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Stalling during sustained (warm) idle
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gdea73
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PostPosted: Thu May 12, 2016 6:30 pm    Post subject: Stalling during sustained (warm) idle Reply with quote

I recently bought a 1971 Ghia with a 1641 and dual Weber IDFs. I have driven it a fair amount and had no issues until recently—the other day, it stalled while I was sitting at a red light for a while. It was over 90 degrees that day. Started back up without much difficulty, but then it became increasingly prone to stalling when idling on my way home.

The idle RPM would suddenly lower, and the generator light would flicker, until either I gave it some throttle or let it stall.

I've read many threads about this type of issue, but I was hoping to get some help troubleshooting as I investigate. There could be many causes to this problem.

Since it began suddenly, my first guess was that the fuel filter was clogged. The PO had installed it in the engine compartment, between the fan shroud and the T junction of the fuel hoses. Not the worst location, but I wanted to move it out of the engine compartment. I've yet to complete this job (which has included installing new fuel lines), because I realized that it was to be extremely difficult with the car on the ground. Hopefully, when I get my jack, I can pull apart the rubber line just front of the firewall and get a new filter in there.

However, I may be looking in the wrong place. Once I rule out that filter, I'll see if setting the points may have helped, and adjust the valves and change the oil.

Is it likely that one or both idle jets are clogged, and if so, how much of the carb linkage must I disassemble, if any?

Thanks in advance!
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Danwvw
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PostPosted: Thu May 12, 2016 6:48 pm    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Does it have the stock vw mechanical fuel pump?
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gdea73
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PostPosted: Thu May 12, 2016 7:11 pm    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

I believe so. It appears to be mechanical. I'll have to check to see if there's a VW emblem on it.
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Danwvw
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PostPosted: Thu May 12, 2016 7:21 pm    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Probably what is going on is now that the weather is warm the fuel is boiling and the pump is vapor locking. The ethanol fuel we get these days is not too good in these engines so see if you can get non ethanol fuel for it until you can get an electric fuel pump installed perhaps up front under the fuel tank where it's nice and cool. You may want to run the electric fuel pump off of a relay so it shuts down if the alt/gen light comes on. They make some pretty nice electric fuel pumps that will work with your carbs. CB Performance Electric Fuel Pump and Electric Fuel Pump Relay Circuit. It should be a pretty easy installation as all the wires you need are already up front. Key on power and gen/alt light wire perhaps add an override switch.
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Mellow Yellow 74
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PostPosted: Thu May 12, 2016 11:12 pm    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

gdea73 wrote:
Once I rule out that filter, I'll see if setting the points may have helped, and adjust the valves and change the oil.


Also check the timing - if it is too retarded it will stall at idle but go ok (but will run hot) at higher revs.
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gdea73
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PostPosted: Fri May 13, 2016 7:34 am    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Thanks for the suggestions! I will check timing after I adjust the valves and see if that may be the cause. I'll also consider getting an electric fuel pump (and pressure regulator), while in the meantime seeing if Shell 91 makes a difference (supposedly has no ethanol).
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thruhiker74
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PostPosted: Fri May 13, 2016 8:33 am    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Danwvw wrote:
Probably what is going on is now that the weather is warm the fuel is boiling and the pump is vapor locking. The ethanol fuel we get these days is not too good in these engines so see if you can get non ethanol fuel for it until you can get an electric fuel pump installed perhaps up front under the fuel tank where it's nice and cool. You may want to run the electric fuel pump off of a relay so it shuts down if the alt/gen light comes on. They make some pretty nice electric fuel pumps that will work with your carbs. CB Performance Electric Fuel Pump and Electric Fuel Pump Relay Circuit. It should be a pretty easy installation as all the wires you need are already up front. Key on power and gen/alt light wire perhaps add an override switch.


Does ethanol affect the boiling point? My '61 does this as well, out here where temps can easily climb over 100. Most of the time it's fine, but when it gets hot, I get unreliable idle. If it is somehow related to the ethanol in the fuels (can't get straight gas in Tucson), do you know if the additives for dealing with ethanol might have a positive affect on this?
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Danwvw
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PostPosted: Fri May 13, 2016 10:25 am    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Well it used to be that regulations only allowed Ethyl Alcohol to be added to gasoline in the winter and at only levels 10% or less and gas sold at higher elevations did not have it because it vaporizes easer at high altitudes.
Back In 2005 I took my 67 beetle out to Colorado, it had a hot running 1641cc single port with the non-dog dog house fan system with the stock steel oil cooler, W-100 cam etc, Pict-28 and stock fuel pump mounted to the block. It would start stalling on me anytime I got ahold of ethanol gas. I could get gas in the mountains and it was ok but get gas in town at stations that sold low elevation gasohol gasoline and it would begin it's stalling behaviour. But I installed an electric fuel pump. Just one of those Facet 2.5-4 psi ones up front under the tank away from the engine heat and that solved the problem.

By the way, quick fix for a vapor lock is to dump a cup of Ice Water on your stock Fuel Pump!

Found this, it looks like gasoline could have various boil points depending on the mix.
Image may have been reduced in size. Click image to view fullscreen.

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bhartwell59
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PostPosted: Fri May 13, 2016 10:52 am    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

curious, if it is indeed vapor lock, isn't there a simple way to reroute the fuel line/s?

Or would vapor lock happen no matter where in the engine bay?
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Danwvw
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PostPosted: Fri May 13, 2016 11:14 am    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

You could probably run some of the fuel back to the fuel tank and solve the problem.
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gdea73
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PostPosted: Tue May 17, 2016 4:56 pm    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Danwvw wrote:
You could probably run some of the fuel back to the fuel tank and solve the problem.


If you could elaborate on how that might be done, I'd really appreciate it.

I also do not have a fuel pressure regulator right now, though it had been running fine with the stock fuel pump directly attached to both carbs.

I guess the question is how I would route only excess fuel back to the tank.
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gdea73
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PostPosted: Sat Jun 18, 2016 3:02 pm    Post subject: Re: Stalling during sustained (warm) idle Reply with quote

Since last time, I changed the oil and removed the post-pump fuel filter. I installed a new one between the hard line from the tank and the hard line to the engine. I got some 92 octane gas, which (I think) couldn't contain ethanol, or at least not E10 like 87 octane. It had been running well in moderately warm weather 70-80°F, but today after driving around the city in 90 degree heat again, the idle would drop too low to sustain without prodding the gas.

Perhaps this is still vapor lock, but I still need to adjust the valves and check the timing. Before the stalling began, it did feel like it hit redline faster in a given gear (and thus was slower).
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