Looking for a gas tank and low pressure pump

#31

[quote=“ffej” post=71505][quote=“jlevie” post=71504][quote=“ffej” post=71503]Great opportunity to Cross-Post…

Want to doublecheck fuel pump part numbers. I want to make sure that this - 16141184022 - is the low pressure pre pump.[/quote]
That is the in-tank high pressure pump as used with the 63L tank. The low pressure transfer pump, as used on a 53L tank is part 16141179415[/quote]

Thanks Jim. Every time I see that part, though, I see a picture of what looks like half a pump or the inline unit. I need the in-tank pump to feed the other in-tank pump that I’m installing (the late model 318is unit) for the two pump solution. Example of why I’m confused: http://www.ebay.com/itm/BMW-3-Series-Fuel-Pump-16141179415-C366-/350510859325[/quote]
That part is a replacement pump only, not the whole assembly that you need.

That is the full pump assembly, similar to what you need. Though that one is the high pressure pump used with the 63L tank.

The pump can be replaced without replacing the entire assembly. Since that is the cheaper route it is more commonly found on ebay. A competitive source for the pump you need would be http://www.rmeuropean.com/Part-Number/Fuel-Pump-(Pre-Supply-Pump)---In-Tank-Suction-Device-__16141179415_CON_9586A474.aspx

#32

Gotcha. Thanks for the clarification. I was beginning to wonder if it was just a replacement component for the full unit…

#33

Ok, so I have been following along here. From what I can see, this pump is what I would buy to put on the driver’s side (LEFT) and somehow hook this up to the other tank, which mine being a later model with a single pump was not designed for (1989). Does the siphon hose hook directly up to the high pressure pump?

I’m confused on how this is all going to hook up. My car is in the air right now as I swap the clutch and am debating about whether or not I can get this done without dropping the tank.

#34

[quote=“Foglght” post=71522]Ok, so I have been following along here. From what I can see, this pump is what I would buy to put on the driver’s side (LEFT) and somehow hook this up to the other tank, which mine being a later model with a single pump was not designed for (1989). Does the siphon hose hook directly up to the high pressure pump?

I’m confused on how this is all going to hook up. My car is in the air right now as I swap the clutch and am debating about whether or not I can get this done without dropping the tank.[/quote]
It might be possible to snake a line across the top of the tank with it in the car, but I suspect that you will have to drop the tank. You will have to replace the right side pump with one for a late model 318is.

The siphon is in the left side of the tank and the hose from the engine bay carrying returning fuel connects to the siphon on the lower left of the tank.

#35

What is different between the 318 pump and my large tank 325 pump?

#36

The 318is pump has a return line tube that the 325 pump does not have; so in the two in-tank pump solution you can easily run a line from the low pressure pump on the driver side directly to the pump on the passenger side, instead of having to do additional plumbing.

#37

Correct!

#38

So, the return line now goes directly back to the tank on the driver or passenger side?

The new setup would have the return line going to the driver side, with the output of the low pressure pump going to the return line of the passenger side high pressure pump? amirite?

#39

Lots of good information here on using two pumps in the tank.

http://www.r3vlimited.com/board/showthread.php?t=278695

#40

[quote=“Foglght” post=71528]So, the return line now goes directly back to the tank on the driver or passenger side?

The new setup would have the return line going to the driver side, with the output of the low pressure pump going to the return line of the passenger side high pressure pump? amirite?[/quote]

Sort of. The return line from the motor would still plug directly into the tank, you’d plug the return on the low-pressure pump and run a line from the output of the low pressure pump to the return on the high pressure pump.

At least, that’s how I see it working best. Since it’s pretty much Jim’s fix, he can tell you more.

I also think you can do this without having to completely remove the tank and disconnect everything, just lower it enough to get the fuel line from the driver to the passenger side.

#41

[quote=“ffej” post=71530][quote=“Foglght” post=71528]So, the return line now goes directly back to the tank on the driver or passenger side?

The new setup would have the return line going to the driver side, with the output of the low pressure pump going to the return line of the passenger side high pressure pump? amirite?[/quote]

Sort of. The return line from the motor would still plug directly into the tank, you’d plug the return on the low-pressure pump and run a line from the output of the low pressure pump to the return on the high pressure pump.

At least, that’s how I see it working best. Since it’s pretty much Jim’s fix, he can tell you more.

I also think you can do this without having to completely remove the tank and disconnect everything, just lower it enough to get the fuel line from the driver to the passenger side.[/quote]
That is correct.

#42

why wouldn’t you keep the stock pump and just reroute the return line to the low pressure pump and run the transfer pump where the return line goes, unless that is in the same cavity…thus being pointless?

#43

The stock return line goes to the siphon, which is in the left side of the tank. The point of the transfer pump in the left side is to pick up fuel and drop in directly into the cup that surrounds the intake of the right side pump. The siphon works, but it’s flow rate is pretty low as compared to a transfer pump. Furthermore, the cup is roughly 1-1/4" tall so you have to keep more fuel than that in the right side to keep the cup full. In right hand turns fuel wants to slosh away from the cup and over the hump into the left side.

#44

OK, I’ve tried to follow this post, but I’m not too smart.

I have a 1987 SE30 now. This system, as I understand it, has a 55L tank, with a low pressure pump on the passenger side, a crossover tube on the bottom, and a HP fuel pump on the driver side rail somewhere next to the tank.

What I’d like to do is swap in a 63L tank, and make it so it can pick up as much fuel as possible. That said, I did not fully understand the above posts, because I don’t think anyone was doing a 55L to 63L swap in conjunction with the changes to the pump.

I apologize for being dumb, but can someone please explain exactly what I need to order and do to put a 63L tank in this 1987 and have it pick up as much fuel as possible, and hopefully have the fuel gauge still work. I would greatly appreciate it.

-Scott

#45

After doing more looking around, here is what I am thinking:

Recall that my car is a 1987.

I will put in a 88+ 63L tank.

In that 63L tank I will put 2 early low-pressure lifter / supply pumps, each feeding into a big surge tank mounted in the trunk. I will cap the return inputs on the low pressure pumps.

The surge tank in the trunk will gravity feed back to the stock high pressure pump, which will continue to feed the stock fuel rail.

The return line from the fuel pressure regulator will also feed back to the surge tank.

The surge tank overflow line will go back to the return/siphon line on the 63L tank.

A concern was raised regarding running the driver side low pressure feed pump dry, since the low pressure pump and whatever the siphon capability is will drain the left side. Is there any way to alleviate this?

Where do I put the fuel filter in this arrangement?

Where can I order two good low pressure pumps from?

Is there a way to get the fuel gauge to work with this setup?

I have to believe this setup will drink up every drop of fuel that is in the tank.

Thoughts?

#46

Jim Levie isn’t on the forum much these days and he’s the guy to talk to. Email him at jim(at)entrophy-free(dot)net

#47

There are several ways to do this, but all I will describe is the easiest and simplest.

You will need the 63L tank, the transfer pump & level sensor from a 55L system, late production high pressure pump from a 318is (it has the fuel return fitting), some hoses, connectors for the low pressure pump and level sensor, the fuel filter bracket for the 63L system (optional), and the fuel gauge from a 9/87 or later 325.

There are three minor difficulties, but all are easily dealt with. The first is that a right side level sensor is grounded, but we need to be able to wire the sensors in series. Fix this by enlarging the hole in the pump frame and the mounting holes in the sensor. Use a thicker than normal gasket (or doubled/tripled gaskets) between the sensor and pump frame, plastic sleeving over the studs, and a plastic washer under the nuts to isolate the level sensor from the tank. The second is that the mounting tabs on the left side of the tank are such that the pump frame won’t go in the way we need it to with the fittings pointed to the right. Easily fixed by taking a little material off the sides of one or two tabs (at about 5 o’clock) with a file. The last is that the early gauge expects the resistance of a single sensor. But the 63L tank needs two sensors wired in series and thus a gauge that expects the doubled resistance. Fix this by swapping the gauge in the cluster for a late 325 gauge.

You will plug the return line fitting on the transfer pump and route the output fitting to the 318’s return fitting. Returning fuel from engine bay will go to the fitting on the left side of the 63L tank. The output fitting of transfer pump takes a large hose, but the return fitting on the 318 pump takes 8mm hose. There is very little room above the tank, so use a reducer at the low pressure pump.

The rest is pretty much just splicing in the level sensor and pump wiring, putting the tank in, connecting everything up, and swapping the gauge. If you don’t use the filter bracket for the 63L system you will have to come up with a mount.

And there you go. This system will allow you to run the tank down to a just a few gallons before starvation occurs. At Roebing I ran the tank down to 2-3gal and just got a hint of starvation in turn 9 on the last lap.

#48

Jim, thanks for explaining that.

I’m not sure that I will have time for the full tank swap before the first enduro, so in the interim here is what we’re going to try.

I’m going to run the 55L tank. Someone before me monkeyed with the low pressure pump, it actually had a big walbro pump in there feeding the stock high pressure pump. They butchered the low pressure fuel pump carrier, too. What I’m doing to do is cut off everything on the carrier except the flange and the two outlet hoses. I will make up a dummy pickup from stainless steel rod that will go down until 1/4 off the floor of the tank. To that pickup on the top side I will route some fuel hose and then will mount a small 3-4 psi external in line fuel pump in the trunk. That fuel pump will feed into the side of a swirlpot. I will take the return from the fuel injectors and run that into the side of the swirlpot. The top of the swirlpot will return into the other line coming out of the flange. The bottom of the swirlpot will feed the stock external high pressure fuel pump, which I am moving to the trunk, along with the fuel filter. I will remove the pulse smoother unless someone tells me that it is a great idea to keep it.

I think this will be simple and should work. I will keep you updated. If anyone has a comment about this, I’d like to hear it.

-Scott

#49

Removing the pulse damper should be fine.

#50

You can do this and it will work, but there are a couple of concerns. Fuel pumps are generally intended to push fuel, rather than lift it. Make sure the pump you get is intended to lift fuel at least a foot. You would probably be better served by getting a new BMW transfer pump. The swirl tank needs to be metal and the hoses in the trunk need to be armored. Additionally you will have to seal the rear bulkhead with metal.

I’d suggest that you rethink this. You are going to go through a good bit of work and expense to wind up with a solution that is not as good as the 63L tank system. Also remember that the 63L tank holds an additional 2gal of fuel, which is important in an enduro that doesn’t have timed fuel stops.