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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 1:40 pm Post subject: Fuel pump loses pressure when hot. |
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Ive got a 71 super and the pump puts out about 6psi at idle and after about a minute of driving it stalls out and then will fire up again after 30 seconds and idle but pressure drops to about 0.5 psi. Any ideas? |
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Cusser Samba Member
Joined: October 02, 2006 Posts: 31271 Location: Hot Arizona
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Posted: Tue May 30, 2017 2:23 pm Post subject: Re: Fuel pump loses pressure when hot. |
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wafflecopter wrote: |
Ive got a 71 super and the pump puts out about 6psi at idle and after about a minute of driving it stalls out and then will fire up again after 30 seconds and idle but pressure drops to about 0.5 psi. Any ideas? |
Waffle - there are about 12,031 types of fuel pumps out there, you need to identify exactly what you have. I believe a 1971 originally had a dome-top Pierburg with a screw on top of the dome. and my guess is that yours does not have that. _________________ 1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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Q-Dog Samba Member
Joined: April 05, 2010 Posts: 8689 Location: Sunset, Louisiana
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Posted: Tue May 30, 2017 2:45 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Remove the pump and check the pump push rod. The rod needs to slide inside the plastic block with zero effort. If it is sticky at all it could get stuck when the engine heats up. _________________ Brian
'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 2:46 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Its a generator style aftermarket with the dome crimped on. |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 2:48 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Q-Dog wrote: |
Remove the pump and check the pump push rod. The rod needs to slide inside the plastic block with zero effort. If it is sticky at all it could get stuck when the engine heats up. |
Once it stalled i pulled off the pump not even 30 seconds after and the rod was perfectly fine and didnt have the slightest resistance. Once the motor cooled down the pressure went right back up. |
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Q-Dog Samba Member
Joined: April 05, 2010 Posts: 8689 Location: Sunset, Louisiana
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 2:52 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Q-Dog wrote: |
Well, fuel pumps do fail. |
Even with less than 500 miles? I mean i know it was a generic autozone pump but id still expect more than that. |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Tue May 30, 2017 2:59 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Ten seconds is enough to cool down, especially if the engine isn't super hot. The fit of the phenolic block is important here.
I would also remove the fuel sender and check the gas tank for a rag or other debris. Any dirt in the fuel filter?
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 4:00 pm Post subject: Re: Fuel pump loses pressure when hot. |
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asiab3 wrote: |
Ten seconds is enough to cool down, especially if the engine isn't super hot. The fit of the phenolic block is important here.
I would also remove the fuel sender and check the gas tank for a rag or other debris. Any dirt in the fuel filter?
Robbie |
The gas tank was the first place i checked for a clog but im skeptical that its a clog of any kind because i take it down the road and it dies in literally the exact same spot every time. A clog would be a little more random than that. Somethings causing the pressure to go to zero once its driven with a load for about a minute or so. |
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Mudpump Samba Member
Joined: May 11, 2007 Posts: 750
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Posted: Tue May 30, 2017 4:26 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Seems to me I've read threads where people were having trouble with aftermarket versions of the plastic block. When it gets warm it swells and restricts movement of the rod. You might check it and see if there signs of the rod rubbing against the inside |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 5:15 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Mudpump wrote: |
Seems to me I've read threads where people were having trouble with aftermarket versions of the plastic block. When it gets warm it swells and restricts movement of the rod. You might check it and see if there signs of the rod rubbing against the inside |
Its an original plastic piece but to be safe I already sanded down the base where it can restrict it and like I said above not even 30 seconds after the engine was off I had the pump off and the rod had no resistance at all. |
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David_nc_72std Samba Member
Joined: August 22, 2015 Posts: 841 Location: Winston-Salem, NC
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Posted: Tue May 30, 2017 5:36 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Is your fuel tank vented properly? If you are going approximately the same distance each time when it stops you could be developing a vacuum in the tank, easy test is to try driving with the fuel cap off. |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 5:48 pm Post subject: Re: Fuel pump loses pressure when hot. |
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I tried driving with the cap off too. I know its gonna be something really dumb and obvious but i just cant find what it is. |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51057 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Tue May 30, 2017 5:54 pm Post subject: Re: Fuel pump loses pressure when hot. |
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The line through the tunnel may be choked with rust, or the screen in the tank is covered in crap. Try draining the tank via the inlet line to the pump, jack the front of the car up and leave the gas cap on and see if it flows freely and makes a few gallons in 10 minutes. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Tue May 30, 2017 6:22 pm Post subject: Re: Fuel pump loses pressure when hot. |
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Im gonna pressurize the tunnel line and make sure its clear and holding in the morning. |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Wed May 31, 2017 12:12 am Post subject: Re: Fuel pump loses pressure when hot. |
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David_nc_72std wrote: |
Is your fuel tank vented properly? If you are going approximately the same distance each time when it stops you could be developing a vacuum in the tank, easy test is to try driving with the fuel cap off. |
For the record, Mom's bug was a routine 60 miles with a vacuum-sealed fuel tank. Now with a vent, we'll be driving it until the world's oil supply runs out.
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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wafflecopter Samba Member
Joined: May 29, 2016 Posts: 35
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Posted: Fri Jun 02, 2017 9:13 am Post subject: Re: Fuel pump loses pressure when hot. |
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I put a 1.5 to 4 psi electric pump on it and still didnt work. Aside from the tank the entire fuel system is brand new now. There may be a listing for a 71 super beetle in the classifieds soon if i dont figure this out. |
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hitest Samba Member
Joined: September 30, 2008 Posts: 10296 Location: Prime Meridian, ID
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Posted: Fri Jun 02, 2017 9:52 am Post subject: Re: Fuel pump loses pressure when hot. |
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wafflecopter wrote: |
I put a 1.5 to 4 psi electric pump on it and still didnt work. Aside from the tank the entire fuel system is brand new now. There may be a listing for a 71 super beetle in the classifieds soon if i dont figure this out. |
I may have you confused with another thread with the exact issue, bear with me. Did you pull the tank and replace/service the pickup tub on the underside of the tank? Either you or the other poster said they had not- yet never followed up. If your brass pickup screen (the stock fuel filter) is collapsed you will experience exactly what you are.
Nobody ever listed their car for sale because of this simple an issue. We're not letting your off so easy. _________________
EverettB wrote: |
I wonder what the nut looks like.
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'62 L390 151, '62 L469 117, '63 L380 113, '64 L87 311, '65 L512 265, '65 L31 SO-42, '66 L360 251, '68 L30k 141, '71 L12 113, '74 ORG 181
FU#5 |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Fri Jun 02, 2017 10:48 am Post subject: Re: Fuel pump loses pressure when hot. |
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wafflecopter wrote: |
I put a 1.5 to 4 psi electric pump on it and still didnt work. Aside from the tank the entire fuel system is brand new now. There may be a listing for a 71 super beetle in the classifieds soon if i dont figure this out. |
Ouch. Where approximately are you located? _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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obx71super Samba Member
Joined: December 16, 2012 Posts: 340 Location: Outer Banks NC
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Posted: Wed Nov 29, 2017 11:17 am Post subject: Re: Fuel pump loses pressure when hot. |
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I'm having the exact same problem with a buggy I just finished. Held 3psi at idle, would drop below one when revved some. Did that a few times, last time I revved it it dropped to nothing and didn't bounce back. New tank behind the rear seat all brand new lines and filter. I'm guessing I just need a new pump. Sucks cause this ones new! I don't know how people that turn wrenches for a living deal with all these crap new parts these days!! _________________ 71 super auto stick basically original minus a couple resprays
73 Westy automatic with a 2 liter gex, soon to be a 1.8 liter Headflow masters
Newest Addition!! Solid straight 74 thing totally disassembled!! YEEEWWWW |
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