I think my fuel pump is on the way out and am looking for a bit of advice before ordering the the replacement:

'04 TD5 - about 130,000km | Original fuel pump
Here are my symptoms:
1. Under heavy throttle, it will buck / kangaroo when entering the highway or in a forced down-shift (as if passing). This has been pretty consistent for a couple months.
2. Fuel level is just below a quarter - pump primes for 30 seconds on a sloped driveway and makes a bit of a cavitating sound (similar to the sound made immediately following a fuel filter change). Will re-fill - but am wondering if this is contributing.
3. Wife reported a non-start condition earlier today. Disco kicked over and then dropped out. She pumped the accelerator (possibly triggering the purge / prime cycle?) and its started normally since that time. Today was a first for that behavior.

Here's what I know:
- Waste gate moves normally and hoses connecting to the diaphragm to the modulator servo are okay. Servo is about 3 years old and clicks when I cycle it with a Nanocom in the driveway.
- Fuel filter is about 6 months old. No reason to suspect fuel quality - just completed a 800km trip Saturday without any big issues.
- Last cleaned the ECU / injector harness about 6 months ago when I had an occasional misfire.
- I have a small intake air leak (pressurized / downstream of the intercooler) where the last intake hose connects to the EGR blank. I've tightened the jubilee clip, but still get a pressurized bit of oily air passing through. I think this is a red herring / unrelated issue.
- No ECU errors stored / displayed on the Nanocom - checked tonight.

Here's what I thought:
- Maybe fuel pressure regulator: I repaired the regulator about 4 years ago when it leaked - just bought an OEM / complete unit but haven't installed yet. I thought this may be a lead as the the bucking / kangaroo started only after about 1 second of heavy throttle (as if it couldn't maintain fuel pressure).

I assume preventative replacement of the fuel pump isn't a bad idea - but it looks like a 6 hour job in the driveway, so would prefer to get it right.

Thoughts?

Detroit Disco said:

- Last cleaned the ECU / injector harness about 6 months ago when I had an occasional misfire.

Click to expand...

if it was oil there and you didnt replace the injector loom immediately you should start with that

Thanks for the tip - I'll take a look at the harness and see how it looks. I replaced it in '16 - but did not use a genuine loom. Presumably, the aftermarket looms leak more quickly - or these simply become a consumable. To date, I've just figured cleaning the ends isn't so terrible.

Thanks also for the input on the SLS ECU - I'll take a look at the box itself first and verify that I've got clean connectors and grounds. Used ECUs are readily available on Eb@y - perhaps that's worth a try.

Again, appreciate the input.

To close the loop:
10,000 km later, the fuel pump finally gave up the ship. Symptom was increasing whine, followed by a non-start one morning in the driveway.
Replacing the fuel pump was very simple - here are my consolidated observations:
- Don't remove a thousand trim pieces to 'safely' remove the carpet. It can easily be pulled back and replaced with all plastic bits in place.
- Do thoroughly clean the top of the pump and retaining ring. If your Landie has ever done time in a truly dusty environment, it will be a mess. Brush, vacuum, wipe-down, repeat.
- Don't waste your money on a retaining ring spanner, a screwdriver and rubber mallet worked great. When tapping the ring loose, more dirt will appear - re-vacuum. Anyone want to buy a Paddock fuel tank ring spanner - never used.
- Do make sure your new sealing ring is installed correctly. This hour-glass shaped ring needs to straddle the lipped edge of the tank opening. You'll know you have it wrong when the retaining ring won't grab. NOTE: the fuel pump has an 'ear' at 3 o'clock that registers with the locking ring of the tank. This will interlock when the sealing ring is correctly fitted.
- The retaining ring (BMW labeled on my TD5) has a small, horizontal 'stop' that is the register to start the threads.
- After buttoning everything up and replacing the fuel filter (no filter, no warranty) - depress the accelerator 5x after key 'on' to trigger a purge cycle.

New pump is very quiet.
Unfortunately, did not resolve my bucking issue.

If it's an auto your airflow meter is probably the culprit mine does same on forced down shift or full throttle just kangaroos up the road

Bucking is normally overboost. Wind it down a couple of threads (So more are showing) on the wastegate rod and see how it is.