Hello,
Does anybody know the proper way to test the injector harness on a 89 c4?
I have the node test light and have had several attempts to test the lines. I start the vehicle and the light just dims a little, is it supposed to blink on and off? Also is the light supposed to be on when I turn the ignition switch to acc or right before crank? It does not make sense if the injectors are activated then the latent fuel pressure in the rail would just drain down. Some advice would be greatly appreciated.
Thanks

 

When the engine is running, I would imagine the electrical pulses to the node light are fast enough that the light is going to give an average value of light. I would think you would just want to crank the engine without starting it to see it flash.
Except for the LT5, which was always sequential fire, Corvettes before '94 had batch fire injectors, after that they were sequential fire. With batch injection, all the injectors on each bank fire at the same time -- there are only two injector drivers in the ECM. Sequential fire has an injector driver for each injector.

Tom Piper


[Modified by Tom Piper, 8:16 PM 7/1/2003]

 

If the light connects between the injector and ground it will glow with ignition on and go out when the injector is pulsed as the ECM pulls the line to ground to pulse current to enerjize the injector.

But at idle of say 600rpm the injector is pulsed at 5Hz so, which is likely to fast to see a blink.

You can also test the static resistance of each injector unplugged to see if all are in the same range.

 

injector harness,not injectors.
plug in the noid light, and crank the engine for a few seconds. A STEADY or NO LIGHT indicates a malfunction.
(plager alert) :cheers:

 

I just replaced my injectors so while this is fresh in my mind, I may be able to offer a little input.

The best way is to begin by recording the BLM and Integrator numbers your ECM is outputing by using a scan program like DataMaster,WinALDL,Ease oven AutoXray.
Everybody doesn't have this stuff so we'll go on to the 'normal home mechanic' methods.

You still must have a minimum of equipment like a good ohm meter. Doesn't matter if it's digital or analog.

Here's some simple procedures that will work for you:


1) Use an Ohm meter and check the resistance of EACH injector.
They should be in the range of 16 to 17 ohms.
If you find one that is a lot different (in my case 10 ohms) then that's a sure sign the injector needsd to be replaced. It "may" still work somewhat but it's not going to work much longer.
Since this IS a batch fire system, one bad injector can affect the whole bank.
This is an EASY test and the first thing to do.

2) Connect a fuel pressure gauge to the fuel rail connector. Turn on the key (do not start engine) and check the fuel pressure. Turn off the key and wait 5-10 minutes. Check the FP again. It should NOT have leaked down in that period of time. If it DOES then you have a leaky injector OR fuel is leaking back thru the pump check valve.

3) Actron makes a relatively inexpensive fuel injector system testor that will actually pulse or activate an injector for a precise amount of time.
Go and purchase one with tne money you're going to save by doing this yourself. (about 60-75 bux) Less than the cost of one injector from the dealer, btw.
Connect the testor to the injector you want to check.
Leave your FP gauge connected. Turn the key on (10 seconds or so) (do not start) and then turn the key back off.
Puilse the injector with the tester and then see how much the FP dropped.
Check each one and record the value.
This is called an 'injector balance' test and is performed to see (in a not so scientific way) if all the injectors release the same amount of fuel.
If one is way different then it's a bad one.

4) If they have over 100,000 miles on them go ahead and get a whole new set. It's time to replace them as a general maintenance item.

Hope this helps.



[Modified by VetNutJim, 8:55 AM 7/2/2003]

 

Thanks for all the info, Have already done testing on the Injectors themselvs, they are fine. I am getting a steady lite on all the harness plugs when the ignition key is on. We had replaced the computer as we had a spare and the condition did not change. Is there any sensor or controllere that would make the ecm send a signal like this? One person I spoke to said it could be the Water temp sensor. I can chage it or check the resistance values, any other systems Ineed to look at?
Thanks again