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Car Forum / BMW Cars / September 2008'88 325 fuel pump woes resolved at last!
Touch wood. Last fall I asked for advice about my newly aquired BMW 325 which had a replaced fuel pump and tank clean out, but still ran out of fuel and stopped intermittently for months, making me the frequent object of pity and derision. This always happened on the way to a job interview or the late ferry or 25 miles down a deserted logging road at night etc. None of the local $80per hr exalted worthies could fix it. It turns out there are two identical relays positioned side by side on the 325; one is the fuel pump relay, one is the oxygen sensor pre-heat relay. If the pre-heat relay fails, opens or becomes intermittent, the fuel pump relay will not work and you will sputter to the side of the road. I think the pre-heat heats the Ox sensor which sends voltage to the computer input once it gets warm which turns on the fuel pump relay but who knows. Checking continuity between lugs 87 and 30 should produce nothing. Applying 12v to the remaining two lugs should close the relay and produce continuity between 87 and 30. I opened the case with a penknife and closed the gap slightly with some nose pliers rather than pay $103 for a new one- that's just my way. I have been fully operational ever since for now. I just thought you should all know and thanks to those of you who offered advice at the time. På Thu, 28 Aug 2008 11:40:32 +0200, skrev cosmo <itsafake@itslead.com>: > fully operational ever since for now. I just thought you should all > know and thanks to those of you who offered advice at the time. Thanks for posting back. Good and valuable info there. Cheers,  SignatureBBO, DoD#2101 >Touch wood. Last fall I asked for advice about my newly aquired BMW >325 which had a replaced fuel pump and tank clean out, but still ran [quoted text clipped - 16 lines] >fully operational ever since for now. I just thought you should all >know and thanks to those of you who offered advice at the time. $103 for a new relay? The original Bosch ones should be under $20. You can get Chinese cheapies in the same package for $2. Are you sure the relay that is the problem is the O2 sensor preheat relay? There should be a main relay and a fuel pump relay which both need to be closed for it to operate, but you should be able to operate without an O2 sensor relay at all. This is handy, because when other relays fail you can often use the O2 sensor relay as a rapid replacement to get home. I'd suggest replacing both the fuel pump and main relays right now. It won't cost much, and it will be more reliable than fiddling with them. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > I'd suggest replacing both the fuel pump and main relays right now. It > won't cost much, and it will be more reliable than fiddling with them. Many relays give problems due to dirty contacts. If they are the type than can be easily opened up a good clean will often sort them. Signature*If horrific means to make horrible, does terrific mean to make terrible? Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. >> I'd suggest replacing both the fuel pump and main relays right now. It >> won't cost much, and it will be more reliable than fiddling with them. > >Many relays give problems due to dirty contacts. If they are the type than >can be easily opened up a good clean will often sort them. True, but the way the Bosch relays usually fail is that the contacts get rough from arcing. It _is_ possible to carefully burnish them, but it's a painstaking job and not worth it to save $7. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >> I'd suggest replacing both the fuel pump and main relays right now. It >> won't cost much, and it will be more reliable than fiddling with them. > >Many relays give problems due to dirty contacts. If they are the type than >can be easily opened up a good clean will often sort them. You say that Dave but I can remember some 25 years ago I had a BMW 5 series or it might have been early 7 (can't remember) in from a body repair friend of mine. Repaired the front damage Ok - looked like new but couldn't get the power windows to work. Now I knew that they were fitting all sorts of safety gear on the cars at this time like flashing lights for seat belts and door open warnings etc and I remembered something about fail safe windows - opened in a crash or something. Pulled the kick panel from the drivers side (RHD) and hooked out a large relay. Took the plastic top off (Hella unit) and found a thin hair wire with a lead weight half way along had broken from the top mount. New relay £45 then - about £145 now - so I soldered the wire back on its top mounting after checking with my local Hella dealer (wife's uncle) that I was correct in my assumption that the wire was meant to break at the lead weight and not pull off the top mount. Anyway - put the thing back together and - hey presto electric windows all working again. SignatureSir Hugh of Bognor The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it! Hugh Gundersen hsg@h-gee.co.uk Bognor Regis, W.Sussex, England, UK >>> I'd suggest replacing both the fuel pump and main relays right now. It >>> won't cost much, and it will be more reliable than fiddling with them. [quoted text clipped - 22 lines] >Anyway - put the thing back together and - hey presto electric windows all >working again. Correction ---- it was the central door locking system -- unlocked the doors in the event of a crash..... Hugh SignatureSir Hugh of Bognor The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it! Hugh Gundersen hsg@h-gee.co.uk Bognor Regis, W.Sussex, England, UK >>Touch wood. Last fall I asked for advice about my newly aquired BMW >>325 which had a replaced fuel pump and tank clean out, but still ran [quoted text clipped - 26 lines] >relays fail you can often use the O2 sensor relay as a rapid replacement >to get home. Using the technique in the Bentley manual I could hot wire the main relay and make the fuel pump motor with the key on. The main and fuel pump relay tested fine using my primitive, by the side of the road method as described. The 02 relay failed this simple test. I hot wired the 02 socket and the car started and ran so I diagnosed a bad 02 relay. I adjusted the 02 relay and now the car starts and runs. That's all I'm basing my "knowledge" on. Sorry if this was misleading. There was nothing at Napa, Carquest etc. I called the dealer in Seattle and they were an expensive special order item. I was quoted over $80 per for a part comprising $8 worth of the most primitive electronics imaginable at most. Rather than wait 3 days in someone else's driveway I got out my trusty pliers and drove home. It's my first BMW. It kind of feels like owning a boat. I guess I should get on board and order things by mail. >I'd suggest replacing both the fuel pump and main relays right now. It >won't cost much, and it will be more reliable than fiddling with them. >--scott Makes sense if they're that cheap. >There was nothing at Napa, Carquest etc. I called the dealer in >Seattle and they were an expensive special order item. I was quoted [quoted text clipped - 3 lines] >first BMW. It kind of feels like owning a boat. I guess I should get >on board and order things by mail. There are two kinds of relays in those things, and you should have some of each on hand. Bavarian Autosport has the 5-prong ones for $9, and the 4-prong ones for $8, for original Bosch parts. The dealer will usually charge about twice that. There IS a special 7-prong fuel pump relay that some BMWs of that era have, and it's about $50. I don't think you have one of those on a 325, though. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >>There was nothing at Napa, Carquest etc. I called the dealer in >>Seattle and they were an expensive special order item. I was quoted [quoted text clipped - 13 lines] >325, though. >--scott Thanks for the tip, Scott. They had them in stock. I got all 3 delivered to WA state for $29 in 8 days. Vrooom!! |
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