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Discussion Starter #1
In April I asked about fuel cavitation issues in hot weather on my 74 GTV with SPICA and received several helpful responses. I proceeded to change fuel filters, wrap the rear portion of the exhaust in header wrap, place reflective material on the outer wall of the fuel tank, and put an aluminum sheath on the fuel line between the tank and the fuel filter. I also learned my SPICA unit was rebuilt by Wes Ingram about 7-8 years ago. This past weekend I experienced fuel starvation with 3/4 full tank and about 88* ambient temperature. I'm beginning to wonder if this is a <85* driving car or I need to completely move the fuel pump to a cooler location!!! Your further thoughts would be appreciated.
 

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Verify your Spica’s inlet fuel pressure and that the fuel pump is receiving at least 12 V (check via fuse terminal outlet). If the fuel pressure light is flickering during these starvation episodes, reduce the Spica pump outlet restrictor diameter to 1/16" . This can be done by soldering the existing outlet and drilling a 1/16" hole or finding one from an Alfetta. The 1/16" restrictors will raise fuel pressure at the Spica pump to compensate for:

1.) fuel filter canister pressure relief valves that still allow some fuel to pass below the 17 psi threshold, thereby reducing optimal SPICA inlet pressure

2.) electric fuel pumps that are slightly worn and don’t generate their original / ideal fuel output.
 

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If everything's working as it should, at this ambient temperature it should not be a problem. I've used numerous Spica cars all over Calif, including hot hot places like Buttonwillow and Willow Springs track events, in the summer, and never had a problem.
I'd urge you not reengineer anything til you ensure it's all working as Alfa engineered it.
Andrew
 

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See Hans's suggestions. I would measure voltage at the delivery pump, measure pump pressure and flow with a T/gauge setup at/near the injection pump (see Wes's book on how to do this). Pull out the restrictor fitting (front fuel line fitting) and make sure it's clear and about the right size, and pull off the rear fuel fitting and make sure it's clear.
7-8 years can be a long time, both in use and if the car was just sitting. So there could be a problem with the pump itself, though the symptoms don't sound like it.
And you're certain it's fuel starvation, not ignition? The old joke, largely true, is 90% of fuel problems are actually ignition problems (bad wires, plugs, coil, points, electronic box, whatever), which could be related to heat/length of operation.
Where are you located and what altitude?
Is the delivery system all stock with a stock delivery pump and filters? These cars just don't get that hot, especially on the intake side, where the fuel comes in.
Andrew
 

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Discussion Starter #6
Thanks for your further suggestions. I will do these as well as Hans suggestion. I live in eastern TN, about 900' above sea level. From what I can tell everything is stock on the delivery system. The car runs so well outside of the high ambient temperature I have to believe the two events are related. I have also heard rumblings from others about encountering the same problem symptons from time to time. Most describe it as a vapor lock type of experience-particularly those who have air cooled cars or motorcycles.
 

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Yes, sounds symptomatic. I just wonder if the heat is causing problems elsewhere, which you're attributing to the fuel delivery. That's not really hot, though, nor are you high enough to really make a difference to the pump.
I can only point to my considerable experience driving in 100+ temps in the Mojave Desert and San Joaquin Valley, never with a problem. Made a 1000-mile tour last June in my GTV with AROSC from Bakersfield to Tehachapi, Mojave, Rosamond, all super-hot, on to LA, back to the Bay Area, and the car didn't miss a beat. My system was totally stock.
Andrew
Andrew
 

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Discussion Starter #8
Andrew, I wonder if our high humidity and dew point might make a difference? From where you described those areas would be very low humidity although high temperatures. Over the weekend we had dewpoints in the mid 70's, very uncomfortable but I'm not sure if it would impact the pump operation in any way.
 

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Don't know. I wouldn't think so. The desert is very low humidity, the Valley less so, with all the agriculture. But still likely a lot drier than where you are.
Again, with difficult problems, I find it useful to go back and check the basics, even ones you think are outside the symptomatic range.
Has the car always done this, or did the problem develop? If so has anything else changed? You could do worse than to swap in a known-good delivery pump and see if that solves it, if you can get your hands on one.
Andrew
 

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Check The basics

-Make sure the fuel is not contaminated (gunk or water in your tank)
-Check both fuel filters. If condition is unknown replace them.
- Check that the air-inlet valve (in the trunk next to the black plastic expansion tank) is not cloged.


Hope this helps, and that I did not go over stuff you had already checked:D
Luis
 

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Good point re the check valve. Does the gas tanks seem to be "oil canning" as it empties? If so, easy check is to run it with no gas cap (temporarily as a test) and see if that solves the problem. Air needs to get into the tank to replace the gas, or you end up with the delivery pump pulling against a vacuum, and the tank collapses.
Andrew
 

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Determine if the symptoms occur at low fuel tank levels. Way back in the early SPICA days, the Alfa club of Colorado warned people coming to their 1973 convention to keep their tanks at least half full to prevent partial vapor lock from overheated fuel when driving at high altitudes.

Ooops. I rushed to respond and didn't read your comment about a tank 3/4 full.

UOTE=timpryan;1034674]Any suggestions on where to look next?[/QUOTE]
 

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Maybe a long shot, but I had a similar problem awhile ago and discovered that when really warm, my (way too old) hose from the gas tank to the fuel pump was so flexible that it would partially collapse. I replaced it and the problem went away.
 

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Also, when this problem happens, do you notice any change in the sound of the fuel pump (like a higher pitch)? This was the clue that led me to change the hose.
 

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Discussion Starter #15
Haven't noticed any change in the sound of the pump during cavitation but will remember this the next time it occurs. I did notice when cranking the car the next day after both fuel cavitation events there was a black, sooty exhaust with moisture droplets mixed in the soot. Don't know if this is a further clue or not.
 
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