E30 Fuel Pumps

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Thaumaturge
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Thu Jan 10, 2019 12:14 am

Hi all. New member here and completely new to car mechanics. I've had an F reg 318i SORN for a long time in an underground garage and thought i'd do what work i could myself in getting it back on the road to learn something and cut costs. I bought a replacement fuel pump on ebay which the seller, having asked for my reg, assured me was the correct part. Too late now for a refund but the point is once i opened the tank i find i have the two-pipe setup and the new pump is single pipe. Can the actual pump part of the unit work in both versions or do i need to order a whole new unit?

thanks
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Brianmoooore
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Thu Jan 10, 2019 10:01 am

Assuming the new pump is of a similar design, the pump itself can be swapped over. The only difference between the two is that the second (fuel return) pipe is cut off at the top, capped off and only used as a support for the pump.
Your tank uses the returning fuel to prime a siphon system that transfers fuel from the RH side to the left.
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paultv
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Thu Jan 10, 2019 10:02 am

Have you got any part numbers? or a link to what you bought? and did you check your VIN on Realoem to see what your car should have?

Paul :-) and what Brian said!
4th May 1990 325i Convertible.

BMW E30 Cabriolet Best Mod Ever:

http://bmwe30cabriolet-wdm.blogspot.de/
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martauto
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Thu Jan 10, 2019 3:23 pm

I have no idea about this but the guys above are pretty darn good.lol

Welcome to Zone as well mate :beer: :beer:

Pics are most welcome .

Mart.
E30 316 coupe 1986 (rip)
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E36 318ti Sport (rip)
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Thaumaturge
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Fri Jan 11, 2019 6:07 am

Thanks for he replies and welcomes :)


I'm attaching pics of the pump purchased. I didn't check it against realoem as it's completely new to me.


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As i say i'm new to car mechanics so not really understanding the explanation of differences between the pumps. If fuel is being combusted, why is it returning? And does the siphoning mean there are actually 2 tanks i need to drain?


Part number on the new pump reads

G4V18PC0328-04


Here's a link for the purchase/ad

https://www.ebay.co.uk/itm/NEW-Electric ... :rk:1:pf:0


So if i strip the pump portion of this i should be able to put it into the older unit?
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Brianmoooore
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Fri Jan 11, 2019 10:54 am

That pump looks like it can be transferred to your original frame.

Fuel is pumped from the tank by a pump that is capable of producing several bar of pressure. The fuel goes to the injector fuel rail , connected to the 'in' end of the injectors via a filter.
Also connected to the fuel rail is a pressure regulator, where the fuel in the rail acts against a spring loaded valve, allowing fuel to escape. The spring tension is such that the valve opens at 3 bar (for a 2.5 litre engine), so the pressure in the rail is stabilised at that pressure.
The fuel that 'escapes' from the regulator is fed back to the tank, where it enters via the second pipe on the pump on the smaller 55 litre tank, or via a pipe on the side of the tank in the case of the 62 litre tank, where it primes an internal siphon system.

Yes, on the 62 litre tank, there are effectively two tanks to drain, unless you keep the fuel pump running by 'hot wiring' it.
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Thaumaturge
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Fri Jan 11, 2019 11:41 pm

I see, thanks for the explanation. I'll pull the pump out and see what's what. On the offchance it isn't compatible do you think a benchside run through some degreaser would be good enough? The whole reason i'm doing these bits is the car has sat for a decade with stale fuel.
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Brianmoooore
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Fri Jan 11, 2019 11:58 pm

If the fuel in the tank predates when a small proportion of ethanol was added, then the pump my be savable. Ethanol absorbs water, and corrodes anything ferrous it comes into contact with.
It's possible to carefully bend back the crimp on the bottom of the pump, remove the black plastic base, free up the pump, then put the base back exactly where it was and bend the crimp back again.
Having said that, most original E30 pumps are a bit long in the tooth now, and either the commutator of the motor is nearly worn away, or the pump gears are worn and prone to jamming.
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Thaumaturge
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Sat Jan 12, 2019 12:21 am

Hmnn.. i did add a bit of fuel more recently when i tried to see if it would start so, if doable i'll try the swopover first. Finger's crossed! Draining fuel wise.. do i just need to remove that other panel on the LHS of back seat to get to the extra tank?
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Brianmoooore
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Sat Jan 12, 2019 10:00 am

Under the other panel you will find a second fuel level sender, required because the levels in the two tanks differ from each other. The second fuel sender fits into the tank in an identical way to the fuel pump.
P.S. Probably should have mentioned earlier that to remove the fuel pump, you have to remove the level sender fitted to it first, otherwise the assembly will not come out of the hole in the tank, and trying will damage the level sender's tube.
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Thaumaturge
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Mon Jan 14, 2019 2:49 am

Thanks again and no worries. I watched a few youtube videos of these being removed which showed the fuel level sender etc.
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