Fiat 128 1.3L Doesn't Run and Barely Walks...It Stumbles

Triestino

Triestino

Daily Driver
Hello All,
Yesterday, I ran into an interesting situation that points to a functional but inefficient electric fuel pump....perhaps. I haven't changed the pump since I purchase the Fiat three years ago. When I bought it, I drove it 75 miles on the highway to my home without a hiccup. I haven't used it much since I've had limited time and was working on suspension and other projects. I do run the car monthly. The fuel is fresh and only two months old and the tank is half full. Now that it's finished, I am having a hard time starting from cold. When it starts, it idles great but as soon as I try to give it some gas with the pedal (even a small amount) , it stubbles and eventually stalls out. I checked the carb, in-line fuel filter, one-way check valves and all seemed fine. BTW, everything is stock. I even blew out the lines to make sure no blockage. I then took a plastic bottle and placed the fuel line (feeding the carb) in it and realized the fuel flow was super slow and very little volume... seemed like a trickle. I even checked the return line just to be sure. No fuel flow, as expected. To be clear, I did these tests directly were the fuel lines come up near the passenger side strut tower and directly connecting a hose to the metal feed lines. My guess is that the universal pump under the car (near fuel tank) simply doesn't have the lift capacity (anymore ?) to feed the carb and it may have gone bad. I did an experiment and let the pump run with the ignition key 'on' for two minutes to allow the fuel to build up in the carb. Sure enough, the car instantly started and ran great at idle. As soon as I gave it gas, it stumbled. Restarted it and the idle is irratic....at best. I'm wondering if I should replace the pump? I'm thinking of getting a Facet FEP60SV Gold model. Having said all this, could the floats be off even though I never touched the carb and it past the California stringent smog test 'as is' last year? Any thoughts or help would be appreciated.
Thank you!
 
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Seems like you have found the problem. Enough fuel is getting pumped to run at idle but not enough for actual work. It could be the fuel pump or it might be a few other things.

Your past use could have dislodged some crud that is blocking the intake of the pump so it may not be the pump is bad but that there is something in the line. It may be possible to clean the pump if you remove it.

Another possibility is the sock in the tank could be clogged up from past lack of use and old gas from previous owners. Try pulling the sender out of the tank to inspect it. You may be able to replace the filter sock or may want to replace the sender.

If you find it is the pump and not the intake sock, consider putting a filter in front of the pump to keep large particles from entering the new pump.

Good luck.
 
Hi Karl,
Thank you for the suggestion to look at the pump intake side and the sock in the tank. I'm thinking that having poured 4 - 5 gallons of fresh fuel in the tank (just prior to starting the car after sitting a month) may have resulted in some tank sediments getting into the pump intake side or perhaps clogging the in-tank sock. Before I purchase a new pump, I will check these two items you mention. It's certainly worth a try. I'll keep you posted.
 
You said you checked the carb - to be clear, did you remove the jets and blow them clear? It is very common to get a plugged jet that causes erratic running. Also, be sure you have 12-volts at the solenoid on the carb (if the carb is equipped, such as on a 32 DATRA). I went back to mechanical pumps after having some bad luck with electric pumps (but the electric ones do get an empty float bowl filled more easily).
 
A quick update.
Well, I spent some time under the car today to remove and bench test the Airtex electric fuel pump (near the fuel tank). To describe the setup, hose from tank straight to an inline fuel filter (2" metal canister type) then into the fuel pump and out to the metal fuel line feed that goes from the back of the car all the way to the engine compartment. To my surprise, after separating the connection between the filter and the pump, about 2 oz of fuel came out of the filter and then it stop altogether. I was anticipating a rush of fuel given that the tank is half full. Since it was getting dark, I had to stop for the evening. It appears that either the fuel filter ahead of the fuel pump is almost completely clogged or the sock in the tank (as Karl mentioned) may be clogged. Bench testing the pump, it didn't sound good and will need to be replaced. It may have been damaged from fuel starvation. Stay tune for more learning fun :)
 
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Assuming the start of the problem is in the tank I would follow it up with a run through the carburetor as Courtney (long term experience with 128s) suggested above along with replacing/cleaning any other filters in the system.
 
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