B230FT Fuel Problem

Hello,

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)?

Thanks in advance for any help.

 

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.

Mike

 

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.

Bob

 

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.