[T3] On and off hard start FI 73 type 3 ?

William Jahn willjahn975 at gmail.com
Fri Jun 24 08:09:50 PDT 2022

  My 73 was not really old when I bought it in 85. I did need all the
vacuum line and fuel hoses and other work. It had an issue where it would
idle then begin to drop RPM and blow black smoke. I happened to have a
voltmeter connected and saw the voltage drop when the black smoke happened
, took a VR to fix that, Later discovered the fresh air box  drains were
plugged while washing it to prepare to paint it the floor had a few inches
of water plus someone was chasing this found a few red positive battery
plastic protectors and a regulator that was just rust.

 I don't know why it used to start easy back then even though it did not
have the fuel line covers. I didn't know they ever existed . In fact the
starting issue seemed to show itself gradually. I noticed instead of 4
turns of the key to prime it I needed more.

 I don't know, I only assume the ethanol added to the gas plays a part , as
the % of ethanol through the years has increased it has become more
difficult to start. Didn't have this issue with leaded gas or lead free.

 I also don't know during the heat soak after shutting down how the % of
ethanol  reacts to heat. I know it attracts moisture from the air , but I
don't know since the fuel is still under pressure and in a closed system
how that would be possible. Since it's been in the mid 80's in the day here
and 60's at night plus very humid I suppose it's possible the fuel in the
tank has absorbed just enough moisture overnight so that is the first bit
of fuel that enters the system.

 I'm just guessing, I only know this seemed to begin when ethanol was added
to the fuel.

On Fri, Jun 24, 2022 at 7:25 AM Jim Adney <jadney at vwtype3.org> wrote:

> The question you never asked was, "Why does this happen now when it
> never happened when our cars were new." The short answer is, "I don't
> know, but I can guess."
> For what it's worth, my startup experience is EXACTLY the same as yours.
> When our cars were new, there was grey vinyl sleeving over all the FI
> hoses
> in the engine compartment. My GUESS is that this sleeving served as a bit
> of a heat shield, keeping those lines just a bit cooler in the heat soak
> after
> shutdown. When those hoses were replaced over time, the vinyl sleeves
> were thrown away, because the new hose was a bit too big to fit inside the
> sleeves and the vinyl may have shrunk a bit, too. It's also worth
> remembering that even when my '68 was new, I'd sometimes turn the key
> ON and OFF a few times to make starting easier. Later FI engines tended to
> run richer and cooler, but they had the same thermostat, so I'd expect the
> heat soak to be the same.
> Back in the day, I bought a roll of the sleeving from VW, but it came in
> black
> rather than grey. I figured that black would not be as good a heat shield
> as
> grey, and the hose I had at the time was still too large to fit inside it,
> so I
> never tried it. I have smaller hose now, so I might try it next time I
> replumb an
> engine, but the primer switches work great, so there's little incentive to
> look
> for a solution that still needs some use of the primer switch.
> Jim
> On 23 Jun 2022 at 15:31, William Jahn wrote:
> >  I have a prime switch and use it until I hear no more air then cycle the
> > key once pump the pedal once and most of the time it starts fine.
> Sometimes
> > it will start then quit yet I try the key again and it starts right up.
> > Once it starts I can drive it and shut down and it always starts right
> up.
> >
> >  I drove it yesterday and it started fine , today it quit once then
> > started.
> >
> >  I  replaced the fuel pressure regulator back in the mid 90's yet even
> the
> > original worked fine , never had any issues starting or air in the fuel
> > lines where I needed a primer switch
> >  I just turned the key and it fired right up.
> >
> >  I have checked everything and have power to the ECU from the power relay
> > and the pump relay always times out every time. The connector that feeds
> > the ECU from the power relay is clean and tight.  I replaced the fuel
> pump
> > with a 2 port type and it's been fine. I also replaced the fuel filter
> and
> > don't have many miles since both were done. Not long ago I took apart the
> > power relay and cleaned the contacts and replaced the ground wire since
> > half of the  1/4 " female crimp was missing.
> >
> >  All I can think of is that the fuel pressure regulator is bleeding down
> > overnight. The fact that once it's started then runs and starts right up
> > every time after tells me it's not a wiring issue.
> >
> >  The odd part is usually if it starts and tries to die if I feather the
> > throttle it will keep running. It's when it starts and runs for a minute
> or
> > so then just quits that has me baffled. This has only happened a few
> times.
> >
> > William
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> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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