Polarity Posted August 31, 2008 Share Posted August 31, 2008 Hey guys, got my speedometer installed finally and the dash back in, now the car won't crank. Fuel pump comes on, car turns over. But nothing else happens. I was going to disconnect the speedo later today to see if it starts up again. Just curious if anyone had any idea why this might happen. -polarity *Edit: I guess I should add some details. The car is an 81 ZXT with a LT1/4L60e. Had an Autometer tach already installed and working, I copied what they did with the tach to install the speedo (you can see my project under the Members Projects 280zx area, shows how I cut to make it all fit), wire was already run to hook the speedometer up, do I need another wire back to the ECM to make it crank? Quote Link to comment Share on other sites More sharing options...
deja Posted August 31, 2008 Share Posted August 31, 2008 I don't know how your speedometer works but you need one setup to acept that signal. I am running TransAM gauges in my car and as far as I know the only signal you need is VEHICLE SPEED SIGNAL (VSS) which is the dark green/white wire coming from the PCM B8. I don't understand what you mean by I copied what they did with the tach". I'd check for a blown fuse, maybe you shorted something out during the install. Is your fuel pump running when you turn on the ignition? Quote Link to comment Share on other sites More sharing options...
Polarity Posted August 31, 2008 Author Share Posted August 31, 2008 80LT1 talked me about the gauges that could work, the autometer electric gauges should work fine. As far as copying what they did with the tach, when I purchased the car the LT1/4L60e were installed along with a tachometer that works. I just did the same thing they did with cutting the assembly in order to mount the speedometer. Also I was told to put the wire (VSS) to the speedometer and not the computer, apparently something about signal strength? -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted August 31, 2008 Share Posted August 31, 2008 The VSS is the output from the PCM that makes the speedometer work. Where does the wire from your speedometer go? What did you do with the dark green/white wire that comes out of the PCM B8? I'm thinkig you have the wrong signal connected to your speedometer. Also I was told to put the wire (VSS) to the speedometer and not the computer, apparently something about signal strength? -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted August 31, 2008 Author Share Posted August 31, 2008 OK, I'm home from work finally and I found my first mistake. Didn't pay enough attention to where wires were supposed to hook on the back of the speedometer, hooked the VSS up to the 12v plug. Moved it to proper plug and car cranked fine. Now the car cranks but neither the speedometer or the tachometer are working. Tach jumps when I turn the car to ON, jumps again when cranking, then just sinks to 0 instantly. Speedometer does nothing at all, I thought I only needed the VSS and the ground hooked to the speedometer, does it need VSS/12v/ground to work properly? Of all the things I don't understand, wiring is probably my worst.. Any help would be appreciated guys. -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted August 31, 2008 Author Share Posted August 31, 2008 Sorry didnt see your reply, here is how the wires are currently run. If you remember the original connector on the back of the cluster that is a circle, looks like he has a wire spliced out of there running to the tachometer. Then a wire running from tach to the metal to ground. Don't see a green/white wire inside the car, he told me he ran a wire for the VSS to the cluster. There was 1 blue wire run straight behind the cluster. I hooked that wire up to the SIG input on the back of the speedometer, also hooked a ground to the same place he has the tach ground. I have my digi cam and can snap any pictures if it would help. Sorry for the confusion but trying to understand how someone else wired it is hard, even harder for you listening to someone else describe how another person wired it. Thanks again -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted August 31, 2008 Share Posted August 31, 2008 Do you have the instructions for the speedometer? I would assume you need +12v and ground to make it work plus the VSS signal. You probably have another +12v line for the speedometer light. Its possible you damaged the PCM VSS output by connecting it the the +12v input the the speedometer, I hope not. Why the tach no longer works is not a good sign. Disconnet the speedometer completely and see if the tach still works. OK, I'm home from work finally and I found my first mistake. Didn't pay enough attention to where wires were supposed to hook on the back of the speedometer, hooked the VSS up to the 12v plug. Moved it to proper plug and car cranked fine. Now the car cranks but neither the speedometer or the tachometer are working. Tach jumps when I turn the car to ON, jumps again when cranking, then just sinks to 0 instantly. Speedometer does nothing at all, I thought I only needed the VSS and the ground hooked to the speedometer, does it need VSS/12v/ground to work properly? Of all the things I don't understand, wiring is probably my worst.. Any help would be appreciated guys. -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted August 31, 2008 Author Share Posted August 31, 2008 Yeah I got the instructions, I put the speedo down until I get the tach working properly again. Right now I have it hooked up exactly as it was before and nothing. I don't think hooking it up to the 12v connector on the back could have hurt it as there was nothing but VSS and ground hooked up at the time, then again I'm the one here asking questions. Where is the signal for the tach supposed to come from (it was hooked up when I got it). -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted August 31, 2008 Share Posted August 31, 2008 The tach output from the PCM is on A13 and is a white wire. The problem with hooking the VSS to the wrong connection is possibly the circuit in the PCM is not designed to handle the amount of current the speedometer wiil demand. If the tach output and VSS output come from the same circuitry inside the PCM its possible they are both damaged. Again I hope not, and hope GM designed them right so they could take a shorted output without damage. Yeah I got the instructions, I put the speedo down until I get the tach working properly again. Right now I have it hooked up exactly as it was before and nothing. I don't think hooking it up to the 12v connector on the back could have hurt it as there was nothing but VSS and ground hooked up at the time, then again I'm the one here asking questions. Where is the signal for the tach supposed to come from (it was hooked up when I got it). -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted August 31, 2008 Share Posted August 31, 2008 BTW the another thing that can prevent the speedometer from working after you get it wired correctly is the VSS input to the PCM from the transmission. Make sure this connection on your 4L60E is hooked up. http://shbox.com/page/index.html is an awesome site for LT1 information. Its about a '95 Z28 but not much is different for other years. Mine is a '94 and this site has helped me a lot. Quote Link to comment Share on other sites More sharing options...
Polarity Posted August 31, 2008 Author Share Posted August 31, 2008 Thanks for all your help deja, I still have no luck getting the tach working so for now I'll try speedo and see. I just hooked up with 12v/VSS/ground and the light comes on the speedo now, looks ok. I'm about to try taking it up the drive way to see if it registers as moving. I'll report back and let you know. -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted September 1, 2008 Author Share Posted September 1, 2008 Nothing happens with the speedometer while driven. Looked under the hood, found a green and white cable labeled "VSS OUTPUT", nothing hooked to it. so I'm guessing I need to run a new cable from "VSS OUTPUT" to speedometer, then get under the car and make sure that connector is there. Thanks again for the help, if you have any other things I should try let me know, otherwise I'll report back when that's done (might be a while, supposed to start getting bad weather here soon from Gustav, expecting power outages for a few days so I'll report back when I can) -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted September 1, 2008 Share Posted September 1, 2008 Yeah that needs to be hooked up. Hey man, good luck with Gustav. Gonna be a rough ride, sure hope eveyone stays safe over there. Dale Nothing happens with the speedometer while driven. Looked under the hood, found a green and white cable labeled "VSS OUTPUT", nothing hooked to it. so I'm guessing I need to run a new cable from "VSS OUTPUT" to speedometer, then get under the car and make sure that connector is there. Thanks again for the help, if you have any other things I should try let me know, otherwise I'll report back when that's done (might be a while, supposed to start getting bad weather here soon from Gustav, expecting power outages for a few days so I'll report back when I can) -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted September 7, 2008 Author Share Posted September 7, 2008 Hey all, update time. Traced out the wire that went to the sig input on the tachometer, it comes out of the PCM (white wire just like you said) but has been spliced, looks like that came loose. I removed that piece of wire, put in a new one and ran it to the tach and presto the tachometer started working again. The speedometer on the other hand, still no luck. Ran a wire from VSS output to SIG on the speedometer. Hooked up 12v and ground, lights come on (nothing in the odometer box except the backlight is on) but needle doesnt seem to move any when I drive. Checked transmission to make sure that connector was there, everything looked fine. If I get a program like tunercat can that tell me that the PCM is sending the signal by recording speeds or? I've kind of run out of ideas here if anyone has one please let me know. -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted September 7, 2008 Share Posted September 7, 2008 I hope you soldered that wire that was spliced. I can't believe people trust crimp on connections in a car. As far as the speedometer I don't know if those scanners you can borrow from auto stores would be of any help. If you can get your hands on a LT1 scanmaster that will tell you if the PMC is outputting the right signal. It hooks up to you OBD1 port and will monitor a bunch of stuff. http://www.fullthrottlespeed.com/itemdesc.asp?CartId={39E071EB-D845-EVEREST4159-9DBE-ED9497521159}&ic=050SCANLT1&eq=&Tp= Its expensive for a simple monitor unless you know someone local that has one. Too bad you don't live closer. I picked up one on Fbody.com at a good price. Recheck all your wiring and make sure the line running from the tranny isn't damaged. That cable can get pinched against a Camaro firewall very easily. The donor car I bought had the tranny replaced and that cable was smashed, no wire damaged but the sleeve was crushed pretty bad. BTW there are 2 green/black VSS wires coming from the same pin on the PCM. One goes to the speedometer and the other goes to the cruise control module under the hood. Make sure neither one is shorted to something. But again it possible you blew something up in the PCM when you had the signal hooked to the +12v input on the speedometer. I don't know what program modes you've made to your PCM but if you can borrow another PCM it might be worth a try. quote=Polarity;930349]Hey all, update time. Traced out the wire that went to the sig input on the tachometer, it comes out of the PCM (white wire just like you said) but has been spliced, looks like that came loose. I removed that piece of wire, put in a new one and ran it to the tach and presto the tachometer started working again. The speedometer on the other hand, still no luck. Ran a wire from VSS output to SIG on the speedometer. Hooked up 12v and ground, lights come on (nothing in the odometer box except the backlight is on) but needle doesnt seem to move any when I drive. Checked transmission to make sure that connector was there, everything looked fine. If I get a program like tunercat can that tell me that the PCM is sending the signal by recording speeds or? I've kind of run out of ideas here if anyone has one please let me know. -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted September 7, 2008 Author Share Posted September 7, 2008 Don't have a scanmaster close but I did have an idea. I have a "Car Chip Pro" in my daily driver for work (just records driving times, speeds, rpm, braking, basic stuff). So I hooked it up in the Z and took it for a drive. Unfortunately the laptop to read it is at work so I won't know if it received anything until tomorrow, but I thought it might work. Also I didn't see two green/white wires coming out of the PCM which means one must be run somewhere and in a loom already, I'm heading out to the garage now to see if I can track that little bugger down. Can't thank you enough for all the help Deja, wouldn't have made it this far without it =) -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted September 7, 2008 Share Posted September 7, 2008 That might work. VSS is on B8 (thats the black connector) should be dark green/ white and there should be two of them. Don't have a scanmaster close but I did have an idea. I have a "Car Chip Pro" in my daily driver for work (just records driving times, speeds, rpm, braking, basic stuff). So I hooked it up in the Z and took it for a drive. Unfortunately the laptop to read it is at work so I won't know if it received anything until tomorrow, but I thought it might work. Also I didn't see two green/white wires coming out of the PCM which means one must be run somewhere and in a loom already, I'm heading out to the garage now to see if I can track that little bugger down. Can't thank you enough for all the help Deja, wouldn't have made it this far without it =) -polarity Quote Link to comment Share on other sites More sharing options...
Polarity Posted September 14, 2008 Author Share Posted September 14, 2008 Deja does the VSS wire (green/white) also have voltage? -polarity Quote Link to comment Share on other sites More sharing options...
deja Posted September 14, 2008 Share Posted September 14, 2008 Deja does the VSS wire (green/white) also have voltage? -polarity I don't know what voltage level it is but it is a pulse, not a steady voltage. It is 4000 pulses per mile. But I don't know what t would look like sitting still. I'd go look but I'd have to dismantle too much stuff to get to the computer of my gauge cluster. Quote Link to comment Share on other sites More sharing options...
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