Fuel injector resistance testing
Thread Starter
Heel & Toe
Joined: Oct 2001
Posts: 22
Likes: 0
From: davison mi
Fuel injector resistance testing
Anyone know how to identify a week injector with a resistance test ? I tested them hot and cold . Should I be looking for injector to injector values, or
hot to cold values on each injector ? Or wasting my time. Thanks to anyone
willing to take the time to share some info....
hot to cold values on each injector ? Or wasting my time. Thanks to anyone
willing to take the time to share some info....
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Fuel injector resistance testing (rd91)
I've read that some injectors have 15Ohms and others maybe 9Ohms. The key is to look for discrepency between injectors, they should each measure about the same value.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Fuel injector resistance testing (rd91)
The coil has to be in pretty bad shape to be able to find a bad injector by measuring its d.c. resistance. I suspected injectors for a rough run problem and I measured the coil inductance and "Q" with an impedance bridge and found one that had a "Q" of 1/2 all the others (lossy coil). I replaced the injector, but it didn't make any difference. The problem was something different, but I am sure that that injector coil had internal turn to turn shorts and replacement was necessary.
Burning Brakes
Joined: May 1999
Posts: 760
Likes: 1
From: Greenwich, CT
Re: Fuel injector resistance testing (rd91)
1. Seems to me the DC resistance was supposed to be more like 16-18 ohms, lower is bad.
2. I agree that even though the resistance checks OK the injector can still be plugged or leaking.
3. There are test procedures in the Helms manual to check the injectors - but you have to take the fuel rail up to run the tests.
4. Once you have gone that far with your labor, you might just as well put in new ones and be done with it - I think Jegs sells SVO injectors for about $200/set - it's less work in the end than trying to diagnose/fix the old ones. TLD sells GM 'O' rings for the injectors which I believe are thicker than the SVO parts - I made the switch last summer to correct a tuning problem, worked out great.
HTH
drj
Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
Re: Fuel injector resistance testing (DOCTOR J)
Injector resistance check is an inexpensive first check if you suspect an injector problem. For an L-98, value cold should be around 16-17 ohms, hot will be a little lower but also be consistent, i.e., they should all drop approximately the same amount hot from their cold values. Values of 10 or less should be replaced. If you suspect that the injectors are giving you a problem, and the resistance values check, then you must move to a balance test.
For background, the resistance can be reduced for several reasons, including too much injector cleaner, but the net effect is the break down of the insulation on the coil.
For background, the resistance can be reduced for several reasons, including too much injector cleaner, but the net effect is the break down of the insulation on the coil.
