Hey guys. My mechanic says I've got a bad injector, but wants to charge me
an additional 300.00 pull the plenum off my 94 Grand prix with a 3100 to
find out. I can get the plenum off myself with no trouble, but how does one
go about testing the fuel injectors? I put a long screw driver on each
injector while the car is running, and left the tick-tick-tick that each
injector makes .. one is slightly less .. powerful than the rest, but I'm
not sure if that is a clear indication of an injector failure or not ..
What does he think is wrong with the injector?
Electrically, you can test the resistance.
For leakage, you can remove the injectors and fuel rail as an assembly,
run the fuel pump, and wait.
For clogging, well, depending on the injector, hard to find.
If you have a misfire on a specific cylinder, you could swap the injector
with another cylinder and see if the misfire moves to that cylinder.
You check the injector's resistance by disconnecting the connector from the
injector and measuring the resistance of the injector across its two pins
(on the injector, not the wire) with a digital multimeter. I don't know
if I'd trust an analog ohmmeter, but I suppose it should work.
I'd go the swapping injector route. Find out which cylinder is misfiring,
swap that one injector with another cylinder, and see if the misfire
moves. If the injector is "not opening fully" as alleged, the resistance
check should still be good.
Not sure mortal man has the equipment to properly check an injector. I
thought they should be around 12 ohms but that's only one check. They can
have the right resistance buy still be partially clogged. How much do you
trust your mechanic? If you want to DYI, I solved a misfire problem in a 98
Montana by installing a set of reconditioned injectors from
www.lindertech.com There's a bunch of places selling recond. injectors but
I read of this outfit on another board. Not sure of cost for the 3.1 but it
was around $150 +/- for the 98.
How about this: yank one plug at a time and bend the electrode shut, shorting
it out. Put it back in and run engine, if it runs worse, obviously not that
cylinder, move plug to next, etc. until you find the suspect cylinder/injector
and service just that one. Comments??
Never do that. If anything remove the spark plug wire from the plug.
Hold it with something with rubber grips (such as pliers), pointed at
something like an exhaust manifold. To which it will arc, rather then
to your hands.
It's basically a dead cylinder test. Driving on a dead cylinder is
something to avoid. It can be anything from a hole in the piston, to a
valve that is stuck closed. Some time's it's just a fouled out spark
plug, a bad terminal on a DIS or distributor tower, or even a bad plug
Knowing which cylinder is dead is a good starting point. Yet with
fuel injectors, you may have one dead. Yet find out 2 or 3 are below the
required readings. With injectors you should First check for pulse with a
noid light (signal from ECM). Then check pulse voltage. After that test
all the injectors.
Two injectors with issues will cause an engine to run bad, yet it
may seam like it only has one injector down.
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