1991 525i fuel pump voltage problems

On Sun, 2 Mar 2008 12:22:43 -0600, "John J"
wrote:

>I have a 1991 525i that has no voltage at the fuse for the fuel pump. I have
>changed the relay for the fuel pump already, can someone tell me where to
>check next?
>

The ECU controls the pump and it also connected via the speed limiter which in
your case is not needed as the car won't touch 155mph but it is still controlled
by the ECU - perhaps it gone dead.

--

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
hsg RemoveThis @h-gee.co.uk
Bognor Regis, W.Sussex, England, UK
 >> Stay informed about: 1991 525i fuel pump voltage problems 

That was it, I swithced the relays around. There were three of the same
type. Thanks a lot.
"Scott Dorsey" wrote in message

> In article ,
> John J wrote:
>>I have a 1991 525i that has no voltage at the fuse for the fuel pump. I
>>have
>>changed the relay for the fuel pump already, can someone tell me where to
>>check next?
>
> Okay, as I recall, the fuel pump is powered by the fuel pump relay, which
> is powered by the main relay. Main relay has power at all times, which
> it gets through a fusible link right off the battery, right?
>
> The electrical manual will tell you for sure, and barring that you can
> take
> the fuse box apart and see where the wires go. You sure the main relay is
> good? Put the relay you took out of the fuel pump position into the main
> relay spot.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."
 >> Stay informed about: 1991 525i fuel pump voltage problems 

John J wrote:
>That was it, I swithced the relays around. There were three of the same
>type. Thanks a lot.

My local dealer insists that the Bosch relays "never fail" and that if
there is some electrical problem the relay is the last thing to check.

He's wrong. And there are a _lot_ of relays that all need to be working
right.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 >> Stay informed about: 1991 525i fuel pump voltage problems 

My 1991 318ic has the same issue and the relays have been replaced. At
two separate times the car stalls and will not restart even after
sitting for a few hours. But a short ride on a tow truck seems to shake
the car enough that it will always restart and run.

The first time this happened the local BMW shop tested the pump and
replaced the relays but they could not reproduce the problem.

Any suggestions on what can be the source of this?


--
RandyD
Message origin: TRAVEL.com
 >> Stay informed about: 1991 525i fuel pump voltage problems 

RandyD wrote:
>
>My 1991 318ic has the same issue and the relays have been replaced. At
>two separate times the car stalls and will not restart even after
>sitting for a few hours. But a short ride on a tow truck seems to shake
>the car enough that it will always restart and run.
>
>The first time this happened the local BMW shop tested the pump and
>replaced the relays but they could not reproduce the problem.
>
>Any suggestions on what can be the source of this?

A bad fuel pump. The commutator wears out and develops dead spots.

Next time it happens, connect a test lamp up to the fuel pump connector
and I bet a nickel it will light up just fine for a few seconds when you
try and start the car. The ECU will shut it off after a few seconds.

In a pinch, banging on the fuel pump or tank with a piece of 2X4 will
often shift it enough to get it to move again.

This is assuming you have verified that it really IS a fuel system problem.
You've disconnected the line out of the regulator when it refused to start
and didn't get squirted in the eye, etc. Because crankshaft position sensors
also sometimes fail intermittently, but when they fail you still have plenty
of fuel pressure, just that the ECU doesn't know the engine is turning so
it never opens the injectors or fires the plugs.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 >> Stay informed about: 1991 525i fuel pump voltage problems