FAQ
TL;DR: For a Grande Punto 2007 1.3 Multijet with P0089, an injector overflow of 20 ml in 30 seconds flagged leaking injectors; “It seems to me that the injectors need to be replaced.” [Elektroda, golabek008, post #16973498]
Why it matters: This FAQ helps owners diagnose P0089 (pressure regulator performance) that appears under load and decide next steps efficiently.
Quick facts:
- P0089 here corresponded to “pressure regulator 1 performance,” showing under load, not at idle. [Elektroda, golabek008, post #16968829]
- Observed rail pressure: Approx. 300 bar at idle during troubleshooting. [Elektroda, golabek008, post #16970337]
- Injector overflow example indicating fault: 20 ml per injector in 30 seconds at idle. [Elektroda, golabek008, post #16973498]
- Edge case: Blocked in-tank sieve can mimic low-rail-pressure symptoms. [Elektroda, rob4028, post #16969585]
- Final fix reported in-thread: faulty injectors replaced/confirmed. [Elektroda, golabek008, post #16985089]
Quick Facts
- P0089 here corresponded to “pressure regulator 1 performance,” showing under load, not at idle. [Elektroda, golabek008, post #16968829]
- Observed rail pressure: Approx. 300 bar at idle during troubleshooting. [Elektroda, golabek008, post #16970337]
- Injector overflow example indicating fault: 20 ml per injector in 30 seconds at idle. [Elektroda, golabek008, post #16973498]
- Edge case: Blocked in-tank sieve can mimic low-rail-pressure symptoms. [Elektroda, rob4028, post #16969585]
- Final fix reported in-thread: faulty injectors replaced/confirmed. [Elektroda, golabek008, post #16985089]
What does error P0089 mean on the 1.3 Multijet?
In this case, P0089 referred to “pressure regulator 1 performance.” The check light appeared mainly during driving, not at idle. That pattern points to a fuel-pressure control problem manifesting under load. The thread’s diagnosis focused beyond sensors once load-specific symptoms were clear. [Elektroda, golabek008, post #16968829]
Why does the check light trigger only under load?
During acceleration, rail pressure can drop if injectors leak or can’t hold pressure. The ECU detects the drop and logs a regulator performance fault. One contributor explained that injectors not holding pressure cause rail pressure to fall when accelerating. [Elektroda, ozon79, post #16969653]
Is 300 bar at idle a concern for this fault?
The poster observed about 300 bar at idle while chasing P0089. The engine idled and revved normally when stationary. Symptoms appeared on the road, so attention shifted to load-related fuel pressure losses rather than idle readings. [Elektroda, golabek008, post #16970337]
How do I confirm bad injectors at home (no test bench)?
Run an injector overflow (return) test at idle. Collect each injector’s return in equal containers for a set time. Compare volumes to spot excess return. As one member advised: “Do the injector overflow test.” This quick check can reveal injectors that don’t hold pressure. [Elektroda, ozon79, post #16970457]
What overflow result from this thread indicated a leaking injector?
One injector returned about 20 ml in 30 seconds at idle. That level of return coincided with load-induced pressure loss and P0089. The finding led the poster to conclude injectors required replacement. [Elektroda, golabek008, post #16973498]
Could a clogged in-tank sieve cause similar symptoms?
Yes. A blocked pick-up sieve can restrict supply, starving the high-pressure system under load. A contributor suggested inspecting the tank for a blocked sieve when diagnosing P0089-type rail-pressure issues. [Elektroda, rob4028, post #16969585]
Should I re-check the fuel filter even if it’s new?
Yes. A member urged re-checking the fuel filter during diagnosis. New filters can be incorrect, damaged, or improperly installed, and restrictions here can mimic regulator faults. Re-verify flow direction and seals when troubleshooting. [Elektroda, rob4028, post #16971571]
My overflow volumes look similar—can injectors still be bad?
Similar returns don’t guarantee healthy injectors. The poster initially saw hardly any differences yet still had load faults. Subsequent testing pointed back to injectors despite the near-equal returns at first glance. [Elektroda, golabek008, post #16970475]
What did the in-tank pump behavior show during testing?
With the module out, it pumped normally when the canister was full, but not once pumped out. The poster noted fuel also feeds back via return, highlighting how low-supply states can complicate diagnosis. [Elektroda, golabek008, post #16970475]
I replaced the rail sensor and regulator, plus a new fuel filter. Why does P0089 persist?
The thread author did the same with no improvement. Load conditions still triggered P0089. That pushed the diagnosis toward injectors and supply restrictions rather than just sensors or the regulator hardware. [Elektroda, golabek008, post #16968725]
What was the final fix reported in this thread?
The author closed the topic confirming an injector fault. Replacing or repairing the faulty injectors resolved the P0089 and load-related check light. [Elektroda, golabek008, post #16985089]
What does “injectors aren’t holding pressure” actually imply?
It means internal leakage through the injector raises return flow, dropping rail pressure under demand. As one expert summarized: “They don’t hold pressure.” This condition triggers the ECU to flag a pressure regulation performance issue. [Elektroda, ozon79, post #16973509]
How do I perform the injector overflow test (3 steps)?
- Warm the engine and fit clear hoses and measuring vials to each injector return.
- Idle for a fixed interval, then stop and compare volumes across cylinders.
- Mark any injector with notably higher return for further bench testing or replacement. [Elektroda, ozon79, post #16970457]
Can cleaning the tank pump or module restore normal operation?
Cleaning helped reveal behavior but did not fix the fault here. Even after cleaning, the same load-triggered error persisted until injectors were addressed. Use pump inspection to rule in/out supply issues, then proceed. [Elektroda, golabek008, post #16970475]
Does a new filter guarantee fuel delivery is fine?
No. The poster confirmed the new filter was okay, yet the issue continued. This reinforces checking injectors and rail pressure under load, not just replacing service parts. [Elektroda, golabek008, post #16971597]
