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MG MGB GT V8 Factory Originals Technical - Fuel pump ticking noise
|At idle, there is a ticking noise from the back of the car (right side I think). I assume this is the fuel pump. Can anyone tell me if a ticking noise is normal or whether my fule pump is about to pack in?|
Thanks as always.
|Normal for the OE fuel pump.|
|Depends on the rapidity. For mine, from cold and with the choke out somewhat it's a couple of clicks a second, when warm with no choke a little less than one a second.|
Significantly faster than that you could have a pump problem.
Like many things, the time to worry is when it stops making its usual noise!
|If you have a non-original type pump, you may get a constant ticking noise. If the pump is original and everything is working correctly, the ticking is as Paul Hunt describes.|
The original SU brand pump is a cylindrical device about 2" in diameter and 6" long. The body is cast iron, with a black plastic cover on one end and an aluminum casting at the other end where the fuel lines attach. It is mounted in the battery box area on the RH side of the car. Original pumps are mounted in a large rubber grommet inside a metal bracket, to isolate the noise from the car body. When people install aftermarket style pumps, they usually just bolt them to the body directly, rather than using a rubber isolator. Not only are aftermarket pumps noisier than the original, mounting them without rubber amplifies the noise.
|Here's another artifact of owning an original Factory V-8 - the SU pumps sometimes sound louder because the heat in the engine bay causes the fuel to evaporate out of the carb float chambers each time you stop and leave the car for a length of time. The next time you start the car, you hear a series of rapid clicks until the pump has filled the float chambers. |
Four cylinder cars don't heat up and evaporate the gas as often, so you just get a click or two when you turn the key.
I kind of like this idiosyncracy, because the clicking tells me that the pump is working. I turn the key to the on position, wait for the satisfying series of clicks to end, then turn the key to start the engine.
"A GT with less than 8 doesn't rate!"
|When I switch on after a long layoff, the pump actually chatters madly, easing off to individual clicks which soon slow down and stop. Perhaps I have a small leak, or the float bowls experience some evaporation over time. I've gotten used to this pattern of noise, and carefully listen for it at the first start of the day. |
Once the engine starts, I'm sure the pump goes into its normal clicking mode, but the engine noises completely drown it out! (Speaking of the 4-cyl here, not one of those dead silent, glass-smooth V8's).
|If the pump clicks continous couldn't it be a valve leak in the carb or an air leak in the supply line to the carb?|
|Or the diaphragm itself!|
|What Bob described is exactly correct for normal operation.|
|I had continuous ticking from my B SU fuel pump caused by sucking air past the brass banjo union. Simply cured by nipping it up. You might need new washers, fibre or copper.|
|My '71 N/A spec. in 4 cyl had a problem with the float bowl needle-in-seat seal sticking open. The rapid clicking would occur and gradually slow (normal) as the float chambers filled, just as Bob describes, but it would not actually stop. The float would fail to push the needle sufficiently into it's seat, likely due to debris in the fuel, and the pump continued to pump fuel right up through the vapour vent pipe into the charcoal canister and then onto the ground. Very dangerous!! Note the previous owner had "detoxed" the car and it's likely this might not happen if all emission control plumbing was left as stock on the N/A spec. car (very sluggish). Still, hot gasoline can ruin your whole day. I invested in some ball bearing type float chamber seals, I think from Moss-cheap-and disposed of my rusting fuel tank. Also, check your float level and adjust per manual if needed. The car ran fine with the float set about 2mm low for added bouyancy, but if your pulling big G's it might not. Just to be safe, I pulled the four cyl out and took the whole car apart. Do you smell gasoline? Angus|
This thread was discussed between 25/01/2000 and 11/02/2000
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