Took my ’84 GSL SE on a long road trip last week. I felt pretty confident in doing so, as the vehicle has consistently run great since I purchased it 6 months ago, and it only has 72K original miles.

I stopped at the Mazda Dealership in Colorado Springs on the off chance they might have some trim pieces I am looking for (no luck – unfortunately). When I returned to my car, it wouldn’t start. It acted like it wasn’t getting fuel.

I went back in to the dealership and they were INCREDIBLY helpful. A 30+year Mazda mechanic came out to do some diagnostics. After relieving the fuel pressure to hook up test gauge, car started fine. He did note, however, the fuel pump was making a constantly intermittent “whining” sound. He stated that I was most likely experiencing fuel pump failure.

The dealership didn’t have a fuel pump in stock, and wouldn’t be able to have one for a few days. They did offer, however, to install one if I could locate it in town.
After a pretty exhaustive search, the only pump I could find was from a national chain discount parts store. The pump was sold with a fuel filter, and I was informed that the filter must also be installed to validate the warranty on the pump.

Dealership installed new pump and filter. The car ran fine. However, they pointed out that they were very concerned that the new pump made a constant whining noise (louder than the noise from the old pump). They recommended that I strongly consider taking the new pump back for exchange when I returned home.

The next day’s drive concerned me a little, because I was headed 3 ½ hours up and into the mountains. Altitude, as it turned out, didn’t seem to be a factor in the problem. In fact, the whining noise from the fuel pump was much quieter.

On the third day, I began the 200+ mile trip home, coming down from cool mountain country to 100 degree Kansas heat. At one point, while driving down the highway, the engine began to cough and hesitate as though running out of fuel. As I coasted to a stop (in gear – hoping engine would begin running again), I rolled down the windows and listened for the fuel pump. It was making no noise whatsoever.

After stopping, I opened the gas cap and found that the fuel was under unusually high pressure. In fact, some fuel (about a cup) spewed from the fill spout. After a few minutes, the car started again. With the fuel pump louder than ever. I figured I should keep driving – the worst that could happen would be permanent fuel pump failure at some point, but at least I’d be that much closer to home. This same thing happened 75 miles later, with the same eventual results.

Now home, I’m searching for answers. Did I simply get a bum fuel pump replacement? Or is there a bigger problem? Would the pump whine due to a voltage problem (power cutting off, etc.)? I wouldn’t think so.

Seems more likely to me there is a constriction somewhere in the fuel lines causing strain on the pump and weird fuel pressure problems. But I’m just guessing.

I probably sound pretty dumb about this stuff – I’m certainly no mechanic. But I greatly appreciate constructive comments and suggestions.

 

Charcoal canister gets clogged. It happened on mine due to the purge valve probably going bad not allowing engine vacuum to constantly pull vapors out of it.

Temp solution: pull the 3/16" line from the charcoal canister and go for a drive. The tank should not fill with pressure now.

 

Thanks, Jeff20B. I pulled the 3/16" line and went for a drive. The tank definitely didn't have a pressure buildup as before. However, the fuel pump still whines.

In the next couple of evenings, I'm going to test the pump by disconnecting it from the fuel system, and just try pumping from a gas can to see if it still whines. If it does, then I guess I'd conclude that the pump is either faulty or just irritatingly noisy (as I've heard some can be). On the other hand, if the pump functions without whining when not hooked up to the car's fuel system, then wouldn't it be possible that there is something constricting the fuel lines and putting a strain on the pump?

 

Could be your lines or tank. Go through everything including dropping the tank. There is a drain plug and the tank isn't that difficult to drop. Don't be surprised if you see a lot of rust. Good luck.

 

On the fuel rail, there's a feed and a return line - if the return is blocked it will cause your fuel pump to work overtime trying to pump fuel pressure against a deadhead. Being EFI, this is somewhere around 40-50psi and much higher if no return is available. Check the return line and your fuel pressure regulator on the fuel rail to see if it's leaking at all, as something is causing the blockage.

My guess is your fuel pump(s) are whining because they're unable to push any more gasoline through the lines, and the pump impeller is cavitating, loudly. While the charcoal canister is a good bet, you may also try driving with the gas cap loose to allow any pressure to be released until you get it nailed down. Might also be worth blowing out the fuel lines from the tank to the firewall just to be sure it's not internal corrosion blocking the system.

There's not much there, so have at those suggestions and welcome aboard!

 

I had a similar problem before with one of my SE's last summer. I thought it was vapor lock, but ended up being the purge valve on the chassis underbody. the check ball was not working.
in my case, the pump would not whine, but the car would cough and sputter to the point of stopping.
Pump was weak also, so I replaced it as well.
Not related to your problem but worthy of mentioning to readers is that the small microscreen filter on the pump itself sometimes gets packed full if crap/sediment from the tank and will impede the flow of gas to the point of blocking it off completely. It can be a bugger to diagnose , but needs to be pulled and cleaned, fixing the problem.