Another No Spark, No Start, but . .

[8Mud]

I remember vaguely from my reading that the MAP gets a baseline atmospheric reading when the key is first turned through the run position, on it's way to the start position. What I can't remember is exactly what happens when it doesn't get a baseline reading, either you get a no start or it defaults to full rich are the likely outcome. I sure can't remember.

I have the battery out of my 88 right now, anybody with an XJ, willing to pull the plug on the MAP try a start and see what the results are?

 

[Ecomike]

IIRC if you pull the MAP vacuum hose it will start, if you pull the electrical connector it will not start, at least that is how my 87 worked when I tried it once.

 

[8Mud]

IIRC if you pull the MAP vacuum hose it will start, if you pull the electrical connector it will not start, at least that is how my 87 worked when I tried it once.

That is what I thought, but I wasn't sure. Getting old sucks.

 

[Ecomike]

That is what I thought, but I wasn't sure. Getting old sucks.

IIRC the two must have signals for the ECU to fire injectors and spark are MAP and CPS signal. Then the next possible signal that might also be needed is the IAT intake air temp sensor, used to calculate air density mods for air temperature.

 

[djgrayxj]

Note from DJ
I think this is what information 8Mud is referring to.
I am getting old to but I try and store Renix info in my computer when I get the chance.
Ecomike your MAP info will be stored.

This information is from Complete Renix Fuel injector manual [ON line version).

KEY “ON” MODE
When the key switch is turned to the ON position the ECU receives information from the following inputs:
Coolant Temperature sensor (CTS)
Manifold Air Temperature sensor (MAT)
Manifold Absolute Pressure sensor (MAP)
Throttle Position Sensor (TPS) NOTE: From the flat three pin connector

Voltage is supplied to the fuel pump relay and the ECU completes the pump relay ground circuit for 1 to 3 seconds to prime the fuel line. The systems power latch relay is energized for 1 to 3 seconds. The ECU stores the MAP sensors barometric pressure input in the anticipation of a startup. The heating element in the oxygen sensor is activated by the ECU through the normally closed heater relay.

The EGR solenoid is energized by the ECU which restricts operation. On manual transmission equipped vehicles, the shift indicator light is illuminated to check the lamps operation.