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Discussion Starter #1
I have a guy working on my Alfetta Sedan. He is an old time Alfa mechanic who knows how to set up a Spica. He has gone through the engine and it is running spectacularly, EXCEPT.

Except cruising at part throttle about 3500 rpm. It hums along, but has a miss. It really stutters hard about every 5 seconds or so. He's tried about everything inlcuding switching the spica pump. Any ideas?

The ignition is Marelliplex. He replaced the cap, rotor, and plug wires. No help.
 

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I have a guy working on my Alfetta Sedan. He is an old time Alfa mechanic who knows how to set up a Spica. He has gone through the engine and it is running spectacularly, EXCEPT.

Except cruising at part throttle about 3500 rpm. It hums along, but has a miss. It really stutters hard about every 5 seconds or so. He's tried about everything inlcuding switching the spica pump. Any ideas?

The ignition is Marelliplex. He replaced the cap, rotor, and plug wires. No help.
Have you checked fuel pressure? Changed the fuel filters? Both of them?

About the only things left would be the fuel pump, connections to the fuel pump (check the fuse too!), and the ignition/coil.

Is it heat related?

bs
 

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A similar thing happened to me when I was running an MSD ignition box with a Bosch blue coil. Once it got nice and hot, the CD nature of the box showed how it didn't like the coil much.

Kind of a shot in the dark, but something.
 

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Discussion Starter #4
He switched the entire ignition system with a Bosch electronic one off a spider last night. Hasn't driven it yet. We'll see.

Brian, I bugged him about the fuel pump, filters and so forth, but he claims that the light never comes on and that the fuel supply system for a spica is not that critical. Especially since the car runs great at full throttle, I kind of agree.

However, if the ig. swap doesn't fix her, I guess that I will try to talk him into refurbing the whole fuel supply system. That pump is no confidence builder as it is noisy as hell. And it never hurts to replace all the old lines, filters and etc. In for a penny...

If none of that works, I am getting off the dime, and having my twinspark engine put together and installed. It may cost me a couple grand, but it'll cost me $800 for a rebuilt spica pump and then I still have the ts gathering dust in my garage.

Thanks for the feedback guys!
 

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It sounds like you have an ignition problem. As you drive the car, the ign module heats up and then breaks down under load producing a miss. Fortunately, the MarelliPlex ignition modules are a GM part and can be bought for a few bucks at a NAPA store. MarelliPlex's are pretty bulletproof so if you should be able to get your working. Are you using the original MarelliPlex coil?

The SPICA injection pump makes noise or is it the fuel pump at the tank? If you can hear the injection pump running then you've got a serious problem. It doesn't sound like you've got a fuel pump problem because when the miss happens you should also be able to see the F/P light come on. If it doesn't you don't have a fuel pressure problem causing the miss.
 

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Discussion Starter #6 (Edited)
The fuel pump at the tank is noisy, but the f/p light does not come on. The spica pump is quiet, and the car idles and runs at full throttle perfectly.

The coil may well not be correct. Where can one buy a correct Marelliplex coil? So the ignition module is a GM part, what about the coil? I have also heard that the sender is a GM part as well, true?

Can anyone point me to GM part numbers?
 

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The coil may well not be correct. Where can one buy a correct Marelliplex coil? So the ignition module is a GM part, what about the coil? I have also heard that the sender is a GM part as well, true?
The coils in the 'Plex's are low resistance coils. MSD and ACCEL sell good ones. Just make sure its low resistance and does not have a built in ballast resistor and you'll be OK.

The ign module is attached to the bottom of the heat sink. You can see the flat connectors sticking out of the side of the heat sink. It's easy to take off so you can just take it into a parts store and by a replacement. They're cheap: about $10 or so. The GM style modules come in 2 and 3 prong styles. I can't remember what the MarelliPlex uses. In any event the GM module will bolt right in.
 

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Discussion Starter #8
It's not the ignition. He completely change the system - same issue. I am convinced that the engine was massaged in some unknown manner that makes it not suitable for a stock Spica pump. However, even if I was willing to blow the dough on a Wes Ingram high performace pump, what would I tell Wes? I don't have any idea what was done.

Eff it. Twinspark here we go. Unless anyone has any other ideas or knows some way to precisely calibrate the engine's breathing so that Wes could build a pump to suit...

:mad: :(
 

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Discussion Starter #9
Update!! I bought a Wes Ingram HP pump. Harry installed it. The problem was still there! :( :mad: :eek:

Then Harry found an old set of Spica injectors he had pulled off a good running GTV way back in the day. He switched out mine. Guess what? Problem solved. This weekend I will be driving my very sweet running Sport Sedan. Whee!

I thought about trying to return the pump to Wes, but I think that I will be happier driving the car with the proper pump. It has moderately hight compression: 175 on all four and 10.4mm (as I recall) lift on the cams, so Wes said the HP pump is a good fit.

Bad Spica Injectors: Who'd a thunk it?!?

Now for my Series One dashboard implant, and NOS heater box install :p

Who wants to buy a Mondial t? :D
 
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