Technical Fuel Pump Shenanigans

[vinjones]

Hey all, I am a senior in high school working on a 1971 Fiat 124 Spider with my dad and we are having problems getting the car started. It used to start well and all we would have to do is pump the gas pedal 3 times and turn the key and it would fire up. Now after jacking the car up on various angles during our brake replacement job the car won't start anymore. The previous owner put an electric carburetor in which seems to be working fine, but also a new fuel pump system that is super loud when turning on the car, looks super fishy, and seems to be ineffective. We put a few gallons of gas in so we know there was fuel in the tank, but after turning the key and the engine turning over and over the car just would not start. We took the fuel line off the carburetor and held it to a rag to see if the fuel was even pumping to the front and sure enough nothing came out. I will attach pictures of the current fuel pump system. We also poured a little fuel on a rag and held it above the carburetor and the engine started.

You can see fluid in the clear section of the line that we are unsure if it is a filter or not, but we are sure that fluid does not move through that chamber even though it appears that it should. The pump with the red label on it is really loud when you turn the key to acc and then start, and doesn't quiet down. Should we go back to the standard fuel pump system? Is there a vacuum seal issue preventing the pump from pumping? It is also weird that the contraption does not work anymore and used to work consistently before our brake job.

Ask further questions or for more pictures and any help is appreciated!

 

[bugsymike]

Hey all, I am a senior in high school working on a 1971 Fiat 124 Spider with my dad and we are having problems getting the car started. It used to start well and all we would have to do is pump the gas pedal 3 times and turn the key and it would fire up. Now after jacking the car up on various angles during our brake replacement job the car won't start anymore. The previous owner put an electric carburetor in which seems to be working fine, but also a new fuel pump system that is super loud when turning on the car, looks super fishy, and seems to be ineffective. We put a few gallons of gas in so we know there was fuel in the tank, but after turning the key and the engine turning over and over the car just would not start. We took the fuel line off the carburetor and held it to a rag to see if the fuel was even pumping to the front and sure enough nothing came out. I will attach pictures of the current fuel pump system. We also poured a little fuel on a rag and held it above the carburetor and the engine started.

You can see fluid in the clear section of the line that we are unsure if it is a filter or not, but we are sure that fluid does not move through that chamber even though it appears that it should. The pump with the red label on it is really loud when you turn the key to acc and then start, and doesn't quiet down. Should we go back to the standard fuel pump system? Is there a vacuum seal issue preventing the pump from pumping? It is also weird that the contraption does not work anymore and used to work consistently before our brake job.

Ask further questions or for more pictures and any help is appreciated!


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It sounds to me as though fuel is not getting to the fuel pump, whether fuel is lower than yoou think or there is an air leak or blockage between the tank and the fuel pump.
Incidentally, the pump is a good after market make , but would sound a lot quieter if it was rubber mounted, normally on those little rubber "cotton reels" and not solid to the metal of the car.
Note if you do this improvement put the earth strap for the pump in the right place.

 

[Twink80]

Hey all, I am a senior in high school working on a 1971 Fiat 124 Spider with my dad and we are having problems getting the car started. It used to start well and all we would have to do is pump the gas pedal 3 times and turn the key and it would fire up. Now after jacking the car up on various angles during our brake replacement job the car won't start anymore. The previous owner put an electric carburetor in which seems to be working fine, but also a new fuel pump system that is super loud when turning on the car, looks super fishy, and seems to be ineffective. We put a few gallons of gas in so we know there was fuel in the tank, but after turning the key and the engine turning over and over the car just would not start. We took the fuel line off the carburetor and held it to a rag to see if the fuel was even pumping to the front and sure enough nothing came out. I will attach pictures of the current fuel pump system. We also poured a little fuel on a rag and held it above the carburetor and the engine started.

You can see fluid in the clear section of the line that we are unsure if it is a filter or not, but we are sure that fluid does not move through that chamber even though it appears that it should. The pump with the red label on it is really loud when you turn the key to acc and then start, and doesn't quiet down. Should we go back to the standard fuel pump system? Is there a vacuum seal issue preventing the pump from pumping? It is also weird that the contraption does not work anymore and used to work consistently before our brake job.

Ask further questions or for more pictures and any help is appreciated!


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This type of fuel pump will run constantly while powered
I assume your car has a Carb but no mechanical fuel pump?
It looks like you might have 2 fuel filters, 1 on the suction side, 1 on the pressure side
I would replace both with 8mm plastic disposable filters you csn get on ebay
I would replace the fuel hose & clups too as they look a bit ripe
Then its a question of being methodical and checking fuel flow at each joint

Note. These aftermarket fuel pumos have no pressure regulation and if too high may overcome the float shut off in the carb. The carb float regulates fuel level within the carb. If the pump has sufficient pressure to overcome the float the fuel flow will not shut off and leak into the engine

Yes these pumps are noisy, it is mounted without isolation to a bulkhead so the noise will resonate

If you fit a stock mechanical fuel pump and drive the car infrequently it can take 3-4 very long cranks to suck fuel up to the engine and fill the carb, so the battery needs to be well charged. For this reason people fit aftermarket fuel pumps, but these come with other issuesz

 

[bugsymike]

@Twink80 raises good points worth checking, I know on some carb vehicles they had a return from the carb to help keep the fuel cooler, but with a noisy electric pump that probably is not ideal.
I see at the start of post the OP mentions pumping the gas pedal, obviously this squirts extra fuel via the accelerator pump in carb, normally if an automatic choke vehicle often one press of pedal will allow choke flap to go across and also brings in the fast idle.
As an apprentice we often had to adjust those and even later in mid 70s working on brand new Mazdas I recall some had been set too fast, so when they started the engine was doing 3000rpm and the bearings would rattle as no oil drawn up, so I would reset them to a safe roughly 1200rpm from memory.