Bug lost power while driving. wont start

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Re: Bug lost power while driving. wont start

Post by Piledriver » Tue Sep 06, 2016 6:34 pm

rrb6699 wrote:
so, my last issue is the engine dying after a 20+ mile drive when I stop for less than 30 minutes it wont start.
...no crank hot? The "hard start" relay mod helps the latter common issue.

...For no fire hot, put a set of points/condenser or spare distributor in it to test.
Pertronix have been known to fail like that.
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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 5:55 am

sorry. I didn't give specifics, just results.

the car cranks and fires fine. but, it only cranks when I have this issue. if I spray starting fluid it catches, but once that's used up it dies and doesn't catch. if I wait 30 minutes it will start fine.

the fact starting fluid works makes me think everything's working except fuel delivery. I wrote about it earlier in this thread bcause I think starting fluid didn't work every time this occurs. it hasn't happened lately bcause I usually plan my trips of 20+ miles out so I don't try to start it shortly after I stop. sometimes it's an inconvenience but, better than stalling out on a highway.
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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 6:06 am

the car is starting every time I try now. it was one or both of those ground straps.

I probably still have what I'll just refer to as the "vapor lock" issue when I try to start too soon after any longer drive.
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Re: Bug lost power while driving. wont start

Post by SCOTTRODS » Wed Sep 07, 2016 6:48 am

Did you ever pull the tank and replace the outlet screen sock and fittings? Your description always seems to come back to that for this particular problem. If you can spray it to start (most times) then fuel issue seems most likely. Not firing even with spray sounds like ignition issues... 2 problems knocking you around...
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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 9:11 am

I was unaware of the tank having anoutlet sock and screen. I did have the tank out and cleaned it by shaking fresh gas and brass bbs in it a few years ago when I was working on sealing up corrosion on the front wall. I suppose it wouldn't hurt to pull the tank but, I would have remembered the items you mentioned. all I remember is connecting a fuel hose to the tank and replacing the float assy.
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Re: Bug lost power while driving. wont start

Post by SCOTTRODS » Wed Sep 07, 2016 6:30 pm

On the Tank outlet (where your fuel line goes) the fitting is installed with a sock that sticks up inside the tank. There are many things that get in gas as well as bad gas, that will gel around the sock at the bottom and sometimes enough of it can grow to completely clog the sock filter. Looks like the one at this link...
http://www.mooreparts.com/stock-fuel-ta ... AhOL8P8HAQ

the kit is pretty cheap too. This may not be the correct one for your beetle, but it looks like the ones I've done in the past.
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Re: Bug lost power while driving. wont start

Post by Marc » Wed Sep 07, 2016 7:36 pm

It actually still could be an ignition issue - ether (starting fluid) doesn't need nearly as strong of a spark to light off as gasoline does.

A clogged pickup screen will usually cause you to lose power/conk out under sustained high fuel-demand conditions (i.e. highway driving), not likely that it's causing a lack of fuel delivery on hot-start.
The crud which accretes around the strainer when fuel flow is vigorous tends to fall away from it after shutoff - which is why its often misdiagnosed as a temperature-related problem, in the 15 minutes or so that it takes for gravity to act the engine/coil have cooled down some.

My first suspect from the symptoms described would be a "vapor-lock" problem. Next time you shut off when hot, open the hood before you walk away to let the engine compartment cool down - if that helps you must be on the right track.
If it turns out that the fuel pump is having difficulty pushing fuel against the vapor bubble in the line to the carb inlet, restricted supply flow can exacerbate it so the tank strainer's still worth checking out - it's just not common that the first symptom it would cause would be this one.

No pickup screen's not necessarily a bad thing - some folks prefer to let the moisture & crud get out of the tank and be caught in an external inline filter instead. Downside to that is that it has no "self-healing" ability like the stock setup so once the filter plugs you go nowhere until it's replaced...but particularly where it gets very cold in the winter, IMO it's preferable to leaving water in the tank that can freeze solid (that's no fun to thaw out on a chilly morning).

Some cars came equipped with relief valves that were plumbed in parallel to the pump to relieve excess pressure back to the suction side (most of those were tossed long ago by folks who didn't realize what they were for, so they're pretty rare anymore) and some pumps have that feature built into them. Another possibility is that the fuel pump pushrod is hanging up in the intermediate flange when hot so the pump's not getting enough stroke. It's rare, but something to rule out...with the pump off, the pushrod should drop freely of its own weight when lifted & released. If not, it may be slightly bent or the flange bore may need to be reamed out (an "O" letter drill is the ideal size for that).

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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 8:34 pm

I did not see or remember a nut around that spout. but, its been a couple years since the tank was out. if I saw it I may have thought that its replacable if it became damaged. I did not remove it. I did clean the tank thoroughly before putting it back. ill probably take the tank out soon to check under there to see how the work I did is holding up.

I hear you on the sock, but, it doesn't make sense why that would only clog up when I run hot. I'm going to steam clean the engine underside to make sure all the fins are clear, etc. I had thought since my nephew didnt put a new filter on when changing oil last time to replace it this oil change with a K&N filter. good oil flow is essential imho on ACVWs. I've done a host of other things except a larger oil pan but not considering that yet.

I have a Carter 4-6psi electric fuel pump I'm waiting for an excuse to install. a guy at a bug shop just gave me the cap off for the manual fuel pump should I go that route.

still deciding. if you read prior I have an 8-pass additional oil cooler plus a Weber 2bbl DFAV which may be mis marked because there's a contact tab on it for electric choke. maybe it's a DFEV. more to come.
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Re: Bug lost power while driving. wont start

Post by Marc » Wed Sep 07, 2016 8:43 pm

The clogged tank-screen "syndrome" has nothing to do with temperature, just the length of time driving with high fuel demand - detritus that's been laying harmlessly at the bottom of the tank gets drawn up by the exiting fuel and coats the outside surface of the strainer until it obstructs flow enough to cause you to conk out. Just sitting on the side of the road for 15-30 minutes is usually all it takes for enough of the crud to fall away that the engine can be started and driven normally again - at least until the next time it happens. During that "rest" time, everything in the engine compartment cools down, so naturally folks tend to blame heat for the problem rather than a dirty tank/screen.

A poorly-vented gas tank will cause nearly identical symptoms but is simple to confirm - when the car conks out, jump out and crack the cap - if you hear a hiss from the inrush of air, the fuel pump's been trying to collapse the tank because something's amiss with the vent system.

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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 8:53 pm

would just disconnecting the fuel line and draining the fuel out fix that potential issue. I could run it almost empty and try it. I usually run it within a half gallon of empty before I fill it to the top again. I'd think the problem would show itsel when fuel gets low too.

oh I have a temp fuel cap on it that really doesnt seal at all. are there vented fuel caps I can buy?
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Re: Bug lost power while driving. wont start

Post by Marc » Wed Sep 07, 2016 9:01 pm

If the temporary cap doesn't seal, the tank will effectively be vented well enough that it won't be an issue (other than the introduction of atmospheric moisture/rain into the tank).
`70-up Bugs have a fairly intricate vent system compared to earlier years - for "evaporative-emissions" control. The tank vents via an expansion chamber in the trunk to an activated-charcoal-filled canister inside the RR fender (there's a small metal tube running back along the channel where the pan-to-body bolts go). When you start the car, air pressure tapped off of the fan shroud purges the fumes in the canister into the aircleaner so they can be burnt off, rather than exiting as unburned hydrocarbons.

Older cars just had a hose that came off the filler neck and looped upwards, then down through a hole in the spare tire well to drip on the ground...

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Re: Bug lost power while driving. wont start

Post by Piledriver » Wed Sep 07, 2016 9:02 pm

You still have to oil cooler blocking the air intake?

Really needs to be by the transmission with an electrically controlled fan.
Putting it over the cool air intake is like installing damage, known issue for going on 40 years.
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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 9:18 pm

the carb has a top air intake with a rectangular filter (also K & N). nothing is blocking the air intake there.
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Re: Bug lost power while driving. wont start

Post by Marc » Wed Sep 07, 2016 9:37 pm

The question is, did you get rid of the aftermarket oil cooler that's mounted to the fan shroud? Unlike the stock doghouse cooler setup which vents hot air outside of the engine compartment after it passes over the cooler, the aftermarket cooler keeps all that heat inside the engine compartment which can contribute to "hot-soaking" (and that causes vapor lock). This is why I suggested leaving the deck lid open when you shut off after a run, to let that heat out.

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Re: Bug lost power while driving. wont start

Post by rrb6699 » Wed Sep 07, 2016 10:15 pm

ok yea I open the lid at least for a couple minutes when I stop to let that initial rush of trapped heat out. but close it up when I go shopping, etc. usually im in the store long enough to start ok when I leave.
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