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post #2 of 29 (permalink) Old 11-04-2011, 01:35 PM
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Unfortunately there is no test for the computers themselves. Once you make sure all the inputs are 100% the only thing left is a faulty computer.

Where are you located? Swapping in a known good computer sounds like the next step.

- - Eric
don't read this
~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina

L-jetronic Spider diagnosis (1982-1989)
L-jetronic V-6 diagnosis
OK injectors - fuel injector cleaning
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post #3 of 29 (permalink) Old 11-04-2011, 01:37 PM Thread Starter
In Charlotte....do I need to replace both FI and main ECUs?

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John (JP) Perry

1972 Montreal - in process!
1991 164B - sold 8/2013
1989 Milano Verde - sold 11/2012
1986 Spider Quad - sold 1/2012
1991 164L - sold 11/2011
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post #4 of 29 (permalink) Old 11-04-2011, 02:42 PM
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No spark

The two ECUs operate independently, if one is bad only that one needs to be replaced.

You said the fuses are good. Did you check them electrically or visually?


When you turn the key to ON, do you get 12v at:
  • the fused side of fuse 7
  • the (+) terminal of the coil
  • the fused side of fuse 8
  • ignition ECU connector terminal 10, green/black wire to/from Drive relay terminal 15, via connector G121
  • ignition ECU connector terminal 4, violet wire from igniton switch terminal 50, via connector G121

Two black ground wires, originally located on engine near injector 4 go to ignition ECU terminals 1 and 19. Is there continuity?

When the engine cranks, does the (-) side of the coil change voltage?

I've read not to probe the terminals of the ECU directly as damage will occur. I can neither confirm or refute this claim, but to be safe check voltages and continuity through the harness only while disconnected from the ECU.
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post #5 of 29 (permalink) Old 11-04-2011, 03:21 PM Thread Starter
Good feedback 86spider. Did a visual and pulled out and reinserted. All contact points were clean.

Will run your check in the am and report back.

Thanks, JP

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John (JP) Perry

1972 Montreal - in process!
1991 164B - sold 8/2013
1989 Milano Verde - sold 11/2012
1986 Spider Quad - sold 1/2012
1991 164L - sold 11/2011
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post #7 of 29 (permalink) Old 11-05-2011, 11:24 AM
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Quote:
Originally Posted by alfajp View Post
Tested this AM.....

When you turn the key to ON, do you get 12v at:

the fused side of fuse 7 - zero volts
this means fuse 7 is bad or you are not getting 12v to the unfused side of fuse 7 which gets power from the on position of the ignition switch. bad switch or bad wiring


Quote:
Originally Posted by alfajp View Post
the (+) terminal of the coil - - zero volts
this 12v comes from the hot side of fuse 7. no power getting here from ignition switch. bad switch or bad wire


Quote:
Originally Posted by alfajp View Post
the fused side of fuse 8 - zero volts
this means fuse 8 is bad or you are not getting 12v to the unfused side of fuse 8 which gets power from the on position of the ignition switch. bad switch or bad wiring


Quote:
Originally Posted by alfajp View Post
ignition ECU connector terminal 10, green/black wire to/from Drive relay terminal 15, via connector G121 - zero volts
this 12v comes from the hot side of fuse 8. no power getting here from ignition switch. bad switch or bad wire


Quote:
Originally Posted by alfajp View Post
ignition ECU connector terminal 4, violet wire from igniton switch terminal 50, via connector G121 - zero volts
this 12v comes from the hot side of fuse 8. no power getting here from ignition switch. bad switch or bad wire


Quote:
Originally Posted by alfajp View Post
Two black ground wires, originally located on engine near injector 4 go to ignition ECU terminals 1 and 19. Is there continuity? - Yes
Good.

Quote:
Originally Posted by alfajp View Post
When the engine cranks, does the (-) side of the coil change voltage? - No
This is because the 12v to the (+) side of the coil is missing. The ignition ecu will pull the (-) side of the coil to ground to make spark.

Quote:
Originally Posted by alfajp View Post
Assume this means fried ECU?
Not yet. There seems to be a theme developing here. You need to get 12v from ignition switch to fuse block connecting the unfused sides of fuses 6, 7, & 8 together. This is a brown wire.

You could try jumping 12v at the fuse block. Fuses 1-5 are tied together on the hot side and are connected to 12v all the time. If you jump 12v from the hot side of fuse 5 to the hot side of fuse 6 or 7 or 8 the ignition circuitry should get power.

Repeat measurements, or turn key to start, see what happens.
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post #8 of 29 (permalink) Old 11-05-2011, 11:26 AM
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There is a power supply problem.

Check for voltage at the input (unfused) side of fuses 1 thru 5. Is there battery voltage? If not, disconnect the battery and clean the connections at the junction block (on left inner fender) and at the starter. If there is voltage at the fusebox, check for voltage on the red wire at the ignition switch. If no voltage, repair wiring between fusebox and ignition switch. If there is voltage, replace the ignition switch.

Jim

Series 2 USA 1750 GTV (in Series 1 European clothing)
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post #9 of 29 (permalink) Old 11-05-2011, 11:32 AM Thread Starter
Will do and keep posted.....great insight and did not think the ignition switch (which now seems obvious).

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John (JP) Perry

1972 Montreal - in process!
1991 164B - sold 8/2013
1989 Milano Verde - sold 11/2012
1986 Spider Quad - sold 1/2012
1991 164L - sold 11/2011
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post #10 of 29 (permalink) Old 11-06-2011, 06:03 AM Thread Starter
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post #11 of 29 (permalink) Old 11-06-2011, 07:17 AM
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Wow, now this is the fastest and most complete electrical diagnosis of all time via a forum!!

From the fist post to the last, Amazing. Excellent work to all :-)

Jon '74 GTV RIP Tifosi
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post #12 of 29 (permalink) Old 12-02-2011, 11:26 PM
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Polished Grounds Again

When you turn the key to ON, do you get 12v at:
the fused side of fuse 7 Yes
the (+) terminal of the coil Yes
the fused side of fuse 8 Yes
ignition ECU connector terminal 10, green/black wire to/from Drive relay terminal 15, via connector G121
ignition ECU connector terminal 4, violet wire from igniton switch terminal 50, via connector G121 Yes if-------
if you count the holes in the connector from back to front, whether or not it has a metal connector inside. I'm pretty lost on this tests. I feel that if I strip apart the big sealed connector to the computers just to see the wire colors, when this thing ran fine a couple of months ago, I'd be setting myself up for scrapping it.

I do not have 12V at terminal #4, if that's how i'm supposed to count it.



Two black ground wires, originally located on engine near injector 4 go to ignition ECU terminals 1 and 19. Is there continuity?
Took the grounds off, and the neg side of the coil, repolished the polish, and applied dielectric grease.
Ignition ECU terminal#4 to ground, no voltage.

When the engine cranks, does the (-) side of the coil change voltage?
Checked again. Voltage drop from pos 12.4V to 10.2V.

Help guys. This is a low mileage unmolested Spider that I knew I was doomed when I brought it home. I've spent much more time trying to keep it running than driving and enjoying it.
The only difference between when I garaged it in July and when I tried to start it in late August is a mouse nest under the rear package shelf.
It ran splendidly when I parked it.
It would not fire Thursday night.
It fired up and idled and ran fine Friday night, when I was sure that I could drive it to the Italian Car Fest where I was entered, despite getting home the night before with nine broken ribs (blatent sympathy ploy.) Never fired again.

Back after 3 days in the ER and still driving the 41 Cadillac to Cars & Coffee and then the parts store hometown fest the same day.
Might be easier to do FlatHead Fest than Italian Car Fest.

Help! It almost has to be something simple?
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post #14 of 29 (permalink) Old 12-03-2011, 09:04 AM
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I had re-polished both grounds before this last round of testing.
I replaced the coil and the rotor, just to appease the parts god with an affordable offering.
I still don't understand the COIL SIGNAL - START SIGNAL diagram as it relates to the relays and the sequence that must succeed in order to energize the coil. I don't seem to be building spark in the coil to fire the plugs.
I have never located an inertia switch on this car. Supposed to be near the washer bottle and the flywheel sensor connections, but nothing there.
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post #15 of 29 (permalink) Old 12-04-2011, 12:47 PM
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The coil should be 'energized' by simply switching on the ignition. The ignition ECU then controls coil output (spark energy) based on the inputs it gets from the flywheel sensors (position & speed). The distributor then switches which spark plug gets the coil output.

The 'start' signal & relays are involved in power to the fuel pumps. When the key is turned to 'start' there should be 12V supplied to the fuel pumps. When the engine starts & the key is released back to the 'on' position, the drive relay takes over supplying 12V to the fuel pumps as long as it gets the expected tachymetric signal from the coil. Thus, if the engine is not running (i.e. stalls) the fuel pumps are not powered on (or - the fuel pumps will not remain powered on if the drive relay is faulty or the tachymetric signal is missing...).

- - Eric
don't read this
~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina

L-jetronic Spider diagnosis (1982-1989)
L-jetronic V-6 diagnosis
OK injectors - fuel injector cleaning
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