Engine only runs when starter is engaged - Alfa Romeo Bulletin Board & Forums
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post #1 of 39 (permalink) Old 03-31-2019, 10:52 AM Thread Starter
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Engine only runs when starter is engaged

Hello, I've been lurking here ever since I couldn't figure out how to rest my password a few years ago. Now I have a question so I figured I'd re-register.

I just picked up a 1979 Alfetta Gt that's been off the road for a few years and I'm trying to diagnose a starting issue. It only runs while the starter is engaged and dies as soon as the ignition switch is turned to run. It has SPICA and marelli plex ignition. The coil has battery voltage as well. Any thoughts on this would be greatly appreciated.

Thanks!

Jay

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post #2 of 39 (permalink) Old 03-31-2019, 11:26 AM
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Welcome back!

My guess is a faulty ignition switch. The internal contacts in the 'run' section may have burned out. In theory, these contacts should be self-cleaning - the contacts are usually designed to wipe against each other as they operate. So, again, in theory, you might be able to revive the switch by repeatedly operating it (disconnect the battery so the engine won't keep starting and the contacts won't keep arcing.

- - Eric
don't read this
~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
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post #3 of 39 (permalink) Old 03-31-2019, 11:43 AM Thread Starter
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Thanks for the tip I'll definitely give that a try. I was hoping it wasn't a $200+ switch that needs to be replaced right off the bat. The car also had the starter run on issue but I did the cold start mod and that seems to have fixed the issue.
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post #4 of 39 (permalink) Old 03-31-2019, 01:19 PM Thread Starter
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Update

I bypassed the ignition switched +side 12v coil lead and ran a jumper from the Alt and its still dying after the starter disengage. Does that rule out the ignition switch? Is the hei module bypassed when the starting circuit is engaged?
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post #5 of 39 (permalink) Old 03-31-2019, 01:23 PM
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Maybe
Try using a wire from the battery + to the coil + and start it
If engine keeps going= faulty ign switch
+ = positive

1972 105 GT Veloce 2000
1976 2L Spider
1984 GTV 6 3 litre
1967 GSGT 2 litre
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post #6 of 39 (permalink) Old 03-31-2019, 01:25 PM
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I don't know the wiring on your car, but generally there are two power feeds to the coil. One applies a full 12V to the coil while cranking, and then during running a second line carries power to the coil through a ballast resistor. Dunno how the Alfetta is set up, though.

See if you're getting 12V at the coil with the ignition in the run position, and if not troubleshoot from there.

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #7 of 39 (permalink) Old 03-31-2019, 01:26 PM
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Hi again Jay

I do what I do above
I guess using the alternator positive is the same,,but I do it my way which bypasses alternator and possibly other wires and relays etc.
I go direct= Batt + to coil +

1972 105 GT Veloce 2000
1976 2L Spider
1984 GTV 6 3 litre
1967 GSGT 2 litre
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post #8 of 39 (permalink) Old 03-31-2019, 01:41 PM Thread Starter
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The battery is in the trunk so I moved the jumper from the Alt to the battery side of the starter solenoid but still the same outcome.
Honestly I'd rather be frustrated for another few hrs with something hopefully simple than buy a new switch.

Here's the car.
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post #9 of 39 (permalink) Old 03-31-2019, 02:52 PM
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Quote:
Originally Posted by Motoital2.0 View Post
I bypassed the ignition switched +side 12v coil lead and ran a jumper from the Alt and its still dying after the starter disengage. Does that rule out the ignition switch? Is the hei module bypassed when the starting circuit is engaged?
Uh, what's the "hei module"? Is that like a Marelli Plex, that uses the same electronics as GM's HEI ignition? If so, where does that get it's power? Is it powered from the coil "+" terminal? Or does it have a separate power connection from the key? If the latter, I suppose that could be the problem.

Does the car die immediately once the key is turned from "start" back to "run"?

Might the electric fuel pump be getting shut off when the key goes back to "run"? Can you still hear the electric fuel pump running after the engine dies?

Are the warning lights on the dash illuminated with the ignition switch in the "run" position?

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

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post #10 of 39 (permalink) Old 03-31-2019, 03:15 PM Thread Starter
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Yes it has Marelli Plex with the GM module under the coil and its powered by the green/black wire from the + side of the coil.

I think it might actually be the rear fuel pump. I don't hear the fuel flowing through the filter in the engine compartment like my 74. I didn't know that the starting circuit energized the fuel pump on its own. I've ordered an Alfetta manual but it's not here yet.

Thanks again for all the tips. At least the engine starts on the first crank now so that's a plus!

Edit: no warning lights either.

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post #11 of 39 (permalink) Old 03-31-2019, 04:16 PM
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I don't hear the fuel flowing through the filter in the engine compartment like my 74. I didn't know that the starting circuit energized the fuel pump on its own.

no warning lights either.
OK, it's starting to make sense.

My guess is that your ignition switch is faulty. It is supposed to supply current to the coil, warning lights and fuel pump in both the "run" and "start" positions. And of course, send current to the starter solenoid in the "start" position.

But it sounds like your's isn't supplying current to the coil, pump, etc. in the "run" position; only in "start".

Quote:
I bypassed the ignition switched +side 12v coil lead and ran a jumper from the Alt
When you said you "bypassed the ignition switch" did you mean that you pulled the factory connector off the coil "+" side when you connected the jumper. If so, it might be interesting to put that wire back on there, as well as the jumper to the starter solenoid battery lug. That way, you'll be supplying +12V to the fuel pump and warning lights back through the ignition switch wiring. It should continue running in that configuration, though the only way to shut it off will be to pull the jumper.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

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post #12 of 39 (permalink) Old 03-31-2019, 04:29 PM
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Here's a sketch of the Spider's ignition switch connections. If your car's is the same (seems likely) find the connectors and jump #1 to #3 (on the car side, not the switch side). This should power on all the switched circuits. Then add a temporary connection to #2 and the starter should operate. When the engine starts remove the connection to #2 - the starter should stop and the engine keep running. If so, the ignition switch is likely faulty.

Another thing to check - actually before doing the above - is the fuses. The aluminum strip fuses especially are known to look OK but fail to allow electrons to flow. I prefer the fuses with a brass strip. But if they are of unknown vintage it is probably a good idea to replace them. Clean the contacts and if necessary squeeze them together to ensure a tight fit with the fuse.
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- - Eric
don't read this
~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina


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post #13 of 39 (permalink) Old 03-31-2019, 05:51 PM
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Another thing to check - actually before doing the above - is the fuses.
Those fuses and their holders are highly unreliable, so checking them is good preventative maintenance. And the fuel pump circuit is probably fused.

But if a fuse or it's holder were bad, it wouldn't pass current in either the "start" or "run" positions. The fact that the fuel pump works with the ignition switch on "start" suggests to me that its fuse is OK.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L
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post #14 of 39 (permalink) Old 03-31-2019, 06:00 PM Thread Starter
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Alfajay,

Yes I removed the green/black wire from the coil but I will try it with it attached along with the jumper.



ghnl,

I will take a look at the switch harness and try jumping those two terminals. That diagram definitely helps!



Its definitely suffering from old fuse syndrome but I was able to confirm that the fuel pump is getting power. More so after I cleaned up the fuse. IPD, the volvo retailer has high quality brass fuse kit and I've already ordered some.
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post #15 of 39 (permalink) Old 03-31-2019, 06:09 PM
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The fact that the fuel pump works with the ignition switch on "start" suggests to me that its fuse is OK.
Likely true. But channeling Click & Clack (unencumbered by the thought process) and knowing nothing specific about the Alfetta, I'm left with random thoughts. Is there any sort of bypass circuit activated when the key is in the 'start' position?

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


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