Date: Thu, 15 Jul 2010 16:10:14 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: fuel pump producing bubbles
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
My first hunch or thought is ..
'that's not it, the bubbles' ..
however....'pin head size air bubbles' ..
sounds odd.
I would think if it's air being drawn in ..
it would be upstream of the fuel pump ...
like the pump-to-tank hose..
or even the new tank itself .
like a poor weld in the pick up tube inside the tank, something like that.
I suppose fuel pump itself is possible.
I would try another fuel source input the fuel pump ..and maybe a known-good
used fuel pump to see if that makes any difference.
besides 'inline 4 gassesr'..
what year and size engine, and what fuel system Difigant, Motronic, CIS-E ,
etc. what ? ? ?
normally I just look at fuel pressure and that's about it ..
in gasoline anyway, diesel is a different story about air in the fuel.
and 'cleaned injectors' ...
if they are anything other than original good working ones I get a little
nervous.
I'll give you are a real good air-in-fuel story ..
and I've never seen this in gasoline ( would be nice to know what fuel
system you have ..
like EFI or CIS ...would help to know which one ....it will always help
people help you if you give the the full compliment of pertinent info, I'm
sure you realize ) ...
but I was getting servere combustion gases ( which look like air bubbles )
coming back out from a tdi injector..
and there sure were bubbles in the return fuel there !
Never saw that before though ..
quite sure of it ....combustion coming up out of an injector into the fuel
system ..
though I've never seen that in gasoline, ever.
does it have an air flow meter ?
I assoicate surging with tired air flow meters.
don't make us guess which fuel system it is please.
----- Original Message -----
From: "Kenneth Lewis" <kdlewis@NORTHSTATE.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, July 15, 2010 12:48 PM
Subject: Re: fuel pump producing bubbles
> Sam,
> I have never heard anyone ask this question before. Try looking at the
> spray pattern of one injector and report back.
> Does the surging occur if you unplug the O2 sensor?
> Ken Lewis
>
>
>
> On Thu, July 15, 2010 5:22 am, Sam Payne wrote:
>> I have an '86 vanagon which has been running slightly erratically (+/- 75
>> rpm) at all speed ranges. I ran a fuel pump output test and the pump
>> tested within range, and ran quietly. But during the test while pumping
>> the gas into a glass beaker, I could see a fine, constant stream of pin-
>> head sized bubbles coming out of the return hose--I'd guess 10-15 per
>> second. I pumped 2 extra liters to check and the stream of bubbles stayed
>> constant. I'm guessing that the bubbles could cause the surging I've been
>> experiencing as injectors pick up the air bubbles and the air/fuel ratio
>> fluctuates and the oxygen sensor and idle valve struggle to compensate.
>> Make sense?
>> The gas tank is a new aftermarket tank with a 12mm output from the
>> pickup screen to the pump, so I doubt that the pump is fuel-starved. I'm
>> running a new large stock Bosch filter after the pump, not using small
>> square pre-filter, which was supposed to cause problems.
>> Could the fuel pump be cavitating because of age? Is this typical?
>> I'm running an I4 engine, not the wbx-er, but I don't think that bears
>> on the issue.
>>
>> Thanks in advance for help, and thanks to the list! Sam Payne
>>
>>
