Died on Highway: Fuel Issue

hey_allen

Veteran Member
Joined
Nov 25, 2006
Location
Altus, OK
TDI
2000 Jetta TDI
Any chance it's the banjo bolt copper washers at the outlet of the pump head, where the return hose/pipe assembly is attached?

Between the washer under the check valve and the pump, and the two bracketing the pipe, there are 6 sealing surfaces that could possibly leak, if there was a flaw in the surface or how they were installed.

They're relatively cheap, and easy to replace if you want to test that.

Another possible diagnostic aid would be to put a length of clear hose between the #4 injector and the return pipe at the pump, to see if the bubbles are coming from the injectors or at the pump. I would expect that some basic 1/8" small engine fuel hose would work, at least for a short period of time.
 

tacolifestyle

Well-known member
Joined
Mar 16, 2017
Location
Detroit, MI
TDI
2003 Jetta Wagon
I have witnessed the bubbles coming from the IP return through the clear tubing. I have replaced all banjo bolt crush washers, thermo-tee and o-rings. I have installed all clear tubing between injectors and the # back to the pump. It took weeks for the air to purge from those lines. How much movement should I see there and how much if any air remaining there is acceptable? When I witness the bubbles from the IP there is no movement of the fuel in the #4 return or between the injectors.
 

hey_allen

Veteran Member
Joined
Nov 25, 2006
Location
Altus, OK
TDI
2000 Jetta TDI
Okay, I missed it if the injector bypass return hoses were mentioned earlier.

As to acceptable numbers, I don't know, as I've never noticed any returning in my pump return fuel hose, though I will often see a small bubble in the supply hose when the car has been parked overnight.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
I have witnessed the bubbles coming from the IP return through the clear tubing. I have replaced all banjo bolt crush washers, thermo-tee and o-rings. I have installed all clear tubing between injectors and the # back to the pump. It took weeks for the air to purge from those lines. How much movement should I see there and how much if any air remaining there is acceptable? When I witness the bubbles from the IP there is no movement of the fuel in the #4 return or between the injectors.
I don't think the return lines from the injectors see a lot of fuel, the pump meters the amount of fuel and returns a lot. Maybe up to a dozen small bubbles in that big line is normal, but they should go away.
Are we still troubleshooting the issue that caused the car to die at speed?
 

tacolifestyle

Well-known member
Joined
Mar 16, 2017
Location
Detroit, MI
TDI
2003 Jetta Wagon
The original dying at speed issue has been solved. The whole process has motivated me to dig further into start-up issues. I wouldn't say it's bad but often I will get significant white smoke at initial start up. Usually at a semi-warm engine state. I want to eliminate any air infiltration while I am at this.
 

Grady

Veteran Member
Joined
Feb 4, 2000
Location
NW Oregon
TDI
'01 Jetta
What is the condition of the O-ring on the threaded stem the CAT filter threads onto? That seal needs to be viable, or you will have an accumulated large air bubble such as the one you noted, several hours after shut-down.
Some background about where the air originates in an otherwise tight suction side fuel system that operates under a vacuum.
http://www.hastingsfilter.com/Literature/TSB/94-6R2.pdf
 

maxmoo

Veteran Member
Joined
Jan 19, 2011
Location
Lakefield, Ontario, Canada
TDI
2000 golf, 2001 golf, 2000 beetle, 2003 wagon, 2004 golf, 2004 jetta, all diesels
What is the condition of the O-ring on the threaded stem the CAT filter threads onto? That seal needs to be viable, or you will have an accumulated large air bubble such as the one you noted, several hours after shut-down.
Some background about where the air originates in an otherwise tight suction side fuel system that operates under a vacuum.
http://www.hastingsfilter.com/Literature/TSB/94-6R2.pdf
Interesting.
 
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