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Discussion Starter #1
I just finished cleaning up all the grounds and installing a new O2 sensor on my 1984 GTV-6 and now it will not start. Engine turns over but will not start. I am assuming, the smoke has escaped from my ECU while I was replacing some grounds and an O2 sensor. I think the key that let the smoke escape is I did some of this work without disconnecting the battery and had the ignition on a few times, which blew fuse 5. The results of my testing and references used are included below. What else would you test or monitor or is it time to order an ECU?

For troubleshooting, I followed Greg with Hiperformance store write-up titled Bosch L-Jetronic system, and another write up on the fuel relay titled “Double Relay Demystified”. A summary of the testing results are provided below;

Fuel pump is not receiving power, but it does work. I powered the fuel pump with another 12-volt source, and it spun up to full pressure quickly.

Installed a new Bosch Double Relay. The new relay is part # 0 332 514 121, which, I read, replaces the original discontinued relay # 0 332 514 127. Now, when I, barely open, the flap on my AFM I hear a contactor in the new double relay energize. Yet even with a new double fuel relay power is not being sent to the fuel pump?

No power to fuses 9-14 with the ignition turned on and the flapper on the Air Flow Meter (AFM) open? Fuses 1-8, 15 and 16 are fine. The copper fuse holders have been polished to remove oxidation, the clamping pressure of each fuse was adjusted to firmly hold the fuse and all the fuses are new (Copper).

Tested some components of the Fuel Injection system, such as all temp related, roll over and altitude sensors. Aux. Air valve and throttle position switch. Testing was completed per the specifications outlined in the write-up on the Bosch L-Jetronic system, by Greg with Hiperformance store. Greg’s write-up can be found at (L-jetronic Fuel Injection Technical Troubleshooting Article) and is great. I hope its correct? All my component are now within factory specifications or have been replaced.

Tested and cleaned the Cold Start valve. It opens and closes (put it in freezer) but does not close completely. It works. I will adjust it later.
 

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Are you saying that you actually saw or smelled smoke from an electrical short? If so, that might be your answer. What will instantly fry an ECU is attempting to crank the engine with the grounds disconnected, but even key-on is not a great idea.

Fuses 9-14 have nothing to do with the ECU, however; they are all fuses for the exterior lights, and all are powered by their respective switches. I'd stop focusing on that for now.

The fuel pump side side of the double relay has terminal 86 its relay coil powered by pin #4 of the ECU, so make sure you are getting that input.

The telltale for the ECU will be if you are getting a switching signal to the fuel injectors. You can use a test light or noid light at one of the injector connectors to verify this. The light should flash rapidly while cranking. If not, and all of the other ECU inputs test good, then a solid test light likely means that the fuel injector driver(s) in the ECU got fried. Luckily, used GTV6 ECUs are relatively cheap!
 

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Discussion Starter #3
With the ignition on and flapper on the AFM open I have 0 volts DC at terminal 86 on the dual relay. FYI, I removed the plastic cover on my AFM to Deoxit the carbon strip and adjust the copper fuel shut off switch in the control box. Since its open, I’m opening the flap by moving the potentiometer arm inside the AFM.
I do have power to the dual relay. Contactor 86a opens (breaks contact) when the flapper on the AFM is opened, but 86b doesn’t close (make contact) and no power to 86.
When I opened the ECU there was a mild familiar smell of burnt resistor. I’ve looked closely at the boards and resisters and I do not see any indication of a short and no burn marks, flashes or fire damage, looks OK. I’m going to the parts store tonight to pick up a noid light to finish. I’ll update status tomorrow.
Thank you, CDA951
 

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The "double relay demystified" page that you cited does a good job of explaining how the system works:


The engine does not generate enough airflow while cranking via starter power alone to close the contact switch in the AFM. Therefore, the power to the fuel pump while cranking the engine in the "start" position comes from pin 4 of the ECU and to terminal 86 of the relay. Once the engine fires (and the key is released), there is sufficient airflow to close the AFM contact switch and the fuel pump side of the relay remains energized.

So, you should check for power at pin #4 of the ECU; if nothing is there, double check the primary ignition circuit. The ECU is signaled to activate the injectors via pin # 1, which is connected to the negative terminal of the ignition coil.

If you have the switching/flashing input from the ignition coil at pin #1 while cranking the starter, but no steady voltage output from pin #4, then the ECU is at fault.
 

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Discussion Starter #5
Maybe good news, yet the car still does not run. I picked up a noid light set to test the fuel injectors and the light blinks when cranking the engine. I’m guessing, but I see ~1-2 flashes per second while attempting to start the engine. I tested cylinders 5 and 6. Any additional input would be appreciated.
Thank you
 

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Maybe good news, yet the car still does not run. I picked up a noid light set to test the fuel injectors and the light blinks when cranking the engine. I’m guessing, but I see ~1-2 flashes per second while attempting to start the engine. I tested cylinders 5 and 6. Any additional input would be appreciated.
Thank you
OK, that means that you have power to those injectors via the double relay, and the ECU does seem to be switching them.

But, you do need to investigate why the fuel pump isn't activating, if that is the case. Do you have any sort of factory wiring diagram?

You should check the ECU pins 1 and 4 while cranking as mentioned in my previous post and go from there.
 

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Discussion Starter #7
OK, that means that you have power to those injectors via the double relay, and the ECU does seem to be switching them.

But, you do need to investigate why the fuel pump isn't activating, if that is the case. Do you have any sort of factory wiring diagram?

You should check the ECU pins 1 and 4 while cranking as mentioned in my previous post and go from there.
I do have the cardisk Deluxe GTV6 manuals and will trace 1-4 out now. Thank you ,CDA951
 

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Did you disturb the wiring harnesses near the double relay when replacing the o2 sensor harness? Likely yes. It sounds like everything is working properly except your fuel pump supply wire is broken or the connection at relay is weak. I think it’s the pink wire. Open AFM door to energize relay and wiggle your connections. Listen for fuel pump or the fuel rushing sound through rail etc.

Do you have an inertia switch? This interrupts the fuel pump power supply and if bumped hard it will disconnect power.


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If you energize the fuel pump with an external power source (direct wire it to to run), will the engine fire? Once I had a GTV6 that intermittently would loose 12v+ from the ignition switch to the dbl relay. Rather than opening the steering column covers or the wiring harness, I spliced a wire from the coil + post to the underside of the dbl relay. Good luck! Please post all the details.
 

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Discussion Starter #10
Did you disturb the wiring harnesses near the double relay when replacing the o2 sensor harness? Likely yes. It sounds like everything is working properly except your fuel pump supply wire is broken or the connection at relay is weak. I think it’s the pink wire. Open AFM door to energize relay and wiggle your connections. Listen for fuel pump or the fuel rushing sound through rail etc.

Do you have an inertia switch? This interrupts the fuel pump power supply and if bumped hard it will disconnect power.


Sent from my iPhone using Tapatalk
In March, I purchased the car registered PNO (Parked Non 0peration) in California. Per the PNO registration, the car had not been driven since 2015. So yes, I have disturbed every part of the car and inspected, tested and cleaned everything. I bypassed the inertia switch with a jumper wire and I do have power thru the (pink/white) conductor wire now when i open the AFM flap. I'll o post a troubleshooting update soon. Thank you, Sobol
 

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Discussion Starter #11
If you energize the fuel pump with an external power source (direct wire it to to run), will the engine fire? Once I had a GTV6 that intermittently would loose 12v+ from the ignition switch to the dbl relay. Rather than opening the steering column covers or the wiring harness, I spliced a wire from the coil + post to the underside of the dbl relay. Good luck! Please post all the details.
Yes, I disconnected the existing + wire from the pump and attached the battery (+) to the fuel pump and the car starts. This allowed me to test the pump and the existing ground. All good, but still getting power on 86. I'll post a trouble shooting update soon. Thank you, Sobol
 

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Troubleshooting update: Still not running. I did retest the Thermo Time Switch (TTS) yesterday and found it failed, miserably (36 ohms @80 F and 40 ohms @150 F). I guessing its deteriorated to the point it no longer provides a ground to circuit 86 on the Double Relay (DR). I’m assuming circuit 86 on the DR needs ground from the TTS and Cold Start Valve (CSV) to energize. Makes sense to allow for the electrical switch over from cold start to normal operating conditions. I hopefully have the replacement tomorrow and that it.

The good news is:
  • I now know where everything is, and the electrical system components have been cleaned, tested, and replaced, as needed.
The goodish bad news is:
  • Purchased a new Bosch Double Relay to check out the existing relay. It seems the original double relay was working. So now I have 2 working double relays.
  • Fuel pump is not receiving power, but it does work. I powered the fuel pump with the battery and the car started. It ran a bit lumpy and did not like when I pushed the gas pedal, but it started.
  • All the grounds in the engine bay, dash, back seat, and battery box have been cleaned, polished and reinstalled.
The BAD news is:
  • NO power to terminal 86 on the double relay and the fuel pump.
  • I will not have a new TTS until tomorrow.
So, the plan is to work on other items until the replacement TTS arrives. Any info from anyone else’s prior struggles with the TTS or you know what’s wrong. Please let me know.

Thank you, Sobol
 

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I thought that the TTS only closes the circuit to power the cold start injector. Has nothing to do with powering the dbl relay to run the fuel pump. Keep in mind my fix with running a wire from the coil to the dbl relay.
 

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Discussion Starter #14
I thought that the TTS only closes the circuit to power the cold start injector. Has nothing to do with powering the dbl relay to run the fuel pump. Keep in mind my fix with running a wire from the coil to the dbl relay.
I restored power to the Pink/White wire at the Double relay shortly after reading this. So I didn't need to run power to the double relay. Thanks, I figured it out, see below..
 

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Discussion Starter #16
Troubleshooting update: Status is running. The offender was the Pink/White wire. I found a break in the wire at the firewall penetration. Looks like it has been rubbing there for a long time. Luckily, none of the other wires in the loom were damaged.

For now, I spliced in a new section of wire and I'm happy to say the car started immediately. So now, I just need to put the whole car back together and then tI can take it out for a drive down the coast. I certainly could not have done this with out all your help. Thank you CDA951, Racingswim2006 and Andylarry for sticking with me thru this, your input helped greatly!

Pics of the damage section and repair are included below.

Thanks again, Sobol


IMG_0620.JPG IMG_0624.JPG IMG_0625.JPG
 

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Good job Sobol! Makes you wonder how that wire broke when you were installing the new 02 sensor. This is another good lesson for all of us to rule-out wiring problems before we begin to replace components.
 
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