From digest.v7.n1213 Sat Feb 28 04:34:57 1998
From: Scott Miller <sdmiller_at_hotcoco.infi.net>
Date: Fri, 27 Feb 1998 20:59:27 -0800
Subject: E30 Fuel Pump Replacement <Long>

Are you sitting down? OK, I’ll now depart from my usual habit of raising controversial legal issues and actually provide some technical content. Sorry for the length, I don’t have a web site to post this on.

I just got done changing the fuel pump in my 1990 (E30) 325i. This post will hopefully help out a few newbies, thought I doubt this is news for the veteran wrench-turners. (Veterans scroll down now.) Some of this stuff isn’t covered in the Bentley manual.

First, the symptom that led to suspect the fuel pump: The car would turn over and start, then die within 2 seconds. This was intermittent for a bit (I managed to get it to run for about 3 minutes). I ran this past Golden Gate Chapter tech inspector extrordinaire Bill Arnold, and he proclaimed this to be the classic E30 fuel pump failure mode.

Club racer Darrel Lunge was nice enough to use his race car trailer to tow my car to my home. (BTW, his Dodge 1-ton Ram long-bed, extended cab, 2WD V10 diesel monster truck is for sale, in case anyone needs a tow vehicle.)

Now for some testing. Pulled the rear seat bottom out and removed the access cover (4 screws, but one was missing - evidence that someone had been in here before). The fuel pump is driven by a relay which is powered through the Motronic computer. To eliminate the relay and computer as suspect parts, I pulled out the relay and jumped the 30 and 87 terminals. (The terminal numbers are on the relay, not on the socket.) I also checked the #11 fuse, not that I suspected it, just checking - and a 15 amp fuse was there where the 7.5 amp fuse should have been, further evidence that someone had messed with this before. Maybe the pump was drawing more than the 7.5 amps, and instead of replacing it, they just upped the fuse capacity. This is bad.

With the jumper wire in and the key on, there was no noise or vibration from the top of the fuel tank. This was further evidence that the pump had gone bye-bye.

The good news: I had a spare fuel pump. The bad news: I couldn’t remember if it was for my current car or the 1987 325is I used to own. Through the 1987 model year, there was a low-pressure pre-pump in the tank, and a high-pressure pump next to the tank. Starting with the 1988 year, they switched to a single high-pressure pump in the tank. It wasn’t until the next day at my favorite parts supplier that I discovered my pump was for the later set-up. I also picked up the O-ring that you’re supposed to replace when you pull the old pump out, which I didn’t know I needed until the pump failed.

About playing around with gasoline: In previous posts I’ve explained my paranoia on legal issues. That’s nothing compared with my fear of working around open containers of gas. I interpreted the "well ventilated area" warning to mean I should work outside, not in the garage, and with the doors and sunroof open.

OK, per the Bentley manual:

• Disconnect the negative battery terminal. (This is standard for everything from engine removal to wiper blade replacement.)
• Seat bottom and access cover were already out.
• Pull the electrical connectors off of the pump and sending unit.
• Disconnect the fuel hose. Bentley warns of impending fuel spillage, but there was little. They also warn of the dangers of arcing wires, but that isn’t likely with the battery disconnected.
• Remove 4 nuts holding the sending unit and remove the sending unit. Instead of waiting for the sender to drain, I placed it in a plastic container to finish dripping. NOTE: Gas causes some kinds of plastic to disintegrate, making a white gooey mess. Use glass. I figured this out the hard way.
• Now the pump assembly unscrews out of the top of the tank, by rotating counter-clockwise about 10 or 15 degrees. The manual fails to tell you this: Carefully note the EXACT position before removal, even maybe mark it. Twisting the assembly around different ways is necessary.
• Remove and discard the O-ring.

Now, about getting the right parts: My spare part was a fuel pump, NOT a fuel pump assembly. I don’t know the price difference, but the separate pump is Bosch part # 0 580 453 019. I don’t know the BMW part # for either this or the assembly. The German-made O-ring is either 111 919 131 A, or else 3 040 001 019D, depending on which number is correct (both are on the sticker). Bentley’s instructions are for the assembly. To install the new pump into the old assembly, you have to remove the pick-up filter screen thing from the bottom (pulls off), force/slip the bottom of the pump out of the bracket (note position of the rubber thingie), remove the upper fuel line coupler dealie (note positions of more rubber thingies), and then unsolder the wires. Doing the pump assembly tear down/rebuild/solder job adds about 15 minutes to the job (not even half a beer).

Assembly of the assembly and re-installation is the reverse, as they say, but use the new O-ring and lubricate said O-ring with gas. This is where you find out that the assembly could go in more than one way, but only one is really right, and careful noting/marking will have saved you about 15 minutes of confusion.

Comments: The filter screen thing is only press-fit into the bottom of the pump/rubber thingie, nothing else holds it in there. This seems weak. The filter was surprisingly clean, not much crud on it, after 67K miles on the car (who knows if it was ever cleaned or replaced before). Test it all to check for leaks before you put the access cover and rear seat back in. The car started right up, there must have still been plenty of gas in the line. Finally, if you live where El Nino has caused much rain this winter, don’t trust the weather guessers when they say it won’t rain today, it will just because you’ve got doors and sunroof open and the car smells like gas.

Enough for now, eh? It is about a two Molson (or insert your preferred beer brand) job, including all the testing before and after and soldering, but I didn’t drink mine until after completion, because of my afore-mentioned fear of open gas containers. I sure hope this helps someone get past the Bentley manual’s few shortcomings.

Scott Miller
Golden Gate Chapter
BMW CCA #44977