This has been driving me crazy. Several months ago, the fuel pumps in my '95 E320 (W124) wagon started making noise. I bought a couple new Bosch pumps on eBay and installed them along with a new filter. Noise gone...for about a week. Before I change the filter again, the noise stopped and the pumps were quiet for a couple months. Then one day, my wife calls me and says the car died. Forward pump was making noise and seemed to be straining. She was able to get the car safely parked and I picked her up. Later, I went back to check on the car and it started up and made it home...pump making noise.

Ok, so I change out the forward pump again (filter too) with a Bosch unit from a reputable local vendor. Noise is gone again...for about a 4 days.

Should I just try another new filter? Is there something in the system that could be deteriorating and clogging the filters? What else should I check?

Thanks!

__________________
Glen Tokuhara
Beauty & the Beast and the wagon that could!

By the way, the DM had codes 3, 4, and 10 which I just cleared so I'll see if they come back.

Pin 14 had code 11 stored.

What pin is generating codes 3, 4, and 10?
Is CE check engine light on?
Did it go into limp mode?
Was OVP relay ever changed? What's its part #?
Bob

The DM (diagnostic module) is pin 3, I believe.
No check engine light.
No limp home. Car runs great when it runs...it eventually died when (I think) the fuel filter clogged...causing the pump to overheat.
OVP is original, as far as I know.

__________________
Glen Tokuhara
Beauty & the Beast and the wagon that could!

maybe you should also consider a tank cleaning too

On my 94 e320 Wagon: my fuel pumps are original and they [or at least one of them] make a high pitch noise that I understand is normal. I have to have ear close to wheel to hear it. When standing up, my 60 yr old ears don't hear the noise. It's been more than a year since I changed fuel filter, so memory is a little foggy. But if memory is correct, there is minimal hose to detoriate and although metal lines can look terrible on outside they're quite durable and not likely to detoriate inside.

The durability of the fuel delivery system and your comment regarding the codes makes me think your problem might not be fuel delivery.

If you're using Arthur Dalton's Code reader; you can read codes from pins 1, 8 & 14.

Knowing the specific pin/code combo will make it easier for others to help you.

I'd pull codes for all 3 pins then check part # of OVP. OVP is behind battery. Easy to do if you remove battery, but you'll clear some codes when you disconnect it. 10 mm nut / bolt secures OVP bracket. Makes it easy to read part #.

Has main engine harness been replaced?

Bob

Main harness has been replaced. I can read the codes but at the moment I can't find my file with the code descriptions.

I'm pretty sure the problem is fuel related, as every time I open the fuel system, either changing a pump and/or filter, the pumps startup quiet. I should also make clear that even when the pumps are making noise, the engine runs perfect. The engine died WHEN the pumps were making so much noise that I assume the filter was very clogged and the pumps shutdown.

What's the best way to drain the tank? It appears that there is a debris screen in the bottom of the tank that is replaceable. Should I try that?

Is there any way that the fuel pressure regulator could be malfunctioning? That is, in such a way that even though the engine is getting enough fuel, it's not flowing enough fuel back to the tank to cause the pumps to have to work against the FPR? Just taking a WAG here.

Is there anything else besides the filter than can trap debris and/or obstruct flow to the engine?

Ok, found my code file. Pin14 is the CC/ISC module and code 11 is 'Fuel safety shut-off to LH-SFI control module.' What does this module do? It sounds related to my problem...

Good to hear "main engine harness" replaced.

Fuel system: Is your gas cap holding pressure?

The "debris screen" or "fuel strainer & seal" part #1114700686 tighten to 39 Nm. Drain tank - I'd disconnect fuel line before fuel pump and let gravity do the work. I'd only drain tank after checking other potential causes.

Fuel pressure regulator
Vacuum hose into it should be dry. From Arthur Dalton in regards to an o2 sensor test "A side benefit to testing the 02 sensor output by removing the vac hose to the fuel regulator is that by seeing a change in the voltage of the 02 sensor when doing so also indicates that the fuel reg is working....when the vac hose is taken off, the fuel pressure goes up, so the engine naturally runs richer... so...if, with a good sensor, there is no change when putting the reg vac hose on and off, you can assume the reg is not regulating..[aside from other fuel pressure probs]" I can send you Arthur's o2 voltage test procedure.

Also consider "regeneration switchover valve" it's labled MOT located on driver side fender. It has vacuum from intake manifold and another to purge canister [goes to fuel tank]. MOT vibrates when working. If not, squirt WD-40 into hose to regeneration valve and lightly tap. Sometimes WD-40 releases valve.

Pin 14, code 11
Also is "Closed throttle recognition signal to eng control module.
Can also be caused by sticky and/or insufficient slack in throttle linkage.

Bob
PS I'm an amature at diagnostics. Hopefully, one of the gurus will get to this thread and help you.

Thanks Bob.

re:
Pin 14, code 11
Also is "Closed throttle recognition signal to eng control module.
Can also be caused by sticky and/or insufficient slack in throttle linkage.

I didn't realize this. Actually, some time ago, I adjusted the throttle linkage to remove excess slack...maybe I took too much out. I'll check it this weekend.

Ok, I think I figured out the pump noise problem! Turns out the rear pump was failing intermittently, that is, sometimes it would start and sometimes it wouldn't. Strange. But, I replaced it again and so far both pumps are running quietly.

I also added a little bit of slack to the throttle cable and adjusted the bowden cable slightly. The arrows were off just a bit. Car is running great!

__________________
Glen Tokuhara
Beauty & the Beast and the wagon that could!