Pending fuel pump doom...

Rick Lee · Rick Lee's Garage

It sounds like a buzzing/whirring noise when I stand outside my car while it's idling. It happens whether it's cold or hot. I just changed my fuel filter a few minutes ago and I still have the noise. Car has 91k miles on her. I really don't want to get stranded, but I also don't want to drop the cash for a CIS fuel pump. How long do these things usually last? Any telltale signs or ways to test? Thanks.

kach22i · kach22i's Garage

I'm giving this thread a bump, because I have not done my fuel pump yet.

I have always had all kinds of weird sounds. Some of it I assumed was oil flowing through the Trombone oil cooler, and perhaps there have been a few whizzing noises up front that could of been the fuel pump.

All I know is that it's all a rather strange mix of exotic, erotic and "Chitty Chitty Bang Bang", all at the same time.

MovOvr1 · MovOvr1's Garage

Could it be the bearings in the alternator?

Brian

Rick Lee · Rick Lee's Garage

Alt. is almost new. Noise sounds like it's coming from the front and it's definitely not the oil going to the cooler, since the noise appears as soon as I fire her up after a week of sitting and is the same after hours of hard driving.

Gunter · Gunter's Garage

Rick: Jumper the pump with pins #30 and #87a without starting the engine. You should hear the pump when you turn on the ignition. The procedure is in the Bentley manual 240-11. Don't have the manual? Get one from Pelican for X-mas. With 96k, and for peace of mind, get a new pump.

Jesset100 · Jesset100's Garage

My 82SC makes the same noise. Mine is so loud that when I turn the stereo down I can hear it when I'm in stop and go traffic. I think that when it stops making that "buzzing/whirring noise" and starts making a grinding or no noise at all is when you have trouble. JMO I'm going to keep on driving until it makes a different noise.

Rick Lee · Rick Lee's Garage

Jesset, how long have you gone on like this? I want to swap the pump, as I am all about preventative maint. But I don't have time to do it before X-mas and I have about 500-600 miles to drive round trip that weekend.

no substitute · 12-19-2004, 05:47 PM

It went "zip" when it moved and "bop" when it stopped,
And "whirr" when it stood still.
I never knew just what it was and I guess I never will.
-Tom Paxton-

My SC fuel pump is, and always has been, quite noisy and has lasted thousands of miles.

Gordo2 · Gordo2's Garage

My fuel pump made a loud somewhat high pitched buzzing noise. One day after a nice drive I parked it on the street to give me room to clean my garage. Went to start it up and it wouldn't fire. Immediately noticed that it didn't make it's normal buzzing noise. Sure enough, my fuel pump died. Fortunate that I was home, could have only been better if I had parked it in the garage. Would have been bummed if I was left stranded.

Mine buzzed since I owned it, about 1 & 1/2 years. From a search on the topic, most recommend replacing if you have a lot of noise. On a good note, it's a no brainer to troubleshoot if a noisy pump dies.

My new pump is totally silent. If it dies I won't know where to look.

Good Luck, Gordo

Rick Lee · Rick Lee's Garage

Ok, I think I'll last through the weekend then. My Carrera left stranded in the sticks on a very hot day with poor cell reception and nothing to drink. That was a very bad day. R&R of fuel pump was no picnic either in a hot parking lot a few days after the tow home.

Anyway, is there a way to R&R the pump without having to drain the tank? Can I pinch off the supply line somehow, or just fit it real fast onto the new pump? Even draining 6 gal. last time really sucked.

anthony · 12-19-2004, 06:34 PM

In the past when I've changed fuel pumps (never on a 911 though) I've just plugged the end after I took the pump off. And since you can plan for the job you could intentionally run the tank low before you do the job.

Gordo2 · Gordo2's Garage

Rick,

If your fuel lines are in good shape you can pinch off the rubber supply line with a vice grips. Recommend covering the ends of the vice grips with electrical tape so they don't tear into the rubber. I found this tip after I finished the project. Turned out fine, but could have caused a leak.

The line still dripped a little while it was pinched off, the bolt stopped it.

I can't imaging being fast enough to replace it without stopping the supply line, fuel pours out of there pretty fast.

Nothing like a gasoline shower to get your skin nice and clean though.

Good luck, Gordo

'78 SC · '78 SC's Garage

Rick,

You said you changed the filter. Did you check the in-tank filter? My pump graduated from the normal buzzing to sounding like it was crushing rocks. I pulled the front filter (had to drain the tank, of course) and found considerable rust accumulation. The fuel return passages around the base of the filter were also fouled.

Ultimately I had to remove the tank and clean it. Once the tank, lines, passages and filter were clear the pump returned to its normal buzzing.

Rick Lee · Rick Lee's Garage

WHAT?!?!?! There's a front filter? Never heard of it. Oh, that's all I need. My car is super duper clean and it's never sat in the rain or snow. Where is this front filter? And what the hell is that plastic cylindrical-looking, filter-housing behind the normal fuel filter in the engine room?

'78 SC · '78 SC's Garage

Rick,

The front filter (actually more of a screen) is a cylindrical element that screws into the bottom of the tank. You should see a large hex socket in its base. I inserted the head of a large bolt held with vise grips to unscrew it.

Remember to take appropriate precautions draining the tank. You can siphon out most of the fuel and drain the rest from the fuel pump connections.

The rear filter is a conventional paper media filter that will trap all the itty bits. My problem was with chunks of rust accumulating on the front screen and in the passages around it.

Good luck and be careful.

Rick Lee · Rick Lee's Garage

Oh, ok. I know about that screen. I'll deal with this as I work my way down the project list. Fuel pump is getting done ASAP though. Thanks.

Jim Richards · 12-20-2004, 07:03 AM

RL, if the screen is clogged, R&R'ing the fuel pump might not improve things.

Early_S_Man · 12-20-2004, 07:16 AM

Noise alone is not a good reason to change the pump if the car is new to you ... making the distinction between the OK, normal sound of a Bosch rotary fuel pump and excessive noise of a straining, worn-out pump can be difficult at times, especially to different sets of ears!

Check the current drain of the pump by inserting multimeter leads [meterset to 10 Amp DC range] into red fuel pump relay socket # 30 & #87a while ignition switch is on without engine running. Any drain measurement over 8.0 Amps is cause to replace the pump.

Rick Lee · Rick Lee's Garage

Warren, you da man!

mtelliott · 05-09-2005, 06:58 PM

Quote:

Originally posted by Early_S_Man

Check the current drain of the pump by inserting multimeter leads [meterset to 10 Amp DC range] into red fuel pump relay socket # 30 & #87a while ignition switch is on without engine running. Any drain measurement over 8.0 Amps is cause to replace the pump.

Can someone tell me which is 30 and which is 87? Sorry, but I'm not an electronics expert and I'm hearing a big old wine that wasn't there before. Don't have time to crawl under the car tonight to see where it's coming from. At first I though it was the washer pump (brand new). I pulled the fuse and it still makes the same noise so that can't be it.

If someone could explain to me precisely where I put my multimeter leads to, I would greatly appreciate it.

Michael