My '88 325i cranks but would not start. Fuse #11 is good. I am
investigating the fuel pump system, removed the fuel pump relay and
measured the voltage between the socket coresponding to terminal 30 of
the relay and ground - it is battery voltage. Then I measured the
voltage between sockets corresponding to terminals 30 and 87 and I get
nothing. I have tried with a fused jumper wire that has a toggle
switch as well but the bulb in the switch does not light up and I
can't hear any noises coming from the fuel pump (because there is no
voltage present at the fuel pump, I've measured there as well). At
this point I'm stuck, what should I do next? Is this a fault somewhere
in the wiring and if so how can I debug this through the maze of
I would appreciate very much any suggestions/ideas, maybe I'm on the
wrong track investigating this problem?
On 21 Mar 2005 05:38:13 -0800, email@example.com (Dan Brenner)
Pull the back seat and remove the cover over the fuel pump (passenger
side). Remove the two pronged connector and put a test light across
the terminal in the connector. Have someone turn the engine over. If
the light comes on, buy a new fuel pump and enjoy driving your car. If
not, post a reply here and we'll go from there. I'll guarantee your
pump has died...
On 30 Mar 2005 15:02:57 -0800, firstname.lastname@example.org (Dan Brenner)
Is the check engine light on and if so, have you checked the codes?
Silly question but...
Was this with the fual relay jumped or with the fuel relay in place?
If the relay is jumped, try it with the relay in place. If it still
gets fuel, this will rule out one possible ECU failure. The relay is
grounded through the ECU. I remember you stating you checked the fuse
so I won't go there. I am assuming you've tried to start the car since
you've ensured you're getting fuel to the rail.
This clears the reference sensor (had that go out on me).
This could be an ECU failure. Did you had to jump start the car or
anything severe electrical happen right before this problem surfaced?
I haven't heard of jump starting killing an ECU but it's probably
possible. I know it can knock out the ABS system. If you're worried
about the timing belt, pull the front cover and check it. For the $30
or so it takes to replace it (and the tensioner pulley) I'd do it
while you have the covers off. If the belt looks good and most
importantly the timing marks line up, I wouldn't worry about the
valves. I'm leaning more towards a fuel issue. You have fuel to the
rail but the injectors may not be putting it into the cylinders.
I forget the details, but was the car running until recently or did
you acquire the car in it's current condition?
The check engine light was never on while the engine was running
(before it has started developing this no-start condition). Right now,
since it does not start anymore the check engine light is useless I
The fuel relay was in place while cranking the engine and getting fuel
at the pressure regulator hose. Yes, fuse #11 is good.
I had to jump-start the car about 2 years ago and after that the On
Board Computer (OBC) started displaying PPPP Km/h, PPPP l/100km etc
instead of the actual values. I had read after the fact that I was
supposed to remove some fuses before trying to jump-start the
car...well...I guess I fried the OBC in that occasion. However, the
car has had an erratically hard-to-start condition when engine warm
mostly (and sometimes when engine cold, sporadically) since I had the
car (and that's 2001). That jump-start apparently hasn't affected
anything else for the next 2 years. This hard-to-start condition, one
cold December 2004 morning, all of a sudden became a no-start
condition and since then I wasn't able to start the car anymore - it
just sat in my garage for the duration of the winter and now I'm
trying to put the pieces together on what this problem could be.
I've answered above.
This past weekend I've checked the compression and these are the
Cyl 1 2 3 4 5 6
Compression (psi) 140 140 140 135 130 100, 115,
For cylinder #6 compression was 100 initially, then I've taken 3 more
measurements and compression increased with each measurement as shown.
The car has 192,000 km. Based on this I would say that the values
indicate only worn piston rings and not damaged valves, right? And the
engine should start even with lower compression on cyl #6. By the way,
all the spark plugs were black and oily but I guess that's the result
of endless crankings with no result in starting the engine.
So you suspect that the fuel injectors might be at fault? How can I
test them? Do I need any special tools? Assuming one or two injectors
might have become defective, shouldn't the car still at least start
(and run roughly afterwards)?
On 4 Apr 2005 05:54:36 -0700, email@example.com (Dan Brenner)
Maybe, maybe not. Might be a code that helps diagnose the problem.
Ok, this is what I was trying to figure out.
Ok, the OBC just has to be reset but that's a different problem. We'll
resolve that later...
Compression is good for the specified mileage and would run if all
else was good. Clean the plugs real good (or better yet replace them)
and try again. Dirty plugs will foul and not fire the fuel mixture
causing a no start condition.
I don't suspect the injectors themselves being bad. As you pointed
out, one or two being bad the car would still start. After you clean
or replace the plugs, turn the engine over and then pull a plug to see
if you're getting fuel in the cylinders. The ECU could still be at
fault but I'm willing to bet it's something simpler. Check the codes
to see if there's anything stored as the computer keeps the codes
until it is cleared and surely there is at least one code present
after all of the attempts to start the car. The fuel injection system
relies on several sensors to provide data in order to deliver the
proper amount of fuel. If you're getting fuel to the cylinders, it's
probably too little or too much which is causing the problem. Could be
a stuck or bad mass airflow sensor, stuck or bad idle control valve or
several other things. All of the sensors in the system are monitored
by the ECU and it will know if one has gone south.
First of all I want to thank you for your taking the time to answer my
problems with valuable suggestions, I really appreciate it.
I will try to get the codes, clean the plugs and everything else and
then I'll post an update here within the next day or so.
You can get the codes by pressing the gas pedal all the way to the
floor five times with the key in the on (not start) position and
counting the flashes. I don't have the chart handy on what the codes
are but I'll look for it.
On 5 Apr 2005 06:17:28 -0700, firstname.lastname@example.org (Dan Brenner)
I've replaced the spark plugs with brand new ones and...the first
cranking I did, the car started for a split second and died right
after. Subsequent tries yielded no more positive results, back to
no-start condition. I removed 4 plugs and looked at them, they were
smelling gas, but weren't wet, well maybe just an idea...I'm not sure
what I should have seen, should they have been soaked?
I'm thinking maybe the injectors are not opening because of lack of
signal from the Motronic unit...
I had no luck trying to getting the codes...the moment I switch the
ignittion on, the check engine light starts blinking regularly (approx
1 blink/sec) and is unaffected by my pressing the gas pedal. I've
tried pressing it to the floor 5 times within 5 seconds several times
at different speeds and switching the ignittion off and on between
tries. Nothing but the constant, uninterrupted blinking that does not
tell me much.
I have included a link that lists the fault codes in case you hadn't
found them. The fact that it started does at all does indicate the
ECU/injection system IS working. There is something that is too far
out of parameters preventing it from running. You definitely need the
ECU codes, whether you get them from the CEL or a code reader. I don't
think there's any way around this one other than to just guess and
start replacing parts. PROHIBITIVELY expensive and not the way I would
want to go.
On 7 Apr 2005 09:25:59 -0700, email@example.com (Dan Brenner)
Yesterday, after weeks of investigation finally I was able to start
the Bimmer! I think I've checked pretty much everything (except the
timing belt which I was about to check this weekend) and I was kinda
desperate because everything so far was checking ok. The last thing I
checked was something I wasn't expecting much from, the idle air
stabilizer valve. Took it out, submerged the half mechanical part of
it into some carburator cleaner for the night, made sure the inner
cylinder is moving freely (before cleaning it it wasn't moving that
good), assembled it back and...the car started like a charm! I would
not have believed that this idle part thing could have such an
importance that the car would not start...I mean not even the computer
could not compensate for the excess air...and the book didn't mention
that this part could lead to no-start conditions...only idling
So after all, everything amounted to some cleaning...was that
simple...but how many headaches!
Thanks to everyone who helped me with their suggestions.
Before finishing, I would like to post another question: how do I
reset the OBC so it doesn't display PPPP anymore? This started
happening after jump-starting the car 2 years ago. I have disconnected
the battery several times since then but it did not help reseting the
On 22 Apr 2005 06:02:16 -0700, firstname.lastname@example.org (Dan Brenner)
It should not have prevented it from starting if you feathered the
gas pedal while starting. If it were stuck closed, the car wouldn't
idle. Stuck open, it would idle but run lean. Doesn't matter as it
fixed the problem. After rereading one of your last posts, I should
have caught the IAC valve. Sorry about that.
Unplug the cable from the back of the OBC for a few days, this seems
to clear out whatever residual electrical charge that keeps it from
Actually, that is incorrect. The IAC is *after* the AFM (Air Flow
Meter) and is merely an air bypass around the main throttle plate.
This means the mixture will remain the same richness (or lean-ness)
regardless of how open or closed the IAC valve is. So if it was stuck
open it would just have a very high idle. Stuck closed would be low
idle speed and stalling.
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