love-my-V8-280Z Posted September 26, 2004 Share Posted September 26, 2004 Anyone, I'm ready to hear my 95 LT1 run but for some reason the PCM does not ground the injectors. I have double checked every hot and ground wire to the PCM and they are fine. made sure things were correct when key was in start mode also... When I spray fuel in the intake it pops and bang something horrible! I do not have the raditor hooked up or the VSS. but I can view the PCM useing tunercat and I have uploaded some changes such as disabling the VATS and the EGR..... I double checked all my spark plug wires, I received only one data code, it was for throttle opened to far or something like that, I did put the petal to the floor thinking I may have flooded it. I have power the injectors, but when I check the ground at them while turning the motor over nothing.... Any advice anyone??? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted September 26, 2004 Share Posted September 26, 2004 According to my local dealership tech., the engine to chassis grounds are very important. I even ran 2 extra ground wires from the intake (2 rear bolts) to the chassis. Try that...... Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 27, 2004 Author Share Posted September 27, 2004 Thanks Tim, do you know what drives the injectors? I would guess a crank shaft senor or something like that? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted September 27, 2004 Share Posted September 27, 2004 There is no crank sensor. Everything runs from a signal from the optispark distributor. Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 27, 2004 Author Share Posted September 27, 2004 Tim, What do you think about the poping and banging when I shot fuel in the intake? I have spark, could my optispark be bad and do you know how to check it? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted September 27, 2004 Share Posted September 27, 2004 Check the basics: Plug wires routed correctly and not arcing or in bad condition (LT1s are very sensitive to spark breakdown) Make sure you have fuel pressure (invest in a pressure gauge that screws into the shraeder valve on the rail) If the opti is going out, you will usually have a slight miss at idle and a hesitation under load...it should at least fire unless its completely bad) Check for vacuum leaks. Make sure that all unused ports are plugged, esp. at the throttle body. Try unplugging the MAF, and let the PCM default to speed density. That way if you do have a leak somewhere the PCM can account for the extra air. Tim Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 27, 2004 Share Posted September 27, 2004 #1. Flooring the gas or holding the throttle plate all the way open on a fuel injected engine will turn off the injectors. What is your TPS voltage when the throttle is fully closed, engine off. It should be at about .5 and no less than .23V or it will set a code. When I installed the my 58MM Holley TB I had to round out the holes on my TPS sensor to get it back down to .3V so that it would stop setting the Code 21(TPS too High). Heres what I suggest. Go to http://www.alldatadiy.com and buy a subscription for a 1995 Camaro with the 5.7. Its way better than a Haynes and it gives trouble shooting info and lots of pictures. Its $25/year for your first car and $15/year for any car after that or for resubscriptions. IMHO its money well spent. I would have spent way more time screwing around on forums asking questions and not getting the info that I need to get my LT1 running like it should if I hadnt have bought that subscription. Trust me on this one! I could give you the info for a 93' LT1 but the injection system isnt wired the same because the 93' is bank fired and not sequentail fired like yours is. Guy Quote Link to comment Share on other sites More sharing options...
Tim240z Posted September 27, 2004 Share Posted September 27, 2004 Go here: http://shbox.com/1/4th_gen_tech1.html One of the very best diagnostic LT1 sites out there. Tim Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 27, 2004 Author Share Posted September 27, 2004 Guy, THANKS. Im at the web site now, and yes the is the only code I got... You might have just solved my problem.. I will be checking my volts tomorrow... Thanks again... Terry Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 28, 2004 Author Share Posted September 28, 2004 Well, still no go, checked out my tps and its perfect.. I cleared the codes and tried to start it again and still not grounding of the fuel injectors by the computer... No codes either... The no codes stumps me, that must mean everything is working as it should.. now I have read the VATS will do this but I disabled the VATs using tunercat and even downloaded the file after uploading it and it showed me I had the vats box unchecked! ???????????? Bad computer? Does anyone think this could be the case? Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 28, 2004 Share Posted September 28, 2004 Now when you used TunerCat to change stuff in you PCM you didnt mess with the injector settings, did you? I am not familiar with TunerCat because I cant use it on my LT1. With TunerCat all you do is go in and change stuff to the original programming and then save it as another file correct? Or do you have to make a program then download it on to the PCM? Guy Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 28, 2004 Author Share Posted September 28, 2004 It first reads the PCM and than you have a copy, than you change that copy and upload it., It erases what is in the PCM and writes your upgrade. I did not change much at all,, A lot of things on the computer seem to be working fine, I pulled the fuel rail out and watching the injectors nothing happens... Disabled the vats, egr and the a/c stuff Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 28, 2004 Share Posted September 28, 2004 Well I dont know if this will apply to you but I have "flashed" aka reprogrammed PCMs at work and sometimes the program doesnt get fully downloaded and the vehicle will not run because the programming is not complete. You could try downloading it again? (or have you already tried this?) Can you watch the sensors with Tunercat hooked up the DLC? Kind of like a scanner? Guy Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 28, 2004 Author Share Posted September 28, 2004 I down loaded what I had already uploaded and it looked fine. Also I have been running datamasterEE to see the data codes and I can run the program while the car is turning over.. it even collects a graph while turning over... My fuel pump does the 2 sec run once in a while when I turn the key on and off, not everytime just some times, seems like that is a good sign.. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted September 28, 2004 Share Posted September 28, 2004 You can use Freescan to datalog....doesn't help if the thing won't run though..... Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 28, 2004 Author Share Posted September 28, 2004 Tim, I tired freescan and all it would do is go in is odd loop, just sit and scrool a couple commands over and over very fast.. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 28, 2004 Share Posted September 28, 2004 Ok so you are getting power at the injectors. (check with a volt meter or test light) You should have power at the pink wires on the injector harnesses. Make sure your oil pressure sensor is hooked up and working. The PCM will run the pump for 2 seconds then if there is not atleast 4 psi of pressure on that switch or if the switch is bad it will not turn on the fuel pump. As a backup system to the fuel pump relay the fuel pump also can be energized by the fuel pump switch and engine oil pressure sensor. The sensor has two internal circuits. One operates the oil pressure indicator or gage on the instrument cluster, and the other is a normally open switch which closes when oil pressure reaches about 28 kPa (4 psi). If the fuel pump relay fails, the fuel pump switch and engine oil pressure sensor runs the fuel pump. An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump switch and engine oil pressure sensor energizes the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi). If your not sure if your oil pressure sensor is ok then just jump I beleive the orange and the black wire. There is only 3 wires there. Just jumper 2 of the till you hear your pump turn on. Then try to start the car. Also make sure your fuel pump is running when you are cranking the engine over. Fuel Delivery Modes MODES OF OPERATION The Powertrain Control Module (PCM) looks at voltages from several sensors to determine how much fuel to give the engine. The fuel is delivered under one of several conditions called modes. All modes are controlled by the PCM and are described below. Starting Mode When the ignition switch is turned to the "ON" position (before engaging starter), the PCM energizes the fuel pump relay for two seconds allowing the fuel pump to build up pressure. The PCM first checks speed density, then switches to the Mass Air Flow (MAF) sensor. Engine Coolant Temperature (ECT) , Throttle Position (TP) , and Manifold Absolute Pressure (MAP) sensors are also used to determine the proper air/fuel ratio for starting. This ranges from 1.5:1 at -36°C (-33°F) to 14.7:1 at 94°C (201°F) running temperature. The PCM controls the amount of fuel delivered in the starting mode by changing how long the injectors are energized. This is done by pulsing the injectors for very short times. Clear Flood Mode If the engine floods, it can be cleared by pushing the accelerator pedal down all the way. The PCM then pulses the injectors at an air/fuel ratio of 20:1. The PCM holds this injector rate as long as the throttle stays wide open and the engine speed is below 300 RPM. If the throttle position becomes less than 80%, the PCM returns to the starting mode. RUN MODES The run mode has two conditions called "Open Loop" and "Closed Loop." Open Loop When the engine is first started, and engine speed is above 400 RPM, the system begins "Open Loop" operation. The PCM ignores the signal from the HO2S and calculates the air/fuel ratio based on inputs from the ECT, MAF, MAP, and TP sensors. The system stays in "Open Loop" until the following conditions are met: Both HO2S have varying voltage output, showing that they are hot enough to operate properly (This depends on temperature.). The ECT sensor is above a specified temperature. A specific amount of time has elapsed after starting the engine. Specific values for the above conditions exist for each different engine, and are stored in the Electrically Erasable Programmable Read Only Memory (EEPROM). When these values are reached, the system begins "Closed Loop" operation. Closed Loop In "Closed Loop," the PCM calculates the air/fuel ratio (injector on-time) based on the signal from various sensors, but mainly the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1. ACCELERATION MODE When the driver pushes on the accelerator pedal, air flow into the cylinders increases rapidly, while fuel flow tends to lag behind. To prevent possible hesitation, the PCM increases the pulse width to the injectors to provide extra fuel during acceleration. The amount of fuel required is based on throttle position, coolant temperature, manifold air pressure, mass air flow and engine speed. DECELERATION MODE When the driver releases the accelerator pedal, air flow into the engine is reduced. The corresponding changes in throttle position, manifold air pressure, and mass air flow are relayed to the PCM, which reduces the injector pulse width to reduce fuel flow. If the deceleration is very rapid, or for long periods (such as long closed throttle coast-down), the PCM shuts "OFF" fuel completely to protect the warm up three-way catalytic converters. BATTERY VOLTAGE CORRECTION MODE When battery voltage is low, the PCM compensates for the weak spark delivered by the distributor by: Increasing the amount of fuel delivered; Increasing the idle RPM; and Increasing ignition dwell time. FUEL CUTOFF MODE To prevent possible engine damage from over-speed, the PCM cuts off fuel from the injectors when the engine speed is above approximately 5500 RPM. To prevent tire damage on vehicles equipped with base tires, the PCM also cuts off fuel from the injectors at vehicle speeds above 108 mph. More and more I am leaning towards the oil pressure switch/sensor. Guy Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 28, 2004 Share Posted September 28, 2004 Ok I take that back feed power, on the oil pressure sending unit connector, to the gray wire. That should turn on your fuel pump. Guy Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted September 28, 2004 Author Share Posted September 28, 2004 Guy, Whats this talk about the oil sending unit? I do not have it hooked up. I thought it was for the gauges only.. Could this be my problem? I don't see a spot to hook it up at the computer. I have fuel pressure, I have not checked it because what I have found is that the computer is not grounding the fuel injectors... The fuel injectors are feed 12 volts, that is there, when the computer needs them to fire it grounds out the injector. I checked continuity from the injector ground side to the battery ground and turned the key, the meter never moved... Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 28, 2004 Share Posted September 28, 2004 If you do not have oil pressure sensor/switch hooked up this could be your problem. After the initial 2 seconds that the fuel pump is on the computer will only turn on the fuel pump & maybe the injectors also if the computer "sees" 4psi from that sensor. Let me see what I can dig up on as far as a wiring diagram.... Guy Quote Link to comment Share on other sites More sharing options...
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