Ωhm

Not sure here but KNOCK might only come into play here during WOT when ECU is in OP.

When pinging occurs is ECU in OPEN LOOP (OP) or CLOSED LOOP (CL)?

Check Instrument Cluster (fuel sender) page in the Electrical Manual.

Check Instrument Cluster (fuel sender).

Wouldn't the black wire enter the tank using that grommet used by the other two wires? If so, then pump and gauge are finding ground thru the metal tank & straps.

Not sure on the 2.5L if the electric fan is ON when the AC clutch is engaged. Since heavy duty cooling was an option needed for Dealer Installed AC, might not have all the necessary wires. Not sure here.

The 4.0L uses a Fan Diode Assembly (C246) which allows the electric fan to kick ON when the AC clutch is engaged but will not allow the AC clutch to kick ON the electric fan.

Using a voltmeter or 12vdc testlight (preferred) check for Battery_Voltage on the following pins (use battery_negative terminal for ground): D1_5: Battery_Voltage (Hot at all times) D1_6: At KEY ON, (Hot for 2-3 seconds). During CRANK, (Hot at all times). D2_4: At KEY ON, (Hot at all times). During CRANK, (Hot at all times).

Drawing matches the stuff I/we have. _mj1988electricalmanual_1.pdf

Shifting the CPS either CW or CCW only fools the ECU to thinks a cylinder is at TDC when it is not. Shifting will also shift, for each cylinder, when KNOCK looks for ping and when the INJ fires. The ECU seems to be able to handle CPS ADVANCE, not sure on CPS RETARD. I'd pin it out, back to the ECU just to make sure.

Welcome. One more thing to look into, it's about grills. Click Here

Anyone with a REM hookup. Do you see the same voltage (VLT) as listed below? This displays the current voltage of the Battery. Note: On 4.0L this may be the Fuel Pump/o2 Relay Circuit which will normally read 0v after 3 seconds when the engine is off. This will read correctly when the engine is running. – Engine Off (~12.4-12.8) A healthy battery will rest around 12.6 Volts – Engine Idle (~13.5-14.5) A healthy Alternator should supply 13.5-14.5 Volts

Click here: Check connector C102.

What is Battery Voltage (VLT) on the REM?

Pump prime is a two-fold process. 1. Allow fuel pump to run for 2-3 seconds. 2. Check valve to prevent fuel drain-back through the fuel pump to the tank when fuel pump is OFF. Question is ‘Does fuel pressure drop once the pump is turned OFF?’ Faulty check valve. I’m not saying this is your cranking issues, but it sure could help here.

Battery Voltage with ENGINE RUNNING. This is a quick test. If GOOD, need to check O2S heater on the component itself. Disconnect C229 and on the component side connector check for resistance between pins C229_A and C229_B. Looking for ≈6 Ω's. If TRUE, circuit is GOOD. Note: This view is harness side.

With ENGINE RUNNING, check for Battery Voltage on D2_9 (O2 Heater Circuit).

225 PSI refers to when the pump deadheads (ON but no flow). IDK what SPEC is, might say with the pump's paperwork.

Might be off base here but doesn't the ground wire for the sending unit on the pump, ground at the bottom of the resistor for RENIX and at the top of the resistor for SBEC. Can't tell from the photos. Gauge still should work with half tank of fuel. Does Coolant Temp Gauge peg pass 260° when KEY is in the CRANK position? If NO, check GAUGES FUSE (7.5A). If GOOD, look for voltage on C203_6 & C203_18.

Great photo.

With a leaking fuel pressure regulator, fuel would be sucked directly into the manifold via the vacuum hose connection. Disconnect hose and look/smell for fuel. Reinstall your factory injectors. INJ PW=9.6mS and LTFT=84 is most confusing, for me at least.

Few more items for your check list: - Higher than normal fuel pressure - Leaking fuel injector(s) - Leaking fuel pressure regulator/check for fuel in hose to manifold IAC=Idle Air Control

What if the orifice (2.6mm) is removed/enlarged. This would increase the draw into the manifold. I think the IAC would compensate for this additional air draw while STFT and LTFT would maintain the fuel ratio (stoichiometry). Might help.

Right handed/Left handed lug nuts & studs. For the new, old guys now, they can make a fool of you. Ask me how I know.