Hello everyone, so my wife’s 1998 Mercedes A160 (W168, 1.6 petrol, returnless system) is making me crazy
I’m scratching my head and looking for your wisdom on this one and would really appreciate a sanity check !
Full disclosure, I used chat gpt to gather my thoughts below.
Main symptoms: • car is hard to start (now 5–6 cranks) • Big bog if I hit throttle quickly (almost stalls ) • Smooth if I accelerate slowly • Drives fine at steady speed • O2 drops to ~0 V during bog → (clearly going lean)
Those symptoms appeared with the old pump, the new pump didn’t change things
Fuel pressure (measured at rail): • Old pump: ~1,5 bar at idle • New aftermarket pump (supposed 4 bar): • Key ON → ~1.5 bar for 1 sec, then drops to 0 (Video) • No pressure retention
Work already done: • Replaced complete fuel pump/regulator unit • Fuel filter ~9000k km ago • New coil pack + recent plugs • Cleaned throttle body • Fixed engine ground • Checked intake for leaks
No improvement.
So I’m thinking low pressure + no pressure hold + lean under load = fuel delivery issue… but I’m surprised the brand new pump behaves basically the same (or worse).
Would you guys go straight to “bad/incorrect aftermarket pump/regulator module”, or is there anything else that could realistically cause: • Low rail pressure • No pressure retention • Lean bog on throttle
Thanks, I would appreciate any input, just trying not to throw parts at it blindly 🙏