Checking fuel tank sender
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mbouse
dan - i think you have my old 32 Weber. traded it to Logan for some other parts not that long ago.
rick - changing out that 28/32 and the intake to an 1800 intake and a better carb (several to choose from) will produce SIGNIFICANT, not mild, performance boost, especially if you dump the stock air breather for a lunch box....then once you replace that 4-1 exhaust and the cat for either a header setup or a 4-2-1 & a test pipe.......LOOK OUT.
rick - changing out that 28/32 and the intake to an 1800 intake and a better carb (several to choose from) will produce SIGNIFICANT, not mild, performance boost, especially if you dump the stock air breather for a lunch box....then once you replace that 4-1 exhaust and the cat for either a header setup or a 4-2-1 & a test pipe.......LOOK OUT.
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spider79
As luck would have it, I need both exhaust and carb work, so it's an excellent time to upgrade, I think.
My cat is actually not in bad shape, and the ANSA muffler on it looks decent. However, the pipes and first muffler have seen better days for sure. Hopefully, I can convince my local exhaust shop to ditch the cat and replace the piping and first muffler. I already have the 4-2-1 manifold, so I'll save the header for later.
I'm thinking that the stock carb is definately not worth messing with, so it's an excellent time to upgrade.
My cat is actually not in bad shape, and the ANSA muffler on it looks decent. However, the pipes and first muffler have seen better days for sure. Hopefully, I can convince my local exhaust shop to ditch the cat and replace the piping and first muffler. I already have the 4-2-1 manifold, so I'll save the header for later.
I'm thinking that the stock carb is definately not worth messing with, so it's an excellent time to upgrade.
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mbouse
no offense, but how did you determine that your cat was in good shape? is it a 28 year old Cat? i suggest that it is NOT in good shape. if your local shop will not drop it from your system, http://www.fiatparts.com sells a bolt in test pipe for under $100
and, if you drop the cat and the resonator pipe, and upgrade the intake, you may end up with some popping from the rear end on deceleration. might think about taking that whole exhaust thing a step at a time. zero back pressure sounds like a good idea, but some back pressure gives some practical advantages.
and, if you drop the cat and the resonator pipe, and upgrade the intake, you may end up with some popping from the rear end on deceleration. might think about taking that whole exhaust thing a step at a time. zero back pressure sounds like a good idea, but some back pressure gives some practical advantages.
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spider79
The cat is visibly a fairly new replacement. It may be completely rotted inside, but the outside looks new compared to the rest of the exhaust system. I was planning on putting a resonator pipe on it on it, but eliminating the cat, mostly because it seems like a lot of weight hanging from the stock spring arrangement.
Thanks for the tip on the "test pipe".
Thanks for the tip on the "test pipe".
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manoa matt
- Posts: 3442
- Joined: Thu Oct 26, 2006 4:28 pm
- Your car is a: 1978 Fiat 124 Spider 1800
- Location: Honolulu, Hawaii
Mike,
I also had that popping sound when decelerating or when going down a hill with high rpms. Kind of sounds like RUUBB.. BUB.. BUB... BUB.....BUB
If you push in the clutch while coasting down hill then it stops.
Its pretty embarassing to have people look at you and think your car is backfiring.
I saw something in the factory service manual about this condition. Apparently on 77's and 78's there is NOT a valve that prevents raw gas from being sucked into the intake upon rapid deceleration above 2500 rpms
I wonder if there is a way to take a valve from another year and retrofit it to a 77 or 78. I don't even know where the valve would be located.
So Cal Mark do you know anything about this valve or how to reduce the popping?
I also had that popping sound when decelerating or when going down a hill with high rpms. Kind of sounds like RUUBB.. BUB.. BUB... BUB.....BUB
If you push in the clutch while coasting down hill then it stops.
Its pretty embarassing to have people look at you and think your car is backfiring.
I saw something in the factory service manual about this condition. Apparently on 77's and 78's there is NOT a valve that prevents raw gas from being sucked into the intake upon rapid deceleration above 2500 rpms
I wonder if there is a way to take a valve from another year and retrofit it to a 77 or 78. I don't even know where the valve would be located.
So Cal Mark do you know anything about this valve or how to reduce the popping?
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manoa matt
- Posts: 3442
- Joined: Thu Oct 26, 2006 4:28 pm
- Your car is a: 1978 Fiat 124 Spider 1800
- Location: Honolulu, Hawaii
OK, sorry to lead yo guys in the wrong direction. I was thinking of two different things.
The popping sound is from a faulty or non functioning Deceleration throttle positioner system (fast idle electrovalve)
according to Chilton's repair and tune up guide:
Uncontrolled deceleration causes a high vacume condition when the throttle plate closes with the engine in the middle to upper rpm range. This high vacume draws in raw fuel which causes an overrich condition. With the throttle positioner holding the throttle open to the fast idle position, extra air is admitted with the fuel, leaning out the mixture and reducing emissions.
Intestering note taken from lower on the same page: This circuitry is fused through the windshield wiper system; therefore, if that circuit is inoperative, the device will not function.
The other thing was from the Fiat factory service manual page 10-126.
Catalytic temperature protection tachymetric switch(75-76). To prevent excessive temperatures in the converter, the fuel is shut off from the carburetor during decelerations. The tachymetric switch senses engine speed from the coil. Withe the throttle closed durring decelerations above 2650 +/- 50 rpm, the switch energies the idle shutoff solenoid. This shuts off idle fuel flow inside the carburetor. The tachymetric switch is located under the glovebox.
So Fiats from 1975 thru 1978 have only a fast idle electro valve, and Fiats from 1975 to 1976 have both fast idle valve and tachymetric switch.
I guess i need to adjust my fast idle to eliminate the popping.
The popping sound is from a faulty or non functioning Deceleration throttle positioner system (fast idle electrovalve)
according to Chilton's repair and tune up guide:
Uncontrolled deceleration causes a high vacume condition when the throttle plate closes with the engine in the middle to upper rpm range. This high vacume draws in raw fuel which causes an overrich condition. With the throttle positioner holding the throttle open to the fast idle position, extra air is admitted with the fuel, leaning out the mixture and reducing emissions.
Intestering note taken from lower on the same page: This circuitry is fused through the windshield wiper system; therefore, if that circuit is inoperative, the device will not function.
The other thing was from the Fiat factory service manual page 10-126.
Catalytic temperature protection tachymetric switch(75-76). To prevent excessive temperatures in the converter, the fuel is shut off from the carburetor during decelerations. The tachymetric switch senses engine speed from the coil. Withe the throttle closed durring decelerations above 2650 +/- 50 rpm, the switch energies the idle shutoff solenoid. This shuts off idle fuel flow inside the carburetor. The tachymetric switch is located under the glovebox.
So Fiats from 1975 thru 1978 have only a fast idle electro valve, and Fiats from 1975 to 1976 have both fast idle valve and tachymetric switch.
I guess i need to adjust my fast idle to eliminate the popping.
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So Cal Mark
in your description of the fuel shutoff system during decel, it states the cutoff solenoid is energized during decel. When the solenoid is energized, it opens, allowing fuel to flow thru the idle circuit. This is the normal condition when the car is running. It would have to be de-energized to cut off fuel flow.
I do recall seeing some cars with a switch on the carb throttle lever to show when the throttle is closed, but I'm not familiar with a fuel cutoff on decel. I'll have to look that one up. It sounds like a system that could create some problems
I do recall seeing some cars with a switch on the carb throttle lever to show when the throttle is closed, but I'm not familiar with a fuel cutoff on decel. I'll have to look that one up. It sounds like a system that could create some problems
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Danno