I helped a local shop replace both fuel pumps in a customers car over the weekend and all went relatively well.

I got a call today that the pumps are making a loud screech or high pitch noise. Similar to how a transformer makes a humming sound this is a very high pitch noise.

Here is the interesting thing. This only happens with both relays plugged in. I back-probed the voltage on positive and ground on pump 1 and 2.
All Voltages are between 12.74-12.88 for the positive and the ground, either pump.
The voltages do not change when running both relays or only one relay while other is pulled.
Running pump 2 only I have same voltages but no screech noise. Running pump 1 only and same voltages and no screech noise. Running both relays same voltages but horrible "nails on chalkboard" sound.

Only thing I can think of is some kind of electrical interference but I am no expert in this so I am open to any ideas. I'm lost on this one...........

Edit to add Video:
View My Video

 

What brand were the pumps? I think some people here have had success more with one pump or the other.

On the electrical side, maybe you could build a low-pass in between a pump and the relay to stop the noise/smooth things out? I'm not sure if it could cause other issues, but that's my first thought on killing the noise. Or somehow isolate the pumps electrically from each other with cleverly setup diodes?

 

One pump was Airtex and the other was Delphi. For some reason they could not get two or the same brand in time frame.

I don't imagine that this would be an issue but this is a bit past my area of expertise...

Added a video in first post. If you listen close there is a high pitch noise, stops when relay removed, back when both in, gone again when second relay removed.

sound quality sucks....

 

Local shop replaced mine for PO a while back, it makes a high pitch elec noise also 😞 living with it for now, it's not annoyingly loud....yet

 

I don't think I can live with letting this go. I'm sure once the insulation and carpets are back it will quiet things down I just cannot stomach both not doing a perfect job as well as understanding what is happening.

I called a few other car guys that know much more about electronics than I do and no one had any ideas.

 

Well, I'm betting there's a bad pump (mechanically or electrically), because the secondary pump doesn't engage until the ECM tells it to when the S/C comes calling. So if this is doing it at low R's, then it sounds like a short either in a pump or in the wiring. It may also be a badly seated impeller on the shaft just spinning freely, thus no voltage changes. Has the car been driven to see if performance is lacking?
Are you sure those are the correct pumps also? I put new ones in mine about 2 yrs ago, Denso 950-0172, and have had no issues and super quiet.

 

You do not state whether it is mechanical or electrical. Is the noise coming from the audio system speakers??

Did you eliminate the suppression devise in the short fuel pump link leads??

Are BOTH pumps actually running together at idle?

bob

 

Noise is electrical. The sub is out for repair.

Not sure what that is. Maybe I did but not knowingly

This is what I have been thinking about most of the day. I'm on way back to look at it again but with noise only when both are plugged in it could be possible.

I am going to check fuel pressure with gauge and take it for a drive. The car also has a hesitation under load. Not sure if it is fuel or not.

 

I did a forum search for 'fuel pump noise suppressor' because I remembered a dialogue about this a while ago.

https://www.jaguarforums.com/forum/x...ed-help-89344/

bob

 

Thanks for link. Looking over it now.

I checked fuel pressure and was at 15psi -ignition on. Went to 40psi at idle. I pulled relays and noise went away. Pulled main fuse to run second pump and the car slowly died as fuel pressure dropped.

I had no choice but to go back in again. I already have it opened up but need to drain some fuel. I will read over the link and see. It also looks like one of the pump filters is laying over another. I'll go back to square one and pull both pumps, look over/fix wiring. See where I am at that point.

 

update:
Yesterday pulled pumps, wire harness and everything back out.

I replaced the harness with 14gauge stranded wire from tank-cap harness to pump harness. I couldn't locate new harness pins so I took each of them off the old wires and cut, solder, re-fit and size the larger wires with old pins back into the original harnesses.---What a pain!!

I looked over both pumps again closely and made sure everything looked good. The first time I replaced these I did one and then other, this time with both out I noticed that they are not same size pumps. One is Airtex e2471, correct fit for car (also the one making the horrible noises). The other pump isn't even a Denso that the box came in. It is actually a Walbro GSS310.

Customer is rightfully pissed. It's hard to find specs on pump but looks like a 45 psi/26 gph pump, similar to Airtex.

So I hooked them both up in tank to test both the pumps and the new wiring. I was rushed so I went direct from Battery to alligator clips 2 on each lead, to the wire into the harness into the fuel pump (supplied) line. Battery>alligator clip>alligator clip>new 14 guage wire ends>harness>fuel pump wiring harness and pump. With the quick set up I got roughly 10.5V on the Walbro pump with both sets of wires I swapped. Testing the Airtex I got 8.8V with both sets of leads.
The battery tested at 12.5V.
This doesn't make sense to me. Any ideas on why I would get low voltage now? Is 14 gauge wire with soldered ends into same harness too much and I'm getting resistance?

Additionally I have asked to have customer just get a new pump to replace walbro but until I can figure out while things don't add up it seems early.

Should I put everything together and fire it up "regular" and see what happens? Not sure where to go from here. I'll head back over this evening and see what I can do.

 

If you have 14 gauge wire from the EVAP flange to the pump, you have eliminated the suppression device in the short link harness.

I remember the XJ40 had a suppression device in the link harness from the main harness to the EVAP flange (OUTSIDE the Fuel Tank). The X300 moved the device(s) to 'inside the tank' in the short link harness EVAP flange-to-pump.

As for the voltage drop in the pump wires-------- I would suspect the EVAP flange plastic connector pins are 'burnt' or corroded??

bob

 

Yes, I eliminated the suppression devices. I used new 14gauge wire and soldered the old terminal links (pins) and harness/clips over to new. If the larger size wire is not causing the voltage drop and the ghetto set up of multiple alligator wire clips connected is not culprit it would have to be the pins.

Just to clarify, I did not run this test setup through the tank lid/EVAP flange. Wire clips to leads direct in tank to pumps.

Any chance with pumps not having any backpressure from fuel lines they just weren't pulling all power?

 

I finally got a chance to go back to this car and check on a few things. with all the different wires and harnesses there was a bit of resistance. I made 2 complete new harness/wires for both pumps. I have finally located part of the loud noise/issue. It seems that one pump (wired to pump2) is making a loud squealing noise. It seems to be coming from the pressure release valve. I was able to cover the top of the tank with some glass and run the engine. With only pump one running things were fine, once the second pump was plugged in, the walbro, the high pitch squeal returned and the release valve was pumping gas up to the top of tank. It almost came out the gaps of the plate I put over it. There is some serious pressure blowing off. I do not think this much pressure should be coming back out of the pump. The fuel return line (for engine) is seperate. It almost seems that the secondary pump is running at all times and when both relays are in and both are running there is too much back-pressure on fuel lines and it is blowing excess through the release valve. Does this make sense and seem correct? At this point everyone involved is annoyed. Should we just replace the second fuel pump with the one original working one?

 

Have you tried swapping the pumps to see if it does the same? That will tell you if its the pump or the connection and save buying a pump only to find out it wasn't. Obviously something is telling the ECM to engage the secondary pump, that needs to be found out. Has the kick down under the pedal been looked at?

 

Swapped pumps. Had 2 new and 2 old out and bench tested them a few days ago. One original pump was bad. Other three worked perfect. I no longer have the original wiring harness but have made 2 set of new ones with 14gauge and 16 gauge wire to swap around to find any issues. Have not checked the kickdown pedal yet. Went over to the shop and drove the car this morning. With Airtex on pump one, getting over 12V while running and back-probing terminals. That is good. Pump 2 I used the old OEM pump. So far it seems to work ok. Drove about 10 miles. Limp mode almost whole time. Knock sensor bank 2 was cause. Clearing it and it came back immediately.--I couldn't test secondary due to this. After drive felt the relays and the secondary was stone cold, the primary was a bit hot. Doesn't seem like secondary pump is staying engaged.

The fuel trims are hitting +25% on both banks. I am heading to store now to pick up fuel pump gauge to see if I am losing pressure. I checked FPR and it seems ok. Noticed at front of bank 1 (passenger side) lots of black wet dust and grease. Fresh spray on the hood liner as well. Wondering if the fuel injector rail has a leak. Started it and at idle did not see anything. Also checking the seal around the Fuel injector.
Off to store.