I have a 87 760 Turbo that will not start due to a fuel problem (spray starter fluid into the air filter and it vrooms). I have verified fuel is being pumped into the injector rail. I have also verified the injectors are okay. I am now ohming out the ECU to see if I can find anything odd. Everything has checked out so far except one of the throttle switch points (#12). Is it possible a maladjusted or broken throttle valve switch could prevent the vehicle from starting?
If not is it more likely to be fuel pressure or air control problem (I have not checked this on the ECU yet)?
If the throttle switch is open the idle will go high... around 2000 rpm. It's possible the Air Mass Meter is defective - unplugging it will produce a default setting that will let the engine start and idle.
In a 1987 my first suspect is the wiring harness. You probably see a number of places under the hood where the insulation has fallen off the smaller wires. I would be tempted to unplug the injectors (they are wired in parallel with only the ballast resistors isolating them) and measure across the connectors for a short circuit.
As far as the air control goes, the only trouble spot I can think of there is the short hose that connects the Idle Air Control valve under the throttle body to the intake manifold. The one in my '85 hardened and broke while I was on the road... I made it to the side before the engine died. If you have an air problem the leak will produce a very short and fast "vroom" with the starter fluid.
First of all, a turbo only has the idle position contacts operational. The fukk load contact set is unnecessary since the load signal from the air mass meter at full throttle is more than sufficient.
Use you DVM to verify that you are indeed getting a pulse to the injectors when the engine is cranking. Check the wiring to the resistor pack on the left front fender (driver's side) and make sure you have continuity through the pack. The injectors on a turbo have a low resistance aluminum wire winding for faster throttle response. IIRC they measure 2 Ohms each as opposed to the copper wound coils at 4 Ohms each on the NA motors.
Look for a relay with 1323592 molded on it. This is the oddly named radio suppression relay. It's really an injector power relay and without it the car won't start. In another life it would be the auxiliiary fan relay. Actually on your car the Aux fan relay is right next to the Injector relay hanging on a bracket behind the power steering reservoir, or maybe it's hanging from the coolant reservoir. No mater the two relays are identical. Turn the key to the run position and ground each of the terminals on the aux fan coolant temp switch through a test light. One of them should cause the cooling fan to run. If true then swap that relay with the one by the power steering pump. Repeat the test. Chances are the second relay will not run the cooling ran. In which case the good relay is in the injector position and the car should start.
If not then ground the negative #1 terminal on the coil and crank the engine. If the light flashes once or not at all or very faintly then the ignition amplifier is not working and it needs to be replaced. It's located right by the resistor pack. If the amplifier doesn't produce impulses then the fuel pump relay won't close and the fuek injection control unit won't fire the injectors.
If it has the original engine wiring harness then that is almost certainly the problem, and if it isn't causing the current no-start, it will soon enough.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.