[T3] Question re F.I. fuel pump cutoff

[Joe McDiarmid]

Jim laid it out pretty well, but I should point out that I HAVE seen this
type of failure when the internal ground in the ecu is no longer functioning
properly. This however can only be determined after ALLL the other things
Jim pointed out have been checked. there is an internal grounding switch
circuit that eventually outputs on wire 11 -- if that internal grounding
switch is stuck closed, then the pump will run continuously. I've had this
happen on two ECU's, Another internal type failure involves the trigger
contacts -- if the internal circuit for that has failed, the pump can also
run continuously. prove it to yourself by leaving the car off and the key
turned on -- now remove the distributor and (leaving the FI plug connected)
spin the shaft. the pump will come on, or would if it was acting normally,
and run until you stop spinning the shaft.

On Fri, Apr 15, 2011 at 12:15 PM, Jim Adney <jadney at vwtype3.org> wrote:

> On 15 Apr 2011 at 12:43, Robert Bills  wrote:
>
> >  The fuel injection fuel pump for my '73 Squareback is supposed to run
> 1-2
> > sec. when the ignition switch is turned to the "on" position, then stop
> > until the engine fires.  Mine did, but now runs all the time when the
> > ignition is turned to "on."  Since the cutoff is a safety feature to
> prevent
> > the pump from running when the engine quits, thereby preventing a
> gasoline
> > catastophe, I need it to work properly.
>
> > My reading of various fuel injection manuals for the Bosch D-Jet
> suggests,
> > but does not clearly state, that it is the fuel pump relay that controls
> > this function.  Is this correct?  (makes sense to me, because this is an
> > open loop system.)  If not, what does?
>
> Yes, it's a very good idea to keep this feature working correctly.
>
> The fuel pump relay controls the pump, but the relay and its timing is
> controlled by the brain. Unless someone has changed the wiring for your
> relay
> or some of the FI wiring, I don't understand how you could get the failure
> you
> describe in a '73. I think failures in the brain should make the pump run
> ALL
> the time or none of the time, but I suppose it's possible that a failure in
> the
> brain timing circuit MIGHT give the symptoms you describe. I've never seen
> that
> happen.
>
> If the pump actually runs continuously as long as the key is ON, then I
> THINK
> the problem has to be that either the relay has been rewired to be
> controlled
> by the key, or the relay has been bypassed so that the key feeds the pump
> directly.
>
> Look at your pump relay. Pull the white plug off it and see if the pump
> still
> runs. If it does, move one of the 2 red wires to a different terminal. If
> you
> have an AT, there will be 3 red wires and finding the correct solution is
> slightly more difficult to describe.
>
> In general: There are 3 tabs on the relay that are available after the
> white
> plug is installed. 2 of those are close together and are, in fact, the same
> connection. The red wire from the fuse box should go to the 3rd tab.
>
> The other 1 (or 2 for AT) red wire(s) connect to the 2 tabs that are close
> together.
>
> The red wire to the fuse box goes to a fuse that should serve no other
> load.
> That fuse should be hot all the time, not controlled by the key.
>
> If pulling the white plug off the pump makes the pump not run at all, let
> me
> know and we'll think about other possibilities.
>
> --
> Jim Adney
> jadney at vwtype3.org
> Madison, WI USA
>
> _______________________________________________
> VWType3.Org mailing list - type3 at vwtype3.org
> http://lists.vwtype3.org/listinfo.cgi/type3-vwtype3.org
> Contact gregm at vwtype3.org if you need help with the list.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.vwtype3.org/private.cgi/type3-vwtype3.org/attachments/20110415/08de8693/attachment.htm>