help e34 intermittently failing to start

[steve sport]

thanks any help would appreciated.

steve

[pingu]

I'm about to post a piccy but with regard to your photo, my car is different.

On mine, the starter relay is directly between the relays that you've marked 1 and 2 - but in your relay box that's a vacant spot without a relay!

I'm not sure how you get access to the relay - my Indy did this for me. I wonder if it's quite tricky as they basically levered up the relay socket (the socket is now loose) rather than undoing the screws etc.

P.S. It might be worth completing your profile in more detail - we can't tell what sort of car you've got.

[pingu]

To answer your question, the starter relay has two wires: they're both black with a yellow stripe and quite thick (thicker than the other wires that go to the starter relay).

One of the black/yellow wires goes to the ignition switch. The other goes to the starter motor solenoid.

If you splice in a wire to the black/yellow solenoid wire, then by connecting the other end of your splice wire to the B+ terminal, you'll be able to energise the starter motor. Make sure your engine isn't in gear!

[pingu]

Although using a spliced wire to connect the solenoid to the B+ terminal works, I got fed up with that after a while (especially when it was raining).

To banish the problem once and for all, I used a booster relay.

The "original" (I fitted a replacement relay from the dealer but this didn't have any effect on the starting problem) relay is marked "1" on the photo.

The booster relay is marked "2" on the photo.

The original relay 1 is now only used to energise the coil of the booster relay 2 (the original relay 1 is no longer connected to the starter motor solenoid).

Of the switched contacts of the booster relay 2, one now connects directly to the B+ terminal. The other switched contact of the booster relay 2 is connected via the black/yellow wire (the one that previously connected the original relay 1 to the starter motor solenoid) to the starter motor solenoid.

Of the two wires that you can see leaving the relay box, the red one is the wire to the B+ terminal. The black wire provide an electrical path to chassis for the coil of the booster relay 2. I had to make a small notch in the relay box to allow the black and red wires to exit the relay box. The brown gunk is sealant to stop moisture from getting in to the relay box.

Good luck!