Main fuel pump makes buzzy noise

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Old 03-22-2019, 07:59 PM
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Default Main fuel pump makes buzzy noise

OK, I successfully replaced both fuel pumps. The tank fuel pump was replaced a couple of weeks after I replaced the main one, and Immediately I could tell the difference; there was no 'hesitation' when pushing the gas pedal.
Two days ago, my wife went to start the car for a trip to the store, and it immediately died. As in, it would crank and start up, but then just die a second later. If I started the car and gave it some gas, it would stay running and eventually idle on its own, but I noticed a buzzing noise coming from the main fuel pump. I had no choice but to drive it to work the next day, and it ran fine; no problem from start to idle, but the pump was buzzing. When I got home, I noticed it wasn't buzzing anymore, so I thought the problem had gone away. I decided to check it out anyway, and while troubleshooting with fuse jumpers (remove fuse #4, wire from left side of fuse #6 to either side of fuse #4 location), I noticed it buzzing again.

What could be wrong? Do I need to replace the brand new fuel pump? Could something have gotten into the intake hose from me messing around with the tank pump, and now it's jamming up the works? My wife needs to go the store again...
 
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Old 03-22-2019, 08:35 PM
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Are we talking about a 240 or 740 . What year. What brand FP did you install. Did you change the filter too. Usually a noisy pump means the in tank pump is not working. Also how much gas is in the tank. Is it over half full or below half fill.
 
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Old 03-23-2019, 12:03 AM
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Sorry, I meant to put that information in, but it slipped my mind.
1990 Volvo 240 DL. Bosch pump. Filter changed along with the pump. The tank pump makes the normal happy little humming noise when I do the fusebox test. Fuel level was over half a tank when this started happening, but I've been back and forth to work since then, so it's more like a quarter-tank now.
 
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Old 03-23-2019, 07:38 AM
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When you replaced the tank pump did you also replace the rubber hose between the pump and the metal tube. Also did you replace the little filter sock on the pickup tube. If the car starts , runs and shuts off it usually is a fuel pressure problem . A loud FP usually means it is working harder then it should . If you can check fuel pressure and go from there.
 
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Old 03-23-2019, 12:56 PM
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The rubber hose between pump and tube was the original molded flex hose, still intact with no deterioration or damage, so I didn't replace it. The pump looked exactly like the old one, same size and everything, unlike some pictures I've seen where the replacements were slightly longer, requiring a different tube altogether. I replaced the filter sock. Actually, I replaced it twice because the first time I attempted to change the tank pump, I got the filter sock on backwards, and hilarity ensued; see my thread here: https://volvoforums.com/forum/volvo-...what-do-99398/
I just looked up how to check fuel pressure, and it looks like I can get a loaner tool from Autozone. I'll be back...
 
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Old 03-23-2019, 06:03 PM
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Autozone didn't have a fuel pressure test kit, so I went at it old-school; I pulled the tank pump again, and with the help of a switch and some very long wires, I was able to jumper it from the trunk. I caught the gas in a small emergency fuel jug, and the pump happily poured fuel from the tank into the jug. I observed the strainer sock was still in place, so I put everything back.

I recorded what the main pump sounds like, tell me what you think:
 

Last edited by edvard; 03-23-2019 at 06:18 PM.
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Old 03-23-2019, 06:35 PM
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bad main pump .. take it back and get another ... it should NOT sound like that ..<br />i had some sounds from mine that were way less than that so i left it and now is all quiet just a slight buzz for a second when<br />turning on the ignition pre start...which is normal..
 

Last edited by silvermine; 03-23-2019 at 06:37 PM.
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Old 03-23-2019, 07:24 PM
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Wow, too bad; it was a Bosch that cost me almost $200 with tax. I can't find my receipt or I'd take it back after getting a replacement.
 
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Old 03-23-2019, 08:10 PM
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Bosch ain't what it used to be! Lots of crap these days come from once "reputable" German companies, and no, that pump is no good.
 
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Old 03-23-2019, 11:12 PM
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I'm about to give up. I bought a new pump, an "Import Direct", made in USA cause that's all that O'Reilly had. I had to cut off the old electrical connectors and splice on these new ring terminals. Not entirely happy with that, but what else am I gonna do? I needed a new pump. Put everything together, cranked it until the fuel could make it through to the engine, and once again, the fuel pump is buzzing like mad. I start the car, and it immediately dies. If I push on the accelerator a bit, I can keep it going, and after a bit I can take my foot off and it idles fine, but it sounds like I tied a 10-pound wasp under my car.

Did I simply get another bum pump? The package was opened when I bought it, which I thought was kinda fishy, but I was desperate... Or could something else be wrong? Tomorrow I'm going to call around about a fuel pressure diagnosis kit and go from tail to stern.
 
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Old 03-24-2019, 02:11 AM
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Yeah, sometimes especially if in a rush it's hard to be choosy. But I get your frustration, two bad pumps in a row, what are the odds? I have many spares on hand to swap things around as needed...
 
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Old 03-24-2019, 07:08 AM
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Could it be that the in tank pump is one of those that is wired backwards ??? As for your pressure test you need to see if it is putting out around 43 lbs at the fuel rail . Think about it , if you let the car sit and try to start it there should be fuel in the fuel rail. It will start and drain the fuel and stall. It means your injectors are working and you have spark. Other then that maybe you have a bad FP relay which is intermittent but you would think it would finally fail. Need to start looking at the fuel pump circuit.
 
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Old 03-24-2019, 07:30 AM
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Originally Posted by edvard View Post
Wow, too bad; it was a Bosch that cost me almost $200 with tax. I can't find my receipt or I'd take it back after getting a replacement.
that's really too bad, think we all have to start or continue to buy from fcpeuro or like firms that offer a lifetime warranty on their parts...
 
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Old 03-24-2019, 12:33 PM
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Originally Posted by jagtoes View Post
Could it be that the in tank pump is one of those that is wired backwards ??? As for your pressure test you need to see if it is putting out around 43 lbs at the fuel rail . Think about it , if you let the car sit and try to start it there should be fuel in the fuel rail. It will start and drain the fuel and stall. It means your injectors are working and you have spark. Other then that maybe you have a bad FP relay which is intermittent but you would think it would finally fail. Need to start looking at the fuel pump circuit.
I thought it might be wired backwards, but I confirmed the wiring the last time I had it out of the tank. Also, a few posts up, I mentioned testing the pump and it was indeed pushing gas in the correct direction, so I'm satisfied with that.

As far as fuel pressure, what should be the pressure out of the tank pump? When I replaced the main fuel pump, there was enough back-pressure in the line to spray my hands when I loosened the check valve (my mistake, I forgot to clamp the hose first). Would a faulty relay cause the pump to make the buzzing noise?

Personally, I'm thinking I either got two bad pumps in a row, or there's something up with the hose between the tank and main pump. I may have chewed it up a bit trying to wrestle it off the tank pump outlet, could there be a crack in it which is now letting air get sucked into the line? That would perhaps explain the noise at the main pump.
 
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Old 03-24-2019, 06:29 PM
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Originally Posted by edvard View Post
I thought it might be wired backwards, but I confirmed the wiring the last time I had it out of the tank. Also, a few posts up, I mentioned testing the pump and it was indeed pushing gas in the correct direction, so I'm satisfied with that.

As far as fuel pressure, what should be the pressure out of the tank pump? When I replaced the main fuel pump, there was enough back-pressure in the line to spray my hands when I loosened the check valve (my mistake, I forgot to clamp the hose first). Would a faulty relay cause the pump to make the buzzing noise?

Personally, I'm thinking I either got two bad pumps in a row, or there's something up with the hose between the tank and main pump. I may have chewed it up a bit trying to wrestle it off the tank pump outlet, could there be a crack in it which is now letting air get sucked into the line? That would perhaps explain the noise at the main pump.
The in tank pump puts out somewhere between 5-10 psi which is sufficient to pump fuel to the main pump. The main pump should have pressure at 43 psi at the fuel rail. Just because you feel pressure doesn't mean you have enough at the fuel rail to push through the injectors. You need to check it at the fuel rail with a fuel pressure gauge when you start the car. Also when the car shuts off does the fuel pump stop (no noise). If you have a crack in the fuel line it will not suck in it will spray (leak) fuel out. If you test the Bosch FP out of the car (hot wire it) does it sound normal. Put an intake hose in a gas can and pump it into another gas can.
 
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Old 03-24-2019, 06:52 PM
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...AAaaaand stumped again. Put new hose on from the tank pump to the main pump, and the thing started right up with no problems, but the main fuel pump was still buzzing. Time to check the fuel pressure so I got the kit and for the life of me I couldn't undo the fitting at the fuel rail. I was risking damage to the flare nut, so I stopped there. My next attempt was to hook it up at the pump. Luckily, there was a banjo fitting adapter in the kit that fit the output side of the fuel filter, so I hooked everything up and started up the car. Start, then die. Start, then die. Start and push on accelerator until I heard the RPMs go up just a bit, and let off the gas, the thing sputtered for a bit, then idled normally. Fuel pump buzzing like a horsefly with road rage. ~28-30 PSI. When I push on the relief valve of the pressure gauge, there seems to be a lot of air expelled, but maybe that's because the relief valve isn't sealed. Dunno.
 
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Old 03-24-2019, 07:04 PM
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Originally Posted by jagtoes View Post
The in tank pump puts out somewhere between 5-10 psi which is sufficient to pump fuel to the main pump. The main pump should have pressure at 43 psi at the fuel rail. Just because you feel pressure doesn't mean you have enough at the fuel rail to push through the injectors. You need to check it at the fuel rail with a fuel pressure gauge when you start the car. Also when the car shuts off does the fuel pump stop (no noise). If you have a crack in the fuel line it will not suck in it will spray (leak) fuel out. If you test the Bosch FP out of the car (hot wire it) does it sound normal. Put an intake hose in a gas can and pump it into another gas can.
Woops, I posted before I saw your reply. I couldn't get the fitting off of the fuel rail, so I tried it at the filter output; see above. If I didn't have enough pressure at the rails, wouldn't my car run rough? Once everything is running and idling, it runs like normal (although with a seriously noisy fuel pump). When the car shuts off, so does the fuel pump. I'll try to hot-wire the Bosch pump, see what's happening there.
 
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Old 03-24-2019, 07:30 PM
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The Bosch pump handily transferred gasoline from one receptacle to the other with no buzz, just the normal pump whine. What. The. Heck. is going on here?
 
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Old 03-24-2019, 09:37 PM
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Originally Posted by edvard View Post
The Bosch pump handily transferred gasoline from one receptacle to the other with no buzz, just the normal pump whine. What. The. Heck. is going on here?
By the way have you replaced your fuel pump relay. Also pull the vacuum hose off of the fuel pressure regulator and see if gas comes out.
 
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Old 03-24-2019, 11:35 PM
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Originally Posted by jagtoes View Post
By the way have you replaced your fuel pump relay. Also pull the vacuum hose off of the fuel pressure regulator and see if gas comes out.
Haven't replaced the fuel pump relay because I didn't see how that would be related to the fuel pump noise, but I might as well while I'm at it. I replaced the Fuel Pressure Regulator because at some point I thought maybe that was the problem, pulled the vacuum hose off and it smelled like gas. None came out, but I didn't want to let it get any worse.

I had to button it up for the day, because I have work tomorrow. Drove into town to return the fuel pressure test kit and after driving around a bit, it doesn't stall when I start it up. I could still hear the fuel pump buzzing, but more in the background compared to the road noise. We'll see how it does tomorrow. I commute ~15 miles to and from work, so that'll give it a workout.
 

Last edited by edvard; 03-24-2019 at 11:39 PM.

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