CIS-E Running Problems

[Bob Rossato]

Trying to help out a friend sort out some problems on one of his track cars.

Patient is an '85 Coupe GT.

Symptoms - lack of power, rough running.

Diagnostics - Monitoring injector pressure shows about 4 bar, then at about
3800rpm the pressure starts oscillating between 2 & 3bar at approximately a
1hz frequency.

My friend had swapped out the ECU & CIS-E fuel injection assy as a unit
(fuel distributor, differential pressure regulator, diaphragm pressure
regulator, sensor plate potentiometer) with known working units out of his
other track car ('86 CGT).  The injector pressure oscillation did not go
away.

When I showed up last night we swapped out fuel pump relay (the fuel pump
would not kick in for the typical 1-2 seconds when turning on the ignition)
and noticed that fuse # 24 for power to the ECU was missing.  With the
swapped FPR and power to the ECU the motor ran better (could at least rev it
to 5k+) but the injector pressure oscillation remained.  Though you could
power through it and it would go away.  Stay at partial throttle and it
would oscillate.  I'm assuming the car was running in Limp Home mode before
we installed the fuse for the ECU.

We also checked the pin outs at the ECU harness for the various parts of the
CIS and all resistances were within spec, and we verified we had power to
the ECU.  We have yet to check system pressure or differential pressure on
the fuel distributor but given that swapping them out did not change
anything, and the suspect part ran fine in the donor car, we're assuming the
fuel distributor, & pressure regulators are fine.

Any suggestions, thoughts, sympathies will be appreciated.

Bob