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Discussion Starter #1
Howdy peeps, my apologies if I've posted this thread in the wrong place. Mods, feel free to move it around if needed.

I've converted my EFI 1985 105/115 2.0 Spider to carbs - Runs great! But the car is still operating with both the Bosch ignition and fuel ECUs hooked up. I would like to remove them since now that the car is carb'ed they are rather redundant. I know that:
  • If I disconnect the fuel ECU and leave the ignition ECU connected, the car starts but runs really poorly. So the fuel ECU might still be controlling fuel pump activation
  • If I disconnect both ECUs or just the ignition ECU, the car won't run at all. Correct me if I'm wrong, but the ignition ECU controls spark unless I go with an aftermarket distributor
  • I know the drive relay is responsible for the operation of the pump somehow
  • In the process of plugging/unplugging stuff I've successfully and thoroughly fried the main relay. Fear not, I've removed the corpse of the relay from it's harness, and the car still runs with it disconnected. So I know it does nothing in my current configuration (I believe it controls the now non-existent fuel injectors)
  • Using a forum search I've found the following quote from Papajam (RIP):
Drive relay (short version);
When the key is on, switched power is supplied to terminal 15. The input terminal 30 (fused from battery) and output terminal 87 (to fuel pumps) contacts are open. Fuel pumps do not operate. When starter is engaged, power is supplied to terminal 50. This closes the 30 & 87 terminals to power the fuel pumps. At the same time, an ignition pulse is received at terminal 31b. When the engine starts, this ignition signal keeps the 30 & 87 terminal contacts closed after power to terminal to 50 drops out.
Does anyone know what I should jumper/ground so that the fuel pump operates without ECU control? I get that I may not be able to delete the ignition ECU, but any guidance there would be greatly appreciated as well.

Cheers,
--Andre
 

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I would get rid of the combo relay and the fancy electronic relay that monitors the ignition. You can install a simple relay that pulls in when you turn on the ignition and then powers the fuel pump. There is most likely a dedicated fuse for the fuel pump so wire that in to the circuit. You will lose the safety feature of shutting down the pump when the engine stops running but earlier Alfas did not have that feature and instead used an inertia switch to stop the pump if the car is in a heavy collision. It would be easy to wire in one of those.

I don't see why the L-Jet computer is affecting the car now that you are on carbs. Its outputs are to the injectors that you have eliminated.

I would buy a 123ignition distributor and get rid of all of the existing ignition stuff so that you have a simple system that is easy to understand and troubleshoot. That means that the crank sensors are no longer needed.
 

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Discussion Starter #3
@alfaparticle Got it! I was just missing a stupid ground from the drive relay terminal# 31. I was able to remove the fuel ECU and she runs yet again!

Do you have lots of experience with the 123ignition distributor? Is it as simple as slap it in, pull the ignition ECU out, throw it in the bin, and start the car?

Also, my setup offers no way to pull vacuum for advance/retard. Any issues with running a single ignition curve?
 

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Also, my setup offers no way to pull vacuum for advance/retard. Any issues with running a single ignition curve?
You don't need vacuum advance, There are lots of posts about 123 distributors in several threads going back 10 years. Mine is older than that. I have only used the simpler one with switchable curves and that has been fine for me. Others like to design their own curves with the programmable version. Here is a sample discussion https://www.alfabb.com/threads/wiring-for-123-ignition.686544/#post-8468984
The circuit with an MSD Blaster coil and a ballast resistor makes very strong sparks. You won't be disappointed.
The curve that you choose depends upon the tune of your engine. High output motors like the "D" curve and the "1" curve is a good choice for street 2L cars.
 

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Here is the hook up diagram for a 123 dizzy with a ballast resistor. The resistor is not necessary if the coil primary is more than 1 ohm but it will make better sparks with a coil and ballast resistor each of about 0.6 ohms.

As I mentioned in a previous post, you will have to wire the fuel pump to run from the ignition switch when you dump the current ignition system.
 

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Discussion Starter #6
@alfaparticle NICE, thank you!

Now with the relay properly grounded, if I simply disconnect the ignition ECU the pump will kick in, but I get no spark. I'll do my research on the 123 dizzy, sounds like the way to go.

Thanks again!
 

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RocketAce:

I am very interesting in what your doing as will be attempting the same in the near future with a S3 that I plan to convert to carbs as well. When you say you remove the fuel ECU, are you leaving the existing harness in place (just unconnected in the engine bay) or are you pulling the wires that are no longer needed? Understand what you have now may not be your longer term goal once your up and running. but I am interested in how your working through the problem..Also Let me know if you need the a 84 wiring diagram (close too if not the same for a 85) it may help you in your efforts.

Kamikaze
 

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Discussion Starter #8
RocketAce:

I am very interesting in what your doing as will be attempting the same in the near future with a S3 that I plan to convert to carbs as well. When you say you remove the fuel ECU, are you leaving the existing harness in place (just unconnected in the engine bay) or are you pulling the wires that are no longer needed? Understand what you have now may not be your longer term goal once your up and running. but I am interested in how your working through the problem..Also Let me know if you need the a 84 wiring diagram (close too if not the same for a 85) it may help you in your efforts.

Kamikaze
Hey! Thank you, but I do have the 85 diagram from Papajam. I also have an 86 diagram (if anyone else needs one)

For now I am leaving the existing harness in place, what started the idea was to try cleaning off as many of the the engine bay wires on the passenger side as possible. Eventually I'll pull/trim the wires I don't need. My motivations are primarily aesthetics and dealing with my amateur engineer brain chastising me for having systems installed that I no longer need

If you convert, the car will run fine with both ECUs connected and no vacuum advance. I need to remember exactly what I've removed and what I've re-used during the conversion process outside of the obvious stuff. I'll post here when I do

Your biggest challenge may be converting linkage throttle actuation to cable. I've chosen to fabricate a bracket, weld it on the firewall, and weld in a lever arm to the stock linkage. The result was something similar to this picture below from @vintagemilano:

1604783
 

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How about fuel delivery, are you still using the original fuel tank? I'm assuming you removed the in-line high pressure pump under the car but are still running the in-tank pump or did you go another route. How are you regulating pressure to the carbs.
 

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Discussion Starter #10
How about fuel delivery, are you still using the original fuel tank? I'm assuming you removed the in-line high pressure pump under the car but are still running the in-tank pump or did you go another route. How are you regulating pressure to the carbs.
You'll want to keep the inline pump, that is your main feed pump - the in-tank pump is only there to lift fuel up and out of the top of the tank to feed the high pressure pump under the car (the high pressure pump expects a lot of fuel volume in fuel injection applications.) Instead, simply disable the in-tank pump and leave it installed. Or even better, remove the entire pump sending unit from the tank, remove the pump itself, and substitute it with a length of hard fuel line. Here's how a Montreal sending unit looks like with no fuel pump, for reference:

1604871


That way you reduce the risk of vapor locking the car in warm weather because of line restrictions. To disable the in-tank pump, simply remove the pink/white striped wire on the top of the fuel sending unit.

1604872


You can leave the other connections alone since they report fuel level readings, or whatever else you wiring diagram says they do. I'm assuming you'll want a working fuel gauge :LOL:

Carbs require lower pressures to function than fuel injection applications, usually between 2-4.5 PSI. A fuel pressure regulator will allow you to regulate the fuel pressure coming out of the inline pump. An interrupter pump needs no fuel pressure regulator, it regulates itself. It will feed 2-3 PSI of fuel only when the fuel line pressure drops below a certain threshold.

I am running YZF R1 carburetors on a modified L-Jet intake manifold, I've simply substituted the inline pump with a 12V R1 interrupter pump, wired just like the stock unit. An interrupter pump may or may not work for more traditional applications, in which case I recommend you research a bit on it. You may have to upgrade the stock inline pump with a new pump better suited for carb applications, and/or install a fuel pressure in line somewhere easy to reach for adjustments.

I did eventually get a fuel cell for the car. That's only because the trunk floor was rotting, so I said "while I'm at it, why not." The car ran and drove on that carb setup with the stock fuel tank for about a year with no issues, save for running a bit rich because I've installed the wrong jets :whistle:

Let me know if you need any other info. I've done so much work to this thing I can only remember as I go.
 

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I've had Webers on my 79 Spider for 20 years. It has no in-tank pump and the fuel is pulled from the top by a Carter vane pump and regulated to 2.5 psi by a Filter King regulator. I have tried other pumps and regulators and these are the ones that worked best for me. The fuel pump should be mounted below the level of the bottom of the tank.
 
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