in one day. A proper rebuild, rarely done anymore, is removing the old well plugs and installing the replacement plugs.
Hope this helps,
Mike

 

I AGREE!!! I AGREE!!!, I AGREE!!!
TJ

 

Mike,

With all respect to the others that have posted, your explination seems to make the most sense to me. If the bowl was 50% empty, that likely wouldn't be enough to cause a hard start -- it would have to be nearly empty to go to a fuel-starved situation. The car has been sitting for a bit, so I can test to see if it is dry or not by hitting the accelerator and after the first one, it shouldn't squirt any more gas -- no place to draw it from.

Does that seem reasonable?

That being said, I know that I'll sort it out either way, as I have a fuel pump on order (who knows how old the current one is) and I will likely have that before I have the chance to rebuild the carb.

I haven't looked, but I assume that someone sells a rebuild kit for the Qjet? I didn't find it on Ecklers. How ugly of a rebuild is it?

Brian.

 

1- Recreate the hot situation. Prop the throttle plates open when you shut the engine off with a screwdriver handle or something so the accel pump won't work when you look thru them into the manifold. After a certain time period, say 1 hour, and so on, look thru the throttle plates and see if the inside of the intake if full of fuel.

2- There is nothing from stopping you from taking just the top off the carb with it still on the manifold after a cold situation to see if the bowel is full or not. If it is full after a cold shutdown then the main jet plugs are not leaking.

3- Check your engine oil for dilution and/or gas smell.
That will tell if it is leaking internally, possibly at the fuel pump into the ccase. A fuel pump doesn't have to leak externally.

 

Hi Brian,
Rebuild kits are readily available thru ACDelco, Jiffy kit from Standard/Hygrade, or neighoff. I have rebuilt thousands of quads since 1970 so it's hard for me to say how difficult it will be for you. These are sensative carbs. 2/32 difference in float level will cause adverse running styles.
If you are going to replace the fuel pump be sure to get an ACDelco pump. It's well worth the extra few dollars in price. If you have any trouble locating parts let me know and I can help you out.

Mike

 

Mike,

Actually that information does help, because I was obviously not looking in the right place for the rebuild kits. I have rebuilt 1 previous 4 bbl carb (either carter or motorcraft, can't recall now), but there were issues with the housing -- so my work may have been fine.

It's too late on the fuel pump, as I special ordered it from my local NAPA store, so I'm stuck with it whether I use it or not. The question is: what does the ACDelco pump have over an OEM equivalent that would make me buy another fuel pump and not install this one? (trying to find out if it is worth the extra cost)

Brian.

 

Based on the work I've done with the car so far, I feel pretty confident that #3 isn't the issue ...I just did an oil change and there was nothing unusual about the color or smell of the used oil (and it was an extended drain).

I last ran the car to a nearby town and back, and parked it when it was hot and have not restarted it. If I pull the top off the carb and the bowl is empty, it is likely the result of the hot condition -- although I don't expect to find anything other than an empty bowl. If it's more useful, I can fire it up for 30 seconds and shut it down and then check it a day later to see what the results are. Both are easy enough, so I will give the cold version a go first and report back.

Brian.

 

Brian, Just run it for 30 seconds, just to fill the float bowl. There is no need to pull the top to check fuel level. Use the accelerator pump. With a full float bowl you will get at least 10 good shots when working the throttle. If the bowl is very low or empty you will only get one, maybe two good shots and then it will stop squirting. I would also do as noonie said and prop the throttle open to look for a wet intake. But check it at several hour intervals because once the carb stops draining the gas in the intake will dry up.
Mike

 

I fired up the car and ran it for about 30 seconds this AM and then left it all day long. I came home tonight (about 12 hours later) and pumped the gas 6 times and got fuel each time -- so the bowl wasn't empty after a cold cycle. My next task is to heat it up and then try the same test. I'll let you know how it goes.

I tried to look down inside the intake, but it wasn't terribly easy to see ...I'll only be able to see through the secondaries, I think ...and I can try that after a heat cycle.

So far, it's looking heat related.

Brian.

 

I finally got a chance to heat cycle the carb and this is what I did:

I drove the car to work (37 miles at highway speeds) and then let the car sit all day. When I got back to the car after 9 hours, I pumped the accellerator while watching the jets in the carb. The first two was strong, the third has spitting a little air, and the 4th was very weak. Compared to the process I got after a cold cycle -- so heat is definitely a factor in the fuel leaking out.

I wasn't able to keep the throttle plates jacked open while at the office, but I do hope this test is revealing.

Does this mean I need to rebuild an replace those plugs?

Brian.

 

Hi Brian,
Yes you definitely have well plugs leaking.
Mike

 

Mike,

Can I trouble you for a few links perhaps? I've spent the last 30 minutes looking around for any of those items, and I came across a couple of kits for $25 and $31 respectively (just sounded too inexpensive) and ACDelco didn't seem to have the parts. Do you have a link to one of the kits? I was hoping to verify the well plugs were included, but none have photos.

Sorry for the trouble.

Brian.

 

Hi Brian,
Let me do some checking. I need the carb number. It will be on the driver side just above the secondary throttle shaft. It will start with 70 or 170 and be 7 or 8 digits long.
Mike

 

Here's what I found:
17057203
0387 AOM

Does that give you what you need?

Also, should the upper gasket look wet?

Brian.

 

Yes, those are the numbers I need. The upper gasket should not wet but is common to be damp. One cause is the two 1/2 carb mounting bolts have been overtightened and warped the body an d top plate.

Mike

 

They make a fuel filter with a check valve that fits where the stock one does usually will cure the problem.

 

Chewy,

There seems to be a variance in opinion regarding the possibility of siphoning fuel out of the float bowl -- and I'm curious what experience you've had that suggests it can happen? Upon closer inspection of my carb, it appears the fuel goes in towards the top of the bowl which would appear to make it impossible for it to siphon the bowl dry.

I'm curious what information I'm overlooking so I can best understand the Rochester product.

Brian.

 

Mike,

Your term is better than mine ...damp is a much better description of the gasket. Considering the bubba work I've found elsewhere, the warping idea isn't out of the realm of possibilities.

Thanks for looking up the kit for me ...I appreciate it.

Brian.