The Tune-Up… continued

Football season has begun and since it’s still hot as hell here, I’ve been taking a break from my beloved jewel and keeping up with my favorite team.  As I mentioned in my previous tune-up post, I’m working slowly through the SPICA mechanical fuel injection pump tuning procedure and here are some things I’ve discovered so far…

I’m using the official Wes Ingram procedure and integrating the other Alfa Romeo club documents in where it makes sense.  The Wes Ingram procedure is very thorough and leaves nothing to chance, so I find each time I run through it I make decisions along the way, deciding if the current step is really necessary.  You won’t need to actually complete every  step each time you go through it.  You’ll instinctively know where you can move on and feel confident after a few times through.

The procedure starts with making the decision regarding the Spica pump being defective or not.  Wes gives steps and guidance on how to determine that for yourself but I’m skipping this step and assuming the work done and information I have from the previous owner is evidence enough that the pump is not significantly defective.  Rather, the pump is just what it is; a Spica pump with over 100,000 miles on it.

Next the procedure tries do address the pump timing which is tied directly to the ignition timing.  As I mentioned in several previous posts, I’m not a  car mechanic and I know very little about ignition timing.  I’ve been studying this part for some time and of course took the opportunity to buy a new tool.  I got a cheap Xenon timing light with advance from Harbor Freight for $29.95.  This step insures the timing of the spark and fuel injection is in perfect sync.  Steps are also included to ensure the fuel supply is good by confirming the fuel light works.  Mine is all good!

Moving on in order, the next step is to get things all setup with the Spica pump gap and thermostatic actuator (TA in some documents).  This basically ensures that when the car is  started cold, the throttle is a little rich until the coolant temperature  come up to spec at 170 degrees.  I did the bench test for my thermostatic actuator and found it was a newer model (refurbished) in the original 1974 Spica pump.  This means that the probe that extends from the bottom of the TA as the temperature rises is longer than the original.  Unfortunately, the phone I took picture with when I removed my TA for testing died and I lost the pictures, however I did document the probe lengths at cold and hot temperature:

  • Cold reading – 24.59mm
  • Hot reading (173 deg.) – 29.20mm

This means that when I adjust the set screw under the thermostatic actuator that it image1bottoms out and I can’t set it far enough in to get the critical .019″ gap (see the documents linked in my first Tune-Up post for details on the .019″ gap).  I found a couple of people who are clearly very knowledgeable about the Spica tune-up procedure on AlfaBB and one of them suggests adding two washers (two modern washers turn out to be 4mm thick when put together) as shims to take up the slack and put the newer TA with a longer probe within spec for an older model Spica pump.  The washers will have to be ground down to allow for the TA mounting screws, so I’m working on getting things shimmed up.  I may just go with one washer instead of two, but I definitely need a shim to get within factory specification.

 

In the follow up steps, the bell crank for the throttle cable that controls the throttle plates are adjusted.  This is an area of concern for me as well.  The throttle plates have to be fully closed when you aren’t on the throttle peddle for correct idle, and the bell crank has to be set to stop at full open throttle.  More on that later but the issue for me is that the set screws should never be touched after factory setting and I have no way to confirm if they are spec or not.  I’m trying to determine if any club members or my local Alfa mechanic have the factory tool to set these permanently.

Once I get the set screws confirmed I’ll work on setting the fuel mixture and confirm the fuel cutoff solenoid is working perfectly.  This will prevent the backfiring I’m getting right now even though I’m lifting my foot completely off the throttle when I let up (a common cause of backfire in the Alfa Romeo inline 4 cylinder engine).

So in a nutshell… here is where I’m:

  1. Pump assumed not defective but well used
  2. Ignition and pump timing assumed good
  3. Fuel light and fuel supply confirmed good
  4. Thermostatic actuator confirmed in spec (but needs shim for new TA in older pump)
  5. Pump gap as close to spec (.019″ at 170 deg.) as possible but shims required
  6. Bell crank, idle stop, and full throttle stop suspect but adjusted accordingly
  7. Long rod and short rod length suspect but adjusted accordingly
  8. Deceleration micro-switch and fuel cutoff solenoid suspect
  9. Fuel mixture still suspect but has been adjusted best effort at 2500 rpm
  10. Cold start device not tested

 

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