AUTOFIX.COM.AU

If you're new here, you may want to subscribe to my RSS feed. Thanks for visiting!

I would like to tell you of a car that we had in our workshop, going back around 3 years ago. The anti-christ was a 1990 Toyota Camry fitted with a 3S-FE engine, essentially a 2.0 litre, 4 cylinder engine fitted with electronic fuel injection.

  The car came in on a tow truck with the owner telling me that for some reason it kept ‘flooding’ itself. It had been to a handful of workshops before coming to us and needless to say the owner was ready to solve the problem with a box of matches and a can of fuel!

  The last mechanic to look at it had replaced the fuel pressure regulator and it behaved itself for about a week before this latest dummy-spit. Numerous litres of fuel had worked their way past the piston rings and into the sump, so the first thing to do was drain the oil and change the filter.

  With that taken care of it was time to go hunting. It was first necessary to figure out whether it was a fuel pressure issue or perhaps leaking injectors (unlikely due to all cylinders being over-fuelled and the amount of fuel present in the sump.) or an issue that was causing the injectors to stay open.

  Fuel pressure was hard to guage as the engine would only run for a few seconds! From what we could see the fuel pressure was within specifications, a tad low if anything, not likely to cause over-fueling on this scale. I had discounted the leaking injector theory based on the reasons stated above. So the only logical theory left was the injectors staying open for some reason.

  Testing the electrical controls of the injectors is a simple procedure. On one side of the connector we have constant power. On the other side the computer provides an earth that is controlled by the computer. Signals from various sensors around the engine combine to dictate when the injector is opened and for how long.

  Out with the test light and with the ignition switched ‘on’ we found we had the constant power and by reversing the polarity of the test light ( clipping the lead onto the positive terminal of the battery instead of the negative ) we found we had a constant earth supply as well. Not good! Even with the engine running the earth would show as a ‘pulsing’ of the test light and with the engine stopped we had a constant glowing test light.

  The first thing that came to mind was a faulty computer. A call to a friend of mine who is a master-mind with electronics revealed that the Toyota computers are on of the most reliable around and it was unlikely to be the cause. Time for a head scratch and a finger and thumb rub of the chin. They make thinking so much easier! Just like having your tongue half out when doing something difficult!

  Things were starting to get confusing. I couldn’t help wonder why the fuel regulator had been replaced, was I missing something? After a longer than usual head scratch we decided the only logical next step was to check the wiring from the connector to the computer. Easier said than done when the it twists it’s way in and around the engine…..

  Then the penny dropped, the wiring was quite tight going around a sharp corner of the cylinder head. Funny enough it was close enough to the fuel pressure regulator to be moved around a bit when replacing the regulator! So we connected the test light again in reverse polarity and while probing the negative side of the connector we wiggled the wiring harness around where it contacted the cylinder head and surprise, surprise the earth dropped in and out. Four hours just to find a short to earth!!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 I spent the next couple of hours repairing and re-insulating the wire that had it’s insulation rubbed through and beefed it up with a piece of bike tube and plenty of insulating tape. Kicked it over and what do you know, ran like a champion! We replaced the fouled-up spark plugs and the car hasn’t missed a beat to this day. The previous mechanic probably thought he’d hit the jackpot with replacing the fuel pressure regulator and for a week or so he did!

  I thought I would share this story to highlight how the smallest things can turn into big headaches for us mechanics, and how diagnosis can sometimes be the most expensive part of the job. If you get charged what you think is an un-realistic amount for tracking a problem down, please think of this story and the amount of hours it took to find such a silly little problem.

Take care and be safe on the roads.

Craig