Testarossa Fuel KE-Jetronic Fuel Injection System

The Testarossa when released in 1984 was fitted with the Bosch K Jetronic fuel injection system. In 1988 this was upgraded to the new KE Jetronic system with elements of electronic control added. USA spec cars featured even more electronic controls in an attempt by Bosch / Ferrari to comply with the strengthening emissions control introduced in many US states.

I recently had issues with my own 1988.5 UK spec car which was 'hunting' under light throttle loads at highway cruise speeds.

Thanks to the input and feedback from my local Ferrari mechanic, Phil Hughes, and the invaluable assistance from the members on Ferrari Chat, especially Steve Magnusson and Jeff Green, I was finally able to diagnose the problem down to incorrect measurement of the fuel delivery which was faulting at the distribution heads.

Here are the things to check and how to go about the various procedures:-

TR Diagnostic Sheet Number 1.

TR Diagnostic Sheet Number 2

TR Diagnostic Sheet Number 3


TR Diagnostic Sheet Number 4


Water Thermoswitch Test

Water Thermoswitch

Measuring voltage on the red wire with engine running I have +14.47v



Coolant Thermister Resister test

TR coolant thermister resistance test. Ambient air temperature here today was 18 deg C. I ran the car for three or four minutes to check idle so it wasn't dead cold but pretty close to cold.

Measuring from pin 21 to pin 2 on the unplugged harness connector.

Rear ECU measured 2265 ohms. Front ECU measured 2173 ohms. I estimate my coolant temp to be around 20 - 25 deg C so looking at the sliding scale on the graph, these figures look about right.



EM Pressure Actuator Coil Resistance Test

TR EM Pressure Actuator Coil Resistance Test

Measuring form Pin 10 to Pin 12.

My car - Rear ECU = 18.4 ohms

My car - Front ECU = 18.3 ohms


TR throttle microswitch resistance test

Measuring between pins 1 and 13 on the ECU Harness.

 These results are inconclusive probably due to the few minutes that the engine ran prior to the test. Rear ECU read 0.03ohms at rest and open circuit when throttle opened even the smallest amount.
Front ECU read 0.04ohms and then straight to open circuit.

  I know this should have read 140 ohms on a cold engine, but this didn't happen. I will redo this test in a few hours when the engine is dead cold again.

See this thread: http://ferrarichat.com/forum/showthread.php?t=184390 for the explanation of how to unplug C12 and C13 -- it's a combination of unscrewing the outer ring while pulling out at the same time
(very common for the outer ring to break easily).


Airflow meter sensor potentiometer test

 Something not right here on my car.

 I removed the two fuel pump relays then connected a wire from the big positive on the starter to the white wire with blue trace which I removed from the starter. There was a small audible click as I touched this which I presume was the relay closing?

 I then tried measuring the voltage between the two bottom pins and an earth point as instructed. I got zero volts yet I should of had 7-8v on each. Both measured zero.

 Then I tried the centre pin which also had zero, and even whilst pressing the airflow plate I had nothing. So I may have an issue here.

 I did all of this with the ECU connectors still off, so not knowing where to go next, I reconnected the two ECU's and tried again. Same result. Zero voltage!!

 Once the ECU's were connected I tried to start the car and it took ages of spinning over before it actually fired. Don't know if that's normal either?