Fuel injectors

[Fivestring63]

Hey all you back yard mechanics.

The specs for ohming my fuel injectors are 10 - 14 ohms. Mine are reading between 8.3 and 8.9 but still runs good.

What is low enough to change them? I'm gonna change them anyway. Just asking.

[56FordGuy]

What type of vehicle?

If it's running fine, I leave it alone. I just did all 8 in my truck, 194,000 miles and 3 of them failing on a cylinder contribution test, along with low power and a starting problem.

[Fivestring63]

99 Nissan Frontier with 136000. No problems at all with it, just thought I'd do a little preventative maintenance before one gets bad.

[tercel89]

99 Nissan Frontier with 136000. No problems at all with it, just thought I'd do a little preventative maintenance before one gets bad.

How many cylinders do you have ? I had a 2002 V-6 and it was the "interference" type engine . You better get the timing belt changed out before you get engine damage if it is near 80,000 miles and the belt breaks . I know that was off-topic , but I wanted to give you a heads up on that .

The 4 cylinders should be chains and are good to go a long time .

[Fivestring63]

Mines 4 cylinder with chains.

[enfield]

Why would the resistance change on a fuel injector, unless a wire breaks and they go open circuit? I'm missing something here.

If you're not measuring the spec resistance, I'd suspect your ohmmeter, not the injectors.

[LagerHead]

Mines 4 cylinder with chains.

Then you better find someone that has a belt and change theirs. Can't be too careful.

[Fivestring63]

I've seen a wide range of ohm readings on injectors. From 1 to 40. They do wear out from use and time.

You measure the ohmage on the injector itself. Not the wires going to it. I'm pretty positive my ohmeter is working correctly.

[enfield]

What causes the resistance to decrease? Does the wire in the coil increase in diameter or get shorter? Shorted turns, maybe?

I'm not an electrical engineer, so I don't understand this.

[Fivestring63]

What causes the resistance to decrease? Does the wire in the coil increase in diameter or get shorter? Shorted turns, maybe?

I'm not an electrical engineer, so I don't understand this.

Remember when you're testing ohmage, you have no power applied. You are only testing the resistance in a wire. Less resistance means lower ohmage.

Resistance will decrease by windings rusting and decreasing in diameter, or windings shorting out causing it to bypass part of the winding therefore less wires

to flow through therefore less resistance.

[enfield]

Copper wire doesn't rust and decrease in diameter, and, if it did decrease in diameter, the resistance would rise, not fall. Shorted turns could cause the resistance to fall, but I don't understand how they would short after the injector was assembled and put into use. Magnet wire has an insulation on it that won't dissolve in gasoline or even acid. I can imagine thermal stress causing a winding to break, causing an open circuit, but I just can't wrap my mind around the idea of a coil decreasing in resistance as it ages.

Just another one of my many shortcomings, I guess.

[bajabuc]

Then you better find someone that has a belt and change theirs. Can't be too careful.

You can come change mine...

[bajabuc]

Check your battery...todays computers need a full charge to operate correctly. If your computer is "under funded" it affects the entire system.

[Fivestring63]

Check your battery...todays computers need a full charge to operate correctly. If your computer is "under funded" it affects the entire system.

Checking resistance has nothing to do voltage or amperage.

[bajabuc]

your computer controls the entire system...if it's not getting fed...nobody gets fed. "If momma ain't happy...nobody's happy"

[enfield]

I looked the subject up on another site. Fuel injectors can fail due to a shorted coil - shorting across the terminals, which is the worst case for shorted turns. So, if the resistance falls, it falls to zero. If you can measure any resistance at all, the injector should be OK electrically. Doesn't mean that it works, just that the coil is intact.

Now THAT makes sense to me.

[Guest TackleberryTom]

Any type of coil with the "magnet" type wire (a solid single conductor small gauge coated wire) is price to shorting inside the winding. As mentioned they are resistant to many chemicals but heat melts the coating and allows them to make contact with each other and the resistance slowly decreases as the number of turns in the coil effectively decreases. It happens often in ignition coils, magneto coils, fuel injectors, electric motors and the list goes on. It is a pretty common scenario. Hence the increase in needing to replace ignition coil packs on engines with coils at each cylinder. They are now located in higher heat locations than they usually were in the old days with single coils that were either in the distributor or on the fender.

[Guest TackleberryTom]

One more quick point, as the resistance decreases, the tint gauge wire then sees a higher current and therefore creates even more heat and eventually burns or the wires break causing an open circuit and hence a dead injectors or coil. We tend to think they died abruptly, though they were often showing signs long before. We just weren't looking. I am impressed that someone would actually measure their injectors and do preventative maintenance.

[Guest 1817ak47]

if they are real consist with each other leave them alone. if one was way of and the others the same then worry. fuel injectors RARELY fail