Weird carb problem

vugbug68 · Posted: Wed Jun 11, 2008 3:04 pm Post subject: Weird carb problem

After about 10 minutes of driving, my car will start to idle unevenly. When im parked uphill (like in my driveway) it idles perfect no matter how hot the engine is. when im parked downhill it will die if i dont give it gas.
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71 Super
66 Corvair
69 Baja Bug

realbugfanatic · Posted: Wed Jun 11, 2008 5:48 pm Post subject:

When the nose is higher gravity works with the flow & your pump won't have to work so hard to pull fuel. Replace your fuel filter & see if the problem goes away. Sounds like you might have some crap in your line which is keeping the fuel pump from being able to draw enough fuel when it's higher than your tank or it could also be your fuel pump itself. Anyway, I'd try with the cheapest & replace your fuel filter. You can also do a little test while your filter is off - park with the nose up & with the motor nice & cool, unhook your filter & let it flow freely while catching it in a margarine tub or something gas-safe that you can see what's floating in your gas. Just make sure you have something handy to shut the fuel flow back off like jam a golf tee into the hose or it will become a mess very quickly.

vugbug68 · Posted: Wed Jun 11, 2008 7:38 pm Post subject:

i have the filter before the engine compartment, the filter is about a month old and was on my old engine. This is a different engine out of one of my friends bugs that i got running last fall, when we first fired it up there was some gunk in the fuel pump that shot into the fuel filter, but it idled fine back then, and since then i have cleaned out the pump and the carb.

I just put the engine in last weekend and made sure the fuel line was clear
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71 Super
66 Corvair
69 Baja Bug

realbugfanatic · Posted: Thu Jun 12, 2008 5:37 am Post subject:

Scratching my head.... still think it has something to do with the fuel pump (diaphragm cracked?) or possibly fuel pump rod.

vugbug68 · Posted: Thu Jun 12, 2008 5:54 am Post subject:

i am gonna take apart the fuel pump today and see what i find, when i cleaned out the carb, there werent any foreign objects in the float bowl that seem out of the ordinary, just a little dirt.
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71 Super
66 Corvair
69 Baja Bug

ashman40 · Posted: Thu Jun 12, 2008 6:34 am Post subject:

Maybe some gunk at the bottom of your fuel tank that clogs the filter inside the tank? When was the last time you changed the filter in the tank (part of the fuel tank outlet tap)?
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AshMan40
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'67 Beetle #1 {project car that never made it to the road Sad

}
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

realbugfanatic · Posted: Thu Jun 12, 2008 6:47 am Post subject:

I too had thought about the fuel tank - possibly the screen - but kind of dismissed it because when he's nose low, it doesn't flow but the crud in the tank would move away from the tank outlet allowing it to flow better & when you'd think the crud would be next to the outlet in a nose-high position, it flows good. Sure wouldn't hurt to pull your float & look in there with a flashlight though.

towd · Samba Member Joined: June 20, 2005 Posts: 2458

park it facing down hill do the start up thing,,, when it acts up.. shut down and take the top off the carb ,, checking to see how much fuel is in the bowl.....

what your talking about sound like a float level problem,, which could also be a clogged or sticking needle valve

a quicker check,, would as soon as you shut down,, look inside the carb to see if the accelerator is squirting ...if not then the fuel level is off.

vugbug68 · Posted: Thu Jun 12, 2008 4:21 pm Post subject:

the weird thing is, it only does it when the engine heats up, after about 10 minutes of driving. if it was a clog i would think it would do it all the time (at least after the choke opens)
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71 Super
66 Corvair
69 Baja Bug

vugbug68 · Posted: Thu Jun 12, 2008 5:02 pm Post subject:

Alright so i just did what Towd suggested, As soon as i shut it down i moved the throttle and a little fuel squirted, but it seemed weak. Then i took the top of the carb off after i drove it around the block and parked down hill (it died by itself) The float bowl was full. The fuel was about 4mm from the gasket
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71 Super
66 Corvair
69 Baja Bug

ashman40 · Posted: Fri Jun 13, 2008 6:21 am Post subject:

Sounds like it's not fuel starvation if you have fuel in the bowl.

Any idea where the fuel in the bowl is when you are parked on a flat surface? It's supposed to be about 0.75" from the top edge of the bowl.

You might have too much fuel in the bowl causing it to overflow when you park nose down? Just a thought.
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road Sad

}
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

vugbug68 · Posted: Sat Jun 14, 2008 8:35 pm Post subject:

just took apart the fuel pump, it was pretty dirty so i cleaned it out and put it back on. when i got it all hooked up i turned over the engine with the ignition off and no fuel squirted out of the pump (i had the hose going to carb disconnected).... that puzzled me.
Then i hooked up the hose and started it up. started fine, drove it for a little bit with no problems except it still wants to die down hill or when coming to a stop.

This is so frustrating.
_________________
71 Super
66 Corvair
69 Baja Bug


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