FAQ
TL;DR: Hard warm-start on petrol points to weak fuel pressure; “the fuel pump is supposed to start for a few seconds.” [Elektroda, psilos1, post #16713359]
Why it matters: This FAQ helps VW Golf 4 1.4 16V owners diagnose gasoline hard-starts, especially on cars with STAG LPG.
Quick Facts
- Symptom: after a few hours, petrol starts take multiple cranks; LPG starts first try. [Elektroda, longer175, post #16712874]
- Normal prime: pump should run a few seconds when the driver’s door opens. [Elektroda, psilos1, post #16713359]
- First checks: fuel injectors and the fuel pressure regulator. [Elektroda, ZeeWolf, post #16712905]
- Key-cycling to pre-pressurize improves starting, indicating pressure loss. [Elektroda, longer175, post #16714181]
- Fix outcome: new regulator improved starting; pump replacement was next if needed. [Elektroda, longer175, post #16741991]
Why does my Golf 4 1.4 16V start hard on gasoline but fine on LPG?
LPG runs independently of petrol pressure. Your petrol side likely loses rail pressure while parked. Weak pump or a leaking regulator are typical causes. “Symptoms indicate a fuel pump – gives too low pressure.” [Elektroda, psilos1, post #16714196]
What’s the fastest first test I can do without tools?
Cycle the ignition two to three times without cranking. Listen for the pump prime. If it then starts easier, the system was depressurized at rest. This points to the regulator or pump. [Elektroda, longer175, post #16714181]
Should the fuel pump run when I open the driver’s door?
Yes. In this platform the pump primes for a few seconds after opening the driver’s door. Lack of this behavior suggests a failed door-lock microswitch. [Elektroda, psilos1, post #16713359]
Could a bad door-lock microswitch cause hard petrol starts?
Yes. If the microswitch fails, the pump may not pre-prime on door open. The engine then cranks longer to build pressure. [Elektroda, psilos1, post #16713359]
What parts should I check first: injectors, regulator, or pump?
Start with fuel pressure: regulator and pump. Check injectors for leakage if pressure holds but restarts remain poor. [Elektroda, ZeeWolf, post #16712905]
How do I measure fuel pressure on the rail?
Use a gauge on the rail test point. Record prime pressure and key-off decay. Abnormally fast drop indicates a regulator or pump check-valve issue. [Elektroda, paszczakq, post #16718742]
Does low petrol level from driving mostly on LPG hurt the pump?
Yes. Running LPG often means little petrol in the tank. The pump loses cooling, wears faster, and pressure drops. [Elektroda, psilos1, post #16714315]
Will replacing the fuel pressure regulator fix the issue?
It can. One owner reported noticeable improvement after a regulator swap, though not a perfect fix. A tired pump may still need replacement. [Elektroda, longer175, post #16741991]
Why does cycling the ignition help my Golf start?
Each cycle primes the system for a few seconds. Pressure builds before cranking, masking a weak pump or leaking regulator. [Elektroda, longer175, post #16714181]
Could the coolant temperature sensor affect petrol starting?
Yes. A faulty cold-temperature reading enriches or leans the mixture incorrectly. Unplugging for a quick test can reveal a sensor error. [Elektroda, lemmak, post #16720034]
Edge case: I always keep 1/3 tank, yet starts are still hard—why?
Fuel level alone doesn’t guarantee pressure. A worn pump can under-deliver even with 1/3 tank. Replace the regulator first, then the pump if needed. [Elektroda, longer175, post #16718679]
What’s a simple three-step pressure-loss diagnosis I can try?
- Open the driver’s door and listen for a short pump prime.
- Cycle ignition several times, then start.
- If starting improves, test or replace the regulator, then assess the pump. [Elektroda, psilos1, post #16713359]
Are injectors a common cause of overnight hard-starts here?
Leaking injectors are possible but less common than pump or regulator faults in this thread. Test them if rail pressure holds steady. [Elektroda, ZeeWolf, post #16712905]
What repair sequence delivered results in the thread case?
Owner confirmed improvement after replacing the pressure regulator. They planned a pump replacement next if the issue returned. [Elektroda, longer175, post #16741991]
Expert tip: what does a normal prime sound like and how long?
You should hear a brief hum for a few seconds at door open or key-on. “Start for a few seconds.” [Elektroda, psilos1, post #16713359]
My scan shows no fault codes—can fuel pressure still be low?
Yes. Mechanical pressure issues often log no DTCs. Use a gauge and observe prime and decay to confirm. [Elektroda, paszczakq, post #16718742]
