My high mileage 95 GSR (236k) shut off twice on the freeway the other day after running for 1 hour. Everything seemed normal until after a long downhill without any throttle my car wasn't running. After pulling over it started again in about 15 minutes.

It happened again in about 1 hour-long downhill/no throttle and the car wasn't running anymore and after pulling over it started again in about 10 minutes or so. Just totally shut off-no sputtering or anything and when I went to start it cranked normally but nothing until eventually it started normally.

I replaced the fuel pump and relay recently, tank was 1/4 full, and it was hot out. I replaced the ign module and coil a few years ago. Coil on there is from AZ. Any ideas?

 

it does sound fuel related, maybe something happened during the fuel pump/relay install?

 

yeah I was thinking that or the coil getting too hot. I'll pull out the fuel pump again and look over it. I can always replace the coil while I'm at it.

 

Sounds like the ignitor.

 

ill check the electrical side, main relay ill bet.

freeway cut offs are usually electrically related whereas

fuel related is if you are demanding some power and then the car cant get it. then ill look at the fuel side. but odd things do happen. bad battery ground etc.

 

what is the main relay? is that the fuel pump relay? I changed that relay when I changed the fuel pump . The old relay should still work.

I changed the ign module with a new stock one a few years ago when the coil was bad.

I admit that I don't really do killer maintenance on this car so maybe it has a bad ground or something. A had a 240sx that was misfiring above 2k revs. Turns out it had a loose bolt that was an important ground. The bolt was low in the engine compartment and you would never see it unless it was on a lift...

Ordinarily if this happened I would immediately test for spark and then fuel by loosening the bolt on the fuel filter to see if it spews gas(of course care taken because he engine is hot). That would answer a lot of questions right there. However, when this happened it was on an interstate so I didn't feel like dicking around with semis going by 5 feet away.

 

I neglected to mention that this car makes some kind of humming sound after its been running for a while. This sound is pretty constant pitch, but if you turn on the turn signal or some other electrical thing you can hear the pitch dip slightly. It stops after you turn off the engine, but a few times this sound keep going for a few seconds. Last night I was listening to see where its coming from-you hear it inside the car and it might be from the fuel pump. Definitely not the normal whine-a fairly noticeable humming. Weird because this pump was just installed a few months ago.

I swapped the relay back with the original one and its starts and runs fine but I haven't driven it long enough to see if it will shut off. Still makes this sound.

The car shut off again at the top of a 3 mile climb after driving close to one hour, then it started again and shut off 2 miles later. Was fine on the return trip. Gas tank was about 1/4 full.

 

electrical.

main relay

 

So I checked this out a little more. Cars is running for a long time and it start doing the humming noise inside the car. Shut it off and the humming stops, but when I turn the key back to "on" I hear the humming again for a few seconds until the relay clicks then the humming stops.

This happens with both the relay that came with the car and the relay that I replaced it with so is the fuel pump making the humming sound? Somehow the fuel pump is F"ed up and it overloads and shuts down?

 

http://techauto.awardspace.com/mainrelay.html

Te best main relay repair article I've found so far.