[T3] [Non-DoD Source] Re: 1970 Fastback FI won't start

Dorough, Don CIV, NPPSC N3/PSD Pensacola don.dorough at navy.mil
Thu Feb 15 06:29:46 PST 2018

Jim, All,

Good news, I found my problem.  At one point I had swapped out the battery and there is a heavy red wire that connects to the positive battery lug.  That wire was lose. When I tightened the positive battery lug TIGHT, that red wire made good contact and the engine came to life!  

Now, one thing you said concerns me.  When I turn my key to the on position, I hear my fuel pump energize and it never stops running.  Something is wired wrong in the fuel pump/double relay circuit.  This would not be a problem with the engine running, but I understand that this is a built in safety feature that is designed to cut off the fuel supply in the event of an accident or the engine dies, etc.  

Do you have a wiring diagram of just the relays/fuel pump circuit?

Thank you ,

-----Original Message-----
From: type3-vwtype3.org [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: Wednesday, February 14, 2018 2:36 PM
To: type3 at vwtype3.org
Subject: [Non-DoD Source] Re: [T3] 1970 Fastback FI won't start

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 somewhat expensive.

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 them.

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 fire.  

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 didn't work.

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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