I am working on a 1977 spider that was changed to carbs with the aluminum spica to carb intake adapters at some point but the car has been sitting a long time and the gas tank was junk inside so I have decided to run an earlier bottom feed tank and mounted a low 2.5 to 3.5 Mr. gasket 42s pump 12" from the tank outlet thus not needing the in tank and regular pump but wanted to know which + line ( in tank or under the car) should I use to power up the new Mr. gasket pump or does it not matter? Does the under the car pump turn on when the key comes on or does it wait to power up once the car is cranking over? The pump that I am using is a low current draw and has a filter before the pump and right before the carbs as well and I am not using a return line to go back to the tank .and I don't think that I need to fuse the pump near the pump but will if others feel that I need to fuse it. Your thoughts on this matter would be appricaited.
77 spider changing to carb and changed fuel tank to gravity at bottom and have an electrical question
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The fuel pump should get switched power and should always be running when the key is turned to on. I don't have a '77 wiring diagram, but if it's like my '74 you should just be able to use the Spica fuel pump power feed, which should already be fused at the fusebox (you always want the fuse to be as close to the power source as possible, not close to the pump).
For safety it would not be a bad idea to retrofit an inertia switch if you don't have one: this will shut off power to the pump if you're in an accident.
You do not need a return line for carbs. My GTV originally had the same 42S pump on it, and even though it's low pressure it was still too much for the carbs and was overwhelming the needle valves at idle, so I would strongly recommend installing a Fispa / Filter King filter-regulator in the engine bay.
centerlinealfa.com
For safety it would not be a bad idea to retrofit an inertia switch if you don't have one: this will shut off power to the pump if you're in an accident.
You do not need a return line for carbs. My GTV originally had the same 42S pump on it, and even though it's low pressure it was still too much for the carbs and was overwhelming the needle valves at idle, so I would strongly recommend installing a Fispa / Filter King filter-regulator in the engine bay.
Fuel Filter/Regulator Carbs | Centerline International
Centerline International is the leading supplier of restoration, performance, and maintenance parts for all Alfa Romeo models fr
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What Tom wrote +1
This 42s pump is used and I was using it with no issues in a porsche 914 in the engine bay. They say to put it by the tank and not in the engine bay but I did both and it still worked fine. I have done some research on the filter king and will add one if I need to but hoping to not need one as they are pretty pricey. I am planning on using the under the car wiring then and will hook up the juice for it next. Thank you for chiming in. I am trying to make this as simple as possible for myself.
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Well, that's what I expected too based on the specs, but I was getting some stumbling off the line which was a too rich condition from the pump overwhelming the needle valves at idle. When I measured dead-head pump pressure on the 42S it was like 4-5 PSI, which was too high.
I would suggest that at the very least you measure what you're getting a the carbs with that pump, as you may be surprised.
They say 2.5 to 3.5 max in the Mr. gasket site but I will add a gauge if I have an issue and see. The car had one of those chrome 1 through 5 psi adjustable pressure regulators but I don't plan on using that or should I? I heard that they were junk.
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I've had mixed results with those. I have one of those with a Facet cylindrical fuel pump on the Giulia and it's been fine for years. I tried to use one on the GTV with the 42S pump, however, and it seemed like the pump was overwhelming the regulator. I just said "screw it" and replaced everything with a new Facet pump and a Filter King regulator and no more problems.
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The combined filter/regulator. I bought this one from Classic Alfa:
classicalfa.com
Make sure you get one with the glass bowl, there have been issues with the plastic ones.
FL053 FILTER KING FUEL FILTER & REGULATOR WITH GLASS BOWL
Buy any part for your Alfa Romeo classic car online. We are the largest supplier for classic Alfa Romeo car parts in the UK. We ship worldwide every day.
classicalfa.com
Make sure you get one with the glass bowl, there have been issues with the plastic ones.
Mine is also near the exhaust. I put the fittings in with pipe tape and the location is easy to see and will have to keep an eye on it. I would have put the fuel pump in the original location but they want it as close as possible to the fuel tank and on a 45 degree angle.
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What you heard is correct.
I have tried 5 different fuel pumps on my '79 with Webers and the Carter P4070 has worked best for me
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