Hello,
I have a '73 1.7 car with fuel injection. Just starting to get it back on the road after sitting for many years. The car starts easily, idles well, and seems to run ok when warming up. Once warmed up and on the road, intermittently the car will stumble like shut off and then just as quickly it will go again. Going around corners, not all corners, it will do the same but for longer periods of time. Pushing on the gas when this occurs, nothing happens. The engine doesn't rev. its like its disconnected.

I recently changed the fuel lines at the fuel pump due to age and cleaned out the fuel injectors. Car has about 5 gal of gas in it.

Any ideas on where or what to look at first? Does this sound like a FI related problem? Thanks for the advice.

EJP914

oooops

Clogged fuel tank filter sock?

What happens to the tach when the engine cuts outs while you’re in gear? If it drops to zero you likely have an electrical/ignition issue. If it shows engine speed you probably have a fuel delivery issue.

To debug this issue, I'd start with a full tank of gas just to take the fuel supply out of the equation. When I first got my 914, I let the fuel get low and the car started dying as I drove. Stop, restart ok, drove ok for about a mile then died. Took off the fuel sender, looked inside and saw the bottom of the tank full of rusty crunchies. Cleaned and coated the tank and haven't had an issue since then. However on both my 914 and 930, I never let the fuel supply get below 1/2 tank.

Yeah, watch the tachometer. That is the very first step in this kind of thing.

Thanks for the tip on watching the tach. Will check that out next time out.
I did put in a new fuel filter figuring there would be some crud in the tank since the car has sat for so long.
I thought it might be a fuel delivery issue too, but wouldn't that show up at idle or when the car is just warming up? Cut out seems to happen only after driving a while and car is warmed up.
Thoughts?

Yeah, packed up filters would be issues across the range. This has all the feels of electrical issues but until you see what the tach is up to...

I actually know someone that got a Del Sol because it was the closest thing they could get to fill the 914 memories.

Could also be a blocked breather for the fuel system. You use the car for a bit and as you do so a vacuum develops in the tank as you pull fuel out but no air goes in. Over time the pump can no longer overcome the vacuum and the car runs poorly. Leave it for a bit and air gets back in somehow and it all works again. One way to check for this issue is to wait until the car runs badly and then remove the fuel filler cap - if you hear the sound of air rushing in that's your likely problem.

Just solved this same issue on my car. Car would intermittently cut out, with the tach dropping to zero even though the engine was in gear…so I knew it was electrical. Specifically… power getting to the fuel pump and ignition harness. Changed the relays but that didn’t solve the problem. Turned out it was a bad connection inside the relay board. Got a rebuilt one from Bruce Stone and all is well. The fact that turning seems to bring this on for you might mean the relays or fuel pump fuse are loose.

I’ve also had similar hesitation from a clogged fuel sock and/or pinched lines under the tank. Car would idle fine, but as I pushed the pedal to demand more gas, the supply couldn’t keep up and the engine would stall.

You’ve got great advice in this thread and I’m sure you’ll sort it out soon…

Many thanks for the replies. One more question about this.
My fuel gauge does not work. Bad sending unit at the tank? Car has been sitting for years. Maybe gummed up
Does the sending unit in the tank do more than just sending a signal on how much gas is in the tank?

Nope, that's all it does.

Super easy to test that before you pull it (which is also easy). Just join the leads together at the top of the sender and see if the gauge jumps.

Just be very very careful cleaning the sender. Some very delicate wires run the length of that tube.