Loses power in 4th

Twitchycat13 · Posted: Tue Jul 22, 2014 9:51 pm Post subject: Loses power in 4th

Hello Samba members! I'm having some trouble with my 1962 Beetle and was hoping for some advice.

Recently it's been acting up on the highways in 4th gear after about a minute. It will be fine but then starts losing power and can barely maintain a constant speed. While this is happening the engine (transmission?) is kind of shuddering like it's not firing on all cylinders or something, but in neutral the engine runs perfectly.

This will only happen if I cruise in 4th gear for about a minute, but will be fine all day in 1st-3rd. I was thinking maybe a fuel line or fuel pump issue but that wouldn't make sense because it only happens in 4th and running higher rpms in lower gears it still does well.

All advice is greatly appreciated! It's my work vehicle so I'm scrambling to figure this out.
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KTPhil · Posted: Tue Jul 22, 2014 10:01 pm Post subject:

It sounds like fuel starvation. A few ideas to think about:
- Does your oil smell of gas? Your fuel pump diaphragm may be split and you are both losing pressure/flow and diluting your oil.
- Is your fuel filter or screen clogged?
- Have you blown out your main jet?
- What displacement and carburetor do you have? Some have a power fuel system for high speed running and the nozzle can get clogged or fall out.

drscope · Posted: Wed Jul 23, 2014 9:02 am Post subject:

I think in this case I would start with checking the ignition points. If they start to close up you will get a power loss that shows up more under load.
It may be there but the lower gears have a little more torque and you may just not be noticing it there yet.

It may be a fuel issue, but if it is it should show up in lower gears with sustained higher rpm's. Easy enough to tell, find a nice road where you can put it in third and drive along at the top end of the rpm range for a half mile or so. If it's a fuel starvation issue it should show up.
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Twitchycat13 · Posted: Wed Jul 23, 2014 11:54 pm Post subject:

Alright so I checked my ignition point gap and it was indeed too close, set it back to .16 and the issue still prevails. I bought another fuel filter but haven't put it on yet because I wanted to try one fix at a time to find the problem.

It runs normally (possibly?) at high RPM's in 3rd but still in 4th it gives out after a minute. I can't gain any speed and it sounds like it isn't firing on all cylinders. This lasts until I get out of 4th and still persists in 3rd, but stops when I come to a halt and then climb back to 3rd.

Is it possible this is a transmission issue (the transmission gear oil was low for awhile but I've since changed it and it's full now). Or even a problem within the engine block? Or is my distributor the most likely culprit?

What can I do to the distributor to test it? It's an 009. Next I will try new spark plugs if you think that may help.
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gears · Posted: Thu Jul 24, 2014 7:43 am Post subject:

Are you running taller than stock 4th gear or larger than stock tires?
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Twitchycat13 · Posted: Thu Jul 24, 2014 12:55 pm Post subject:

I'm not sure about the 4th gear ratio but the tires are larger than stock.
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gears · Posted: Thu Jul 24, 2014 1:45 pm Post subject:

Sounds like typical overheating problems, due to gearing that is too tall. Taller tires = taller gearing. Go back to standard diameter tires, and you won't overheat at freeway speeds.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

KTPhil · Posted: Thu Jul 24, 2014 1:49 pm Post subject:

Would overheating from tires happen in only one minute's time?

Dougy Dee · Posted: Thu Jul 24, 2014 4:45 pm Post subject:

Cracked distributor cap will make it shudder and buck under load...

Twitchycat13 · Posted: Thu Jul 24, 2014 4:45 pm Post subject:

The engine has 13,000 miles on it and the longblock is all new, and has the proper fan and cooling tin. It's a Baja so it's definitely getting adequate cooling yeah? Wouldn't running it at 3k RPM's in any other gear produce the same heat?
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drscope · Posted: Thu Jul 24, 2014 6:34 pm Post subject:

What kind of wheels do you have on this thing? If you have a big HEAVY wheel/tire package, you may just be running out of torque.
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Mother Nature is a Mean Evil Bitch!

KTPhil · Posted: Thu Jul 24, 2014 9:26 pm Post subject:

Twitchycat13 · Posted: Fri Jul 25, 2014 2:05 pm Post subject:

Oooh thank you KTPhil, I've always wondered that and you cleared it up for me! So since fuel consumption is different at 3k RPM's in 4th I'll change the fuel filter now and hopefully it was just that easy. Would that make sense why it takes it a little bit to return to normal when I come back down from 4th, because the fuel builds up in the lines again after being starved?

My rear tires are LT235/75R15, and the entire wheel assembly is 27.5 inches total in diameter. What would cause it to suddenly not have the torque for them anymore?
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jzjames · Posted: Fri Jul 25, 2014 3:23 pm Post subject:

Coil going bad?
(Spark starvation).

KTPhil · Posted: Fri Jul 25, 2014 4:50 pm Post subject:

Did you check your oil for gas smell? If your fuel pump diaphragm is leaking it will lower pressure/flow, and then dilute your oil with gas.

Twitchycat13 · Posted: Sun Jul 27, 2014 4:21 pm Post subject:

I did check for the smell and wasn't sure if I did smell it or was just creating the smell myself, would it be super pungent or faint?

The good news! I replaced the fuel filter and all is well now, thank you so much everyone for your help! It may have been a simple fix but I learned a lot about potential causes that may come in handy in the future.
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drscope · Posted: Sun Jul 27, 2014 6:15 pm Post subject:

Here’s a few thoughts on fuel filters that may help you.

Many VW owners have fuel filters in the engine bay. Most of these are mounted between the fuel pump and the carburetor. That is believed to be the most common reasons for engine fires in VW’s.

So if you have your filter mounted in that location, you may want to move it before you end up having a Car-B-Que!

A good place to mount it is in the rubber line under the fuel tank, or in the rubber line along side the transmission.

2 things normally cause the filter to get plugged up. Water, or crud.

Water molecules are larger then fuel molecules and they get trapped in the filter medium and block fuel from getting through.

Over time water builds in the tank simply from the humidity and moisture in the air. And you can also sometimes pick up water in the tank when you buy gasoline.

In your 62, you may be able to park the car (or jack the car) so the side of the fuel tank with the filler neck is down hill. Then you can look into the tank with a flash light. Water in the bottom of the tank will look like little globs of gelatin.

Crud in fuel supply is usually rust from inside the tank. Again it gets caught in the filter and blocks the flow of fuel.

Changing the filter may have you running fine right now, but it may NOT have completely eliminated the cause.

There should be a sock screen over the fuel pick up in the tank. Sometimes they come loose and fall off. Sometimes they are just plain missing. And sometimes they also get plugged up with crud or water and reduce the flow of fuel that is able to get past.

You would be wise to have a good look inside your tank! If there is crud or water in the tank, it would be a good time to take it out and clean it.

If it’s rusty inside, you need to clean it.
An easy way to clean it is to remove the fuel pick up. After all you want clean or replace the sock screen anyway.

Then put about a 3 or 4 foot long length of chain in the tank, plug off the pick up and the vent tube, add about a gallon of kerosene, put the cap on, and roll it around for a while. The chain will gently knock the loose rust off the inside of the tank.

Pour out the kerosene and repeat the process until the kerosene comes out clean. Then let it dry and reassemble.

If you still have the early style fuel pump with the one center screw that holds the top on, you may also want to remove the top. There is a plastic screen under that top and they are also usually full of crud. Pull that out and clean it and reassemble.

Throw a new spare filter in the glove box so if the problem reappears you can just slip under there on the side of the road and replace the filter and be on your way again.
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Mother Nature is a Mean Evil Bitch!

Twitchycat13 · Posted: Mon Jul 28, 2014 11:36 pm Post subject:

Wow drscope!!! Thank you for all of that, this is the kind of thing I can save to a text file for my VW bible!

When I cleaned the tank I didn't use that method so definitely need to do that. My filter is located next to my transmission because I am all about no Car-B-Ques! The sock screen is there. The filter hasn't been changed in all of the engines 13k miles, is this about the time it would take to crud up normally? The old filter was crudded up with brown gunk that looked like river mud. I went on vacation and left the VW sitting for a month and I realize now I should have left it with a full tank so rust wouldn't accumulate.
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