1990 SC wont start

BrianD1978

Registered User
I recently got a 90 super coupe with 55,000 miles with the automatic trans. I replaced the plugs, wires, coil pack, DIS module, fuel filter, and all the belts just because everything was original and old. I also replaced the bad AC compressor. I started and drove the car after I completed the work with no issues. The car was parked over the winter indoors and now will not start. It cranks over but sounds like the timing is off. I did get it to start a few times, it's runs like crap for about 20 seconds, revs up and down on its own and then dies. Fuel is good. From what I see from Google maybe the crank position sensor is bad? I just need some input before I buy one. Maybe something I'm missing.? Thanks.
 

35th

Registered User
When you are cranking the engine is your yellow up shift light on or off it should be off if it's on that relates to either crank or cam position sensor I believe
 

BrianD1978

Registered User
The yellow arrow shows up sometimes, sometimes not. I did get it to fire last night and it ran ok for a little longer than 30 seconds then just died again. When I cranked it over again it sounds like the timing is off. I can here the fuel pump and the injectors clicking with the key in the on position without trying to crank it over...weird.
 

35th

Registered User
Unplug your cam sensor try to start it with cam sensor unplugged it is supposed to take multiple attempts for it to start without cam sensor note whether it's harder to start or easier to start without cam sensor unplugged
 

BrianD1978

Registered User
Last night I installed a new crank position sensor from Super Coupe Performance. Now with the key on or cranking the engine I get a solid upshift arrow and a check engine light. Now I don't know what to do. Got a fuel pump, fuel pressure. Now what?? Need some real help here. Thanks
 

DOUG H

SCCoA Member
If I understand your 2nd response. You can hear the injectors cycling or energizing with the key on & the engine not even turning as well as the fuel pump turning on & off? I've never heard of that before. The ecm must be getting a signal that engine is running even though its not. Something shorted in cam or crank sensor wiring or more likely a internal fault within the ecm itself causing it to send pulses to injectors. When it does start its so flooded or loaded up with fuel that it just sputters & quits
 

BrianD1978

Registered User
After I replaced the crank sensor I do hear the fuel pump for about 5 seconds with the key in the on position. I do not hear the injector noise like I did before. Maybe the ecm is bad.
 

sam jones

Registered User
Last night I installed a new crank position sensor from Super Coupe Performance. Now with the key on or cranking the engine I get a solid upshift arrow and a check engine light. Now I don't know what to do. Got a fuel pump, fuel pressure. Now what?? Need some real help here. Thanks
Good afternoon

Check crank sensor connector(s) to the DIS harness for corrosion/damaged and secured. Also check the 30 Amp ignition coil fuse in the engine bay power distribution box.


After replacing the crank sensor and now a solid yellow arrow light is on during cranking/no start the air gap to the sensor is suspect.



 

DOUG H

SCCoA Member
5 seconds of fuel pump running is normal & if the injectors have now stopped clicking with key on-engine not running & the upshift light is on now then maybe crank sensor was only part of the issue. There must be something else,if it still wont start, not sure what to suggest next. Strange that more then 2 seperate issues would develop at the same time if it was fine before winter storage? Rodent damage to a hearness?
 

BrianD1978

Registered User
Yeah the car ran fine with no issues before it sat over the winter. I've checked the wires and don't see anything out of the ordinary. I will check the air gap for the crankshaft sensor. There is definitely not a lot of adjustment there. Just wondering why I bought another one of these 25 years later. This is just so frustrating.
 

35th

Registered User
Forgive me if I didn't see your answer but did you ever unplug cam sensor and try and start it while cam sensor was unplugged? I know you replaced it but if the issue is in the wiring not the sensor you'd get the same result with the old one and new one
 

BrianD1978

Registered User
I replaced the engine control module under the passenger side dash tonight. It fired up the first turn of the key. It ran, but the idle was crap and I had to keep my foot on the gas to keep it running. I started it a few times within about 5 min. Started every time, but the idle didn't improve. I took a 10 min break, went back in the garage and the car would just crank and crank and never fire. Pretty much same as before. No upshift light while cranking now.
 

DOUG H

SCCoA Member
When you scanned for codes, what were they? Were there some that lead you to believe the ecm was bad? Is it the same version or calibration as the old one?
 

35th

Registered User
Not sure on the Sc's but some vehicles when the computer is bad the cooling fan will automatically turn on as soon as you turn the key to the on position... Would be an easy check
 

DOUG H

SCCoA Member
Have you followed the trouble shooting guide as suggested by Sam Jones on Apr 21 &/or scanned the system for dianostic codes? Just curious what has lead you to to change the components that you have so far.
 

BrianD1978

Registered User
Have you followed the trouble shooting guide as suggested by Sam Jones on Apr 21 &/or scanned the system for dianostic codes? Just curious what has lead you to to change the components that you have so far.
I got the car to start tonight, but it runs like the timing is off. I have to keep my foot on the gas to keep it running or it stalls. It barely runs. The only code I get is code 11. This car was pretty much untouched when I got it off the 2nd owner. 55,000 miles. All the maintenance items were all shot. The car did run and drive with no issues. I replaced the belts, air filter, plugs and wires, coil pack, oil change, and fuel filter. I only replaced the DIS module and cam sensor when I couldn't get the car to start. After that I replaced the cam position sensor and ECM as a maybe I got some bad info online. I checked the plugs and wires like 10 times and they are in the correct order. Also have 40 psig fuel pressure when it does run. The vac/boost gauge bounces like it has a vacuum leak, but I'm pretty sure it doesn't. It does smell like its burning bad like a old carburetor out of tune. I'm pretty much ready to give up on this thing
 

DOUG H

SCCoA Member
You stated that the vac/boost gauge bounces when running? I'm wondering if a intake valve or valves are stuck open?
That would kind of coincide with it ran fine before it was put into storage, & now it has this issue. Just a thought though.
I know on a naturally aspirated engine that a bouncing vac gauge usually indicates that, but not sure with the supercharger.

Anyone else have any thoughts or know?
 
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