Join Date: Mar 1999
Location: The Island of Luzon
Mentioned: 7 Post(s)
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"We checked everything from the fuel pressure and followed all the steps in the FSM bible still losing negative pulses from the injectors going to ecu."
Your mechanic is....uh....
I'll be charitable here and say you should find another one as he's feeding you a line of BS and does NOT know how the system works.
1) Buy a NOID light.
2) Go to Radio Shack and buy a can of Freez-It
3) The very next time it dies, pull the coil wire out of the center terminal of the distributor. Crank the engine. You will either have spark, or not.
If you do NOT have spark, you WILL NOT get fuel (ECU triggers firing of injectors every third pulse of the coil) Take the the can of Freez-it and blast your igniter. It should then have spark. If not, then the reluctor in your distributor is bad, or the connections between it or the igniter are bad.
Secondary test at this point, plug in your NOID Light and ground the negative terminal of the coil with a short wire jumper against a bare metal ground with the ignition on...the NOID Light should light every third tap. If it does not, see below.
If you DO have spark, plug in your NOID Light and see as you crank it, or as you do the above test that the NOID Light flashes every third spark.
If it does, the injectors may be bad, there may be a fuel issue, but the functionality of the circuit is intact.
If it does NOT flash every third spark produced, check the connection on the blue wire in the left kick panel that pigtails out of the main harness and goes into the ECU Harness. It's this wire that takes the gating signal from the coil to the ECU so it can count "1-2-3-PULSE-1-2-3-PULSE"
If the signal is there, then your ECU is overheating and needs replacement. Check your battery voltage, if you are chronically discharging your car through high electrical draws, the voltage can drop and roast the ECU, it's ground needs to be good or you roast the ECU, if the diode pack in your Alternator is going out and you see faint flickering of your lights, that car roast your ECU.
In short, injector pulses depend on spark pulses. If there is no spark pulse (no spark) there will be no fuel. The most common thing that causes this is an igniter or reluctor going bad. I don't care if you replaced them, it appears you have skipped VERIFYING they work when the problem is present.
This is a very basic system, there is no "negative pulse from the injectors to the ECU"
There is a gating pulse from the COIL to the ECU, and on every third one of those, the injectors get a ground and fire.
I make the ASSUMPTION you have verified your EFI Fusible Link for power to the injectors, as if it overheats and gets resistance, the injectors will not have the power necessary to pull in the solenoid and fire.
Verify what you THINK is "good" before skipping onwards in a rabbit hole wild goose chase searching for a "negative pulse from the injectors to the ECU" which does not, never has, nor ever WILL exist.
All signals originate on the distributor, coil, and ECU. The injectors are stupid solenoids that open when supplied with power from the fusible link, and which ground through the ECU.
If the ECU is not grounding, it's either bad, or it's not getting the imp put from the coil.
What has been will be again, what has been done will be done again; there is nothing new under the sun -- that means
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If I throw a dog a bone, I don't want to know if it tastes good or not. -- Brick Top
Canadians don't get it. Period. End of discussion.