I had the engine and front end redone a couple of years ago and noticed that when I drove it for the first time that I could hear the fuel pump. It seemed loud and I don't remember hearing it from my memory of 20+ years ago. The first question I have is whether I should be able to hear it when in the driver's seat? If not, is that a sign that I should replace it? It has been maJJking this noise for over 2 years and I drive it about 10-15 miles a week. 

I then noticed a couple of weeks ago that as I got on the highway to go 60-70 mph and put it under some load that it started hesitating. I backed off and got it back to the garage and it was idling fine.

My second incident happened a week ago as I was in third gear traveling at 35-45. It was really stumbling badly. I shifted to 4 th gear and put it under some load and it stumbled again. I backed off the throttle (below 2000 rpm) and got it back to the garage.

Yesterday, I had it out and traveled no more than 40-45 mph and noticed no such instance as above, but I did keep the rpm below 2200 or so. Does this sound like an electric fuel pump problem? When a fuel pump goes bad, does it go bad all at once or does it go in stages some times? Would 100 LL fuel be a problem to run? I usually mix it with pump gas ethanol free.

Any insight would be appreciated.

Regards,

JJ 75 280Z

 

 

 

 

 

 

 

Fuel pumps do wear out eventually.  But, when was the last time you changed the fuel filter?  Noise from the pump usually means it's working harder, either pushing or pulling .  You could have a clogged filter or junk in the tank.

In the same vein, on the hesitation, when was the last tune-up?  Pretty common to get so used to a good running engine that you overlook the periodic maintenance.  I remember spending a lot of time looking for a big problem on a car when it just needed new plugs and points.

 A good many years ago I was headed up I-5 (relatively flat section) going a good 75ish mph when suddenly my 71 240 slowed to 45 mph. It was running smooth and being a few miles from my folks house I decided to try a few things, I pulled the choke, no change. Kicked in the clutch and revved it to 6 grand. Let the clutch out and it would not go faster than 45. Shifted into third, no change. Shifted into second, no change. Got to my folks house doing 45mph and I told my Dad (an old school logger) about my car woes. He kind of chuckled and said the engine wasn't getting enough fuel. I countered with the damn thing will rev to six grand but then he explained an engine under a load consumes more fuel and it won't go any faster , no matter what gear I was in because it only had enough fuel to pull the load that speed. It would rev fine because there was no load. Our temporary solution was remove to the underhood fuel filter and blow it out in reverse flow direction. I drove it home the next day (75ish) and had no trouble. Replaced the old filter after that and never experienced the problem again.