Mk1 Cabriolet fuel problem.

[splkng]

Hi guys,

I'm having a strange problem on my 93 cabby (JH engine) at the moment. If I bridge the fuel pump relay contacts, so that the pump stays on with ignition, the car is fine. I bought a replacement relay so I could eliminate the old one from being faulty, however the problem remains..

If I start the car and keep the revs at about 1500, it idles fine. You can rev it as much as you like, it revs cleanly. However as soon as you let the rpm drop below 1000, the fuel pump relay clicks on and off erratically causing the car to stall, or idle very rough.

I had a look through the workshop manual and couldn't find anything really related to this problem.

Any help/guidance would be great!

Thanks,
Dom.

[EwenHayton]

Have u followed all the wires as best u can to see if theres a short some where? No idea myself just a noobs guess

[DognamedElvis]

Check all your earthing points...clicking relays are often a result of grounding issues. Make sure your earth contacts are clean and tight...
Pete.

[splkng]

Check all your earthing points...clicking relays are often a result of grounding issues. Make sure your earth contacts are clean and tight...
Pete.

I'll run over the earths again.

Am I right in saying that the relay gets the tach signal directly from the coil? I may try running a new wire in to the fusebox.

Thanks guys,
Dom.

[roccodingo]

Check earths first, specially the one from rocker cover to Ign coil mount.

If your car is fitted with aircon, it will likely have a pair of auxillary air solenoids that are attached to the right hand strut tower, you will see the hoses going to and from the inlet manifold. One switches on with the aircon, the other switches on when idle speed drops to about 700 RPM, then switches of when the idle is above 1100 RPM. I have had issues with the relay that controls this valve, yes, it also takes engine speed from the tacho signal of the coil.

If you have these solenoids fitted, check wiring and also the hoses for air leaks.

What manual publisher have you got , doesnt show up in Bentley cause 93 US cabrio's were running digifant by then.

[chortle]

there is 2 types of relay.
4 pin and 5 pin. The 5 pin takes a signal from the coil, for rev limiting.
Not sure if this your issue?

cheers

[splkng]

I checked all earths, everything seemed fine.

I ended up finding a new ignition module at work, so I replaced that for the sake of it and the problem is fixed now.

Thanks guys.