1983

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rdou
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1983

Post by rdou » Thu Dec 06, 2018 10:43 am

why am I loosing power to injectors when engine warms up?
starts and runs fine then sudden loss of power to injectors, then will not start
until cooled down?
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andy
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Re: 1983

Post by andy » Thu Dec 06, 2018 12:10 pm

Are you certain its power to the injectors and not loss of spark?

The pick up in the distributor can fail in a way that it works fine cold, but fails when the engine warms up. Too a lot of trouble shooting to figure that one out.
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spider2081
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Re: 1983

Post by spider2081 » Thu Dec 06, 2018 12:40 pm

Referring to the Fiat Manual: Spider 2000 Electrical Diagnostic Manual 1980-1981

Power to the fuel injectors comes from the dual relay. If you are loosing 12 volts to the injector connectors I would check for 12 volts at pin 88e of the dual relay.
The ignition pick up and ignition control module can cause the injectors not to fire. They provide a Tach signal to the ECU. The ECU then with other inputs determines how long the injectors open. The injectors should have 12 volts on their connector as long as the dual relay is activated. The ECU activates all the injectors at the same instant by supplying the momentary ground to complete the circuit.
rdou
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Re: 1983

Post by rdou » Thu Dec 06, 2018 2:12 pm

Thanks for the input, I have have changed the coil and pick up and magnet with spares
still the same, replaced temp sensor ,and battery is good lots of power at coil, I don't have spare injector
relay to try, but if the relay is bad why does it quit only when engine warms up, I know there is fuel and spark
but when it dies its only the power to injectors,I have checked with node light and they are dead until it gets cold
then it starts perfect runs great, all the grounds are solid on intake when its running all the injectors are clicking
even tried spare E C U same, think its a dead short in wiring harness ???
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rridge
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Re: 1983

Post by rridge » Thu Dec 06, 2018 3:07 pm

The ignition switching module under the coil pack is the usual suspect when a hot FI engine stops running. But you say you have spark. I too would suspect a high resistance contact somewhere in the double relay or a connector in the circuit from ignition switch to double relay. If the FI fuse in the fuse holder under the ignition switch is original I would replace it just on age.

Why does a poor contact fail only when hot? The resistance across a dirty or corroded metal converts some the electrical flow to heat and heat raises resistance even further. When resistance is high enough current flow stops until the contacts cool and some conduction returns.

The double relay one of the known weak points in the FI system. It doesn't help that it sits in close proximity to the leak prone heater valve. If you don't have a known good spare and can't borrow one, buy a used one, test it immediately and keep it in the glovebox.

Is there any chance that you might have disturbed the two black ground wires that attach to the intake plenum and provide the ground paths for the FI system? They should be connected by ring spades under two the last two plenum bolts toward the firewall.
Richard
'81 Turbo Spider
Rockville, MD
spider2081
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Re: 1983

Post by spider2081 » Thu Dec 06, 2018 4:37 pm

,I have checked with node light and they are dead until it gets cold
the Node light needs both the power from the dual relay and the ground from the ECU to light. Have you measured voltage with a vltmeter at the injector connector with the ignition switch on and the AFM flap open??
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atruscott
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Re: 1983

Post by atruscott » Fri Dec 07, 2018 3:10 pm

spider2081 wrote:
Thu Dec 06, 2018 4:37 pm
the Node light needs
Noid :)
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spider2081
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Re: 1983

Post by spider2081 » Fri Dec 07, 2018 7:14 pm

I never could spell or proff read. :?
rdou
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Re: 1983

Post by rdou » Mon Dec 10, 2018 10:41 am

Thanks again for all the help electrics are not my strong area, if I understand the dual relay for the fuel system may be bad,
I thought if it was working it was ok, Can it fail when it gets hot and work ok when it cools off?
I took it out last night and it does look original. I see all the white wires on the one plug look the same as the wires to the injectors is this correct?
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rridge
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Double relay failure modes

Post by rridge » Mon Dec 10, 2018 12:03 pm

Can it fail when it gets hot and work ok when it cools off?
Yes, the soldered connections between components and the circuit board crack and separate with age and the continuity of the circuits becomes fragile. Cold start, hot failure is a common way they fail. Park twenty FI Fiats on a large lot for a group photo and after sitting for twenty minutes odds are pretty good that one of them will not start. Odds are even better that at least two other owners will rush over with their spare double relays in hand. Been there, seen it, got the photo.
Richard
'81 Turbo Spider
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