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bigblue72
Samba Member
Joined: November 26, 2014
Posts: 28
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 Posted: Tue Jun 09, 2015 2:41 pm Post subject: Air Getting in Fuel Filter |
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Hey guys,
I'm in Mexico city and just spent the last three days with a mechanic here trying to fix a cavitating fuel pump on a 1980 Vanagon L. We've done countless things to try to fix the problem but we're still getting nowhere.
The problem started after we dropped the tank to seal a part that was leaking. When we put the tank back up, air started getting into the fuel filter causing the fuel pump to make a loud buzzing noise.
So far we have,
Replaced the fuel pump
Replaced the lines
Changed the fuel filter type, in it's original location.
Changed the fuel filter from behind the pump to in front of the pump.
There's also an interesting addition that I'm not sure if it's original. A T comes from the line running from the fuel filter to the fuel pump. The T leads to what looks like a small pump. It's not working and is not in the original manual diagram so we removed the T to make sure that the air wasn't coming in through there but it didn't help.
Also, we tried connecting the line that delivers the gasoline back to the tank, to right in front of the fuel pump. The cavitating and air bubbles stop but the PSI moves frantically from 33 to 40 as opposed to semi idling around 35 when the line is connected to where it's supposed to go.
I'm not really sure where to go from here. Any ideas? |
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bluebus86
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Joined: September 02, 2010
Posts: 11075
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| Posted: Tue Jun 09, 2015 5:21 pm Post subject: Re: Air Getting in Fuel Filter |
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| bigblue72 wrote: |
Hey guys,
I'm in Mexico city and just spent the last three days with a mechanic here trying to fix a cavitating fuel pump on a 1980 Vanagon L. We've done countless things to try to fix the problem but we're still getting nowhere.
The problem started after we dropped the tank to seal a part that was leaking. When we put the tank back up, air started getting into the fuel filter causing the fuel pump to make a loud buzzing noise.
So far we have,
Replaced the fuel pump
Replaced the lines
Changed the fuel filter type, in it's original location.
Changed the fuel filter from behind the pump to in front of the pump.
There's also an interesting addition that I'm not sure if it's original. A T comes from the line running from the fuel filter to the fuel pump. The T leads to what looks like a small pump. It's not working and is not in the original manual diagram so we removed the T to make sure that the air wasn't coming in through there but it didn't help.
Also, we tried connecting the line that delivers the gasoline back to the tank, to right in front of the fuel pump. The cavitating and air bubbles stop but the PSI moves frantically from 33 to 40 as opposed to semi idling around 35 when the line is connected to where it's supposed to go.
I'm not really sure where to go from here. Any ideas? |
could it be some of the tank sealant has clogged the tank's outlet pipe internally??? could rust or dirt chunks clogged that pipe? can you blow air thru the outlet pipe back to the tank to test if there is a restriction or not in the pipe in the tank
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hdenter
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Joined: October 14, 2008
Posts: 2754
Location: San Luis Obispo, CA
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| Posted: Tue Jun 09, 2015 5:41 pm Post subject: |
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How full is the tank? Could the pickup tube have been damaged and air is getting sucked in? See if filling the tank helps....
Hans
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Wildthings
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Joined: March 13, 2005
Posts: 50351
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| Posted: Tue Jun 09, 2015 7:46 pm Post subject: |
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The T may have been for a gas heater that is no longer there, just a guess, don't know.
Have you tried removing the gas cap and seeing what effect that has?
If you remove you hose from the inlet to the fuel pump you should have a goodly flow of fuel from gravity alone.
It certainly sounds like the screen or something is clogged in the tank. I would blow pressurized air back into the tank from the outlet and see what if any effect that has. You need you gas cap removed when doing this and do not want anywhere near a full tank of gas. |
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61Scout
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Joined: November 06, 2011
Posts: 1297
Location: Shoreline/Yakima WA
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bigblue72
Samba Member
Joined: November 26, 2014
Posts: 28
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| Posted: Wed Jun 10, 2015 7:18 am Post subject: |
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We checked the inlet tube and there are no obstructions. The left inlet has more flow than the right one so we tried swapping the hoses but that didn't work either. We blew air in the tubes as well as inserted a metal wiire the size of the tube, we will try pressurized air tomorrow.
We did try filling the gas tank to a little over half a tank and still nothing
As for the pump being louder this is ridiculously loud. We tried driving it yesterday and the more we drove the louder it started getting. It drowns out the noise of the engine when you're inside the vehicle.
We didn't use tank sealant. We dropped the tank, vented out the fumes and welded it.
Tomorrow we will also be trying out the fuel pump on a different system to make sure it's not the new fuel pump.
Thanks for the help so far, any other ideas we could try tomorrow? |
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Wildthings
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Joined: March 13, 2005
Posts: 50351
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| Posted: Wed Jun 10, 2015 8:33 am Post subject: |
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I don't think there is much harm in running with the return line teed into the supply line. A lot of people who have 72-74 Bay which are being converted to FI go this route. The insides of the tanks are fairly convoluted. There is a separate fuel pickup chamber in the bottom of the tank with a pickup screen located in the bottom of it. The screen is attached by a plastic hose to the steel outlet nipple so there are several items that can fail inside the tank. These failures are pretty rare at this point, but I suspect in another 10 years most people will be experiencing them.
FWIW it is always amazing what one finds inside of old fuel tanks. One has to wonder the hows and whys of how the stuff gets there. |
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bigblue72
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Joined: November 26, 2014
Posts: 28
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| Posted: Fri Jun 12, 2015 9:43 am Post subject: |
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We ended up crisscrossing the intake and return, removing the pre-pump filter and adding a post pump filter hoping that the fact that the return had a more ample flow would fix the issue. Indeed, it drove well for a few miles last night. This morning, upon ignition, the pump started making noise again and the engine stalled.
I'm going to recap what's happened so far, hopefully, someone can help!
We have been driving at sea level for the last 6 months with no fuel pump issues, except for one day when the filter was too dirty and the pump started cavitating. We changed the extremely dirty filter immediately and the issue was solved.
For the first time, we rose in elevation to Patzcuaro in Mexico and the vanagon stayed stationary for a week, we turned it on a few times during the week to get the engine running. One of those times, a strange sound came from the enigne which we figured to be a valve issue, but the next time we turned it on the sound was gone.
That day we drove a couple mile and parked it, the next morning, upon ignition, it stalled. upon trying to start it again it would crank but nothing would happen. We assumed the engine was flooded, bled the lines and started it again. keeping a light foot on the accelerator was enough to keep it running without stalling long enough to warm up. It was fine all the way to Mexico City.
A few days later, upon starting, it stalled again. It took us bleeding the lines again, but this time we also had to crank the engine with the pump disconnected, then reconnected the pump (while still cranking,) only then did the engine start.
This is when we took it to the mechanic. The first thing we did was drop the tank and solder the minor leaks. That evening we tried to drive to our hotel but upon driving the highway, the engine started bucking, then lost power, especially uphill, and would only go again after a few minutes' rest. We got her towed back to the mechanic.
Assuming we had a pump issue, we checked the electrical connections to the pump. We checked the back pressure, fine. Since everything else seemed fine, we changed the pump. The new pump started making the cavitating buzzing sound, after driving a bit, same engine bucking, and eventual stalling. We started checking everything more thoroughly, discovered the original closed loop had been modified with the return from the engine coming back to a T between the pre-filter and the pump. We also discovered a non-functional pump:
This pump connected to what is supposed to be the return connection to the tank. We have no idea how long it had been dysfunctional for. After 3 days of trial and error, we eventually removed the whole non-factory modification, removed the prefilter, added a post filter, and used the fact that the return had a stronger flow to our advantage by criss-crossing the intake and return.
It worked! the pump stopped cavitating and upon test driving it, the Vanagon made it multiple miles including uphill with no problem whatsoever.
This morning, we start it, the pump buzzes, the engine stalls. 
wtf?!?!
help?
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Wildthings
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Joined: March 13, 2005
Posts: 50351
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| Posted: Fri Jun 12, 2015 9:54 am Post subject: |
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I am guessing you have something floating around in your tank that is going to clog whichever nipple you choose to use. With the tank design I see no way to remove whatever it is from the tank. Maybe a new tank is in order? Kind of a long shot and not that easy to do when you are out on the road far from home. Maybe getting the tee out of the system and cleaning up the hose routing would help, but I kinda doubt it.
Not sure what bleeding the lines would do as the system is going to self bleed. Also wonder why disconnecting the pump that one time made the engine start, this symptom would point to a different problem than your fuel pump or tank. |
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bigblue72
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Joined: November 26, 2014
Posts: 28
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| Posted: Fri Jun 12, 2015 10:03 am Post subject: |
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| Not sure what bleeding the lines would do as the system is going to self bleed. Also wonder why disconnecting the pump that one time made the engine start, this symptom would point to a different problem than your fuel pump or tank. |
We assumed the engine was flooded, so we figured disconnecting the pump would force the engine to burn off excess gas. Seemed to work. |
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djkeev
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Joined: September 30, 2007
Posts: 32625
Location: Reading Pennsylvania
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bigblue72
Samba Member
Joined: November 26, 2014
Posts: 28
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| Posted: Sat Jun 13, 2015 10:23 am Post subject: |
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| it might be our relay. It's saturday and everyone's closed, does anyone know what fuel pump relay is compatible with a 1980 aircooled vanagon? |
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bigblue72
Samba Member
Joined: November 26, 2014
Posts: 28
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| Posted: Sat Jun 13, 2015 12:15 pm Post subject: |
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it isn't our relay. Turns out our replacement pump was faulty. We replaced the pump for a new one, changed the pre and post filters for new ones, the lines between everything, new. We tested the system with an external tank, perfect. We put our tank back on, back to the same issue.
It seems our issue is from within the tank.
We're in Mexico City, anyone have any idea where we can get a new tank?
Or even what tank is a good replacement tank? |
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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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Wildthings
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Joined: March 13, 2005
Posts: 50351
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| Posted: Sat Jun 13, 2015 1:09 pm Post subject: |
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Remove the tank and try flushing it out with water every way you can think of, sideways, front up, front down, upside down. Maybe you can get whatever is in there out.
As a last resort, you could also braze in a new outlet using 5/16 or 8mm steel brake line. Drill lots of small holes in the part of the line that lays along the bottom of the tank so it is hard for anything to clog it. You will loose some fuel capacity if you do this especially when going up a steep grade so it isn't the greatest idea.
Somewhere here on The Samba is a picture of a cut open tank, you could use that as a guide for trying to add a new outlet to the tank. |
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bigblue72
Samba Member
Joined: November 26, 2014
Posts: 28
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| Posted: Sun Jun 14, 2015 1:43 pm Post subject: |
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before we start fussing with the tank. Last night, we again made some adjustments that lead to a good half hour of driving with no issues. This morning, immediately upon crank, pump is noisy and car refuses to start.
Could this be an electrical problem? Voltage regulator? Bad ground? Any ideas? |
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djkeev
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Joined: September 30, 2007
Posts: 32625
Location: Reading Pennsylvania
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| Posted: Sun Jun 14, 2015 2:13 pm Post subject: |
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You start this thread saying that you have air in the filter and the pump makes a loud buzzing sound.
You tried all sorts of things, switching fuel feed pipe even a new pump..... Same problem.
Well, a 12volt electric motor not getting 12volts does weird things.
Mainly not work properly.
I asked about a bad relay, you insist it is good..... Ok.
You still have the problem.
Dirty, worn, tired electrical bits don't work well. Make bad connections, deliver low or intermittent voltage.
Be it the + or the - connection, same result.
Do this, get a length of wire.....
Hook it up to the + terminal on the fuel pump
Take a second wire, hook it to the - terminal on the fuel pump
Hook those two wires directly to the proper terminals on the battery, jump in start it up and go.
Did it perform well? You've got wiring troubles, go find it/them.
Did it behave the same? It is not fuel pump wiring, go buy a tank or investigate your engine control systems.
THIS IS FOR TESTING ONLY, DO NOT KEEP THIS WIRING SYSTEM!!!
Unhook it immediately upon stopping.
Dave
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Randy in Maine
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Joined: August 03, 2003
Posts: 34890
Location: The Beach
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| Posted: Sun Jun 14, 2015 3:19 pm Post subject: |
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| Could you have a kinked fuel supply hose? |
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bigblue72
Samba Member
Joined: November 26, 2014
Posts: 28
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| Posted: Wed Jun 17, 2015 9:09 am Post subject: |
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Dave, I say the relay is ok because it was tested by an electrician.
Your test sounds logical enough, but the issue is completely intermittent. So I'm afraid it'll run fine for a while, but the issue will come back up again later. For example, yesterday, we thought all was fixed, the car drove for almost 2 hours, we turned it on and off no worries, we installed a pressure gage on the fuel line at the engine intake and checked it the whole ride, no issues.
This morning, we crank the engine and absolutely nothing happens. Pressure is stuck at 0.
Now we're about to check the power to the pump again, as soon as there's space in the shop, but I'm a complete loss as to why this issue happens mostly when cold, after having rested overnight. Is makes no sense to me. If it were electrical it would technically happen anytime, if intermittently. No?
One of the mechanics thinks there's some sort of vacuum issue with the gas being sucked back into the tank slowly. I don't understand completely because of the language barrier. Does that make sense to anyone?
Randy, no kinks in the fuel lines |
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Wildthings
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Joined: March 13, 2005
Posts: 50351
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| Posted: Wed Jun 17, 2015 9:57 am Post subject: |
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| Can you hear the pump run momentarily when you first turn the key to the "ON" position? |
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