T2 78 Multiple relay installation - Hot start and petrol pump

[peagreenbus]

I want to fit a hot start relay, 2 petrol pump relays and an aux battery relay in the engine bay and a fog light relay up front. Petrol pump is off the coil at the moment.

If there are any electrically minded out there who could have a glace at this installation sketch I would be most grateful.

I have some questions -
I think I need 10gg cable from relay to terminal 50 on the solenoid?
Also 10gg from starter relay to earth pin 30?
Also 10gg from starter relay to solenoid terminal 30?

Is it ok to daisy-chain lives and earths? (Within reason as in the diagram - no heavy loads on the daisy chains)

The Alternator blue (same as the Voltage regulator blue) will activate both the petrol pump relay and the split charge relay
which both depend on whether the engine is charging itself or not - correct? OR should I take the live off the VR blue.

Unsure of where to take the live for the fog lamps from. Or maybe better route a new 2.5 from the battery directly.

I’d be very grateful if any errors could be pointed out or improvements given.
Many thanks

_________________
Driving - Cooper 1275, VW Bay '78, 110 Defender
Gone - Herald (topless), Minor MM, Minor 1275, Traveller, Saab 96, P1800, ½ Ton Lightweight
Riding 1150 GSA
Sailing 1962 Fireball

[KentABQ]

Nice job with the schematic! That's impressive.

The person you'll want to chat with is Telford Dorr. He's online often, and should comment on your questions soon.
_________________
-Kent-
1976 Riviera, 1.8l FI chrome yellow VAN - "Chloe"

"I must say, how can you be in a bad mood driving this vehicle full of vibrant color.
Cars of today are so bland in comparison. It's like driving a celebration!" ---WildIdea

Bus ownership via emoticons:
---williamM

[Wildthings]

A fuel pump specific relay has a diode in it so it can be activated by two different triggers, your system would also work.

[SGKent]

FWIW because of the way VW buses need massive amounts of air to cool, in wet season there is a lot of humidity in the engine bay - it isn't like an American car where the air is deflected down and under the car. The air has to get out thru the engine which means it circulates in a larger area. Were it me, I would visit PickNPull or something like that were you can find a relay box out of a junk car that is weather tight, and use that for your relays. If you expose them to the elements, they will last a while but not as long as those sealed up. You can also mount them to the firewall up high near the double relay to avoid some of the wetness.
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

[telford dorr]

A few minor (and one major) changes (as noted in red):

1 - need two wires to the ignition switch to separate the start and run functions.

2 - swap relay terminals 85 and 86 for relay compatibility.

3 - eliminate redundant fuses.

4 - minor rework of start driven relay wiring.

5 - increase main power fuse from 15 amps to a 30 amp slow blow type (starter solenoid initially draws 25 amps).

Other than that, looks good.

_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[peagreenbus]

Thank you Telford dorr
That’s really clear and I see and understand my mistakes!

Will report back when it’s working. Fingers crossed.
_________________
Driving - Cooper 1275, VW Bay '78, 110 Defender
Gone - Herald (topless), Minor MM, Minor 1275, Traveller, Saab 96, P1800, ½ Ton Lightweight
Riding 1150 GSA
Sailing 1962 Fireball

[telford dorr]

Not mistakes - more of a lack of optimization. But that's OK: in the software business we like to say, "beware of premature optimization". After the third prototype (or so), a design gets pretty close. You're only on the first pass (but the direction is correct)...
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[ratwell]

[peagreenbus]

Ah ok so that's where I got 85 and 86 the wrong way round.

On the WR1 relay kit it specifies 86 to ground and 85 to trigger.

This one!
https://www.thesamba.com/vw/gallery/pix/897887.jpg
which is a Bosch. So is that a wrong sketch from the reseller?

My relays aren't Bosch, but "made in EU" other ones, and I've changed earths to 85.
However, it would still work the other way round, wouldn't it as its an electromagnet and I presume no diode...? 4 pin relay.

And is 30A ok for the hot start? Maybe 40A better?
_________________
Driving - Cooper 1275, VW Bay '78, 110 Defender
Gone - Herald (topless), Minor MM, Minor 1275, Traveller, Saab 96, P1800, ½ Ton Lightweight
Riding 1150 GSA
Sailing 1962 Fireball

[telford dorr]

[ratwell]

This is a really good webpage on Bosch relays from several years ago that's thanksfully still around:

http://www.bcae1.com/relays.htm

You'll need to enable Flash in Chrome (Preferences->Privacy and security->Site Settings->Content->Flash Always Ask to [ON]) to get the most from it, although there doesn't seem to be any animations that take advantage of Flash.

[peagreenbus]

Just a short follow-up to this.

I know most of you will get through this little relay installation before breakfast, but in between leaking fuel pumps, porous pipes (now replaced with R14 barricade) all breather pipes replaced, and a firewall respray, it took me a little longer!

Now all done, it works very well.
If I was doing it again. I'd look at a single 5 pin relay rather than two 4 pin for the safety cutout.
Starting with empty carbs was made a lot easier with a little jump lead from battery to relay just to fill them up.

New pump installed on the chassis rail and a petrol king regulator running at 2.1 psi. into FRDA's

Thank you for the help again and I'm afraid my wiring isn't quite as neat as yours. That 10gg can be a devil!

Good to be back on the road! Just a balance pipe / vacuum question now but I'll do that on another post topic.
_________________
Driving - Cooper 1275, VW Bay '78, 110 Defender
Gone - Herald (topless), Minor MM, Minor 1275, Traveller, Saab 96, P1800, ½ Ton Lightweight
Riding 1150 GSA
Sailing 1962 Fireball

[Wildthings]

You can get fuel pump relays with a built in timers so that the pump will run for a second or two when you first turn the ignition switch on like what happens on newer FI'd cars and trucks. This would allow you to prime the carbs just using the key and would also shut the pump down automatically whenever the engine quit for some reason like being in a wreck or if you had an engine fire.

[ToolBox]

[raygreenwood]