[T3] 1970 Fastback FI won't start
jadney at vwtype3.org
Wed Feb 14 12:36:09 PST 2018
On 14 Feb 2018 at 19:29, Dorough, Don CIV, NPPSC N3/PSD Pensacola
> I could use some help. I have a 1970 Fastback (still F/I) and it stopped starting.
> Here is what I have troubleshot so far and what I know:
> I have a new battery, charged up
> Fresh gas in tank
> Fuel pressure is about 30 - 32 without the engine running, but key on. I believe it will drop down to 28psi once it starts
The pump should run for only ~1 second after you turn the key ON. After
that, it should shut down unless the engine is turning over. If it keeps
running, the relay has been bypassed or there's a wiring problem. The
shutdown is an important safety feature. It's okay to bypass it for
troubleshooting, but it should not be necessary for running. If it seems to be
necessary, there's a different problem somewhere.
> (I can hear the gas circulating in the fuel rail and back to the tank)
> The plugs and points are cleaned and gapped property. I have good spark.
> The engine will "fire" for a few seconds if I use engine start fluid in the plenum. But it won't stay running.
> I'm beginning to worry that it is a ECU problem, but I'm hoping not.
The brains have been extremely reliable, so I would not look there.
Check the dwell and timing. Make sure the distributor is all the way down, so
the drive dog is engaged with the drive gear.
Put a clean length of hose on the pressure sensor and suck on it. If it won't
hold vacuum, you have a broken diaphram. I can exchange your pressure
sensor for a good used one that I've cleaned and checked. That will be
Turn the key on and then go back to the engine and depress the throttle.
You should hear a series of quiet clicks from the injectors. Two should fire. If
you hear them, feel the injectors to find which ones are firing. Remember
Turn the key OFF and rotate the engine by hand 180 deg, using a wrench on
the generator pulley. Repeat the test above. The other 2 injectors should
If you find that all 4 injectors fire (at different times) the injectors are working,
the trigger points are working, and the brain is, at least, minimally working.
If only 3 injectors fire, there is probably a wiring problem at the injector that
If 2 (or 4) injectors don't fire (1&4, or 2&3) then there is a wiring problem at
the FI trigger points or there is dirt in one (or both) trigger points. Check the
wiring, then pull the distributor to check the trigger points. You might be best
off at that point to send the distributor to me to be cleaned and adjusted. If
you clean the points yourself, don't file them; just wipe them clean.
Let us know what you find.
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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