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Discussion Starter #1
hello
so im working on a 74 gtv with a spica fuel injection system. the problem im having is a rough idle. the alfa idles with a lope. quite uneven. i know the pump and ignition timing is correct. the alfa when warm runs slightly better. or when driven it runs smoother too. when i lean out the mixture two turns via the fuel shutoff solenoid the idle smooths out and is more consistent. but at this point the mixture seems lean. as under quick throttle i get intake backfiring. i know the atmospheric bellow??? is intact. so far the only thing i can think of is the TA actuator, with the engine fully warm i am only getting about 4mm of the chrome Piston protruding. this piston should extend out more??? even so why when cold does the engine idle so rough?? any ideas
 

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If you get the SPICA tune-up book from Wes Ingram, you will see that each setting must be done in a specific sequence. I thought I had done this, but still had a "lopey" idle. The cure was to set the synchronization between the front and rear throttle body pairs. A quick check is to place a paper strip in the intake hole and close the butterfly on the paper. The retention "grab" should be the same for the front and rear set. If not, there is an adjustment at the connection between the front & rear throttle shafts.

hello
so im working on a 74 gtv with a spica fuel injection system. the problem im having is a rough idle. the alfa idles with a lope. quite uneven. i know the pump and ignition timing is correct. the alfa when warm runs slightly better. or when driven it runs smoother too. when i lean out the mixture two turns via the fuel shutoff solenoid the idle smooths out and is more consistent. but at this point the mixture seems lean. as under quick throttle i get intake backfiring. i know the atmospheric bellow??? is intact. so far the only thing i can think of is the TA actuator, with the engine fully warm i am only getting about 4mm of the chrome Piston protruding. this piston should extend out more??? even so why when cold does the engine idle so rough?? any ideas
 

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Yeah, going through the steps in the Spica manual is the best way. Also, ensure spark and compression are all OK before proceeding with Spica.

Andrew
 

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Here's my guess: The tip of the thermostatic actuator (TA) has a probe that should extend about 5mm beyond the housing into the case of the pump so Wes tells me. That probe goes in an out depending on the ambient temp and acts as the choke to give the motor more or less gas on startup. On my pump the probe was flush with the case. Wes said don't waist your time trying to check to see if the TA is working by putting it in hot water because you won't get an accurate indication of whether the TA is working correctly. First and foremost he said was that the probe must extend 5mm beyond the case and, they usually don't last more than about 10 years. So, while my pump was being rebuilt I had him include a TA for around $250.00 and I sent him my old one so it can be rebuilt.
 

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Discussion Starter #6
Thanks for all the suggestions. when i get out there i will try doing what you guys have recommended. However im still puzzled as to why the throttle lever on the pump does not return to near the set screw when the engine is warmed up. When i take out the TA and push down on the spring that's in the pump where the TA sits i can get the throttle lever to back down. as far as i know that gap between the lever and set screw should be no more than 0.019'' when the engine is fully warm. Am i missing something?
 

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You have to adjust the screw under the plunger of the actuator to get the proper pump gap when it's hot. Could be something's not right with the mechanism of the pump.
Andrew
 

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tangencial issue

My mechanic brought up a good point: The Bosch pump from Centerline(back by the fuel tank) puts out 45psi which is twice as much is as what is needed. I think I read somewhere that 17psi is needed at the Spica pump and any access recycles back to the fuel tank. Why not just get a pump that puts out 20psi for less $ and, reduce the pressure on the system up to the return point? I know this subject has been discussed ad nausea.................but, I haven't seen this question answered. TIA! DB
 

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71 Berlina 74 GTV 17 Giulia Q4
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I have yet to find a pump that puts out 20psi other than the usual ones like the bosch substitute that are cheaper. If you know of one please share:)
There are many reasons an idle can be rough other than the ta. what is the lever gap with the motor at temp? If its not .019 chances are the ta has gone south.
 

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I can see a lot of Bosch replacement pumps on ebay for a lot less that Centerline or IAP but regardless of where you get them there is no mention of what the psi output is. Most say 300LPH, which I assume means litre per hour, no? If so then it would be easy to assume that all pumps that put out 300LPH have the same psi output?
 

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71 Berlina 74 GTV 17 Giulia Q4
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Not necessarily, therein lies the problem, spica needs high gpm and pressure, I suspect most of the others are either high psi or high gpm but not both?
 
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