Electric fuel pump wiring (Novice alert!)

[bigherb]

thank you bigherb. saved me money. Is the VW Heritage one a tachometric relay?

Yes

The connections to the coil, as I understand it then, relay pin 1 goes to the coil and so does relay pin 15. But where on the coil do I connect the wires?

To the coil terminals 1 and 15.

[ben50]

Hi, sorry to jump onto a thread. I broke down last weekend and the RAC bloke pinpointed the problem as the mechanical fuel pump.

I've just finished plumbing in an electric fuel pump and I've wired in the fuel cut off relay as below I used the 12v feed from the coil as power.

been cranking over the engine for about 15 mins on and off and no fuel is getting to the carbs.

I've fitted the fuel pump right up near the tank, after the fuel filter, then run the fuel line along the chassis into the engine bay and into the fuel filter.
does the fuel pump need to be primed before the first use? there is nothing in the fitting instructions to indicate this.

Cheers in advance.

Ben

[bigherb]

Yes 1 in the diagram does connect to the coil terminal 15.
Yes 8 & 7 does connect to the chassis earth.
The diagram shows a tachometric fuel pump relay but unhelpfully does not show the terminal numbers.
As a test of the pump, just connect directly to the coil 15 and earth to see if it works.
If the relay has terminal numbers put them up we can work out which wires go where.

[ben50]

Hi thanks for the reply,

hopefully these will help.

The relay was from csp: http://www.csp-shop.com/cgi-bin/cshop2/ ... sort=&all=

here's the bottom of the relay:


here's the side of the relay:


here's a pic of the relay socket, this came pre-wired with the 12v feed bridged from the terminal 15 feed:


I've got to pop out now, but I'll bypass the relay and check the pump when I'm back this evening.

Cheers,

Ben

[bigherb]

That explains it.
30 & 15 connect to the coil terminal 15
31b connect to terminal 1 on the coil
31 connects to body earth
87 connects to to the fuel pump

CB pumps are a bit voltage sensitive they won't start if the voltage is low. Possibly you have voltage drop to terminal 15 of the coil.
You might have to split the 15 and 30 and connect 30 directly a battery supply via a fuse (usually to the back of the alternator).

[AdrianC]

Stupid question... The pump you've bought - carb pressure, right? MUCH lower than the pressure required for injection, and a generic pump will probably be injection pressure these days. Also - does your carb have a return back to the tank rather than just cutting the flow off and expecting the pump to "run light"?

[ELVIS]

Wired on in the other day, 2 x relays, and appeared to be best of all worlds safety wise. Was energied via ignition live and not battery, was switched from starter solenoid and from alternator.

Has no power at all if key out, if key in position two it gets ignition live but still no power, if cranking it gets power but still won't work if alternator not turning. Only works if everything is in sync.

If alternator belt on your Aircooled snaps, it cuts power

Etc etc etc

Good set up, will try and find diagram online

[ben50]

Cheers guys.

tackling it again now - bit of a sore head this morning though ;o(

AdrianC, I got the fuel pump from briskwerks - it's sold for this application so hopefully it's gonna be ok, there's no return back to tank on my van.

Elvis, that sounds like a proper safe system, gonna have to try and sort it with the bits I have to had today though.

Big herb, I've just split apart the connector between 15 and 30 as you suggested, and I've run a cable across to the back of the alternator, does it matter which of the two reds I splice into?

Cheers,
Ben

[AdrianC]

AdrianC, I got the fuel pump from briskwerks - it's sold for this application so hopefully it's gonna be ok, there's no return back to tank on my van.

OK, good - but keep a very close eye on the carb when you first fire it up. May be worth stripping the carb and replacing the needle valve just in case.

[bigherb]

Big herb, I've just split apart the connector between 15 and 30 as you suggested, and I've run a cable across to the back of the alternator, does it matter which of the two reds I splice into?

Cheers,
Ben

No need to splice into the red wire there is a terminal on the back of the alternator you can connect to. Just make sure you fit an inline fuse close to the alternator.

[ben50]

Cheers, added an inline fuse close to the alternator and connected up to that terminal. Still no luck though ;o(

I'm getting 12v with the ignition off from the terminal at the back of the alternator, and with the engine turning over i'm getting 12v from the coil terminal 15, but 0v from terminal 87.

Could it be that the relay is faulty?

[bigherb]

12v from the coil terminal 15, but 0v from terminal 87.

Could it be that the relay is faulty?

Possibly but double check
But 31b is connected to terminal 1 of the coil?
31 is connected to a good earth?

If you have a 12v test lamp probe it into the 31b terminal of the relay socket the light should pulse on and off when you crank the engine.

If you bridge 30 and 87 on the relay plug does the pump run?

[ben50]

Hi Cheers,

I've just bridged 30 and 87 and the pump runs.

I don't have a test lamp, could I use a multimeter and probe into terminal 31b instead?

31 is connected to the body in one of the old mounting holes for the idle stablizer black box, I sanded around the hole back to bare metal and applied petroleum jelly

31b is connected tot he negative terminal on the coil (the one that also has a green wire attached)

CHeers,

Ben

[bigherb]

Hi Cheers,

I don't have a test lamp, could I use a multimeter and probe into terminal 31b instead?

Yes just test it to check it is not a bad crimp
You should get 12V with the ignition switched on.

Otherwise it looks like a duff relay.

[ben50]

Just checked that, got 12v on terminal 31b with ignition on. So does that mean the relay is duff?

Cheers,

Ben