Car shutting off out of nowhere intermittently

[cooldrew22]

Alright, so I have a 1992 Pathfinder SE, 5 speed, RWD.

first thing i did when i bought the truck was do all preventative maintenance:

new starter

new battery

distributor cap and rotor

spark plugs

all fluids

fuel filter

all belts

checked my grounds and battery terminals.

 

the other night (about a month ago) came home and the truck wouldn't start, crank but no start. seemed like fuel issue so pulled the pump and had a friend turn the key, no prime. So, tapped on the pump while cranking and it came to life. so i figured i have a failing pump, well drove it for another few weeks no problem then it died on me doing 70mph on the highway, just shut off and wouldn't start. so i finally bought a pump. installed the new pump and nothing, no prime, no start, just cranking.

checked the wiring and it's receiving power at the pump and the relay is good. WHILE i was checking codes on ecu i heard the pump prime randomly, decided to try and start it and she started right up. no idea what i did but whatever it ran.

drove it all week and today, pulling out of a gas station shifting into 3rd gear it just shuts off, so i popped it into second but it wont start up again even pop starting it.

now back to cranking with no start and i swear im not getting fuel but i dont know why the fuel pump is not coming on.

i checked and cleaned all my grounds, it has a full tank of gas, reset the ecu, checked my ignition relays, nothing.

anyone have any ideas? or ever seen a car (5speed none the less) just turn off while driving?

any ideas at all, Thanks in advance!

[adamzan]

What about the fuel pump relay? Check that there isn't a break in the wiring?

[cooldrew22]

yeah i checked it with a known good relay and also confirmed that i was getting 12 volts at the coil for the relay.

also, the random time that it did start and run confirms that technically the circuit is all good and intact since it did in fact run fine for a few days, i dono if relay's often intermittently fail.

I've been skimming through the FSM for it and also checked with another source and im gonna go ahead and check Crank Sensor and Cam Sensor and then confirm my ECCS relay is functioning and verify that the ECU is supplying ground for the pump relay

[adamzan]

It could be a break in a wire that interrupts the circuit when the truck hits a bump or is jarred somehow. Did you replace the pump only or the whole sending unit? They are known to corrode at the connections on top.

 

The sensor would be in the distributor. These trucks don't have a CPS/CKS like newer ones do.

Edited September 20, 2016 by adamzan

[cooldrew22]

yeah i realized that a little while after i wrote that haha

and just the pump, but i did check the wire, at the pump terminal and it was receiving a clean 12V. and the ground circuit was dropping a normal 0.03V so that's within good limits.

 

but ya at this point im thinking it's gotta be a bad ground or loose wire in a strange section that's moving around when i drive

[cooldrew22]

update: found the issue!

after messing around with everything and checking the ECU and relay and the pump harness the truck started up. i decided to start messing around with the harness in the tailgate section trying to get the truck to turn off and it did! so i started it up again and kept messing with wires until it shut off until i was able to narrow down what section of the harness had the problem. Turns out there was a harness plug that was becoming slightly disconnected and two wires that were rubbing on a section of the frame, so that's fixed and she runs great now!

[adamzan]

Excellent.