fuel pump hummm on full tank

[3Q Jay]

on the -94a. second time, now. ran down to 1/4 tank, didn't hear the pump at idle from drivers seat. But after filling the tank, it's blatant.

i know i know, 103k, prolly time. But, can't figure out why the hummm diminishes below 1/2 tank, only to re-appear when full.

to add to the story, both fill-ups are after my 'rebuilt' FPCU [junk core that I replaced power transistors and a few other clean-up items]. did notice right away that pump spun faster during key on prime with 'new' fpcu, but was not more noisey at idle until i filled the tank.

[Mr.Q45a]

Hi Jay,

If you need or want an extra set of hands let me know. I did the fuel pump on the 94. Very easy and very quick

Did you see my post from the meet ?

Regards

[3Q Jay]

hi Quash. I did post about your and Kevin's little adventure...the meet was fun. Thanks for the offer, and now I'll encourage you to do your accumulators. I've been in contact with Texasoil and he's helped me with a partial solution to the chatter/groan. It's a different car, now!

[DAEDALUS]

Details? Only partial?

[SpecDRacing]

Noisy at full, goes away at 1/4....hmmm. Well, fuel pumps are nothing more than an electric motor connecting to a tiny dish with fanlike blades on the outter 1/4 of that dish. They also use the same fuel they pump as a lubricant. As these pumps get older, they wear away and become noisy. Its not always a bad ground in the FPCM. Sometimes, its just time to go. I commend you on replacing the transistor in the control unit....wow...never done that! As for the fuel pump though, I'd say just get a new one.

The whole lubrication process though, I just wanted to add a note here. Fuel addatives the claim to clean injectors and deposits are great if used in the correct amounts. Anybody reading this that uses them on a tank to tank basis should prepare to buy a new fuel pump....even if the product has Linkite in it (I think thats how its spelt....found mainly in Zmax). These cleaners do a very basic job cleaning the system...but they also rob the fuel of its ability to lubricate the fuel pump...which increases wear on the pump. We know what happens next.

So back to your whinning noise. Try replacing the pump period. The extra preasure caused by the large volume of fuel may (not definately) aid in the strain on the pump to perform. I hope this helps some!

[3Q Jay]

I can't take full marks on the component replacement---Jesda actually gave me the idea.well, bit the bullet and ordered pump, green relay and o-ring. I'll keep running my solderjob FPCU, and keep the original one as a spare.

[SpecDRacing]

I think you made the best choice. Some money can normaly be saved by using your own skills to correct a situation....but other times, its best to cough up the cash and save yourself a headache down the road. Let us know how it turns out! Thanks!