LT1 Fuel Injection Problem, already tried LT1 Tech ... HELP ASAP
08-02-2003, 08:40 PM
#1
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Join Date: Apr 2003
Location: Pgh, PA
Posts: 2,628
LT1 Fuel Injection Problem, already tried LT1 Tech ... HELP ASAP
MODERATORS, I have posted for this a few times in the LT1 tech and I think this would be a more suitable area since i'm getting no reply's there.
I have a 95 LT1 Z28, its OBD I . The injectors are not functioning rite and i am lost as to what to do. It was totalled and the engine was pulled to fix the frame back in 96, I installed the engine , everything else on the car is functioning besides the injectors ... Here is what i know
- Only has 13 thousand miles on it.
- The car has sat since 96.
- I was going to syphon the gas but cant get a hose in, so i added 6 gallons of 93 octane, dry gas, fuel injector cleaner, and the water removal treatment.
- It has a brand new Delco Fuel Filter
- It IS getting 45 PSI at the Schrader with the key in the ON posistion, which is an acceptable value for an LT1 which should have between 41 and 47 PSI ...
- It wont try in the least to start, no puffs or anything, none of the injectors are getting the ground pulse.
- It IS getting plenty of spark, it fires up INSTANTLY on starter fluid and will run as long as I continue to spray it in the throttle body.
- The plugs for the injectors ARE in the correct places, theyre all numbered by cylinder so...
- I attached a ground strap from the firewall to the back of the intake ( Chevy Dealers suggestion )
- Had a Noid Lite on #2 ( As it was the easiest to unplug ) and in 4 to 5 seconds of cranking , the following happened. It flashed Dim once or twice , then the flash brightened for a couple flashes, then went out.
- I checked several more of the injector plugs with a test light today and no flash while cranking it.
- I checked All the injector plugs with a voltmeter and all of them are getting 12.2 Volts.
- I checked the plug portion on the injectors with an Ohm meter and they all read 12.2 to 12.3 Ohms of resistance. My Haynes manual calls for between 11 and 14 Ohms so this is acceptable as well.
- I held a large screw driver up against the metal portion of the injector while my Dad cranked it, I had my ear against the other end and heard ABSOLUTLY NO clicking or any sort. I tried this for a few of the injectors.
- The car is throwing a SES code ( Which may be related to me not havin all the plugs hooked up for the lights ( Front Nose is off )) but I dont have a scanner, nor can i have the car towed to my cousins shop to check it on his computer.
The injectors are suppose to be getting a grounding pulse from the PCM to alow the injector to open and spray. It clearly isnt getting this ground pulse since the Test/Noid Lights arent lighting when it is being cranked. What all can cause it to NOT get the ground pulse from the PCM ???
This is driving me insane and there is NO WAY all 8 injectors are bad. Also I cant see the PCM being shot because it also only has 13K on it, and it seems to work fine with every other funtion. Does Anyone have a suggestion? I am willing to try just about anything, Please help ...
I have a 95 LT1 Z28, its OBD I . The injectors are not functioning rite and i am lost as to what to do. It was totalled and the engine was pulled to fix the frame back in 96, I installed the engine , everything else on the car is functioning besides the injectors ... Here is what i know
- Only has 13 thousand miles on it.
- The car has sat since 96.
- I was going to syphon the gas but cant get a hose in, so i added 6 gallons of 93 octane, dry gas, fuel injector cleaner, and the water removal treatment.
- It has a brand new Delco Fuel Filter
- It IS getting 45 PSI at the Schrader with the key in the ON posistion, which is an acceptable value for an LT1 which should have between 41 and 47 PSI ...
- It wont try in the least to start, no puffs or anything, none of the injectors are getting the ground pulse.
- It IS getting plenty of spark, it fires up INSTANTLY on starter fluid and will run as long as I continue to spray it in the throttle body.
- The plugs for the injectors ARE in the correct places, theyre all numbered by cylinder so...
- I attached a ground strap from the firewall to the back of the intake ( Chevy Dealers suggestion )
- Had a Noid Lite on #2 ( As it was the easiest to unplug ) and in 4 to 5 seconds of cranking , the following happened. It flashed Dim once or twice , then the flash brightened for a couple flashes, then went out.
- I checked several more of the injector plugs with a test light today and no flash while cranking it.
- I checked All the injector plugs with a voltmeter and all of them are getting 12.2 Volts.
- I checked the plug portion on the injectors with an Ohm meter and they all read 12.2 to 12.3 Ohms of resistance. My Haynes manual calls for between 11 and 14 Ohms so this is acceptable as well.
- I held a large screw driver up against the metal portion of the injector while my Dad cranked it, I had my ear against the other end and heard ABSOLUTLY NO clicking or any sort. I tried this for a few of the injectors.
- The car is throwing a SES code ( Which may be related to me not havin all the plugs hooked up for the lights ( Front Nose is off )) but I dont have a scanner, nor can i have the car towed to my cousins shop to check it on his computer.
The injectors are suppose to be getting a grounding pulse from the PCM to alow the injector to open and spray. It clearly isnt getting this ground pulse since the Test/Noid Lights arent lighting when it is being cranked. What all can cause it to NOT get the ground pulse from the PCM ???
This is driving me insane and there is NO WAY all 8 injectors are bad. Also I cant see the PCM being shot because it also only has 13K on it, and it seems to work fine with every other funtion. Does Anyone have a suggestion? I am willing to try just about anything, Please help ...
08-02-2003, 10:00 PM
#2
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Join Date: Jul 1999
Location: College Station, Tx, USA
Posts: 219
There is one wire that supplies a common +12 for all the batteries, and the pcm activates an injector by supplying it a ground. First I would check for continuity between the +12 on all the injectors and to the battery.
If that works out then you can pull the pcm plug and check for continuity between the injector ground and its' pin in the pcm. If all that checks out fine I would suspect the injector drivers in the pcm - if you can borrow someone else's pcm try that.
Chris
If that works out then you can pull the pcm plug and check for continuity between the injector ground and its' pin in the pcm. If all that checks out fine I would suspect the injector drivers in the pcm - if you can borrow someone else's pcm try that.
Chris
08-03-2003, 08:46 AM
#3
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Join Date: Apr 2000
Location: Charlotte, NC
Posts: 1,614
It is my guess taht the injectors are locked up. I was just messing with some old injector pulls the other day and most that have sit for a while have locked completely up.
I would take the fuel rail off the car and try to crank... watch to see if fuel comes out of the injectors. (should be a nice cone spray)
would explain why it cranks on intake cleaner
I would take the fuel rail off the car and try to crank... watch to see if fuel comes out of the injectors. (should be a nice cone spray)
would explain why it cranks on intake cleaner
08-04-2003, 10:12 AM
#4
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Join Date: Apr 2003
Location: Pgh, PA
Posts: 2,628
I will pull the rails and check the actual injectors AFTER they are getting the ground pulse to them if it still wont fire. It jsut is not getting the pulse...
Also ...
In another Thread a guy said there is a ground that bolts to the Tranny, where is this located at? I currecntly have the car on jackstands, and i glanced around breifly but didnt see it, then again i didnt have a light eitehr but ... At anyrate where is this ground at on the M6 ?
No
With the key in the ON posistion, it reads a steady 19.3 mV ...
That said, Which grounds are we talking about? Where are the grounds located that this would effect?
Also ...
In another Thread a guy said there is a ground that bolts to the Tranny, where is this located at? I currecntly have the car on jackstands, and i glanced around breifly but didnt see it, then again i didnt have a light eitehr but ... At anyrate where is this ground at on the M6 ?
Have you tried to start it with maf disconnected, or tps??
Real quick see how much voltage (in millivolts) you have at the tps ground(black) wire. It should not excede 10 millivolts w/key on. This will give you a rough idea what shape the PCM's grounds are in.
That said, Which grounds are we talking about? Where are the grounds located that this would effect?
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