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autofix
Really Senior Member I
Joined: 23-August-2003
Location: Kildare
Status: Offline
Points: 294
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Posted: 15-December-2005 at 04:22 |
Hi,
I have to say I admire your persistance ![](smileys/Big Smile.gif)
I have read down through the thread and I think I may have a few points to add which may help you.
Since you have the ECU pin outs then I think this should be your starting point. To put it simply, if the ECU has it's required feeds, earths and sensor inputs, if the ECU is ok, then the outputs should be ok too. You need to prove that each of these works ok.
First thing is to prove the supply and earth. Never mind testing the relays. Go to the pin at the ECU because if this tests ok then the relay and wiring must be good too. Make sure the battery is fully charged. If you have battery supply at the pin then you have to test if the supply is good. A reading on a multi-meter or lighting a test light does not prove it is good. 99 times out os a hundred it will be ok but to be sure you need to check it. Easiest way to do this is to use a headlamp bulb. Take a supply from the terminal of the ECU plug and earth it on the battery, if the bulb lights fully then the supply is ok. MAKE SURE YOU USE THE CORRECT TERMINALS FOR THESE TESTS so as to avoid frying the ECU. Check the earths the same way except feed the bulb from the battery + and earth it at the ECU terminals. These tests are done with the ECU disconnected.
Also check the supplies under cranking load. Measure the voltage at the ECU as well as at the coil + terminal and see how much it drops when cranking. Again, make sure the battery is charged for this test.
I know you have checked the ECU in another car but you should be aware that these suffer from dry solder joints. It is possible that you have a faulty ECU which just happened to work ok at the time when tested in the other car.
Strip the cover off ECU plug so you can gain access to the back of the terminals with the plug attached. Remember that just because you have tested a sensor does not mean the the signal is getting to the ECU intact. By checking at the ECU plug you also check the wiring at the same time. Start with pin one and work your way through every pin to check that you have what you should on each one. If you do not know what should be on any pin just give me a shout and I will tell you. If you are unsure of any test procedure or results just ask.
It can be difficult to be sure that the crank sensors are working right. One simple way to check this is to put a capless bulb across the fuel injector terminals and crank the engine. If the bulb flickers then the ECU is commanding the injectors. It will not do this unless it has good crank signals. If it does not flicker then check for supply at one side of the injector.
Hope this helps some
Good luck
Alan
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Drew540i
Really Senior Member II
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Joined: 15-August-2005
Location: The Mansfield Massive
Status: Offline
Points: 632
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Posted: 15-December-2005 at 08:05 |
Some good advice there - particularly about cranking
volts. It may well be that the starter is taking too
much current - my Alpina B9 3.5 (essentially the
same thing) was quite reluctant to start with an
average battery. With a new one it fired up first time.
However...........
autofix wrote:
First thing is to prove the supply
and earth. Never mind testing the relays. Go to the
pin at the ECU because if this tests ok then the relay
and wiring must be good too.
That's what we've been telling the guy - no answer
yet!!
A reading on a multi-meter or lighting a test light
does not prove it is good. 99 times out os a hundred
it will be ok but to be sure you need to check
it. Easiest way to do this is to use a headlamp bulb.
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Er, no - the best way is to use a proper multi meter
(cheap enough now from Halfords) which will yell
you EXACTLY what voltage is there. A headlamp bulb
will illuminate with less than 12 volts which gives a
false impression.
The Bulb to use for injector testing would be one of
the cap bulbs like you say - bulbs out on the back of
a dashboard, i.e the ones that fit into the plastic twist
connectors or a side repeater bulb. Pull the bulb out
(or buy a new one), unfold the wire terminals and
insert them into an injector wire.
But, as we've been saying ad nauseum, the first
thing to check is a 12 volt supply to terminal 35 of the
ECU plug. Until we know if it has/has not got this,
there's no point offering any more advice or help.
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autofix
Really Senior Member I
Joined: 23-August-2003
Location: Kildare
Status: Offline
Points: 294
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Posted: 15-December-2005 at 09:23 |
A reading on a multi-meter or lighting a test light does not prove it is good. 99 times out os a hundred it will be ok but to be sure you need to check it. Easiest way to do this is to use a headlamp bulb. [/QUOTE]
Er, no - the best way is to use a proper multi meter (cheap enough now from Halfords) which will yell you EXACTLY what voltage is there. A headlamp bulb will illuminate with less than 12 volts which gives a false impression.
Hi Drew,
I hope I did the Quote thing right.
I am afraid you are mistaken regarding how to check voltage supplies. When you measure a voltage with a meter all this tells you is how much potential energy you have in the circuit. This potential (measured in volts) can be present even in an open circuit, so is no indication of if the circuit can do any work. If the supply is not strong enough then the circuit will fail. To measure the integrity of the circuit you need to know if it can handle the required current (measured in amps). The only way to do this is to place a load in the circuit. The load has to be heavy enough to test but not too heavy. I suggested a headlamp bulb because this way it is easy to see if the supply is right because the bulb will light brightly thus no need to measure with an ampmeter. Even measuring the resistance of the circuit will not prove for sure if the circuit is ok as there is no load involved. The method I outlined is far more acurate. This is basic electrics which is well proven and has been around a long time. It is known as Ohms law.
HTH
Alan
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UKDaveJ
Really Senior Member II
Joined: 18-November-2004
Location: Bromsgrove, Worcestershire
Status: Offline
Points: 529
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Posted: 15-December-2005 at 09:48 |
Can't imagine BMW main dealers sticking headlight bulbs into things, but that's easy for me to say, I know nothing!
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My 635's.
![](http://members.lycos.co.uk/dnj330d/hpbimg/A635%20profileweb.gif)
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GraemeH
Senior Member I
Joined: 03-November-2005
Location: At the beach, North Wales
Status: Offline
Points: 125
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Posted: 15-December-2005 at 12:59 |
Yes, but the wonderful thing is that here we are reading about Ohms Law! It might not fix the Beemer in question, but I like it nevertheless. The 635csi and Tsiolkovsky's rocket equation next please! Makes me want to go for a drive already! Tsiolkovsky's law says that "for any maneuver or any journey involving a number of maneuvers . . .", and so on and so on. Might well be a useful law as we hit p.7 of this posting, after all. All best wishes. ;-)
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Drew540i
Really Senior Member II
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Joined: 15-August-2005
Location: The Mansfield Massive
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Posted: 15-December-2005 at 14:00 |
autofix wrote:
A reading on a multi-meter or
lighting a test light does not prove it is good. 99
times out os a hundred it will be ok but to be sure
you need to check it. Easiest way to do this is to use
a headlamp bulb. |
Er, no - the best way is
to use a proper multi meter (cheap enough now from
Halfords) which will yell you EXACTLY what voltage
is there. A headlamp bulb will illuminate with less
than 12 volts which gives a false impression. Hi
Drew,
I hope I did the Quote thing right.
I am afraid you are mistaken regarding how to
check voltage supplies. When you measure a
voltage with a meter all this tells you is how much
potential energy you have in the circuit. This potential
(measured in volts) can be present even in an open
circuit, so is no indication of if the circuit can do any
work. If the supply is not strong enough then the
circuit will fail. To measure the integrity of the circuit
you need to know if it can handle the required current
(measured in amps). The only way to do this is to
place a load in the circuit. The load has to be heavy
enough to test but not too heavy. I suggested a
headlamp bulb because this way it is easy to see if
the supply is right because the bulb will light brightly
thus no need to measure with an ampmeter. Even
measuring the resistance of the circuit will not prove
for sure if the circuit is ok as there is no load
involved. The method I outlined is far more acurate.
This is basic electrics which is well proven and has
been around a long time. It is known as Ohms law.
HTH
Alan [/QUOTE]
You're absolutely right of course - but most (if not all)
multi meters also test for amps. Mine does anyway.
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UKDaveJ
Really Senior Member II
Joined: 18-November-2004
Location: Bromsgrove, Worcestershire
Status: Offline
Points: 529
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Posted: 15-December-2005 at 14:23 |
So does mine!
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My 635's.
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Brucey
Really Senior Member II
Joined: 07-March-2004
Location: United Kingdom
Status: Offline
Points: 744
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Posted: 15-December-2005 at 14:29 |
Oh just in case; please don't anyone plug your meter on 'Amps' between a +12V line and ground; the supply or the meter fuse (hopefully) will blow instantly.
The best way is to connect a suitable load to the supply (and BTW a headlight bulb may be too much for some feeds eg out of an ECU) and see if the volts hold up under load.
cheers
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~~~~~~~ Brucey ~~~~~~
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autofix
Really Senior Member I
Joined: 23-August-2003
Location: Kildare
Status: Offline
Points: 294
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Posted: 15-December-2005 at 15:04 |
Hi all,
@ brucey. Very good advise on connecting an ampmeter. This is one of the reasons I didnt mention it. The other being that an ampmeter would be useless to prove the ECU supply unless, as you correctly stated, there was a load in the circuit to cause the current to flow. If you are going to put a load in.then a bulb is likely to be easily available to the average DIY man so it makes sense to use one.
@Drew. "You're absolutely right of course - but most (if not all) multi meters also test for amps. Mine does anyway." Which is why you said that the correct way is to check volts? ![](smileys/Big Smile.gif)
HTH
Alan
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Drew540i
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Location: The Mansfield Massive
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Posted: 15-December-2005 at 17:21 |
autofix wrote:
Which is why you said that the
correct way is to check volts?
HTH
Alan
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Of course. A 12 volt supply is the first thing anyone
would check for. I would.
It's only when I have exhausted all other possibilities
volt wise that I'd start looking at other things. Your
bulb test reminds me of a Peugeot 205GTi with a
non working rear fog lamp. There was a full and
healthy 12 volts there but it just wouldn't work.
Further investigation with a multimeter revealed a
break in the wire behind the bumper with just a
couple of strands of wire left to make the
"connection". In this instance, using a multimeter
soon found the problem. That 12 volt bulb would
have got you very far.........
I always think of volts and amps in a similar fashion
to bhp and torque which isn't too far from the truth.
People are scared of electrics because they can't
'see' it. As we learned in school and physics, the
relationship between volts and amps, resistance
(ohms) etc is why 24'000 volts from an errant plug
lead will give you a shock, 240 volts mains power
could kill you.
Anyway, getting back to something vaguely relevant,
it sounds rather like a lack of power to the ECU and
they don't have a habit of failing on the 635CSi like
they do on the E23 when a screen leak fills them
with water.
Ben, we're waiting on you. Voltage at ECU terminal
35, or not??
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Drew540i
Really Senior Member II
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Posted: 15-December-2005 at 17:59 |
To add to this to those who don't under stand how
electricity works;
Electric current is the flow of a thing called ‘charge’.
All metals are full of charge, period. Charge is
measured in units called AMPS. Imagine a hose
pipe. Amperage (or Amp Hour...Ah) is like gallons
per hour going through that pipe, just like amps
along a wire.
Whenever charge within metals is flowing, electric
currents (charge flow) are created. This is measured
in Amps.
The faster charge moves, (or the more it moves
through a fatter wire), the higher the amperage.
Think back to that hose pipe. A FAST flow of water
through a NARROW pipe has the same ‘Amps’ as a
SLOW flow of water through a FATTER pipe. Get it so
far?
If you doubled the speed of the water in a pipe you’d
double the ‘current’ - right?.
What are Watts? All energy is measured in “joules’.
A joule can move along a wire. A Watt is simply the
flow rate of energy, or one joule per second. So what
is ten watts.........?!
VOLTS:
Voltage is effectively an electrical pressure and static
electricity is mostly volts from an oppsitely
unbalanced charge. The static-electric field is the
voltage, an electrostatic state. (Christ this is hard
work)
OHMS
Go back to the water hose again, now conencted to a
pressurised water tank. Take your thumb off the end
- you will have a flow of water right? Now double the
hose length and the flow of water halves. Imagine
the surface tension of water (or friction) - by doubling
the hose length you’ve doubled the friction or
RESISTANCE. The longer the hose, the slower the
water.
Now imagine the water tank is a battery, the hose is
a wire and the water is charge. The friction or
resistance is OHMS.
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autofix
Really Senior Member I
Joined: 23-August-2003
Location: Kildare
Status: Offline
Points: 294
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Posted: 15-December-2005 at 18:13 |
Hi Drew
Thats all very interesting. How did you use the meter to find the fault with the little Pug? Was the supply or earth at fault? Yes, a bulb could have been used to fix that one.
If you have the time I would love to hear you expand on the bhp/torque theory as i cant quite see it.
Where did I suggest that the presence of voltage should not be checked? Quite the opposite in fact, I said " If you have battery supply at the pin then you have to test if the supply is good.". You attempted to correct me by sayin "Er, no - the best way is to use a proper multi meter which will yell you EXACTLY what voltage is there". Voltage proves nothing. if you meant to say you have to check amps then why not just say so?
I would not be so quick to say the ECU could not be at fault as they suffered from dry joints, I covered that in my post.
HTH
Alan
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Hiabboy
Really Senior Member I
Joined: 05-February-2005
Status: Offline
Points: 325
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Posted: 15-December-2005 at 18:46 |
The ecu is definately o.k, i know because we tried it in a festering poobox of an e28 in my garden!, i wriggled it i hit it i swore at it and the car continued to run perfectly . So i think we can safely eliminate the ecu from the equation , mind you that was several weeks ago!
Edited by Hiabboy
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Profit is more reasonable than justice.
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Drew540i
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Posted: 15-December-2005 at 19:39 |
autofix wrote:
How did you use the meter to find
the fault with the little Pug?
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Very poor earth - plus the wrong bloody bulb. 12 volts
there (just) but nobody home.
Edited by Drew540i
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Drew540i
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Posted: 15-December-2005 at 19:43 |
Not only was the wire almost completely severed, I'd
add that when stripped back the wire was quite
'black' through corrosion.
Can we get back to the subject in hand now please?
Edited by Drew540i
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siscobmw
Senior Member II
Joined: 13-May-2005
Location: North Italy , near lake of Como
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Posted: 16-December-2005 at 03:16 |
Hey Drew540i?
You gave phb a lot of info about wiring diagrams...
Did someone give phb10186 some Ohmic values for sensors, AFM , temp sender....?
If not I will give them! Well he can find them on Haynes manuals...But everyone who read this topic can use them as reference....
Francesco
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autofix
Really Senior Member I
Joined: 23-August-2003
Location: Kildare
Status: Offline
Points: 294
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Posted: 16-December-2005 at 04:15 |
Hi Drew,
I agree, the origional topic is the point and we should get back to it.
My reason for posting was to offer some sound advice as I thought some posts in this thread, while mostly correct, were possibly somewhat misleading. Unfortunately you chose to, incorrectly, contradict what I had posted and then further defend your position thus confusing the issue even more. I was under the impression that the goal was to help the man, not confuse him.
Re your Pug fog lamp. You had 12v potential but a poor earth. The poor earth could not handle the current so the lamp could not light. IF your meter showed the poor earth then you were just lucky as a meter loads the circuit so little that it is not conclusive. Now do you see the point?? You were in effect using the bulb to test the circuit.
To be fair, I should point out to you that I am a professional diagnostic technican, information specialist and I write training courses on this subject.
My appologies to the thread starter. Hopefully you will find something useful in all this.
Alan
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siscobmw
Senior Member II
Joined: 13-May-2005
Location: North Italy , near lake of Como
Status: Offline
Points: 201
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Posted: 16-December-2005 at 05:28 |
This is funny....Ironic, also.
I attempt to start my 635 this morning,I found no signs of life....
I probably was punished for my no-success posts here ![](smileys/biggrinbounce2.gif)
I found no High tension for the sparks....The coil is gone... and a new one fitted(I was lucky enough to have a spare one at home, but not so clever to watch for those advice about Economy gauge needle movements....Sorry).
Yesterday night I found my friend ,He has good BMW knowledge (1 2002 targa, 1 3,0CSL Batmobile,1 3,3Li , 1 e28 535i, 1 735i with Alpina engine,2 M635 and a 7/84 635, then a M5 e34 touring elekta, a M3 3.0 Gt and so on....a lot of them are mint thanks to his DIY restoration and a good partneship with Mobile tradition....I hope this is a good curriculum vitae..)and told me that sometimes happens that a connector near the ECU (3 wires , white socket)has loose connections or , and this is the worse, their 3 wires are strenghtened too much in the loom with those black plastic retainers...and they cut out...3 wires: one green one black and one white,they are attached near the ECU, and they travel under the entire dashboard till the EBC brain zone.... my friend's 635 had that problem, and 2 of those wires were ruined just behind the instrument cluster loom retainer....
Worth a try?
Hope this helps,
Francesco
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Drew540i
Really Senior Member II
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Posted: 16-December-2005 at 05:31 |
autofix wrote:
IF your meter showed the poor
earth then you were just lucky as a meter loads the
circuit so little that it is not conclusive. Now do you
see the point?? You were in effect using the bulb to
test the circuit. |
Yes, I see what you mean about using a bulb to test
the circuit and see if it can actually light a bulb -
rather like a regular test light but more demanding?
I always (wrongly) assumed that to light up a bulb in
a test light there had to be current flow but as you
say, a 55 watt bulb sorts the men from the boys. But
all I'm saying is that the multimeter I have (nothing
special at all) measures DC and AC voltage, DC
current, resistance, diodes and hFE. I used it to
determine (or guestimate) that the earth was
inadequate, simple as. In this instance it was rusty
screws holding the thing on, typical French scrap.
But I admit you're vastly more qualified on this
subject - I won't argue with you again!
As for the analogy between bhp/torque and
volts/amps it was merely that, an analogy - volts and
bhp are the 'obvious' power values, yet it's torque
and amps that really do the job.......
No scientific connection whatsoever though.
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286bhp
Groupie
Joined: 27-January-2005
Location: Herts & Middx
Status: Offline
Points: 88
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Posted: 16-December-2005 at 07:12 |
I had an E28 M5 with this exact problem many years ago..
The fuel pump would run, the plugs got wet, but the B***ard wouldn't run. Anyway , after 4 hours of language, I pulled the engine wiring loom off the engine & cut it open. At some stage the car had been jetwashed under the bonnet. Water had got into the loom, and corroded the wiring inside the loom for the tdc sensor from the flywheel. The wire was intact, but had high resistance, killing the signal from the 'peg' on the flywheel.
The dme only needs to see signal from the rpm sensor ( ring gear teeth) that equates to a speed of greater than 300 rpm to trigger the fuel pump. The plugs will seem wet because the cold start injector runs separately from the ecu - it is controlled by the feed to the starter, and ignition live - no inetrvention from the DME at all. The main injectors & col will need to see the signal from the TDC 'peg triggered' sensor to work.
A few simple tests with a 'Scopemeter or equivalent will prove if this is the case.
As I live in NW london , I can call round and run the tests with you, to try and sort the problem out ??
Regards
Phil
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'01 M5
'02 MB C220 Turbosmoker
'99 323i (sold )
'89 M3 220hp with shrick 284's
'73 2002 cab
it's an Illness ......
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