Full Version: Temperature Inputs to L-Jetronic FI System on 1.8
Can anyone tell me how many temperature inputs are supposed to feed the L-Jetronic fuel injection system on a 1.8 liter and where they are located. My motor is a '75 California code with catalytic convertor (sensor not hooked up), EGR system (intact), no air pump, no evaporative control system. Engine barely running when purchased (way too rich), with lots of intake air leaks which I have fixed. I want to be sure I have the correct inputs to the ECU for proper fuel control. All help welcome.
The only relevant heat sensor is the CHT located in the left side head.
However, I'm sure that the rich condition is still due to air leaks.
Check the big S tube between the AFM and throttle, the J tubes seals and the injectors seals (both).
Also make sure that all the vacuum lines are correctly connected and solid and the vacuum ports for all the removed parts are plugged.
However, I'm sure that the rich condition is still due to air leaks.
Check the big S tube between the AFM and throttle, the J tubes seals and the injectors seals (both).
Also make sure that all the vacuum lines are correctly connected and solid and the vacuum ports for all the removed parts are plugged.
Ok, going by memory here, but the L-Jet has only two temp sensors.
It has a head temp sensor and a surrounding air temp sensor.
The head temp sensor is on the right (Passenger) cyl bank. It has a single spade style connector.
The Air temp sensor is on a bracket at the top of the case, right below the air intake plenum. It has a bosch 2 pin connector, similar to the injector connector.
That is what I remember but it has been years since I fooled with my FI.
Good luck!
It has a head temp sensor and a surrounding air temp sensor.
The head temp sensor is on the right (Passenger) cyl bank. It has a single spade style connector.
The Air temp sensor is on a bracket at the top of the case, right below the air intake plenum. It has a bosch 2 pin connector, similar to the injector connector.
That is what I remember but it has been years since I fooled with my FI.
Good luck!
Well, lets get this right. There's a CHT sensor, same place they always are, and an air temperature sensor inside the air box. NOT replaceable. Air leaks will NOT make the engine run rich. To the contrary, they'll make it run lean. Large air leaks will make it not run at all. And they don't have to be all that big, like a loose oil cap, or a bad oil cap o-ring (one, or both). Adjust the valves, check and/or replace the points, set the dwell and the timing (NOTE: the timing is set in a manner completely different than that of the D-jet engines!) Make sure the vacuum can works. Set the idle speed, set the idle mixture with the screw on the air box. If that doesn't fix it, check the fuel pressure at idle. Then make sure the cold start valve isn't leaking (VERY rare). Should be right about 30 PSI. If it still runs fat, you probably have a bad air box. Good luck with finding one. I have a PDF of the factory troubleshooting guide, available free to anyone with sufficient inbox capacity to get it in an e-mail.
BTW, the sensor under the manifold is the thermotime switch, a part of the cold start system. Has nothing to do with anything once the car is started, and only works when the temps are under 30 degrees F.
The Cap'n
BTW, the sensor under the manifold is the thermotime switch, a part of the cold start system. Has nothing to do with anything once the car is started, and only works when the temps are under 30 degrees F.
The Cap'n
QUOTE(Cap'n Krusty @ Mar 5 2013, 02:56 PM) 
Well, lets get this right. There's a CHT sensor, same place they always are, and an air temperature sensor inside the air box. NOT replaceable. Air leaks will NOT make the engine run rich. To the contrary, they'll make it run lean. Large air leaks will make it not run at all. And they don't have to be all that big, like a loose oil cap, or a bad oil cap o-ring (one, or both). Adjust the valves, check and/or replace the points, set the dwell and the timing (NOTE: the timing is set in a manner completely different than that of the D-jet engines!) Make sure the vacuum can works. Set the idle speed, set the idle mixture with the screw on the air box. If that doesn't fix it, check the fuel pressure at idle. Then make sure the cold start valve isn't leaking (VERY rare). Should be right about 30 PSI. If it still runs fat, you probably have a bad air box. Good luck with finding one. I have a PDF of the factory troubleshooting guide, available free to anyone with sufficient inbox capacity to get it in an e-mail.
BTW, the sensor under the manifold is the thermotime switch, a part of the cold start system. Has nothing to do with anything once the car is started, and only works when the temps are under 30 degrees F.
The Cap'n
Thanks Cap'n. I haven't started it back up since I replaced the injector seals (inner and outer) and the intake manifold tube hoses, sealed up the intake "snorkle" tube (between Air Flow Sensor and Throttle Plate/Switch) and replaced the rubber elbow to the auxillary air valve which was cracked. I'm hooked up to the CHT on the 3/4 bank, and there are two spade connectors from the harness going to tabs on the 3/4 side of the manifold down low. (Sorry no pictures) Those two look more like grounds. I have only one plug that goes into the air cleaner housing and that's for the Air Flow Sensor. There doesn't seem to be any place on the housing that would indicate a missing component. Haven't looked at the points or checked timing yet, but will soon. I'm hoping that eliminating the air leaks and tuning will do the trick.
QUOTE(motorvated @ Mar 6 2013, 11:13 AM)
QUOTE(Cap'n Krusty @ Mar 5 2013, 02:56 PM)
Well, lets get this right. There's a CHT sensor, same place they always are, and an air temperature sensor inside the air box. NOT replaceable. Air leaks will NOT make the engine run rich. To the contrary, they'll make it run lean. Large air leaks will make it not run at all. And they don't have to be all that big, like a loose oil cap, or a bad oil cap o-ring (one, or both). Adjust the valves, check and/or replace the points, set the dwell and the timing (NOTE: the timing is set in a manner completely different than that of the D-jet engines!) Make sure the vacuum can works. Set the idle speed, set the idle mixture with the screw on the air box. If that doesn't fix it, check the fuel pressure at idle. Then make sure the cold start valve isn't leaking (VERY rare). Should be right about 30 PSI. If it still runs fat, you probably have a bad air box. Good luck with finding one. I have a PDF of the factory troubleshooting guide, available free to anyone with sufficient inbox capacity to get it in an e-mail.
BTW, the sensor under the manifold is the thermotime switch, a part of the cold start system. Has nothing to do with anything once the car is started, and only works when the temps are under 30 degrees F.
The Cap'n
Thanks Cap'n. I haven't started it back up since I replaced the injector seals (inner and outer) and the intake manifold tube hoses, sealed up the intake "snorkle" tube (between Air Flow Sensor and Throttle Plate/Switch) and replaced the rubber elbow to the auxillary air valve which was cracked. I'm hooked up to the CHT on the 3/4 bank, and there are two spade connectors from the harness going to tabs on the 3/4 side of the manifold down low. (Sorry no pictures) Those two look more like grounds. I have only one plug that goes into the air cleaner housing and that's for the Air Flow Sensor. There doesn't seem to be any place on the housing that would indicate a missing component. Haven't looked at the points or checked timing yet, but will soon. I'm hoping that eliminating the air leaks and tuning will do the trick.
The circuitry for the temp sensor is incorporated into the air flow meter (AKA, Mass Air Flow Sensor).
The Cap'n
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