Benjamin Posted April 8, 2012 Share Posted April 8, 2012 I made the mistake of welding on the car without first disconnecting the battery and in tuen now have a car that does not start. I still have spark and fuel but it seems the EFI is not working.. Going through the Troubleshooting in the EFI bible I come across this step, I test and my test light does not light so i go to page EF39 of the FSM and get this diagram, And I cannot figure out how to test this circuit. Any one have any advice or can help me? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Benjamin Posted May 2, 2012 Author Share Posted May 2, 2012 Man, I was hoping that someone else made the mistake I did and could help.. I finally had time to further try to diagnose my car today. The ignition Circuit I needed to test runs between the ECU, Coil, Tach, speedo, and what used to be the ignition module. It tested fine so I moved on. Went through the EFI Bible troubleshooting. Nothing tested bad and I moved to the Components check.. Ecu tested good with test light on injectors, Brighter when the temp sensor unplugged. AFM tested good except that Pins 6-8 showed 220homs instead of the factory 180 and the 8-9 pin tested 125 instead of the 100 factory. (EF51) Potentiometer and air temp sensor tested well. Relay switch tested good. Injectors are good. Water temp sensor is new. I did not get a chance to test the dropping resistors, but shouldn't have that shown when I tested the ECU from the injector plug? Does anyone have any ideas why this car wont run? Everything seems to be checking out. I have fuel and spark, actually, alot of fuel. Plugs are saturated. Any ideas? Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 2, 2012 Share Posted May 2, 2012 Saturated plugs is a good clue. Maybe it's fine except for the wet plugs. Dry the plugs, confirm good spark while one or two or all are out (will help dry the cylinders out also), and try again. Add details of what exactly happens when you turn the key to Start - noises, gas smell, popping, etc. "Doesn't start" doesn't really give much to work on. The welding might have had no effect at all. If you want to test a few things first, try the three taps to ground from the negative coil post trick to hear if the ECU is firing your injectors when it should. That will show if the coil is working and if the circuit from ignition to ECU to injectors is right. Quote Link to comment Share on other sites More sharing options...
Benjamin Posted May 2, 2012 Author Share Posted May 2, 2012 Spark is good, confirmed multiple times. It turns over like normal just with no start, You can smell gas and it will sputter if you hold the gas all the way and try to start. But not run. I did the Third tap test on the connector next to the ecu and it tested positive and I tested that circuit for continuity between the connector and coil and it passed. Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted May 2, 2012 Share Posted May 2, 2012 Ben, You probably didn't damage anything with the welding. It sounds like it is just flooded. What were you welding? If it won"t start tomorrow after the plugs are dry, give me a call tomorrow. Sam Quote Link to comment Share on other sites More sharing options...
Benjamin Posted May 2, 2012 Author Share Posted May 2, 2012 Good to hear from you Sam, The Cam towers worked great and the engine ran really well until this. My differential fill plug was seized and stripped so I beat a socket onto it and tack welded it to remove it. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 2, 2012 Share Posted May 2, 2012 Worth a shot. Not to fill you with dread, but I had an ECU go bad and it died by dumping fuel through the injectors like they were stuck open. A couple of muffled pops, some gassy smoke/vapor, then flooded. It was a spare that I was testing and it ran fine for about a mile then stranded me. Put the old one back in and back to normal. 1976 280Z. Quote Link to comment Share on other sites More sharing options...
Benjamin Posted May 2, 2012 Author Share Posted May 2, 2012 Thanks NewZed, that's the kind of info im looking for.. Ill just be happy to know whats broken, at this point thats the entire battle. Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted May 2, 2012 Share Posted May 2, 2012 I seriously doubt that welding on the diff would damage the computer. it's possible, but unlikely. where did you connect the welder's ground strap? Quote Link to comment Share on other sites More sharing options...
Benjamin Posted May 2, 2012 Author Share Posted May 2, 2012 The ground strap was to the socket that was being welded on. Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted May 2, 2012 Share Posted May 2, 2012 Did it start after sitting and drying out? Quote Link to comment Share on other sites More sharing options...
Benjamin Posted May 2, 2012 Author Share Posted May 2, 2012 Nope, Still no start. Its had the chance to dry out and try again a few times now. The car is at my parents so it sat without being turned over for three weeks between the time I started this tread and updated it. Quote Link to comment Share on other sites More sharing options...
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