Good afternoon, Gentlemen! I have been driving my car around and have noticed a fairly noticeable whining coming from the boot area, I can only think that this would be the fuel pump. (This noise seems to be new). Being able to hear the pump a bit prior to startup (but ignition turned on), I am assuming is normal. However, hearing the pump while driving I am thinking constitutes a problem. I have had several times in the past experienced the over voltage light come on, while showing a pegged needle at 17+ Volts.... This stays on for perhaps a minute, the light goes off, and the voltmeter returns to a normal of about 13 volts. Today I realized that when that overvoltage light comes on (which it did a couple of times today with about 70 miles driven), I no longer hear the whining sound from the pump. The car seems to run normally throughout this whole scenario, I am driving maybe 60 mph throughout. No discernible difference in the car's running.

My theory is perhaps the pump is overheating and creates the overvoltage? When it cools down the voltage goes back to normal? I have read a few threads regarding the fuel pump, and I am getting ready to clean out the sump tank, replace the filter in the very near future (replacing fuel sender unit at same time). I was not able to find any posts that talk about the overvoltage and stoppage of whining pump while light is on.

Any suggestions as to how to most efficiently proceed?

As usual, thanks in advance for any thoughts!

John

 

John,

There are others who will understand the circuitry better than me, but I'm not sure I agree with your theory. Whilst there MAY be a linkage between the sound of the pump and the high voltage, I'm not sure it would be the pump causing the high voltage. It seems more likely to be the other way around. Perhaps the pump is struggling, either through being worn or poor wiring connectivity. So under normal voltage feed, it struggles and whines. Then you possibly have a regulator problem which occasionally allows an over-charging output condition. The extra voltage then "helps" the pump run easier, so it sounds quieter. Possible?

I'd start by looking at the alternator output. It shouldn't be able to push 17 volts back to the battery. Maybe fit one of those cheap bluetooth battery monitors to the battery and then watch the alternator / voltage readings on the phone App when you're driving. I wouldn't trust the instrument gauge at all. You really need to accurately know what the alternator is outputting.

Good luck

Paul

 

Voltage is "pushed" through a circuit by a battery/alternator/other power source, amperage is "pulled" from the circuit by the load (the fuel pump) - this is an extremely simple way to think about it but it's pretty accurate. Another way to think about it is like water in a pipe - voltage is pressure, amperage is flow.

I tend to agree with @ptjs1 - my first thought is you might have a fuel pump that struggles at normal voltage, then something else is causing a high voltage which just happens to give the fuel pump enough of a boost to run without the noise.

 

Is the fuel filter new? Even if it is, it might be worth changing it as new ones sometimes plug.
If all well there, then noise = fuel pump going home, so I would change it if it is not already renewed.

 

Good morning!
The fuel filter was renewed in January when I got the car, much of car history unknown. Old filter full of crappy brown fuel, I did not cut it open (probably my mistake). I have another filter on hand and will change it out. To confirm correct flow direction, the OUTFLOW from the filter goes to the fuel pump, correct? (Fuel is filtered prior to delivering to pump). In regard to replacing fuel pump, any suggestions? It seems like there is a wide variety of options here? I know Grant prefers the Bosch, and I see several available at $90- $120 in my market, but there are quite a few (other brands) for less money. I don't mind spending the difference if it is worth it for reliability, longevity, etc.

At this time, it sounds like I should figure that there is no relationship between fuel pump and overvoltage warning.....

I will renew the filter today and post back with results!

Thanks!
John

 

THe fuel filter is located after the pump. The outflow of the filter goes toward the engine. There should be an arrow on the filter indicating flow direction.
SURGE TANK>>FUEL PUMP>>FUEL FILTER>>. If you have the outflow of the fuel filter going to the pump, it installed incorrectly.

 

If the filter is before the pump the pump might be having a hard time getting fuel and causing issues.

 

Thanks, Guys! When I replaced the filter, I installed it as I found it. Apparently it was installed BACKWARDS! Being unfamiliar with proper flow direction, I did not notice at the time..... I will change out filter today, and orient it properly this time! I notice that the pump has slid down in its mounting bracket and is contacting the floor of the boot, and I'm sure it is trying to kink the hose also... Saw a previous post (by WOZ?) where the filter slid, he put some soft rubber and a hose clamp above the bracket, which stopped it from sliding down... Will do that while I am in there.....
John

 

Wrong, John. The fuel pump goes between the sump tank and the main filter. The fuel goes though the main filter AFTER the pump and from the filter direct to the engine.
The sump tank has a sock filter in it which protects the pump and should be renewed if not alrrady done. See part 18 here:

https://parts.jaguarlandroverclassic.com/parts/index/part/id/278.900.1478.4932.21885/brand/jaguar/