Suddenly noisy fuel pump?

I bought this '89 (4.0/AW4/231) in April - 107K, excellent condition. Went for a drive yesterday, and the weather turned out to be pretty warm (low-mid 90s). After about an hour and a half of 65-75 mph driving, I could hear a loud "humming/buzzing" coming from the rear when I came to a stop. Shifting to park or neutral had no effect. No driveability problems - and just for the record, the stock closed system did just fine in some extended stop and go traffic in the heat (A/C on).

I've searched and found that noisy fuel pumps are a known issue for the Renix era, but why would mine be quiet for ~2 months of regular driving, then suddenly get loud? Tank never got below about 1/3 full (have had it lower before with no noise). Indicator of a pump on its way out? New noise, but normal noise? Only happens during extended hot weather operation? Just want to know if I need to budget for a new fuel pump in the near future.

it might be that your fuel pump ballast is having issues.. Trying removing the connectors from the ballast and jumping them with a paper clip. If its the same noise level with the paper clip, as when using the ballast your ballast has issue.

Also, your fuel pump might have shifted in the sending unit and is now laying on the bottom of the tank.. metal on metal..

(the purpose of the ballast is to lower the voltage/amperage to the pump after the engine is started.. this makes it quieter)

Good advice on the ballast resistor.

Could be early signs of an old pump.

Could be a dirty fuel filter--pump is working harder.

Could be splits in the fuel lines inside the tank between the pump and the mounting flange. They deteriorate, split, and the pump has to work harder.

Could be you need a new stereo.

I deleted my ballast this weekend. I like to hear my pump. That way I know it's working.

joe_peters said:

Could be you need a new stereo.

Click to expand...

Funny you mention that, I just replaced the factory stereo last weekend - the old girl went from an inop cassette player to playing songs from a thumb drive.

Will check the ballast resistor. Don't know how old the fuel filter is, might as well replace that as well. Thanks all, for suggested items to check.