No Spark After Replacing Crank Sensor and Water Pump

[NathanD]

I'm new to this forum and to SHO's. Last November I bought a 1993 MTX with 180,000 miles on it. The car is super clean with no damage and still has all the original paperwork from the dealership. When I bought it, it had an aftermarket alarm in it that was very old and making the door locks, hazards, and ignition system go haywire. So one night stranded at a gas station with the engine not starting I pulled the old alarm system out and that fixed the ignition lock, hazards and door locks going off randomly.

Symptoms:

• Randomly shutting off abruptly and turning back on while driving or idling. (odometer would jump to 0 RPMs)
• Not start after sitting for a few minutes. (It would start fine after sitting a few hours)
• Not starting after driving on a bumpy road.

Parts I replaced chronologically:

• Coil pack
• Starter (It was literally falling off and knocked up my ring gear a bit)

Ran a little smoother after those installs. Still randomly shut off and sometimes didn't turn on.​

• Crankshaft sensor (gaped correctly)
• Water pump (both halves)
• Spark plugs (wires are fairly new)

Didn't start after installing those. No spark. (odometer reading 300-400 RPM while cranking)

• DIS Module (with a used one from SHOSource)

Still no spark.

​

I sent it to a mechanic last week that said he'd worked on these cars before and he did diagnostics on it and said the DIS module was not working. Last weekend I reinstalled the DIS module with dielectric grease and grounded the two bottom bolts to a ground point close to the battery. Still no spark. I checked to make sure I was getting fuel and all that was working. I put the old DIS back on and double checked to make sure it was grounded, still no spark. Everywhere I checked on the air intake and throttle body was well grounded. All fuses are good in both boxes. I checked the codes and got 114, 116.

I am completely out of ideas! Maybe the cam sensor? It drove fine before my friend and I replaced the crank sensor, water pump, and plugs. Did I maybe miss connecting a ground somewhere down by the crankshaft? I didn't replace the timing belt because when I took the covers off it looked pretty new.

Does anyone have any ideas???

 

[luigisho]

You can pull the codes. First guess when tach goes to 0 is cam sensor.

http://web.archive.org/web/20090917070939/http://www.shophoenixproject.com/eec/eec.htm

 

[NathanD]

Odometer is reading 300 - 400 RPM while cranking the starter.
Codes were 114, 116.

 

[luigisho]

I don't expect the starter to crank rpm's too high. Dropping rpm on the tach while driving points to cam sensor. However your codes are not consistent with that and you could have an electrical problem somewhere deriving from that alarm system or just normal age and wear and tear.

I would change the cam sensor because it's old anyway, see if you can turn it over and, if not, look at the regional club and look for recommendations for a good SHO tech. I've had enough experience with mechanics to know to ask how they came to certain diagnosis. I have argued with several who would not budge and were way wrong.

 

[NathanD]

The alarm system is no longer in the car but I only pulled out two boxes from under the dashboard. One was a vibration or movement sensor for the alarm and the other was the actual alarm, after I pulled it out and didn't have a problem with it after that. But there are some loose wires still I know one is for the power door locks because they haven't worked sense I pulled the alarm out. I didn't mess with anything under the dash while we were working on the car last week though.

Is it possible that the cam sensor was bad before I replaced the crank sensor and now that the crank sensor is new the computer doesn't know what to do with the cam sensor? There's no way that in the process of working on the car the coil pack shorted out or something? I have +/- 12V going into the coil pack through the red wire closest to the firewall while turning the engine over, but no power going through the spark plug wires. It is grounded adequately.

 

[luigisho]

The cam sensor can go bad independently and provides input for the ignition system.

http://www.doityourself.com/stry/3-symptoms-of-a-failing-camshaft-sensor#b

 

[rubydist]

114 and 116 together suggest that there is a power or ground issue to those sensors on the driver's side of the car, as they are powered by the same circuit off the pcm. It could be the wiring from the pcm, the connector on the pcm, or connectors on the sensors. I have seen wiring go bad inside the loom for no apparent reason, so you will have to pull the pcm connector and ohm out all of the wires in that part of the circuit to find it.

 

[sdpatt]

The tachometer signal is sourced from the CID sensor and when it fails, rpms can show zero. If the CID is failing, the engine can be tough to start as the cam position is provided to the EEC to synchronize the spark. If no signal, the EEC has a 1 in 3 chance of getting the right coil to fire. Has the engine balked at starting at any time?

Also check the DIS module ground to the intake manifold and the manifold ground strap to the firewall at the passenger side rear manifold bracket bolt. This ground path, if not continuous, can cause various ignition maladies.

 

[Off Road SHO]

Pin 6 of the DIS module is fed voltage through the clutch pedal position switch. I don't know which pin of the DIS allows for the coil pack to send out spark but if it's pin 6, you might want to make sure that both red/light blue wires that are heated up by the clutch pedal switch are actually getting juice. The one that goes to the starter solenoid will be easy, if the starter cranks, that red with light blue wire is ok. The other red with light blue wire goes to pin 6 of the DIS.

Keep in mind that at the actual clutch safety switch, located under the dash where you were removing all those alarm wires, there is only one red with light blue wire attached to the switch. However, it splits into 2 on its way to the two aforementioned parts, starter and DIS,

Tom

 

[NathanD]

I'll see what I can figure out as far as the wiring goes. Both the DISs I tested were bad (1 original one and 1 used one from SHOsourse), so I got a new one yesterday from O'reillys that I had tested there and was working. After installing it and double checking the ground there was still no spark. I also checked the grounding strap on the far intake and it was good. Something I did notice was the Anti-Theft light comes on once the starter engages. Is that normal? I tried leaving the key in the running position for a few minutes and still no spark.

 

[luigisho]

What anti theft light?

 

[NathanD]

Oh, nevermind, it's anti-lock not anti-theft.

 

[itwonder]

Download the SHO Engine book from my dropbox: https://www.dropbox.com/l/EeLRPOedZ8ULdnVBrTUGOo
It has the pinout for the DIS. Make sure you have the expected voltages. You can probe the signal leads with an LED test light and should observe activity when cranking. Hard to diagnose from afar, but my first guess is the DIS is not seeing Vbatt, or your new crank sensor is not working.