No injector pulse
10-02-2018, 11:40 AM
#1
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No injector pulse I have an after market harness for Lt1 engine built by Street and Performance. I have no pulse to the injectors. I have 12vdc to red at injector, in fact on both sides of inj. Checked from inj to ecm and hav continuity on both right and left banks. I hav checked ice harness and hav 12vdc on a and d, 3 vac on b, and .2. ohms key off and 7 ohms key on on c. On Opti harness I hav 5vdc on a and, once hav 12vdc, on d show 14.2 ohms w key on and .3 ohms w key off. Hav over 30 psi on oil, over on fuel pressure. Only way engine will run is if Isquirt fuel in throttle body then dies. Oh yes, checked injectors with noid light, no pulse. This motor has not run since rebuild prob 7 yrs ago. Harness is that old or older but still in original box. I don’t no what else to ck. Was wondering about how to ck on vats disable. Any help would be appreciated. Thanks Jesse
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10-02-2018, 01:43 PM
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It's a stock ecm, I don't know the # it's the one w/ the 4 square plugs not the rectangular [ it's like the 92's] Yes. I tried to retrieve the codes by paper clip in upper two holes but won't even give me the 12 12 12 to start.
10-02-2018, 07:29 PM
#11
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VATS is a box (Theft Deterrent Module or TDM) and the ECM. They both combine to disable/enable the engine. The Theft Deterrent Module reads the resistance value in the key, and if it matches what it's programmed to receive it allows the starter to enable (via the Theft Deterrent Relay or TDR) and sends a signal to the ECM to enable fuel.
The fuel enable signal is a frequency signal. So you can't just send a ground signal to the ECM to enable the injectors, it has to be a specific frequency to the ECM to enable the injectors. 50 hz ground signal according to ShBox.com.
You can easily get the starter to engage by grounding the yellow/black wire from the TDR, or jumping the Yellow to green wires together at the TDR. But, in order to enable the fuel injectors you'll need to install a TDM bypass module to replicate the 50Hz signal to the ECM or program VATS to off in the ECM tune (you'll need a new chip for a 1993 PCM).
If you need the Schematics let me know and I'll send them your way.
The fuel enable signal is a frequency signal. So you can't just send a ground signal to the ECM to enable the injectors, it has to be a specific frequency to the ECM to enable the injectors. 50 hz ground signal according to ShBox.com.
You can easily get the starter to engage by grounding the yellow/black wire from the TDR, or jumping the Yellow to green wires together at the TDR. But, in order to enable the fuel injectors you'll need to install a TDM bypass module to replicate the 50Hz signal to the ECM or program VATS to off in the ECM tune (you'll need a new chip for a 1993 PCM).
If you need the Schematics let me know and I'll send them your way.
10-02-2018, 08:09 PM
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Wow, what a good explanation. Thanks! I would appreciate it if you would send me the diagrams. Not knowing if this computer has been reprogrammed to remove vats, I think I will send it off to be reprogrammed or see if I can get a new chip for it with vats removed. You don't have any leads on a place to that done do you? Is this what you would do? I think this is the next step to figuring out what's going on, don't you? Thanks again!
10-03-2018, 03:37 PM
#14
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My site does say 50 Hz, but the site disclaimer reminds the reader that the site is based on the 1995 model year, unless otherwise noted. I have updated/added information that says the signal frequency is 30 Hz for 1993's. Been meaning to do that, but always forget.
shbox.com should have all the schematics needed.
shbox.com should have all the schematics needed.
10-04-2018, 01:31 AM
#15
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Wow, what a good explanation. Thanks! I would appreciate it if you would send me the diagrams. Not knowing if this computer has been reprogrammed to remove vats, I think I will send it off to be reprogrammed or see if I can get a new chip for it with vats removed. You don't have any leads on a place to that done do you? Is this what you would do? I think this is the next step to figuring out what's going on, don't you? Thanks again!
See attachments for the schematics.
Out of the LT1 game for a while. Life got in the way. LOL.
My site does say 50 Hz, but the site disclaimer reminds the reader that the site is based on the 1995 model year, unless otherwise noted. I have updated/added information that says the signal frequency is 30 Hz for 1993's. Been meaning to do that, but always forget.
shbox.com should have all the schematics needed.
shbox.com should have all the schematics needed.
10-08-2018, 03:58 AM
#16
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If VATS is enabled in the ECM you will still get 4-5 seconds of injector pulse when first cranking the engine, just enough for the engine to fire but not start, a noid light will show if you are getting the first couple of pulses before VATS shuts down the injectors. I've used both the early memcal batch fire and later sequential fire ECMs and had the 4-5 second injector pulse with VATS still enabled.