Fuel System (replacing W/ Cell & Pump)

#1

Hi All,

I am HPDE / Autocross prepping my 84 318i for my 16 year old kid. (Spec E30 conversion may come later.) I want to put a piece of track/racing hardware on the 318i; this forum seems like a good place to ask about that.

Due to 20 year old gas in the fuel system, I need to toss the tank and the pumps and start from scratch (nothing works). My idea is to use a racing fuel cell (10 gallon) and a single aftermarket fuel pump. Anyone have experience, wisdom or comments along these lines?

Peace,

Dan Peake
Campbell, CA

#2

With some searching you can pull up some old threads about this. You’ll come across the much missed Jim, “DTOM Racing” Robinson. It was very expensive for the amount of benefit achieved. You can get a brand new tank for <$200 and you can make it work with an aftermarket pump. Just be aware that there’s a number of different tanks, vent, fuel pump and plumbing variations.

If your tank is full of rust you can clean and seal it. Jim Levie has some old threads on that.

The scenario where a fuel cell works well is endurance races. You can put in a big cell that fills in seconds and will reliably deliver fuel until it’s bone dry.

#3

Thanks for the tips. I will sleuth around on the site for the threads you mentioned. It sounds like I oversimplified the process of going to fuel cell.

It appears this car has a low pressure pump in the sender, and a second final pump under the drivers rocker panel; both have failed. Replacing both and the fuel tank would be cost prohibitive.

Can you refer me to a retailer with a tank with the $200 price you mentioned, that is much less than what I was finding online.

Dan Peake
Campbell, CA

#4

Talk to Jim Levie about the kinds of tanks that will fit into a 318 of your model year, and their pluses and minuses. The inexpensive new tanks were coming from some ebay seller over the past couple years, altho you might poke around some of the big Internet outfits like RockAuto and Autoparts123.

Fuel tank plumbing is not Infantry simple and I don’t know enough about it to provide good guidance. Talk to Jim.

#5

The system in the car now has a low pressure transfer pump in the tank and an external high pressure pump. The fuel return from the engine goes to a fitting on the transfer pump. The system used with the 63L (from 9/87 on 325 cars) tank has a single in-tank high pressure pump and two level sensors, but the return fitting is on the side of the tank. The late 318is cars used the 55L tank and an in-tank high pressure pump which has the return fitting.

USautoparts offers new tanks of both varieties (55L & 63L) starting at $173. The least expensive fix in this case would be a 55L tank and the fuel pump assembly from a late 318is. This combination is easy to fit to the car.

#6

Perfect solution - I can’t thank you enough!

Any pointers out there on fuel tank removal? It looks buried, so I am wondering what needs to be removed, and if there are any good short cuts.

THANKS!

Dan Peake
Campbell

#7

It isn’t as hard as it looks, but you will have to remove the drive shaft and rear exhaust section. If you are doing this on jack stands, drain the tank first as those suckers are heavy with much gas in the tank. With the car on a light two works can handle a tank with gas in it.

Before dropping the tank disconnect the vent hoses that run to the right rear of the car and the electrical connections. Tie those up so they don’t wind up out of reach when the new tank goes in.

If you use the 55L tank and the late 318is pump you will need to replace the 10-12mm line that normally feeds the high pressure pump with an 8mm line.

#8

That’s exactly the stuff I was talking about! Thanks.

Just so I am clear, I am bypassing the old high pressure pump under the rocker panel? If I recall, there are sections of steel line and sections of rubber. What I am envisioning is a line directly from the new in-tank single pump, to the steel line under the rocker panel that previously accepted the output of the old high pressure pump. Will there need to be a step-up adapter fitting at that location to go from the new 8mm to the old 10mm (steel)?

Here is the fuel tank I found:
Fuel tank REPB670101 at USAautoparts 55L - looks right to me.

Does the transfer pump and the high pressure pump share the same fuse? Any worries about current capacity/wire gage?

Any gaskets or molded rubber items required for the swap?

At USAautoparts the pump is not so clear. Looks like BEC1520991. There is a Bosch unit that is $35 less, and my inner-wishful-thinker want’s it to be that one, but it does not look right!

Thanks,

Dan Peake

#9

You will eliminate the high pressure pump. The inlet of the high pressure pump and the outlet of the transfer are 10mm. But the outlet of the late 318is pump and the inlet of the filter or line to the front of the car are 8mm. It doesn’t make any sense to me to use 8-10mm adapters on each end of the line that tuns across the top of the tank. I’d replace it with an 8mm line.

There is only one fuse (11) in the fuel pump circuit.

I’ve had too many many problems with aftermarket fuel pumps. I only use OE pumps from my dealer now. They cost more, but the work and last a long time.