P2632: Pompe à carburant B — circuit de commande ouvert
Que faire
If the car hesitates, loses power or cuts out when the tank gets low — and is perfectly fine again after filling up — say exactly that, because it is very nearly the whole diagnosis.
Many vehicles have a tank built in two halves, moulded around a propshaft or exhaust, with the main pump in one half and a second pump to move fuel across from the other. When that second pump fails, the car empties one half and starves while the other half is still full. You genuinely run out of fuel with fuel in the tank.
Note which point on the gauge it happens at, and whether cornering, braking or a hill brings it on — both are useful. This is worth pressing, because the complaint gets investigated as a failing main pump, a blocked filter or a sensor, and all of those will test perfectly, since none of them is the problem. In the meantime, keeping the tank above half will usually avoid it entirely.
Ce que signifie ce code
An open circuit in the control of the second fuel pump.
Most cars have one fuel pump, so the first question is what a second one is doing there — and the commonest answer is a shape problem rather than a capacity one.
A fuel tank has to fit around whatever else is under the floor. On a vehicle with a propshaft, a rear differential or an exhaust running beneath it, the tank is moulded in two lobes joined by a narrow bridge — a saddle tank, straddling the obstruction. The pump can only sit in one lobe. Fuel in the other lobe has to be moved across, and that is what the second pump does: a small transfer pump, or on many designs a jet pump driven by returning fuel, lifting fuel over the bridge into the lobe the main pump draws from.
The consequence of losing it is the most distinctive symptom in this part of the corpus: the car runs out of fuel with a tank that is half full. The main pump empties its own lobe, the other lobe stays full, and the engine starves. Filling up cures it instantly and completely — which is exactly what makes it so hard to catch, because the fault disappears the moment anyone investigates it.
The pattern is unmistakable once it is described: the engine cuts out, hesitates or loses power when the gauge falls to roughly half or a quarter, always at that point, and always cured by refuelling. Cornering, braking or a hill often triggers it, because fuel sloshes away from the pump pickup and the reserve that would have covered it is stranded on the wrong side. A driver who reports this is describing a transfer pump, and the diagnosis is largely done.
The reason it costs money is that this is not what anyone looks for. Intermittent starvation on a car with fuel in it is investigated as a failing main pump, a blocked filter, a crank sensor or a relay — and every one of those tests fine, because every one of them is fine.
On other vehicles a second pump means something else entirely: a low-pressure lift pump feeding a high-pressure pump, or a second in-tank pump brought in only under high demand. Establishing which arrangement a vehicle has is the first step, because it changes the symptom completely.
Causes probables
Commencez ici
- Circuit ouvert dans le câblage de commande · modérée
- Pompe de transfert de carburant défectueuse · modérée
- Connecteur corrodé ou mal enclenché · facile
Moins fréquent
- Fusible grillé ou alimentation hors service · facile
- Faisceau de câblage endommagé · modérée
- Calculateur de pompe à carburant défectueux · spécialisée
Symptômes
Composants concernés
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