Got an older EFI car? Having problems with intermittent misses that you can’t
track down, even by changing the spark plugs, leads and dizzy cap? You might be
looking in the wrong place – try checking the injector plugs. In some cars the
injector plugs are corroded and aged - and the touch-and-go connection that
they’re making with the injector terminals can be responsible for plenty of
intermittent misses.
But a solution is easily at hand. Just rip out the older corroded plugs and
replace them with shiny new ones!
Here’s how.
Firstly, you’ll need to have some crimpers (left) and wire strippers (right).
In fact, you don’t really need them – they just make for a neater, easier
job. If you’ve got them – fine. If you haven’t, needle nose pliers and a razor
blade can be used instead.
And of course you’ll need to have the new plugs. These Bosch plugs were
purchased from Petro-Ject (stores Australia-wide) and cost AUD$48 for six.
They’re to suit a mid-Eighties Nissan V6 and were available off the shelf. If
your car is more obscure and nothing is available new, source the plugs
secondhand – but make sure that they’re a lot better than the ones you’re
replacing!
Before starting work on the injectors, disconnect the battery. Here, a
circuit breaker was tripped to do the same thing. The battery disconnection is a
must-do step as some injectors always have one side of them live – even with the
ignition turned off.
Here’s what one of the old plugs looked like – the plastic old and brittle
and the rubber boot in pieces.
The old plug can be cut off – make the snip as close to the plug as
possible.
Slide the new boot onto the wire, pushing it along the cable until you have
enough length of exposed wires to easily work with.
Using the wire strippers, take off a short length of insulation from the end
of each of the wires. Note that if the exposed copper is corroded, you may need
to cut back further. In extreme cases, where you have to cut back a long way, the wire may then need to be extended.
The plug pin – or terminal – can then be slid onto the exposed conductor.
Note that you may want to slightly close-up the crimp so that (a), it stays in
place on the wire while you get the crimping tool and (b), the tool makes a
neater crimp.
The crimping of the terminal can now be done. If you don’t have a crimping
tool, use needle-nose pliers to carefully fold over the edges of the crimp,
clamping them into the conductor.
One of the completed crimps. The crimp should be firmly fastened to the wire
– give it a sharp pull and it shouldn’t move even the tiniest bit. If it does
come off, revise your crimping technique.
With both terminals crimped onto their respective wires, the terminals (plug
pins) can be inserted into the back of the plug. Make sure that you push them in
with the correct orientation - when they are fully home, a faint click should be
heard from each. Again, give the wires a tug and make sure that they stay in
place.
The rubber boot can then be slid down over the plug, forming a water-tight
shield. If at the other end of the boot the seal with the cable isn’t very good,
wrap insulation tape around this end to stop any water running down the cable,
under the boot – and into your plug!
Before pushing your new plug onto the injector there are a few things to
check. Firstly, make sure that no remnants of the old injector plug remain. For
example, here the old spring clip and some bits of crumbling plastic stayed
behind when the old plug was removed. Also, make sure that the injector pins
don’t have corrosion on them – if they do, use a sharp knife to scrape them
clean.
If access is tight, long nose pliers may be needed to place the injector
plug.
After replacing each injector plug, reconnect the battery and start the
engine. You can easily hear if the injector is running by using a long
screwdriver as a stethoscope. Make sure that wriggling the plug doesn’t cause
the injector to stop – a possibility if there is still some corrosion remaining
on the injector pins.
Work your way through all the remaining injectors – then you’re done. No more
misfiring of the injectors!
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And Not Just Injectors
Plugs are also available for other common connections, like the throttle
position sensor. Replacing this required a 3-pin plug that was bought
off the shelf like the injector plugs. Cost was about AUD$14.
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