i shorted the car last week at the battery junction box, with a braided cable. she has fired up and ran perfectly 3 times since then, after testing individual components. but once knocked off that's it, for another day or 2!
after testing everything it seems my airflow meter isn't getting any voltage.
the ecu isn't getting any output signal from it, which i think is preventing the ecu from telling the spark plugs and injectors to work.
so after testing the harness, the connections on the AFM side have no voltage but do have resistance (extremely high, one terminal has 1.2 million ohms)
while the connections on the ecu side have neither voltage or continuity.
the car is an '87 325is
any thoughts or suggestions would be very appreciated
shorted and killed my 325is. now no voltage to airflow meter
Moderator: martauto
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Brianmoooore
- E30 Zone Team Member
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Car should start and idle quite happily with the AFM disconnected.
Are you aware that there's a fuse for the engine loom power near the battery? It's not a conventional fuse, but is a 'fusible link' connected in the smaller wire from the battery.
Are you aware that there's a fuse for the engine loom power near the battery? It's not a conventional fuse, but is a 'fusible link' connected in the smaller wire from the battery.
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mthreepower
- E30 Zone Newbie
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- Joined: Sat Apr 18, 2009 11:00 pm
i read about that fusible link alright, but never saw it or any like it.
the engine cranks fine.
that small wire off the battery was also checked and confirmed to have voltage yesterday.
the coil has all the correct voltage and resistance figures. just not delivering spark.
the fuel pump and associated relays are all functioning as intended when tested, just not when delivering fuel when in the circuit.
what could be causing this, if not the fact that i have no power to the AFM, even if it can be disconnected without drastic effects.
the engine cranks fine.
that small wire off the battery was also checked and confirmed to have voltage yesterday.
the coil has all the correct voltage and resistance figures. just not delivering spark.
the fuel pump and associated relays are all functioning as intended when tested, just not when delivering fuel when in the circuit.
what could be causing this, if not the fact that i have no power to the AFM, even if it can be disconnected without drastic effects.
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Brianmoooore
- E30 Zone Team Member
- Posts: 49360
- Joined: Mon Jan 10, 2005 11:00 pm
What exactly did you short to what? It's highly unlikely you could have damaged ECU or AFM wiring.
If you have power at the + terminal of the coil, checked by a 12 volt bulb from terminal to earth NOT by a meter, then the battery fuse is OK.
No spark and no fuel pump activity (fuel pump relay not closing) is either the crank position sensor faulty, a missing electrical supply to the ECU, or a faulty ECU itself, in that order of likelihood.
If you have power at the + terminal of the coil, checked by a 12 volt bulb from terminal to earth NOT by a meter, then the battery fuse is OK.
No spark and no fuel pump activity (fuel pump relay not closing) is either the crank position sensor faulty, a missing electrical supply to the ECU, or a faulty ECU itself, in that order of likelihood.
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e30topless
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you have probably blown the CPS, shorting the battery terminals or similar can cause this, esp on early Motronic cars,
it's a simple job to replace so long as the CPS hasn't seized into the bellhousing like most have
it's a simple job to replace so long as the CPS hasn't seized into the bellhousing like most have
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mthreepower
- E30 Zone Newbie
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- Joined: Sat Apr 18, 2009 11:00 pm
i was removing a braided cable and it hit off battery junction box, just above the strut housing. there was a big arc and it burnt the cable leaving an inch diameter black mark, but there was no visible trace left on the junction box- consisting of many cables! 
i have replaced the motronic 1.0 ecu with a working spare, no problem there.
the first i sports's don't have a CPS, instead they have separate speed and reference sensors in the bellhousing of the gearbox monitoring the flywheel. in my case; both have the required 900 ohm resistance and all the wiring checks out at the ecu end of the harness too.
but brian i dont understand why its imperative to use a bulb? i only tested with a meter, but got the results that were expected!
<-- i just saw that lol
i have replaced the motronic 1.0 ecu with a working spare, no problem there.
the first i sports's don't have a CPS, instead they have separate speed and reference sensors in the bellhousing of the gearbox monitoring the flywheel. in my case; both have the required 900 ohm resistance and all the wiring checks out at the ecu end of the harness too.
but brian i dont understand why its imperative to use a bulb? i only tested with a meter, but got the results that were expected!
<-- i just saw that lol-
e30topless
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which is a CPS !mthreepower wrote:the first i sports's don't have a CPS, instead they have separate speed and reference sensors in the bellhousing of the gearbox monitoring the flywheel
are you still using the spare ECU ?
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mthreepower
- E30 Zone Newbie
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- Joined: Sat Apr 18, 2009 11:00 pm
`e30topless wrote:which is a CPS !mthreepower wrote:the first i sports's don't have a CPS, instead they have separate speed and reference sensors in the bellhousing of the gearbox monitoring the flywheel
are you still using the spare ECU ?
yeah thats true.
no i put back in the original.
lovely looking alpina in your pic as well