82 short at battery... no start... dead ECU?

[thewired1]

So I took possession of my 82 Spider 2000 (manual, dealer installed AC, no power windows or locks) last week. I had it idling in my driveway as I looked over everything. Anyways, in the trunk the PO left some extra parts. As I was looking inside, I bumped the positive battery connector (which wasn't secured by PO) and it sparked and then the car shut down. I tried starting her again and get some power to the dash and starter would turn but no running.

This is what I've found and checked so far.

Fuse block had 3 blown fuses. They were a mix of ceramic and glass with various values, so I replaced the entire set with new ceramic ones. I didn't take note of which ones were blown sadly.

Attached to the pink wire at ignition the PO added some wires and fuses for the radio. They were blown. I replaced them and then later disconnected completely while testing.

I checked 3 in-line fuses and all are good. I also tested power at both sides of fuse holder to make sure they were seated correctly. One of the fuses appear to be added or replaced by PO and runs up to dash (or ac) not sure where or what it's doing yet. That fuse isn't on any diagram I've seen.

I've replaced the double relay under the glove box with a new bosch one. No change.

I've manually hooked up a battery to the fuel pump and it appears to work.

I checked values of the marelli ignition coil while disconnected. .8ohms and 1075ohms. That appears correct for a FI car.

THIS IS INTERESTING.... I checked for 12v at coil... nothing! I checked the positive to other ground and 12v!!! So the ground is no good. I traced that ground back to the ECU.

I've read the ECU are fairly tough BUT considering the battery short, I'm not sure about that in my case. Any ideas? Anyone willing to rent me an ECU to test? Anyone know of a good fiat mechanic in Orlando.

[klweimer]

Hi there thewired1,
PM me with your email address and I'll send you scans of the factory FI troubleshooting manual. The FI is tricky in that many of the circuits are completed by the ECU by switching ground, not hot side of the circuit (like the injectors). That said, pretty much the whole system can be checked out with a few simple tools.
Kirk

[spider2081]

I checked for 12v at coil... nothing! I checked the positive to other ground and 12v!!! So the ground is no good. I traced that ground back to the ECU.

I'm not sure what you are saying here. The pink wire and terminal on the coil should measure measure 12v with the ignition key in the start or run positions. the brown/white wire and terminal of the coil receive ground pulses from the ignition control module mounted under/behind the coil on the heat sink. The ignition control module electrically imitates a set of ignition points momentarily grounding one side of the coil. with the engine not turning over both terminals of the coil should have battery voltage on them. With the engine turning over the pink wire should have a fairly constant voltage on it that is near battery voltage. The brown/white wire voltage should be pulsing with the engine turning over. If it is not pulsing I would check the pick up wires in the distributor for deteriorated insulation.

The 6 pin connector for the ignition switch is a common cause of starting problems. It is about 6 inches behind the ignition switch.

[micbrody]

The double relay essentially isolated ECU/fuel injectors from high amperage battery.
I had a similar problem after cleaning my double relay. It turned out I connected the two plugs opposite of where they were suppose to be on double relay.
I don't exactly remember : but the side of double relay with less connection pins is the high amp side with wires coming from driver side dash. The conn connector with a bunch of white wires(ECU) goes to side of relay with more connector blades.

Probably not it.....but easy thing to try

[thewired1]

I'm fairly new with ECU/Fuel injected repairs and troubleshooting. All of my contempary cars have been under warranty, while my previous older fun cars were carburated models.

I assumed when I use a multimeter to check the voltage at the coil I use both the positive and negative terminals. WHen I do that with the key set to ON but car not running I get 0 volts. If I check the postive side and put the negative on the body of the car (ground) I get 12v. I assumed the negative/ground should be grounded at all times and I traced that back to he ECU. I also assumed the coil is powered at all times with the key set to ON and the distributor cap controls how and when the spark plugs are ignited. If I understand you correctly, the negative side is only partially grounded while starting up?

I checked the 6 pin connector. It looks rather old and there are some brown spots near the connectors. I did check with a test light if both ends are getting power while connected but I'll double check with a multimeter and confirm 100%.

[thewired1]

The double relay essentially isolated ECU/fuel injectors from high amperage battery.
I had a similar problem after cleaning my double relay. It turned out I connected the two plugs opposite of where they were suppose to be on double relay.
I don't exactly remember : but the side of double relay with less connection pins is the high amp side with wires coming from driver side dash. The conn connector with a bunch of white wires(ECU) goes to side of relay with more connector blades

Thanks! I'm fairly certain they're in the correct spot. I compared to photos on line of which side goes where.

[micbrody]

Did you check to see if you have spark when cranking?
If you have an assistant, take main output of coil (wire that goes to distributor) and hold it a centimeter from the car body (ground). Have assistant crank car. You should see spark.
I had a flaky ignition control module that caused a no start. Replaced and worked fine.
If no spark, you can also check coil:
http://www.aa1car.com/library/ignition_coils.htm

Should be low resistance in low voltage circuit (the top two terminals on coil. High resistance between output and non-powered terminal.

[thewired1]

I checked the coil with the terminals removed. .8ohms nad 1075ohm. That looks good from what I've read.

I used a spark plug tester and didn't see any spark while trying to start.

I've seen people remove the top of the coil on videos to check for spark there but I'd need my wife to turn it over while I'm testing. I'll try that tonight after the baby goes to bed.

I'm looking into the ICM. No apparently way for me to bench test. thinking about just replacing since they're cheap and instock around the corner.

[micbrody]

I just replaced my icm after testing coil (coil was good). I think I got one from autozone for $25......

[aj81spider]

I assumed when I use a multimeter to check the voltage at the coil I use both the positive and negative terminals. WHen I do that with the key set to ON but car not running I get 0 volts. If I check the postive side and put the negative on the body of the car (ground) I get 12v. I assumed the negative/ground should be grounded at all times and I traced that back to he ECU. I also assumed the coil is powered at all times with the key set to ON and the distributor cap controls how and when the spark plugs are ignited. If I understand you correctly, the negative side is only partially grounded while starting up?

When you are looking at the voltage across the primary of the coil (measuring + to - on the coil) there is so little resistance across the primary that the voltage will be about the same on both terminals and you will measure 0 volts. When measured to the chassis you should see 12 volts on both (to be perfectly accurate there will be a slightly higher voltage on the +, but not much). If the negative side of the coil were actually grounded you would have 12 volts of voltage drop through the coil, which with less than an ohm of resistance would be over 12 amps of current and which would do bad things to the coil. There's other resistance in the circuit besides the coil, so the drop across the coil is small.

Based on your reported measurements, and the fact that the car was running before I would say your problem is probably not with the coil itself.

[ORFORD2004]

http://www.njfiats.org/joomla/images/st ... 124_MM.pdf

[thewired1]

So I removed the coil and replaced the ICM since it's a fairly cheap part. No luck. I did confirm that I'm getting 12v on either side of the coil when the key is set to ON. I haven't been able to check if there is a spark at the top of the coil until my wife can assist tonight.

[micbrody]

The icm is signaled by magnetic pickup. Check continuity of line; I think resistance should be between 700-800 ohms. Though I don't understand why a short in trunk would affect/damage this line.....

[thewired1]

You're probably right but I'm trying to figure out why I have no spark. After blowing 4 fuses during the event, I still think it's a either a hidden wiring problem in the dash somewhere or the ECU. I'm trying to exhaust all possibilities that are cheap since an ECU is $$$$!

[ORFORD2004]

http://www.type17.ch/downloads/Injectio ... ooting.pdf
Just follow the guide