VX fuel cut off relay

[lancialulu]

I have a standard coupe which I am trying to de bug some wiring issues.

As some folk will know the VX adopts the i.e. fuel pump but it also seems to have an interlock on the fuel relay governed by oil pressure switch. I cannot find this interlock/relay/solenoid. It makes a noise of a contactor clunk when switching off the ignition. The pump will not run until oil pressure has activated the oil pressure warning switch.

Does anyone have the details of this relay/cutoff device and where is it in the car. The clunk noise seems to come from low down on the bulkhead on rhd drivers side. (BTW my standard HPE VX also has this clunking solenoid so I am sure it is a standard installation).

I have the VX supplementary information to the i.e. wiring diagrams but there is a black hole regarding this dual relay (mentioned in passing in the notes).

Can anyone help?

[Nigel]

I think we are reading the same notes.
There is a picture, seemingly hand drawn in style, that puts the relays
either located near the power steering reservoir or in a supplementary
box on the nearside front by the horns. On my HPE, this box houses the a/c relays and
the radiator fan relay.
From looking at the relay wiring picture it seems the relays are the standard shape,
square, with 5 pins, and could be coloured red or black, not the more common white.
These colour changes could indicate that the relays are switching in a different way.

I realise this is probably not very helpful. Maybe you can trace a wire that emanates from
the oil pressure switch to one of these locations?

Nigel

[hutch6610]

Yes
Hello lancialulu.
You i assume are looking for the fuel pump / petrol vapour pump relays and the fuel regulator which you call an interlock?
If memory serves the relays are located under that rubber flap that covers the ignition coil on the passenger side. They are to the left of the coil and there is a also a double fuse holder under a plastic cover - you can't miss them as they are the only relays on a (standard UK VX) in that location. Its been years since i have looked at my VX but i am sure that is where they are located.
The clunk you hear when you turn the ignition on is the electrovalve which controls fuel pressure. It is located on a bracket along with another fuse next to the power steering reservoir. The most common fault is one of the fuses melt or don't make proper contact in the twin fuse box.

The fuel pump is energised on cranking of the engine and then the oil switch relay takes over otherwise you would have to crank for ages. The round engine multi plug is where the power takeoff is located below the distributor. The big red wire in the middle is Siamesed and goes to energise the pump on cranking. 

Whats the actual problem you are trying to debug? 

[lancialulu]

Thanks both.

I have established the general picture (attached) with the added bit of information courtesy of Alan Cooper of a mercury switch in series with the fuel pump supply.

I am trying to de bug a few electrical gremlins after a previous owner changed the ignition switch.

At the moment the fuel pump is refusing to run. I am about to test directly the fuel pump but I do not really believe in coincidences (ie pump failing as it was working a few days ago.

Any input would be appreciated.

BTW I have redone all engine bay earths....

[lancialulu]

Making some progress. Wiring is correct at relay but oil pressure switch line (light blue to battery side 6 way connector) is always earth/0v even disconnected from switch.

The light blue wire comes up to the 6 way engine connector and has a piggy back to a 2way (likewise red wire into the other terminal of the 2 way). The other side of the 2 way is yellow /light blue x2 and red on the other side. I think one of the yellow/light blue goes to pin 85 of the fuel pump relay. The other yellow/blue is providing the spurious earth.

So where does this yellow/blue#2 go to as there is no specific complete wiring diagram for the volumex.

[Nigel]

At this stage it may be beneficial to reverse your thinking.

Have you established that you're not getting current to the fuel pump
when cranking? i.e. Is the fuel pump working?

By giving external 12v power to the pump via a separate 12v source, the pump should run.
It's worth disconnecting the fuel line to the carb and directing into a bottle to check fuel flow.
Do this with the coil king lead disconnected at first. Once fuel flow is good, reconnect the fuel line.
If you then have a running engine, tracing backwards
via physical wire checking should establish where the break in communication is.

There are probably several points along the wiring harness where connections front to
back have connectors that may be corroded.

Nigel

[lancialulu]

At this stage it may be beneficial to reverse your thinking.

Have you established that you're not getting current to the fuel pump
when cranking? i.e. Is the fuel pump working?

By giving external 12v power to the pump via a separate 12v source, the pump should run.
It's worth disconnecting the fuel line to the carb and directing into a bottle to check fuel flow.
Do this with the coil king lead disconnected at first. Once fuel flow is good, reconnect the fuel line.
If you then have a running engine, tracing backwards
via physical wire checking should establish where the break in communication is.

There are probably several points along the wiring harness where connections front to
back have connectors that may be corroded.

Nigel

Update

Fuel pump works if I apply 12v to 8amp fuse (I have an inline pressure gauge after an added malpassi regulator and it shows constant 3psi which I am happy with), also works when cranking, and oil pressure switch opens as it should when engine is running. However the oil pressure switch (lt blu)  which is piggy backed at the 6 way connector (see previous photo) goes into 2 x lt blu/yellow wires which stay at 0v so switching off the fuel pump relay..... It is this other yel/blu wire that is not on any wiring diagram I have that is causing the problem. I could disconnect the piggyback and the pump runs all the time with the ignition on - not ideal.

Any ideas on destination of this second yel/blu wire?

[hutch6610]

Gosh i have never seen the two diagrams you have uploaded. I have also never seen a mercury switch fitted.
I think Nigel may be on to something when he mentioned the relays as they are different. Looking at the first one the fuel pump one is a two way and the fan is a plain on off, I wonder if somebody has fitted the wrong one or perhaps they are mixed up. Have you checked these first?


I am going to look at my coupe Monday so will take a photo and trace the Yellow /blue for you and the relay numbers.

[lancialulu]

Yes the fuel pump relay closes with ignition on / no engine running. No fuel pump running.  Fuel pump runs with cranking volts until oil pressure switch operates and drops the relay, then the pump continues with current/volts supplied by the ignition circuit. Except mine does not..... Beginning to suspect a dodgy oil pressure switch although my meter says it is working. Tomorrow I will get back on it.

[SanRemo78]

Does the oil pressure light on the dash go out Tim? That would indicate the switch is working as intended.....

I'm sure I did a write up on the Stratos Replica Club's newsletter about how the system worked having built the replica with a VX drivetrain initially. I can try and look it up but it will probably just confirm the diagrams you've got already.

Guy