fuel prepump

[Robert Bondi]

Anyone ever add one to a 530i? Local independent BMW mechanic swears by the prepump to fix mysterious hot starting issues at altitude (vapor lock).

I'm 99.9% certain the 77 530i doesn't have one, although realoem has "from 8/76" on most all the fuel tank associated items to further confuse this issue. This potential upgrade becomes a whole lot easier if it can be done with the 77 530i gas tank.

[stewart in slc]

I think the pre pump should fit in the tank as all the post 76 tanks are the same. Wiring it and possibly a new fuel level sending unit would be the issues I can see.

[pappentl]

I install a euro 70 liter tank in my US cars, the euro tanks don't run a pre-pump. IIRC the euro cars have a different pump than the US cars, and I believe this accounts for the lack of the in-tank pump. You might look for a pump for a euro car.

...tom



-----Original Message-----
From: stewart in slc <s.c.gilmore@m.cc.utah.edu>
To: tech_forum <tech_forum@firstfives.org>
Sent: Fri, Aug 16, 2013 10:58 am
Subject: Re: fuel prepump

#AOLMsgPart_1_ed61fa8c-5aa0-41f1-a86e-850d924210b2 td{color: black;} I think the pre pump should fit in the tank as all the post 76 tanks are the same. Wiring it and possibly a new fuel level sending unit would be the issues I can see.









Post generated using Mail2Forum (http://www.mail2forum.com)

[Mike W.]

I've had a bunch of BMWs with prepumps and I don't think any of them worked. As far as I can tell the only downside is you can't get it as empty, ie the 16.4 tank will quit running at ~15.4. 77 did not come with it, nor are all 77+ tanks the same, 79+ are the same as E28 which use 6 or 8 studs to hold it all in place rather than the twist lock like E3s/early E12s did. IIRC certain year E21s used a compatible suction device with a prepump which was twistlock, but no reason to bother IMO.

Avoiding vaporlock is a longshot, twice on E28s I had a pump failure/vapor lock under extreme conditions. A long run after starting out in the heat, 100+, then 100 miles with over 110F going uphill for an extended run. A working prepump may have prevented that.