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Re: Ongoing fuel pump buzz at start up Posted by Ari [Email] ![]() ![]() In Reply to: Ongoing fuel pump buzz at start up, John Adams, Mon, 21 May 2007 21:49:56 Members do not see ads below this line. - Help Keep This Site Online - Signup |
When you turn the key to start, the fuel pump will run for a few seconds, and then shut off. The fuel pump is shut off if the engine isn't turning as a safety measure. However, since that would make starting difficult, the pump runs for a few seconds when you first turn the key to on.
So, two things seem to be happening (emphasis on seems).
First, you're hearing the fuel pump. Sorry to have to ask this, but you are hearing the pump from the back of the car, correct? It's under the trunk. Next, how loud is it? Is it a simple hum, or a loud clatter? A hum is normal, a very loud hum isn't out of the ordinary, and a clatter isn't a good sign.
Second, the pump seems to run for more than a few seconds. If it is indeed the pump you hear (see #1), then that isn't a fuel pump issue - that is controlled by the ECU and the fuel pump relay. It is possible that the fuel pump relay is stuck closed - the contacts fused together - and the fuel pump runs anytime the key is ON, because it is supplied by the main relay. Or the signal from the ECU to the relay is stuck on. Same effect.
This is what comes to mind, in no particular order;
(1) You really aren't hearing the fuel pump. If it's coming from the rear of the car, it most likely is the fuel pump, but to be sure, I'd open the trunk and listen, just to make sure it isn't the rear door fans. Sorry to have to bring up the 'idiot lesson' option, but there it is. If it isn't the fuel pump, then obviously it's not an issue.
(2) If it is the fuel pump, then there are two issues - how loud, and why does it stay on?
(2A) - just hearing it isn't a problem, and if it is staying on, that's not the fuel pump's problem. So if it really isn't loud, it is likely not a problem. And if it isn't any louder than in the past, I would be very likely to say not to worry. Even a fuel pump making some noise isn't a sign of a bad fuel pump, but a noisy one.
(2B) if it really is the fuel pump, why is it staying on? I would suspect a bad fuel pump relay (failed in a good position, for once), or the signal from the ECU.
posted by 192.249....
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