Toyota Avensis 2.0Di (petrol) 2005
This vehicle was recovered to the workshop as a non start. Unfortunately it started once it was delivered.
There were no DTC’s stored. I was asked to look at it, as the recovery technician had noted no obvious fuel pump operation.
I tried rattling the fuel pump relay, with no effects.
I set up my scope at the fuel pump, (in-tank fuel pump).
Blue Channel: +- 20 amp
Red Channel: +- 20 volts (differential connection)
You can see in the image above the peak start-up current at 15.5 amps, followed by a very noisy signal.
You can see how the current signal shows a low current of approximately zero amps. In the next image you’ll see more details.
You can see how the voltage signal reflects the pattern in the current signal.
Look at the current signal carefully. It represents a ‘dead zone’ in the segments of the commutator. It doesn’t take much imagination to see how that could have caused a non start condition.
Of course I cannot be 100% certain of the vehicle failure, as it didn’t fail for me, but I can be sure that the fuel pump is bad.
So a new fuel pump was installed.
Let’s take a look.
We can see that the start-up current of the new pump is a little higher than the old. The average fuel pump current is now lower than the old.
More importantly, look at the general signals. Much smoother.
No we’ll look at it zoomed in.
Now you can see a pretty uniform pattern, with no drops to zero amps.
The conclusion:
Although I still cannot be 100% certain the vehicle breakdown was due to this fuel pump, because it never failed on me during any tests. It does show how the scope analysis has come in for an intermittent fault.
It has been several weeks of the vehicle being used before I posted this page.
Mark Stammers Diagnostics 