Fuel pump wiring

[Zcat7]

I fitted an electric fuel pump this weekend but before getting stuck in I came up with a wiring configuration to give me a dedicated fused supply through a relay which protects against the engine stopping/stalling (and leaving the pump running) by using the oil pressure switch. Like the best laid plans it relied upon the oil pressure switch being "normally open" and putting an earth on when it gets pressure. This turned out not to be the case; it was in fact "normally closed" and removed the earth when pressured up...

Anyway, it wasn't the end of the world but ultimately it has resulted in me using an ignition switched +ve supply from the coil to both power the relay and supply the pump. I have fused the supply at 5 amps so I don't think I'm putting to much strain on the circuit but I wondered if anyone could see any problem with loading the coil feed further?
It all works OK, cuts out if the oil pressure fails etc but I thought I'd seek a sanity check! If necessary I have found an oil pressure switch that has both NC and NO connections on it but I'm unsure if it has the correct thread and would need to make an adaptor if not. I would be happy to leave as is if you auto elecs think it's OK as is.

Wiring as follows -

85 - Switched +ve from coil
86 - Earth from oil pressure switch (NC)
87A (NC) - Switched +ve from coil
30 - Feed to fuel pump

So basically if the engine stalls or I get oil pressure failure it will cut the pump by activating the relay and switching to an open terminal (87).
I've also put a manual switch in to prime the pump in case I have trouble starting (as the pump won't run until the engine has generated enough oil pressure) or the bus has stood for a while. This just piggy backs on to terminal 30.

Neil

 

[uber cool]

Sounds why too complicated, just take a feed from the coil or carb cut out switch ( all the same circuit) I doubt the extra load from the pump would blow the original circuit fuse. You wont need the prime switch then.

I'm guessing you are trying to prevent the pump running if the engine has stalled.

The pump should only run until the carb is full of petrol and the float in the carb closes the needle valve, once the needle valve is shut the pressure will rise and the pump will shut off. Hence if the engine stalls etc the pump will probably already be off as the float blow in the carb is full.

Also being wired through the oil switch you run the risk of cutting off the pump if the switch fails or more likely cuting off the fuel on low tick over once the engine is fully warmed on a hot day (on low tick over the oil light can flicker due to the low pressure).

what you need is to make sure the fuel pump is only delivering approx 3 to 4 PSI, either adjusted on the pump or a separate regulator.

 

[Zcat7]

Thanks Uber Cool

I guess I had crash protection in mind more than anything (the carb needle valves won't work with the van on it's side or a ruptured fuel line ) but also protection against oil pressure failure is a bonus. I take your point on hot tickover though so maybe I'll buy a fresh switch and keep my eye on the dashboard in traffic (at the ready to blip the throttle )

It probably looks more complicated than it is, it's a standard auxiliary equipment relay for fog/spot lights, that sort of thing and this is also the basis on which fuel injection pumps are wired I believe. I think my main concern was loading of the coil circuit by running the pump from it but if you think that's OK then I'm happy.

 

[Loxy]

I used a golf FI relay that I bought from GSF when I fitted my electric pump, cant remember the exact details (will try to dig them out) but it takes a feed from the coil and stops the pump when the engine isnt running, but also primes when the ignition is first turned on, has been problem free for a while now.

 

[Loxy]

Try reading here:
http://www.volkszone.co.uk/VZi/showthread.php?t=448416&highlight=Golf+relay+pump" onclick="window.open(this.href);return false;

 

[Zcat7]

Ah, interesting, thanks Loxy. Yes it looks like that has a trip that counts the pulses from the coil. So, it only applies the earth to the relay when it detects pulses (the numbers/diagram on the cover are a bit misleading but I'd say through pin 31b/1 depending on what you're looking at), and this happens as soon as the you start turning the engine. Cut the ignition and you simply switch off everything, cut the engine some other way: no pulses, it drops the earth to the relay and cuts the feed to the pump. Nice, I like it.

Good news however is that mine will work in the meantime as everything else on that post appears to be a variation on what I've done; some using oil pressure switch, some using ignition light but the principle is the same and it works successfully depending on what you want to protect against.

 

[uber cool]

the van on it's side or a ruptured fuel line

true, I wasnt thinking of such serious failures :shock: , maybe I need to rethink my plans :lol:

 

[Zcat7]

I guess there's only so much you can protect against in one go. I read a post from a guy who's fuel line had been severed as the fanbelt broke. As I recall he said he smelt the fuel through the "heating" system before he noticed the generator light (must have been enough momentum in the fan to push the fumes through?). Armoured fuel lines you you say? But then you don't spot it perishing beneath the pretty braiding... . You could go at this all day!

Thanks to all for your advice. Maybe I'll look at a complex series of relays that protect against all eventualities!

Neil

 

[r73]

That was me who had the belt rip the fuel line in half. It only happened cos fuel pump outlet comes out at really stupid angle and place the fuel line right in the firing line. i've looked at plenty of others and it wouldnt have happened.
I do think the best option is the relay wiring to the alternator though (as per VZI thread), you can add a second relay to prime the carbs, or a switch. I am going to ditch the mech pump and go the elecric route, but mount it as near to fuel tank as possible - as you would a fuel filter. i will wire in the relay and also the firetec so if theres a fire it would turn off the pump as well.
You can only do so much!!! - oh yeah one of the reasons i smelt the fuel was the belt tore the fresh air hose off and dumped a load of petrol down it as well!!

 

[Zcat7]

Hope you didn't mind me hijacking your story r73! Incidentally, having read of your experience I made sure that I positioned the electric pump with a flailing fanbelt in mind...

I guess in theory, with the current wiring I have (pardon the pun...) I could protect against both an oil pressure drop and/or a broken fan belt by "watching" for an earth from either the oil pressure sender or the althernator charge circuit; I might take a look at that. I have to say I'm less worried about starting/priming as there's quite a lot of fuel in the float chambers for that and it hasn't been a problem to date (especially since I fitted Pertonix ignition and a Flamethrower coil ).

 

[r73]

Yeah sure that would work for you. each system is going to be slightly tailor made anyway. i do find with twin dells that leaving the bus for a week or more it takes a lot of cranking to get the old girl to fire. i think you can get one way valves for the fuel lines that stop the fuel draining back, not sure how much difference that would make?
http://www.extremeautoaccessories.co.uk/products.php?section=4089" onclick="window.open(this.href);return false;

 

[Loxy]

Yeah sure that would work for you. each system is going to be slightly tailor made anyway. i do find with twin dells that leaving the bus for a week or more it takes a lot of cranking to get the old girl to fire. i think you can get one way valves for the fuel lines that stop the fuel draining back, not sure how much difference that would make?
http://www.extremeautoaccessories.co.uk/products.php?section=4089" onclick="window.open(this.href);return false;

I have twin dells on mine & they start pretty easily if they've been left for a while, just give a couple of presses on the accelerator then start her up.
I have a carter rotary fuel pump wired via a Golf EFi relay as mentioned above.

 

[r73]

Loxy Hi, yeah i want to change to an electric pump and the rotary ones are definatley better. is yours the one that has the filter before the pump?? I would be happier with the filter after it just in case of leaks so there is only one connection from tank pump. i want to mount the whole lot under the bus just after the tank, so i only have one pipe going into the engine bay. i also want to do away with regulator if i can?

 

[Marvel]

I used a golf FI relay that I bought from GSF when I fitted my electric pump, cant remember the exact details (will try to dig them out) but it takes a feed from the coil and stops the pump when the engine isnt running, but also primes when the ignition is first turned on, has been problem free for a while now.

Sorry Loxy, but can you give me a dickheads guide to how you wired yours in please?
And is this the relay you used?
http://www.ebay.co.uk/itm/Fuel-Pump...ts=Car+Make:VW|Model:Golf&hash=item45ff131ddf

Got a new engine and have the CB rotary pump for it, just wondered why you can't just take +ve from the coil and fuse it. Surely the coil only gets current when the key is turned, which is the time you want the pump to start working before the engine cranks.

Hope you can help

Marvel

 

[KateLovesPurple]

I fitted a relay on mine that takes a fused supply direct from the battery to supply the pump and the relay is triggered by the ign light from the alternator. Consequently it only pumps when the engine is running, so if the engine stalls the pump cuts out. As for the problem of no pump running when cranking, well, I have only ever found that to be a problem once after I had left the van for about 3 months without using it. There normally should be enough fuel in the lines and float bowls to start the engine then the pump will kick in straight away. Additionaly I also wired in to the supply line an inertia switch so in the event of an impact the fuel pump shuts off as well.

 

[Marvel]

So I've wired everything in and as the engine has been sat about while I've been faffing I primed the carbs with fuel with a piece of wire which I could hear. But then it cut out after running for a bit. I can't really hear the pump so not sure I've wired the relay properly.

Is this right?

 

[dubdubz]

87 - fuel pump
30 - 12v +
85 - ground
86 - idiot light

image courtesy of speedy jim http://www.nls.net/mp/volks/htm/elec.htm

 

[Marvel]

Yup, cheers. Thought I had the pump and the battery round the wrong way. I now need to check the relay isn't buggered :roll:

 

[shaggyXO]

I fitted a relay on mine that takes a fused supply direct from the battery to supply the pump and the relay is triggered by the ign light from the alternator. Consequently it only pumps when the engine is running, so if the engine stalls the pump cuts out. As for the problem of no pump running when cranking, well, I have only ever found that to be a problem once after I had left the van for about 3 months without using it. There normally should be enough fuel in the lines and float bowls to start the engine then the pump will kick in straight away. Additionaly I also wired in to the supply line an inertia switch so in the event of an impact the fuel pump shuts off as well.

Madman can you please explain how you plumbed in the inertia switch into the fuel pump circuit many thanks Shaggy

 

[KateLovesPurple]

I fitted a relay on mine that takes a fused supply direct from the battery to supply the pump and the relay is triggered by the ign light from the alternator. Consequently it only pumps when the engine is running, so if the engine stalls the pump cuts out. As for the problem of no pump running when cranking, well, I have only ever found that to be a problem once after I had left the van for about 3 months without using it. There normally should be enough fuel in the lines and float bowls to start the engine then the pump will kick in straight away. Additionaly I also wired in to the supply line an inertia switch so in the event of an impact the fuel pump shuts off as well.

Madman can you please explain how you plumbed in the inertia switch into the fuel pump circuit many thanks Shaggy

Yeah, no problem.

From the battery, through the fuse, through the inertia switch through the switched contacts on the relay, to the pump.

Hope that makes sense.