Engine Problems

This battery issue may interest boaties

Recently the 4x4 engine has struggled to start.  Initially I thought it might be a fuel starvation problem as I recently changed both the primary and secondary fuel filters.  Eventually I established that wasn’t the problem.  The issue was the 12V starter battery.  Whilst there was just enough charge in the battery to turn the engine over the voltage was insufficient to cause it to fire. 

I believe the cause is a combination of the vehicle ‘smart alternator system’ and frequent short trips.  The smart alternator system reduces the voltage produced by the alternator.  This make miniscule fuel savings, but when your competing for fuel efficiency and emissions standards I guess every little helps.

Of course these days a vehicle is far more complex than when I first started tinkering with them.  All those on-board computers.  Well I read a forum post where another Isuzu owner had been able to modify his vehicle and disable to smart alternator.  today I did the same taking about 30 minutes.  The cost was horrendous….. 11p.

That money was spent at Jaycars (Maplin equivalent) purchasing a 10K resistor.  Without knowing the load on the resistor I opted for one rated at 1 Watt. 

OK, I had to spend 22p as they came in a pack of two.

I’m going to modify the wiring into the negative battery terminal and circumvent the smart system.

I made a patch lead Using some small spade connectors, spare cable and shrink wrap.  My plan was to make the modification reversible.

In order to trick the smart system into not working I need to permanently connect the sensor wire to a 12V+ supply.  however it also needs a small load which is why I’m using the 10K resistor.

The 12V+ wire was White/Green and the sensor wire Brown/Red.  My plan was to use spade connectors thereby allowing me to reverse the modification should it be a failure.

My patch lead

Heat shrink went over the connections when they were completed.

It was easier to compete the work on the vehicle if the negative post clamp was removed.  This give access to the plug underneath the clamp.  Removing the plug is relatively easy (once I had worked out how).  Place the end of a small flat tipped screwdriver underneath the base of the tag and leaver it up slightly to release the catch.

This is a slightly better view of the tag

the next step was to remove the wiring loom insulation tape from around the wires to gain access.  The wires aren't very thick so they probably don't carry much of a load.  Hopefully my 1Watt resistor is sufficient.

I then cut the Brown/Red wire and connect the patch lead to the battery terminal end.  This was done with spade connectors.  I also put a spade connector on the other end of the cut Brown/Red wire.  this will allow me to reverse the process.

I next cut some insulation off the White/Green wire and join the other end of the patch lead by soldering the join before taped it.

My finished wiring looked like this

A - Patch lead connection to the battery end of the Brown/Red wire
B - Resistor.  It's bi-directional so it doesn't matter which way it faces
C - Other end of the patch lead soldered to the White/Green wire
D - Cut end of the Brown/Red wire blanked off with a spade connector.

I taped the wires back together with black insulation tape and refitted the plug to the terminal before reconnecting the clamp.

The vehicle started <hooray>

My UltraGauge shows the alternator producing 14V.

I thought this was quite good as I've only just finished reconditioning and fully recharging the battery.

 
I'm now going to monitor the alternator output to see if it drops back to those previously low numbers.  Hopefully the battery will now be more fully charged and its life extended.

Interestingly, the vehicle comes with a 5 year warranty…. except for the battery which only has one year.  I assume those clever Isuzu engineers know their smart alternator system is likely to lead to premature battery failure.