hart7631

ok so ive been having problems trying to start this 89 firebird i just bought, i put a new column in it bcuz it didnt have one and it didnt have a key so i made up all 15 resistor combinations and i found one that if i plug in it will let the engine crank but im still not getting signal from ecm to fire injectors. is there a way to test if the pass key module is good? and if its sending power to the ecm? and could this be the starter enable relay doing this? thanks!

CamaroRider

Try these tests and tell us what you find:

Turn off the air conditioner (if you have one) and the blower vent so that they do not block any sounds.

Turn the ignition key from OFF to RUN (but do not CRANK the engine).
Did you hear the fuel pump fun for two seconds?

If you did hear the fuel pump run for two seconds then turn the ignition key from RUN to CRANK (but just for a second). Then let the key fall back into the RUN position. Did you hear the fuel pump run for another two seconds when the key fell back into the RUN position?

hart7631

yes and yes fuel pump is working just nothing coming out of injectors

danielmonster

If the car won't crank with other keys, but will crank with this particular key then the pass key module is working. Also, the module won't stop the injectors from firing. Your problem lies elsewhere.

Get a wiring diagram for the fuel system and start in the middle.

CamaroRider

The first test tells us that the fuel pump relay and ECM are working together for that change from OFF to RUN. And you hear the fuel pump so the fuel pump motor is being energized. This does not mean the fuel pump is providing the correct amount of pressure to the carburetor. But the result of this first test is good.

The second test, I am told, tells us that the ECM is successfully reading DRP (Distributor Reference Pulses I believe) from the distributor. In other words, the ECM has detected the distributor is actually spinning during the CRANK phase. This is good.

If you are getting spark during the crank mode, that is good.

If you cannot detect any fuel squirting from the injectors then I would suggest that you use any tool you have to try to tell if the injectors are being told to fire by the ECM. Look in the forums to find out how others are testing for this on an engine like you have (I do not know what you have). Generally you can use a NOID light or oscilloscope, etc.

If you do find that the ECM is sending the correct pulses to the fuel injectors but the injectors are not spraying fuel then maybe the fuel pressure is way too low to cause a spray OR the fuel injectors are NOT firing (opening) at all.

If they are NOT firing (opening) then I would suspect the fuel injectors are 'stuck closed' due to not being used in a long time. Maybe someone has a way to free them that is easy. If it is a TBI system with two injectors mounted in the carburetor then they could be removed and cleaned in carburetor cleaner. They can then be cycled with about 6 volts across the injector terminals to try to free them up. If they begin to open and close you will hear them click when energized with 6 volts.

Let us know what you discover.

hart7631

ok so i put a voltage tester on the injectors and a test light and i didnt get the slightest bit of power coming off the blue and green wires that lead to the ecm. the wireing looks clean from where i can see it so i dont think they are grounded out

hart7631

is there any other electrical issues that could be telling the computer not to send a signal to the injectors besides pass key ? im lost

CamaroRider

Sounds like you have a TBI like mine with two injectors.

With your test equipment find out if the red and the white wires measure +12 volts (compared to ground) with the key in the ON position. Those normally are a constant +12 volts at that time. Then the ECM grounds out the green and blue wires to allow current through the injectors to fire the appropriate injector.

You can also pull off the injector harnesses and jumper across the two pins of each injector with six volts (just to be safe) (polarity does not matter) and if they are functional they will make a clicking sounds when they open and when you remove the six volts they will make a clicking noise when they close. When mounted in the carburetor they might not be as loud as they would be if they are removed. If they show some kind of life then that is good.

One idea is that the NSS (Neutral Safety Switch) located in the console at the base of the gear select lever might be telling the ECM that it it NOT in neutral and NOT in park. The ECM would then prevent the car from starting (the injectors would not fire).

Maybe someone else has some ideas. I do not have a 'flow chart' for the ECM so I cannot denote each requirement for the injectors to fire. But that is my quest because I see so many problems like this showing up.

My point above about the 'second test' was that if your ECM is detecting the DRP pulses then your VATS (security key system) is probably working correctly. If your VATS system was wired properly you should see some changes in the dash light associated with the system when you turn the key to the ON position (I believe). Here is information on the VATS system. There is mention of the dash light in that piece.

https://www.thirdgen.org/vats_passkey_system

hart7631

ok so i hooked the 6v up to both injectors and they both click. now you said i should be getting 12v from the red and white wire i put the multimeter on it and got 16.7 from both? what does this mean

CamaroRider

The red wire and the white wire are coming through a fuse and should have +12 volts on them compared to ground. Please double check. I do not know where you would be getting 16 volts. But the fact that your are able to click the injectors with 6 volts means the injectors COULD fire if the ECM did its part. In other words, the injectors are capable of being fired and will fire. So we are back to finding out why the ECM is NOT firing them.

hart7631

my bad im an idiot it was reading 16 volts because i had the battery charger pluged in. haha they both read 12 volts.

CamaroRider

Reading back on your previous post, you stated:

''I put a voltage tester on the injectors and a test light and I didnt get the slightest bit of power coming off the blue and green wires that lead to the ecm''

The green and the blue wires will have voltage on them ONLY when they are attached to the injectors. The voltage from the red and the white wires will pass through the injectors and exit in the green and the blue wires and go back to the ECM. When the ECM 'fires' it is actually GROUNDING the green and the blue wires (when appropriate), causing current to go through the injectors which 'fires' them physically (allows fuel to pass through). And these pulses might be as short as 1.5 milliseconds, so it can be a very short flicker on any meter. An oscilloscope would show the pulses when set up properly.

Now are you sure you have enough pressure in the fuel system to actually SPRAY the fuel when the injectors open? Inadequate pressure will not allow the fuel to spray.

If you can monitor the green or the blue wire while they are attached to the fuel injectors and while cranking the engine and you see a flicker in the voltage (it is best to use an oscilloscope because the pulses to ground are very short) then the injectors are indeed firing and your problem might be inadequate fuel pressure.

CamaroRider

In my testing, I took two 'finishing nails' with heads about the diameter of the fuel injector connector contacts and placed them inside one of the fuel injector plug harnesses. Let us say we are using the GREEN and WHITE injector harness. I placed electrical tape in between the nails to hold the nails parallel and give some insulation protection. Then I used clip leads to go from the nail points to the injector connectors (CAREFUL: there is 12 volts being used here, avoid sparks, make it 'foolproof safe' while you are setting this up.) Then I hooked my oscilloscope to the GREEN wire and then I hooked the ground wire of the oscilloscope to GROUND. I then CRANKED the engine and observed the oscilloscope. I saw 12 volts on the GREEN wire before I started to crank, 10 volts on the GREEN wire when I was cranking and I could also see the fast pulse that took the 10 volts to GROUND. So I knew my fuel injectors were being TOLD to fire from the ECM. Maybe you can do this with your test gear. Again, we are looking for the voltage on the GREEN wire to go from about 10 volts during CRANKING to GROUND POTENTIAL. But the pulse is VERY short.

If you see this pulse with your test setup then the fuel injectors ARE being told to fire by the ECM, YOU proved they DO fire with 6 volts, thus the fuel injectors ARE firing, and since you see no SPRAY of fuel you now need to look into a weak fuel pressure problem.

ringo234

Nevermind

CamaroRider

One more thing is that there must be a good ground connection between the ECM and the automobile. The ECM is grounding +12 volts that supplied through a fuse. That +12 volts will be grounded by the ECM at the ECM GROUND. If that ground for the ECM is not perfect you might have many odd problems.

Also, your fuel pump MUST have a perfect GROUND to supply FULL power. Every connection to ground and the battery post terminals must be PERFECT. Ultimately ground is the negative POST of the battery. EVERYTHING else is dependent on CONNECTIONS to that POST. Think about that !! Every CONNECTION that ultimately reaches that negative battery POST must be the best you can possibly make it.
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TBI = ''Throttle Body Injection''

ringo234

Nevermind

hart7631

finally found time to play with the car. am getting no signal from computer to injectors after tests. i did read somewhere that i should be getting 5v from the passkey module to the ecm im only reading 0.7 any ideas?