Something has changed, for the worse...

[MickSz]

Hello everyone!

I’ve been a gleaner of information here at the Samba for the past 6 or so years and am always amazed at the outpouring of help you all offer to those in need.

Well I am in need of your services now. I’ll try and explain everything I know that is happening.

’72 Beetle. 1600 Dual-port rebuilt 6 years ago and has been running strong since the rebuild. No leaks, no smoke, nothing. Stock everything during the rebuild. Proper Solex 34PICT-3 bought from a highly reputable rebuilder and installed on the fresh build 6 years ago. Always tuned up yearly, multiple oil changes per year. The thing has been bulletproof. Previous owner had installed an electric fuel pump which promptly died a year after I got the car. I replaced it with a better quality one, I also installed a fuel regulator at that time to make sure I wasn’t just pouring fuel into the poor engine. Good job I did because it was pushing out something like 7psi. Had it set to somewhere between 2.6 and 3psi and never had an issue. Thing worked great for 5 years and then started acting up. Feeling that maybe these things were not very reliable I decided to install a mechanical pump for the first time. I picked up a beautifully restored Pierburg from a very reliable rebuilder recommend by the carb rebuilder.

Did the install last weekend. I had the fuel pump rebuilder supply the fuel pump stand, gaskets and a proper length rod so I made sure everything was right. Rod distance was bang on 13mm at its highest. While I was at it I thought this was a great time to replace all the rubber fuel lines, right from the gas tank all the way to the carb. Got the proper German braided 4mm but went with the thicker stuff for the section through the firewall, it fit the grommet better. Also installed a new metal can fuel filter at the back of the car, just before the it enters the firewall.

Alright, I think I’ve set the stage…

First fire up, perfect! Ran amazing. Let it warm up like usual, ripped around the block, super happy. No leaks, I’m a happy camper

Second run, fired up great and I decided to take it for a longer run. About 10 minutes into the run I’m pulling up a hill, not a super steep hill but a decent grade and suddenly it bogs right down and I have no power. Doesn’t stall, just feels completely gutless. This hill was never an issue before. I pull over, let it sit idling for maybe 2 minutes, tackle the hill again and no problem. If anything it felt like it has more grunt than with the electric fuel pump. Keep going for a few more minutes, another incline, not even a hill this time: bog again. It feels like it’s not getting fuel. I smell no flooding, it doesn’t stall, it just totally lacks power for a short while. Two minutes later it roars off like a champ.

So I’m thinking what has changed? Clearly I replaced the fuel pump, the hoses and the fuel filter. I replace the fuel filter again with a new one, pulled all the new hoses and they are not blocked at all. So I’m left thinking is this pump a dud? I still have the fuel regulator mounted (but not hooked up) in the engine bay so I thought I’ll put it into the circuit and see what this new pump is reading. Bang on 2.8 psi. I rev it up no change, doesn’t move a hair.

The temps here in Western Canada are around 12 Celsius so not cold but not warm either. Normally perfect driving weather.

So what has happened? I am at a loss….Have a forgotten something? Is it mere coincidence that at the very moment I install the mechanical pump something else has decided to start failing or is the pump causing an issue that wasn’t apparent with the electric one?

Any ideas are greatly appreciated.

Mick

[Dougy Dee]

Your fuel pump pushrod could be binding in the plastic pump stand/isolater as it warms up...

[MickSz]

That's a thought, thanks Dougy!

[rayjay]

You may need to drive the car with a fuel pressure gauge tee’d in and placed where it can be watched while driving. Don’t place it in the interior. Tape on the exterior of the windshield or other glass if you can get a helper to watch the gauge while you drive.

It’s possible to have a sliver of fuel line restricting the flow.

[scottyrocks]

Do 72s use 4mm fuel line? All I've ever seen here is that we all use 5mm line, in stock applications, anyway.
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[vamram]

How is the squirt from the accelerator pump? And can you check the fuel level in the bowl? Pull over when it bogs down, shut it off, and remove the top of the carb, bowl should be at a certain depth (not sure off the top of my head, info is on the samba somewhere and in the Bentley manual.)
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[BIGMIKEY]

How is the gas tank vented? Did you change anything there?

Mike T
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BIGMIKEY

Deserter Series 1 project.
https://www.thesamba.com/vw/forum/viewtopic.php?t=787047&highlight=

1973 Beetle Driver, Marina Blue.

[BIGMIKEY]

[MickSz]

Thanks for the tips guys!

The tank venting is stock and complete and nothing else was changed or altered recently other than the aforementioned pump, fresh lines and filter.

If it was a chunk of fuel line, would it not be restricting the flow all the time? Why would it clear itself after a short time then come back again a few minutes later?

I'll see if I can rig up some way to monitor fuel pressure while driving, that should be an interesting trick

If the fuel pressure does drop, what would that be indicating?

[VW_Jimbo]

Fuel tank might be full of rust flakes. Worth a look. Or drive up hill, till you get a sputter. Then turn the engine off and Coast to the side. Pull the hose at the fuel pump. Any gas pouring out? If not, pull the one at the transmission. Gas? If not, go to the bottom of the tank. Pull the hose. Gas?
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[MickSz]

Tank was cleaned and resealed properly 6 years ago. I'm just having a hard time believing this isn't related to the parts I've just replaced. I have half a mind to reinstall the electric pump just to prove that theory. If it runs fine with the electric pump and the new fuel lines and filter that would seem to make it pump related.

The irony is I installed the mechanical pump to make it MORE reliable lol..

[VW_Jimbo]

[19-VW-74]

I had a similar issue with my '74 last year. It died on me in rush hour traffic on I-15 in Salt Lake City. The car acted like it was starving for fuel, even though the tank had like 3 gallons left, so I had my wife bring me some gas. I still couldn't get it to start. So I had to leave it for a while and come back for it later. I added more gas and got it to limp home. It cut out whenever I got over around 55mph, but I got home.

I tested the fuel pressure and it was fine, but I replaced the fuel pump anyways. The issue persisted.

I pulled off the carb and found that the float valve was blocked intermittently by a small rubber sliver from when I last replaced the fuel lines and filter.

After removing the sliver, I had no more issues.
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-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[MickSz]

Thanks for that, I'll definitely need to dig in this weekend..

[vamram]

[kreemoweet]

FYI, the fuel pressure spec'd by VW for the 34 PICT-3 carb is 3-5 psi.
My own '71 1600 engine with stock carb and fuel pump ran fine for years at a steady 5 psi.

There's also a procedure given in the Bentley manual for checking the volume output of the fuel pump.
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[wimkever]

An electric fuel pump is mostly mounted between the tank outlet and the metal line that's coming out of the chassis in front. I guess you've mounted a new soft fuel line between the tank outlet and the metal line.
There's a possibility that this new softline is kinked somewhere under the fuel tank, resulting in restricting the fuel flow.
Don't ask me how I know.
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[Starbucket]

Is the new metal filter hooked up backwards? If you have points your condenser might be dying.

[OldSchoolVW's]

[MickSz]

• Metal filter is definitely in the right way I triple-checked lol.
• Ethanol safe hose, I checked that too.
• Electric fuel pump was indeed under the tank. I replaced the soft lines there and put in a barbed hose connector where the pump was.
• Those hose clamps are awesome!
• Thanks for your kind words on the engine

I have gone to great lengths to learn and do things by the book and maintain this little guy to the best of my ability and wallet. Thats what makes an issue like this so annoying...