I think I need a new fuel pump for my trusty miata. What started as a random issue is pointing in that direction. 153k miles. Changed plugs, wires, fuel filter, coolant temp sensor, air filter. All less than 8k miles ago when I got it.
Symptoms:
Cuts out in sweepers at autocross with anything less ths 3/4 of a tank.
Drivability issues at highway speeds starting at 1/2 tank. Stop to refuel drives fine after that. No issue when free reving i.e. not under load.
Any thoughts why it might not be the fuel pump?
If it is, what do I replace it with. I am planning on boosting it in couple years or so or tuning for e85 for an sts build. E85 is readily available. Thanks in advance for all the helpful comments.
Drop and drain the tank. I know that is a crappy job in a Miata, but that will at least allow you to make sure you have a clean tank, then check all the rubber fuel lines for cracks. Sounds like the pump is sucking air once it is no longer submerged. I've never seen a Miata fuel system in my life though, so I'm just going on general procedures.
Cracked pickup tube? Being a Japanese car, I would expect there to be a fuel pump access hatch.
I forgot to add a couple of important things.
At the autocross it did not start misbehabing till after about an hour of constant driving.
On the highway, it did not start till after 3 hours of constant driving.
In both cases if I was careful to listen it seemed like the fp was making a higher pitched sound which didnt sound normal. In the higway situatin it almost sounded like someone blowing bubbles through a straw.
Cracked pick up tube sounds interesting. I wil prefer not to drop the tank.
No need to drop the tank, there is an access panel on the parcel shelf.
http://miataturbo.wikidot.com/fuel-pump-install
wae
New Reader
9/4/12 12:32 p.m.
I don't know anything about Miata fuel pumps, but I had a similar experience with the fuel pump in my Neon. I can't recall what it sounded like, however, I finally tracked it back to a fuel pump that would run fine for a few minutes, but once it got warmed up, it would start running very intermittently. I discovered this by warming up the car, putting the fuel line in a bucket, jumping the fuel pump relay, and then just letting the pump push fuel. It would pump gas just fine for a minute or two if the car was cold, but if it had been running, the gas would push okay for a bit, then sputter, then flow, and so on.
Thanks for the pictures. Looks like it us relatively easy to do. I will look for a walbro to future proof my plans.
I swapped out my fuel pump with a Walbro in about an hour, pretty easy job.
Although it didn't solve my problems completely it did make it better.
Wae we must have been posting at the same time. It behaves just like you described. It just takes an hour of hard use or 3 of regular user. By the way, if I buy a walbro, do I need anything else-like a fuel pressure regulator?
