injector voltage test?

Hi,

I am getting a fault with injector #6 but cant remember the fault code no.
but remember being told that its not working and can feel the engine missing.

is there a way the injector can be testing with a meter?
or what would be a good way to find out?

or could it possibly not be the injector?

its a 2000 xj 4.0

thanks for any advise !

The injector itself can be checked for continuity (it's little more than a solenoid) with an ohmmeter - I don't have the spec handy, but I'm sure someone has.

As far as the "firing pulses" for the injector, you can get a "noid light" (about USD5, as I recall...) which plugs in in place of the suspect injector. It will flash each time the injector is supposed to receive a firing pulse from the ECU/SBEC/PCM (whatever ChryCo's callling it this week...)

A helpful hint - when checking the injector for continuity, leave it connected to the ohmmeter, and gradually heat it up with a hair dryer on LOW setting. Somtimes, you get intermittent failures due to heat - so heating the thing up may help to point this out. I'd also give it a shake every now and again while it's under test, just to make sure it's not a vibration issue...

5-90

The injector can also be stuck or plugged and test good with an Ohm Meter.

True - but that's going to be "take it to an injector house for testing and cleaning" time...

Nice thing about being in this area - I can find most industrial shops rather easily...

5-90

I grew up poor and miles from any mechanic. I never had the $$$ just to buy parts to try. I had to learn to be smarter than the problem

Take the "problem" injector and move it to a different cylinder and see if the problem follows. If it does, you have an injector issue. If the problem still stays with the cylinder, you most likely have a bad connector, wiring problem, or bad computer. I have seen lots of intermittent connections right at the computer where plugging and unplugging would clean it up, but first swap a couple of injectors and see what happens.

Before I would buy an injector, there is a product I swear by for cleaning fuel systems and removing carbon buildup. It is BG44k, a fuel system cleaner. It runs around $20 a can. Don't even bother with the STP type crap. It is worthless.

BG44k is somewhat hard to find, but is a standard at dealerships for doing a $79. They pour a $20 can in your tank and charge you $79.

Or swap #6 with #1 and see if the fault code changes to #1.

Were thinking alike again old man

In case Old man's description was confusing, you do not move the injector itself, just the connection. First you test to find which injector is misbehaving, by idling the engine while the injector problem is present. If it is intermittent, wait until it's doing it. Now pull each injector plug, starting at one end. If you pull a good one, the engine will bog a little, then recover. If you pull a bad one, nothing will change. Now when you have found the bad one, exchange plugs with its nearest neighbor, rev up the engine a bit to clear its throat, and repeat the test on the two swapped injectors. If the fault follows the injector it's a bad injector. If it follows the plug, it's in the wiring/computer, etc.

I had a wiring harness problem with a 93 that took some time to figure out, because it only occurred when hot. A bad splice in the common positive line caused one injector to misfire but still gave enough voltage to fire an injector and harness tester. After isolating the problem as described above, I used an ohmmeter to find the fault in the wiring harness and bypassed the splice.

As 5-90 mentions, it's also not unheard-of to have an injector or other solenoid fail intermittently when hot. A common and oft-misdiagnosed problem in days of yore with VW idle cutoff solenoids.

I did mean move the physical injector. Just moving the connection can yield upredictable results since the injectors are timed just like spark plugs. The computer has already said it is #6 cylinder. The issue isn't finding the bad cylinder, that has been done. The point is to move the injector to see if the failure follows the injector or stays with the cylinder.

Besides the code says it's #6 we just want to now find out if it's the injector or the wiring or even the ECU out put.
If you swap the injectors and the problem don't move you know it's not the injector.

old_man said:

I did mean move the physical injector. Just moving the connection can yield upredictable results since the injectors are timed just like spark plugs. The computer has already said it is #6 cylinder. The issue isn't finding the bad cylinder, that has been done. The point is to move the injector to see if the failure follows the injector or stays with the cylinder.

Click to expand...

I have to disagree here. Removing injectors is more hassle than you need for this. Although the injectors are timed, the timing is not that critical. The injection pulse is not timed as it is on a diesel or a direct-injection engine. It is timed to hit before the intake valve opens. My experience is that swapping connectors works quite adequately. It worked for me in exactly the kind of situation that is being described here, isolating the problem between injector and harness. I would certainly try this first, because it is so much easier.

I guess your correct, the code should change from 6 to 5 by switching the wires.

thanks for that, it makes sense to just swop the connectors...

so i can swop with #5 and see what happens, sounds easy enough, hope it is !