East_tx_dad
NAXJA Forum User
- Location
- east texas
1996 XJ 5 speed 4.0. I've got the setup with the fuel pressure reg in the tank with the pump assembly so no return line.
My question is does the ECM have any way of detecting fuel pressure? I don't see any kind of fuel pressure sensor, but the fuel pump will run sometimes for a while before shutting off when the key is turned on instead of just the 2-3 second run time. At first it seemed to be related to fuel line pressure but I've seen it happen several times now with the fuel rail pressure reading upwards of 40 psi. When the pump is running after the key on, the jeep will crank but not start (almost as if the ECM isn't opening the fuel injectors). But as soon as the fuel pump goes through a "normal" cycle (key on, pump runs 2-3 seconds, pump shuts off) it fires right up.
Background, 1000mi on refurbished engine with 370k on jeep. New injectors, plugs, wires, distro with engine. Before engine swap, started having long starts occasionally when jeep would sit for several days or have cold/wet weather. Has gotten worse after engine swap. Fuel pressure reading around 48psi and pressure would slowly leak down after several hours so replaced fuel pump with new Bosch pump (assuming check valve leaking) but it hasn't really changed anything.
My question is does the ECM have any way of detecting fuel pressure? I don't see any kind of fuel pressure sensor, but the fuel pump will run sometimes for a while before shutting off when the key is turned on instead of just the 2-3 second run time. At first it seemed to be related to fuel line pressure but I've seen it happen several times now with the fuel rail pressure reading upwards of 40 psi. When the pump is running after the key on, the jeep will crank but not start (almost as if the ECM isn't opening the fuel injectors). But as soon as the fuel pump goes through a "normal" cycle (key on, pump runs 2-3 seconds, pump shuts off) it fires right up.
Background, 1000mi on refurbished engine with 370k on jeep. New injectors, plugs, wires, distro with engine. Before engine swap, started having long starts occasionally when jeep would sit for several days or have cold/wet weather. Has gotten worse after engine swap. Fuel pressure reading around 48psi and pressure would slowly leak down after several hours so replaced fuel pump with new Bosch pump (assuming check valve leaking) but it hasn't really changed anything.