Intermittent Stall ? Could it be the Oil Sensor ?

[jagonza]

So my car seems to have an abrupt cutoff while running. It's like it is running out of fuel.

I have been through a bunch of trouble shooting - let me just summarize that i have a new fuel pump, filters, lines etc. no kinks etc.

I have now noticed the Fuel Pressure sender ( the fatter sensor by the oil filter vs the skinny oil switch) is leaking - i believe that the car is setup to stop power to the fuel pump when no oil pressure is sensed.

Does that cutoff come from the fat oil pressure sensor or the skinny oil pressure sensor ??
it is a early 77 with 76 wiring.

can i rig / bypass the signal from the oil pressure sensor to test if that is it.

I have a new sensor on order.

car runs truly awesome when it runs - frustrating as heck that i cant trust it to go too far from home...

[aj81spider]

I'm not sure I'm reading what you're asking correctly, so apologies if I am off base here.

However (at least on my '74), neither of the two senders by the oil filter have anything to do with fuel. One sends the pressure to the oil gauge, and the other is a pressure switch that activates a warning light in the gauge when the oil pressure falls below minimum acceptable for running the engine. Neither is wired into the fuel pump (at least on my car and according to the wiring diagrams I have). If I remember correctly, in my car the one on the top is the light sensor and the one on the side is the gauge sender.

You may have a leak and need a new sensor, but that shouldn't affect your car running unless someone has butchered the wiring to make the sender perform a function that wasn't intended in the original wiring.

[klweimer]

I've never hear of an engine shut off wired to the oil pressure. That just doesn't seem right...
Kirk

[nelsonj]

I think the question is: For cars with electric fuel pumps, what is the mechanism that shuts ofd the pump if you crash? And, could that mechanism be malfunctioning and cutting off the fuel pump while driving?

Sorry - I have a mechanical pump so I can't help much here.

If it's not fuel it could be electrical, something as simple as bad wiring to the ignition (equivalent to taking the key out while driving) or something in the ignition/coil/spark. Do you have an electronic ignition or points? If it's electronic, it could be a bad control module or even a bad coil.

Peace.

[blazingspider]

Cars that came from the factory with an electric fuel pump in the trunk did have an oil pressure switch wired into the circuit that was designed to shut off the fuel pump when no oil pressure was detected.

One of the 2 switches you mentioned is going to be the correct one. Assuming the switch when activated provides a ground to the fuel pump circuit I would pull the connectors off one at a time and see what happens. Pulling the connector for the switch that feeds the gauge will make the gauge inoperative. The other one should shut the fuel pump down and eventually (once the fuel in the carb bowl is depleted) kill the motor if your theory is correct.

Also, if my theory that the switch provides a ground is correct, you could pull the right connector, ground it , go for test run and see if you still have the same problem or not.

Don't forget that your issue could also be the ignition switch itself as many here have discovered.

[klweimer]

I had no idea on the oil pressure switch controlling the fuel pump. Always something new to learn on this forum! Good luck sorting it out!
Kirk

[PhillySpider]

My intermittent stall was due to a sticking flap in the AFM...re-worked it and she ran well, but not so smooth at mid range RPM. Replaced it and purrs like a kitten.

[michaelj]

Same symptom on my car just popped up a few weeks ago. I have a new ignition switch so i am tackling that this morning as i suspect that is a problem in its own. SOme times i have to jiggle the key to get things moving. So, i will eliminate that here shortly as a possibility. The car starts and sits at idle and runs ok at all rpms. I suspected the fuel pump was cutting out. So i put an electrical meter on the fuel pump and found it dropped from 12v to 3 v occasionally. Hmmm, Then i went up stream and checked the coil and found coil and found the coil lost its incoming 12v, dropping down to around 3v. It was intermittent, and you have to have patience to see it as the fuel pump would run for 2 minutes before cutting out, and it was then i glanced at the meter.

I have heard of oil pressure cutout switches on many cars so I am reading the wiring diagrams right now and I dont see one of those on my 1976 (great idea though...). All I see are sending units, for gauges and idiot lights. No "control" switches. The lite blue wire from the ignition switch goes right to the + terminal on the coil, and thats where i saw my voltage drop from 12 to 3, so I am gittin on it right now! Will advise.

[spider2081]

The lite blue wire from the ignition switch goes right to the + terminal on the coil, and thats where i saw my voltage drop from 12 to 3, so I am gittin on it right now! Will advise.

Have you got a second voltmeter to check the input to the ignition switch while you are monitoring the voltage at the coil. Maybe the input to the ignition switch is dropping also. I think your ccar has a nylon 3 pin connector on the driver side fender well close to the carbon canister that is troublesome. It has both wires that feed power to the ignition switch in it as well as the red "start" wire to the starter solenoid.

[kilrwail]

I would check and monitor the alternator's output. Sounds like it's dropping from 12 to 3.

[txspider]

I have a 77 and had this exact same issue after I got my car in the mid 90s. Would just turn itself off when running down the freeway. Would restart if I turned ignition off while coasting then restart with key . Very unerving and impossible to diagnose since it was intermittant. One day while going with a group to track my rider plugged his charger into my lighter and everything went haywire and blew fuse. Come to find out that the back of the lighter grounded to bottom of the radio behind the dash and since they were so close it would just happen randomly. Since ignition goes through lighter circuit it would die when touching. I just put some insulation under the radio and never had an issue again. May not be your problem but strange it is the same model year and circumstance. That's my story and I'm sticking to it!

[jagonza]

I have tried many things many things , but this is the first i hear of the lighter causing a problem, i will just pull the power wire to the lighter and see if that helps.

[jagonza]

I have tried many things many things , but this is the first i hear of the lighter causing a problem, i will just pull the power wire to the lighter and see if that helps.

[fiat50state]

I had a problem like that once with my 79, turned out that the ignition switch was failing...jimbo