Let me start by introducing myself. My name is Dave and I just acquired a 94 SHO that turns over strong but won't fire. I checked for spark with an inline tester and got nothing. A little back story from the previous owner...He had the intake and throttle body removed for a port/polish and powder coat job. After reassembly He drove the car for about 2 weeks before he noticed the water pump leaking from the weep hole. He parked the car and had a mechanic colleague from the dealership he sold for replace the water pump as a side job at the dealer. The mechanic suggested he replace the timing belt at that time as well. He agreed. The mechanic indicated he found a corroded wire under the fuel rail and made "repairs". Since the parts were changed the car hasn't run. I know this isn't the best description and I've yet to look into the problem as I haven't picked the car up yet. From what I've read online, the crankshaft position sensor can sometimes go bad due to a leaky water pump. Any and all insight into this matter is both welcome and appreciated. Thanks in advance.
New member 94 3.2 SHO
- Thread starter SHOTRUCK
- Start date
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Off Road SHO
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The block is grounded under the fuel rail and without it I don't think you will get a good spark. While he was doing the belt he should have done the Crank sensor.
Tom
Tom
Thanks. That's the first thing I'll check since it is reasonably linked to all of the info on how this all started. I wonder if this is the wire the mechanic was referring to, and what "repairs" if any were ever made to it.
No codes were found with engine off. I used the jumper method btw.
Everything looks good here from what I can tell by inspecting visually.
So, here's what I have found so far. 2 of the 3 supports for the intake weren't installed. While installing them, I noticed that they appeared to be used as a "contact" point. Possibly for grounding I'd suspect. When I removed the 1 that was on, the contact point of the intake had been powder coated over. I removed the pwdr coat at all 3 locations and cleaned up all contact surfaces when reinstalled. I found the connector to the IMRC was disconnected from a broken clip, so I fixed and reconnected. The green vacuum line from the EGR Vacuum Regulator Solenoid had been cut and was taped together very poorly. Had some vacuum tube with inside diameter the same as outer diameter of broke tube and spliced it with this. Found where a ground strap was supposed to be hooked up to the block at the bottom of the rear passenger side intake support. It had been removed and misplaced between the fire wall and strut tower. Moved it from the firewall to the the dbl nut bolt thingy holding the intake support to the block. Checked for 12 volts at various sensors' controls, and modules. IAC 12v on red with ign on, MAF 12v on red ign on, IMRC 12v on red ign on, Crank Pos Sensor 12v on rd/gr ign on, Cam Pos Sensor 12v on rd/gr ign on, Pin 1 of DIS 12v ign on. One thing I came across while searching the web was that the Crank Sensor, when plugged in and ign on, should read 12v across the rd/gr and or/rd. I found that the rd/gr to Neg post on battery shows 12v. Batt to or/rd shows 12v. However, when I back probe the rd/gr to the or/rd at the connector, I only read 5.38v. This has me stumped as I still have no spark when turning over. Any thoughts would be appreciated. Thanks for everything so far. Dave.
One last thing I forgot to mention. When turning over the engine, the tachometer moves. Just not sure how much it should move and if this decreased voltage would make it appear operational just not accurate. Still unclear if any of this could be definitively linked to my no start issue.
you must have ground from the DIS to the intake manifold and from the intake manifold to the chassis. I would double check that you were successful in getting this ground path established.
I have seen opens in the wire harness before, so you will need to trace down why your 12V is being dropped to 5.3V in the harness. Unfortunately, that is not an easy task. In one case, I just ran a new wire rather than try to find and fix the exact bad spot.
I have seen opens in the wire harness before, so you will need to trace down why your 12V is being dropped to 5.3V in the harness. Unfortunately, that is not an easy task. In one case, I just ran a new wire rather than try to find and fix the exact bad spot.
But it appears both wires are good. Rd/gr to known good grd shows 12v. Known 12v to or/rd shows 12v. Am I missing something? Again, all of this is with the connector plugged into the CKP. I could try to test with it opened and see if anything changes. Does this make sense. Also, I assume the DIS makes its ground connection through the flat surface mated to the intake crossover. Correct? I cleaned these surfaces up and applied EJC as well. If I test from the side of the DIS to the opposite end of intake, I get continuity. I haven't checked from DIS to block for continuity. I will do so now.
I believe I hooked up the ground you were referring to. Still no spark. Was the ground the one that goes from the shock tower to the lower bolt that supports the intake to the block?
yes, that grounds the engine to the firewall (chassis) and if the intake is installed correctly, then it is all grounded.
I guess I'm confused about where your 12V gets reduced to 5.3V...
I guess I'm confused about where your 12V gets reduced to 5.3V...
UPDATE: I got the no spark issue resolved. Believe it or not it was due to one of the DIS bolts missing. This is odd to me because I could test between the exposed metal backing plate of the DIS to any part of the engine or chassis and get perfect continuity. I did fix some other misc. grounds along the way which may have helped too, but if I remove that bolt...no start. Put it in...start. What a relief to finally have this issue resolved. Hopefully this thread/post helps someone else in the future. I will say this...I am a lineman for the local power company...and one thing I can 100% guarantee is that electricity does some completely inexplicable things sometimes...99% of the time, it can be traced back to a faulty ground somewhere. Take that for what it's worth. Thanks to all for the insight you provided while I chased this gremlin. Dave....
