'88 325 fuel pump woes resolved at last!

På Thu, 28 Aug 2008 11:40:32 +0200, skrev cosmo >:

> 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,

--
BBO, 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
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.

cosmo <see above> wrote:
>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.

$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
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article >,
Scott Dorsey > wrote:
> 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.

--
*If horrific means to make horrible, does terrific mean to make terrible?

Dave Plowman London SW
To e-mail, change noise into sound.

On 28 Aug 2008 11:18:48 -0400, (Scott Dorsey) wrote:

>cosmo <see above> wrote:
>>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.
>
>$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.
>

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.

cosmo <see above> wrote:
>
>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.

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

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Dave Plowman (News) > wrote:
>In article >,
> Scott Dorsey > wrote:
>> 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

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Thu, 28 Aug 2008 18:32:37 +0100, "Dave Plowman (News)" >
wrote:

>In article >,
> Scott Dorsey > wrote:
>> 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.

--

Sir 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

Bognor Regis, W.Sussex, England, UK

On Thu, 28 Aug 2008 21:56:28 +0100, wrote:

>On Thu, 28 Aug 2008 18:32:37 +0100, "Dave Plowman (News)" >
>wrote:
>
>>In article >,
>> Scott Dorsey > wrote:
>>> 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.

Correction ---- it was the central door locking system -- unlocked the doors in
the event of a crash.....

Hugh
--

Sir 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

Bognor Regis, W.Sussex, England, UK

On 28 Aug 2008 14:17:19 -0400, (Scott Dorsey) wrote:

>cosmo <see above> wrote:
>>
>>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.
>
>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

Thanks for the tip, Scott. They had them in stock. I got all 3
delivered to WA state for $29 in 8 days. Vrooom!!