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having major no spark issues STILL! what are the functions of the main & drive relays could this be part of a no spark problem also when cranking the car how fast should the roter spin? any test i could run to check relays there is nothing in the manual from I.A.P.:(
 

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The drive relay requires an input from the coil to let it know the ignition system is firing. This input must be 'tachymetric' (as Tifosi calls it - I don't know if that is a real word or one he made up) - the point being the signal to the drive relay rises and falls as the coil fires (when instructed by the igniton ECU). No igniton = no signal to the drive relay = no fuel injection. Off hand I don't recall how the main relay fits into the picture. I do know there have been some good explanations here - try a search for more info. If you find a post by PapaJam study his reply - he knows of what he speaks (writes).

The ECU's (computers) require about 10.3 V to wake up and send the spark/fuel signals. If your available voltage during cranking is below that threshold, no go. Put a voltmeter on the battery and see what it reads while you are cranking the motor.
 

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(papajam learned me the word :p )

The main relay gets triggered by the drive relay after it activates, so you end up with:

Engine turns, ignition fires.

Ignition fires, pulsing/tach-like signal (get it? Tachymeteric?) gets sent to drive relay via the ignition coil.

Drive relay comes on and fuel pumps begin pumping, while simultaniously a steady/non-pulsing '+' trigger signal goes from the drive to the main relay so it comes online which in turn allows the injectors to fire when the ECU starts pulsing the injector '-' signals through the brainbox proper.


EDIT: Will the drive or main relay affect ignition spark? No, not as far as I'm aware of, as they are activated by ignition spark, so they cannot be in control of it. (well, one is activated by spark pulses and it controls the other, so no spark, no activation of either relay)

The L-jet stuff piggybacks on an existing functional system. All it does is control fuel.

Now perhaps the motronic ignition box would have a more significant effect on actual firing, (though the engine can be made to run happily without it using a free-standing aftermarket system), but not the L-jet fuel setup.
 

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Trained (ex)Professional, , 1953-2018 RIP,
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Here's what I know (or think I know).

The main relay powers the fuel injectors when ignition is on/engine either off or on.
The drive relay (called the tachymetric control unit by Alfa) powers the fuel pumps when the engine is running.
Neither relay has anything to do with providing ignition. However, as Tifosi said, the drive relay receives a pulsing signal from the ignition system.

Operation of main relay;
Turning on the ignition provides power to terminal 86 (+ side of pull in coil). Terminal 85 (- side of pull in coil) is grounded through fuel ECU pin 28. Coil pulls in to close the contacts for terminals 30 & 87. Terminal 30 is input battery power and 87 is output to injectors (as well as fuel ECU pins 10 & 29). The injectors fire when the fuel ECU provides a ground to the injectors.

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.

To test the main relay, turn on the ignition and check for power at one of the two wires on any injector. If power, main relay is working.

Not quite sure on how to test the drive relay. I'll need to ponder on it a bit.
 

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Jim, you sound familiar with the drive relay so I have a question for you. My 84 Spider would not start. I replaced the drive relay and now it runs for a mile or two and dies. All the while the drive relay behind the passenger seat makes a high pitch noise. You can touch it and it feels like there is a moving part inside of it. After a few minutes it starts back up and repeat the same after a couple of miles or less. Any ideas?
 

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This question may seem completely out of left field but it may help the diagnosis. Does the high pitch whine lessen, or disappear, under acceleration?
 

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drive relay whines

Well I had to go and test drive to confirm. I don't believe it lessens when you accelerate. It does change pitch but that is not tied to acceleration. I've made a recording of it on my I phone if you'd like to hear it I can email. I though it was a radio thing at first. Thanks for any ideas.
 

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By some chance have the coil connection wires been removed and reconnected recent to when the problem started?

Also, before keeping it running became an issue, did the engine mabe kinda run on for a bit when the key was shut off? (I don't mean that surge, lurch, hiccup and chug kind of run on, but run normally for X amount of time after they key was turned, say a second or longer)
 

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Okay. One last test just to be certain where the noise isn't coming from.
Behind the right rear trim panel is the ignition ECU and a vacuum sensor. Disconnect and plug the vacuum hose to the vacuum sensor. Start the engine. Has the noise changed?
 

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Ok, I'll try. But for sure, the sound is emitting from the Drive Relay. I put my phone near it and made a recording of the sound. Also the Drive Relay has a accompanying vibration that matches the high pitch whine.
 

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Understood. Just don't want to spend a bunch of time trying to diagnose something that isn't broken.
 

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I haven't had a chance to pull the right rear trim panel yet ... but I thought of something else that might be significant. You can start the car and just let it run till it dies (5 or 10 minutes with the drive relay buzz the entire time) but after the engine dies the drive relay stops buzzing and then you can hear the fuel pump continue to run. It will stop only when you turn off the key. It's not suppose to do that, right?
 

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Somebody I think has bypass the Main Relay

Ok guys to recap my problem:

I bought a local one owner alfa for not much because it didn't run (aka drive relay something-another problem) Bought a new relay and it fired right up... but the relay buzzes with a high pitched sound. (the one I replaced did the same... (I thought it was come from a radio speaker but discovered it's the drive relay buzzing) After replacing the relay it will now start up and drive for 5 or 10 minutes and goes DEAD. When it dies the buzzing stops but the hum of the fuel pump can be heard. So I removed the "shelf behind the passenger seats and below is what I discovered. Someone has "pigtailed" the YELLOW wire from the the GREEN wire in front of the Main relay directly to a wire that runs to the fuel pump. The other wire going to the fuel pump has been grounded to the frame. I'm not sure what I'm looking at but it appears someone has run a "hot wire' to the fuel pump and bypassed the Main Relay of the fuel pump. Question what is the correct wiring and 2nd question is, Why anyone would do this? Any Ideas? Many thanks in advance!
 

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As an 84, it's plausible that someone cobbled the wiring back there because they didn't know there (likely) is an intertia switch on the firewall.
Intertia switch trips, fuel pumps don't run for nuthin, and without knowing its there, people start to do silly things to get the pumps to run again.

Look near the windshild wiper resevoir. If there's an odd looking thing (can be cylindrical or rectangular~ish IIRC) with a button on top, that's the inertia switch. Disconnect the wires going to it and connect them directly to each other. This will bypass the inertia switch (you don't actually need it with the way the drive relay functions)

Then, perhaps you can get the wiring under the shelf back to the way it should be using one of those excellent diagrams that papajam makes for us folk.
 

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Question what is the correct wiring and 2nd question is, Why anyone would do this?
1) PapaJam's color coded wire diagrams will reveal all.

b) so they can be nominated into the DPO Hall of Shame.

Here's a snip of PapaJam's wire diagrams:
 

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Intertia Switch

Yes, Tifosi,

I do have a Intertia Switch. It looks like the one you described in an earlier post. So, I should remove it and hard wire the lines leading to it?
 

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okay.. a little good news, but more bad news....
Removed the Yellow wire to the green/black wire and connected the two white with red stripe wires, cranked the ignition and she starts right up. Drive relay still buzzes, thought. Also, let the car run about 5-7 minutes and it died. After it died the fuel pump continued to run. I disconnected the wires fuel pump turns off. I reconnect the wires a few minutes later, restart the car and drive into the garage and turn the key off and the engine turns off along with the fuel pump. So, I guess drive relay is not tell the fuel pump to turn off but how can it continue to run with no key in the ignition???
 
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