Ok I have read post after post about checking the ohms of an injector and getting a bit bewildered here. Last I checked a fuel injector has 3 main systems for operation. Fuel enters a filter on top then either pintle disc or ball but lets just call it the mechanical part that moves so fuel can flow through a precision orifice to meter the fuel last a coil that actuates the mechanical parts so they move and fuel flows at the programed pulse width for that engine cycle. Seems like you can ohm injectors until the cows come home yet never check the other 2/3 of potential problems so a pretty poor evaluation in the end. How does the ohm meter find a bad filter or varnished mechanical parts?

 

It doesn't. A resistance check only finds the injector that is failing electrically.

 

.....and a resistance measurement only finds gross coil failures. You can have a turn to turn short in the coil and an ohmeter will not find that, and this turn to turn short will do serious damage to the operation of the injector. If you were to use an impedance bridge to measure the coil inductance and Q, you can easily find a turn to turn short. I did, the resistance was identical to the others but the inductance and Q were half the other injectors.

 

lets make it real simple. If you have WET COIL design injector 89-93 multecs and they ohm out at less than 10, they are no good. So who really cares about the mechanical part at that time. There is NOTHING you can do with that injector. It has to be replaced. PERIOD. So if you have all 8 injectors that test well with a simple ohm meter, then there is something else that has to be checked, ie mechanical s etc. But, let me reiterate, if the ohm meter shows a bad coil, its bad. This test is the first thing you should do on a 89-93 thats running poorly or has a no start, no pulse. Every week at least 1 to 5 guys on this forum has an injector problem, each time if its a multec they are in the low readings. This test is free, and you can do it yourself. So why not eliminate the common problem first. JMO

 

What I am suggesting is just because they pass the ohm test it does not mean they are good just that the coils are not bad..
Dave

 

And what you are suggesting is EXACTLY RIGHT! With the Resistance Test you can determine that the coil is good, but you are not CONFIRMING that the injector is working properly.

It is much like a visual check on a fuse. You can determine that a fuse is BAD by looking at it, but you can't determine that it is GOOD with a visual check. If the fuse filament is visibly broken then the fuse is DEFINITELY BAD! If the fuse filament LOOKS GOOD, the filament can still be separated where you can't see it.

The same with an injector. As FICINJECTOR says, if the coil is bad, the injector is bad, end of story. That is correct, BUT just because the coil is good does not 100% guarantee that the injector is good. Now, it COULD be that there has never been a case where a failed injector did not show up with a bad coil, but I have had them stick before. In that case it doesn't matter whether the coil is intact or not.

This is why, in the case of a dead cylinder miss, I don't even bother with a Resistance Test. I use a Stethoscope to listen to them. If an injector is making a distinct clicking sound I know that the injector is "working." This does mean that it is clean. It does not mean that it is applying the correct pressure or pattern. It does tell me that it's "working."

If they are all working, it still might be time to change them. If the engine is not running as well as it used to or if fuel mileage is suffering, then an Ohm test might show a few that are not in balance with the others. If the injectors are dirty or not popping at the right pressure, you really don't have any other way to tell.

The GOOD NEWS is that these vendors that are now refurbishing injectors are making it economical to replace them almost on a preventive maintenance basis. If the engine isn't running right or fuel mileage is off, you've already checked the basics and suspect that the injectors could be the cause and they haven't been replaced in a while, then quality rebuilt injectors are most likely money well spent.

Doc

 

Exactly,

The Ohm test doesn't tell you everything BUT, it is a Quick and Easy place to start the diagnosis.

 

Can someone explain how to ohm test 94 LT1 injectors please?.

 

Disconnect each injector electrical connector and use an ohm meter across the injector connector pins to measure resistance in Ohms. You should see something on the order of 16 or 17 Ohms and they all should be about the same.

 

There is a simpler test that requires no tools at all just a working tach and one hand. Pull each injector connector one at a time and note rpm drop.. it might be the injector plug wire or a few other things but you will know what hole is not pulling its own share of the work nneded to stay running well.. Here is the deal lets say all injetors pulled one at a time drop idle 100 rpm but #5 that means that cylinder is not working so pull plug and inspect if fouled check wire and cap if not do compression test and leak dow if seems borderline ok the check valve lift and lash if ok I would bet a bad injector. It is a divide and conquor sort of thing. and yes pull IAC plug so it does not open to fix the idle speed..
Dave

 

Thanks, the car wont start and has been sitting a long time. I do have fuel to the rail but I don't know if I have spark as well.

 

Use your timing light while someone cranks to see if you have spark and spark at the right time!

 

If an injector Fails the Ohm test, Why bother doing any other tests since the injectors performance is already in question.

 

Yep, just drop a measley $170 bucks to replace 15 year old ancient inferior technology with that of the 21st century via the most reputable injector dealer on the planet, Jon of FIC, and forget about injectors being a problem.

Or spend a bunch of time farting around.