I have an ASE A1 test question for you…
A fuel pump module can have an internal leak.
True or False?
The answer is true. Most modern fuel pumps mount the electric pump at the bottom of the tank. Fuel is carried from the pump to the cover assembly using flexible hoses. The hose can develop leaks over time due to chaffing on the support rods. In some cases, the clamps and connection at the pump and cover assembly can start to leak.
Instead of the fuel being delivered to the fuel rail, the pressure is bled off back into the tank. The symptoms of this condition will be low fuel pressure at the rail, hesitation and misfires codes. A scan tool can control the fuel pump on some vehicles bi-directionally. If you can turn the pump on and hear it running and the fuel pressure does not increase, chances are the pump assembly is leaking internally.
On most fuel pump modules, the hoses are not serviceable. In these cases, the entire module should be replaced. If you have a hanger-style fuel pump module, some hoses can be serviced. When installing these hoses, use a hose with an SAE 30R10 rating. It will be printed on the side.
This type of hose is designed to be submerged in fuel. This type of hose uses a special layer on the inside and outside to prevent the core layers from being saturated in fuel. But don’t use it under the hood. R10 hoses can’t stand the heat.
This video is sponsored by Carter Engineering.