Power Steering Fault

Hi, 

I have an mg tf fitted with an mgf 1.8vvc 1997 engine, wiring loom and conversion on the dash to use the TF dash. All runs great apart from the powersteering will cut out and not return until turn the car off and then back on. 

It doesnt happen after turning any amount. It sometimes will cutout when we go above 60mph, other times at 40mph, sometimes at  high revs for along period other times just normal driving. it feels very random. 

I have tried unplugging it from the instrument cluster when it cuts out and replugging to see if that helped - it did not. I have checked all cables are secure, no lose connectors, no broken cables or bad grounds. 

When it does happen the dashboard light doesnt come on, no lights flicker, no suspected voltage drop or outage and have tried brand new battery with the same result. 

Feels like a bad EPAS ECU at this point. Any suggestions or ideas welcome. 

How much f have you transposed into your tf? The later ECU (adjustable column) isn’t compatible with the fixed & vis-à-vis.
As a general comment, if you are considering changing to an adjustable system, fit all the parts from the same donor car & only do the modification if, having asked yourself if you really need it several times & come back with “Yes” the majority of times.
M

My first port of call would be checking the connections from the speedo drive to the EPAS ECU there could be a loose connection.
Everyone immediately  blames ECUs whenever the systems they control go haywire, ECUs are more robust than most people think, the problems are more likely to be the sensors or their connections.

I’m away at the moment & thus don’t have diagrams or notes to compare system but as usual Cobber raises a salient point. The pulse train created to time the ECU is derived in a different way, one to the other. A timing glitch would cause odd problems & nastys might be creeping in.
Just a thought.
M

+1 for an input issue as you have ruled out battery voltage . It will either be the engine run signal or the road speed signal.
I modified an MGF EPAS to work on my MGB and after some thought i got a dedicated double frequency generator to provide both inputs the EPAS needs:

It uses its own GPS sensor to generate the road speed signal to replicate the original speedo input. The engine run signal is a simple fixed frequency. Tiny box, simple to wire up.

As others have said the way the signals are provided differ between an F and TF. The EPAS ECUs may look the same from old to new but they have different signal frequency requirements and my thought is that your car isnt providing what your particular EPAS ECU needs.

Using a similar workaround to mine may be your easiest sure fire way forward as it removes the requirement for the car to supply the signals to the EPAS.

Nan - most impressed.  Most of that post came across as advanced Klingon to me!  I would not have a clue where to start with electrickery.

This is the one I used.   GPS power steering sender  It turns an MGF EPAS column and it's ECU into a self contained system that can be fitted to anything that has wheels and a 12 volt battery.  

The EPAS ECU has a check system to see if it is getting right signals at right time. If it does not see engine RPM and road speed it will disconnect and show EPAS warning light. As you do not have a warning light I would think it is not the EPAS ECU/ Speed signal/RPM signal that is causing the problem, but possibly a power supply problem or earth to the EPAS motor.  Any issue to the ECU should throw an EPAS warning light.

Also, as mentioned earlier there are at least 3 types of EPAS ECU  (E,F & G), that may also give a weird fault with no warning light if wrong one fitted?

I assume you are getting correct self check sequence when starting up . The EPAS is normally last warning light to go off on start.  Hope you find  the problem, intermittent faults are a pain in the but.