How does a fuel pump sound?

[bbig119]

I'm trying to diagnose why my car is losing power, having an irradic idle and frequently unresponsive to throttle.

I'm trying to diagnose fuel delivery as a problem. I pulled the access panel to the pump in the trunk and listened to it while the car was idling, or trying to idle. I wasn't able to hear the pump with the engine running all that well except for right before it was about to stall, and immediately after it did. During this time I heard a hissing sound like it squirted fuel into the lines. When this happened the engine rpms would shoot up for a few seconds. This cycle happens every 5-10 seconds. It'll nearly die, hiss, rpms kick up, then they'll fall back down till it nearly dies again. I realize I need to test more for a definitive answer, but I wanted to see if I could get some feedback while I go out and collect items to put pressure gauge and such.

I just cleaned out the ICV, but it didn't seem to help the car situation at all. Car is throwing code 1221 which is new as of new years eve when this all started happening again. Before then it was throwing 1213 when it was throwing fits, but I don't think it was related as once I changed intake gaskets that code went away.

Thanks, Bryan

[shelbyz4u2nv]

most fuel pumps, (and i say most as a general statement) tend to be noisy when going bad. although some high pressure pumps can make notacible noise. the only way you can really tell if a pump is going bad is to test fuel pressure/volume

also have someone just turn the key to poistion 2 and see if you can here the pump engage, still not a good way to fully diagnose though...

[bbig119]

I removed the fuel pump relay. If I bridge the connections with a wire to operate the pump, can I start the car?

[bbig119]

I constructed my pressure gauge, and the gauge is definitely shitty, but the highest it went up to was maybe 40psi. I connected it to the fuel line entering the engine bay from the driver side.

Unfortunately, I wasn't able to determine if my jumping the fuel relay was working at all. After I released pressure in the lines, it didn't recover until I put the relay back in. Right now I just have some wire going in there and really should crimp it with spade connections for better contact.

[shelbyz4u2nv]

question does the car retain fuel pressure? if it beelds off press quickly you may have a bad regulator, pinhole, ect...im not sure on the exact specs but 40psi at idle seems ok..

[bbig119]

My gauge didn't move even after I bled down the pressure, so I really don't know. Bentley says M60 should be 60psi, but I'm not sure what 30-40psi will do in the grand scheme of things.

[shelbyz4u2nv]

My gauge didn't move even after I bled down the pressure, so I really don't know. Bentley says M60 should be 60psi, but I'm not sure what 30-40psi will do in the grand scheme of things.

well if the book calls for 60psi and you have almost half that...this is deff your problem..or your gauge is screwed...i would change the pump and fuel pressure regulator jst to be safe since there seems to be no bleed off...but that could b b/c of your gauge...do urself a favor and buy a cheap one..also measure pressure as close to the fule rails as poss..hope i helped

[bbig119]

Thanks for the reply. Yes you're definitely helping. Its good to bounce ideas off someone since I've never done this before and buying a fuel pump is a little more than I'd like to spend randomly replacing parts till I get the problem spot.

I went to all the auto places around here in Jersey today to get this gauge. Pepboys, Autozone, Advance Auto Parts, NAPA was closed though. This thing cost $20 and its a POS. I'll spend some time tomorrow testing some more as it was getting dark when I was doing this. Hopefully I'll be able to convince myself a little more that the pump is the problem spot, but its also worth getting a regulator as well.

I'm very worried about the difficulty in replacing the regulator. Its very tight in there, and I'm not sure I'll be able to replace it without some serious demantling around there. Can anyone confirm this?

Thanks again for your help.

Bryan


well if the book calls for 60psi and you have almost half that...this is deff your problem..or your gauge is screwed...i would change the pump and fuel pressure regulator jst to be safe since there seems to be no bleed off...but that could b b/c of your gauge...do urself a favor and buy a cheap one..also measure pressure as close to the fule rails as poss..hope i helped

[bbig119]

One last thing before I order a new fuel pump.

I was able to hear the pump better today. When the car is running I can hear the pump squirting fuel, pulsing, but its irregular. When its idling well its a fairly constant pulse, but when the its struggling to idle the time between pulses is longer.

After looking around, I found out the relay I tried to bypass yesterday was the wrong one, and on the 540 the correct fuel relay is blue and kinda tough to get at. When I did bypass it the fuel pump seemed to pulse a little better, but still was irregular as before. When I clamped off the fuel return line pressure did not change at all. The gauge is still a POS, but I think the irregular pulsing is enough to implicate the pump as the problem spot here.

Voltage when the pump relay was bypassed was constant. I didn't do a volume test only because I hate removing the return line in the engine bay, and since the pressure is low the volume should be low too.

I'm ready to drop the cash to buy a pump, do the symptoms and tests confirm this?

Bryan

[shelbyz4u2nv]

well if the pump is not at a constant drone then i would say thats ur best bet..the pump most likely received more voltage when you jumped the relay causing it to work slightly better...order a new pump...sounds like its on its last leg....

[shogun]

It does not matter if you hear the pump or not, the capacity and the pressure must fit to the spec.
In the last weeks I have replaced on 3 E32 750 fuel pumps, (they have 2 by the way), and some of them made a "noise" as if they were working alright, but testing the pressure and capacity showed a completely different situation. I had several used pumps, installed them and the same problem happened. In total I think I tested 8 fuel pumps on 3 cars.
Either you replace the pump without checking (what I recommend), or you spend more money for testing equipment for which you could buy a new pump.
Let's face ist, a fuel pump has a certain lifetime.
If you replace it, you will have no problem for at least 100 k miles, but replacing it against a used one, is asking for problems in maybe the very near future.

[bbig119]

fuel pump from BMA: $185, about 75 bucks less than I expected. Should be here in time for the weekend.

Is there any reason that I should consider replacing my fuel filters again if I did them in mid-December?

[shelbyz4u2nv]

Is there any reason that I should consider replacing my fuel filters again if I did them in mid-December?[/QUOTE]

you can if you want but it should not b needed

[bbig119]

UPDATE:

New fuel pump in, and car is running nicely. The job was simple. I did notice that a plastic piece at the bottom of the fuel sending unit is broken off, but it appears like it had happened earlier as I couldn't see the piece in the tank anywhere.

The new pump sounds much better than the old one. Its making a constant hum, like its constantly running where before I didn't hear a hum, more of a fluctuating squirting sound.

Thank you for all your help, I'm cautiously optimistic that this issue is ressolved, but I keep worrying about getting stuck somewhere like I nearly did before when it gave me all the problems.

-Bryan