95 No Start - Please Help
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
95 No Start - Please Help
My 95 won’t start, and I’ve checked a few things so far, and need advice on the next steps.
It cranks strong, but no fire. No noticeable tach movement while cranking. Sometimes, after cranking for about 5 sec, it will sputter when I release the key. I checked for codes with the paper clip, and no codes are showing. Then I hooked up a pressure gauge to the fuel rail. Key on gives steady 45 psi. As soon as I turn the key off, pressure drops to under 5 psi right away. Not sure what the next step should be. Any suggestions?
Thanks,
John
It cranks strong, but no fire. No noticeable tach movement while cranking. Sometimes, after cranking for about 5 sec, it will sputter when I release the key. I checked for codes with the paper clip, and no codes are showing. Then I hooked up a pressure gauge to the fuel rail. Key on gives steady 45 psi. As soon as I turn the key off, pressure drops to under 5 psi right away. Not sure what the next step should be. Any suggestions?
Thanks,
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Update
So, I needed to move the 95 to my other garage to keep diagnosing it, so my buddy and I pushed it over there. Hooked up a spare coil wire from coil to ground, cranked it, and got a strong spark. Buddy had to leave, so I plugged the coil wire back on and hooked up a spark test light on one plug, and put a noid light on one injector pigtail. Cranked it over, and I’ll be damned if it didn’t fire right up… Took out the test lights and started it up. Seems to be running good. Couple of exhaust pops when revving it a bit, but it’s still cold. I have headers and muffler eliminators, so it pops occasionally anyway.
The question is, does this intermittent issue sound like an Opti still, or is an ICM more likely? Or something else? It seems to definitely be ignition related. I have a brand new OEM Opti, that I lucked upon a while back, but I’m really not eager to change it, especially if I don’t need to. Any thoughts?
John
The question is, does this intermittent issue sound like an Opti still, or is an ICM more likely? Or something else? It seems to definitely be ignition related. I have a brand new OEM Opti, that I lucked upon a while back, but I’m really not eager to change it, especially if I don’t need to. Any thoughts?
John
Drifting
Joined: Aug 2019
Posts: 1,334
Likes: 225
I would check and clean your connectors to the optispark, and ignition control module. If it runs OK, I'd leave it alone. To change the Opti on a guess would be a waste of time. My thinking is since you guys were moving stuff around checking for spark and pulse, you might have moved connectors just enough to make decent contact.
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
I would check and clean your connectors to the optispark, and ignition control module. If it runs OK, I'd leave it alone. To change the Opti on a guess would be a waste of time. My thinking is since you guys were moving stuff around checking for spark and pulse, you might have moved connectors just enough to make decent contact.
When I return home from Florida in April, I’ll clean up the connectors and see how it runs. I tend to agree with a connection issue, as I’m having a hard time believing that the Opti can go bad, then work well again. I’ll update this thread when I get home.
Thanks,
John
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Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Update: Yesterday , I cleaned the terminal connections on the OPTI, IAC, coil, ICM, and idle speed motor. Used spray contact cleaner, followed by a bit of dielectric grease. Tried to start it, and same as before, no start, with brief partial firing as the key was released. I then pulled the connection at the OPTI in and out several times in a row, hoping to improve the connection. Next attempt, it fired up and ran well. Shut it off, and tried to start it again this morning. It cranked for about a second, then fired up and ran smoothly. It’s hard to see the terminals inside the OPTI connector, but they look to be a bit dark, not shiny. I’m thinking that may be where the intermittent issue is. I do have a new wiring harness that goes from the OPTI to the connector on top of the intake manifold. I may try that harness to see if it helps. If anyone has other suggestions, please let me know! Thanks!
John
John
Drifting
Joined: Aug 2019
Posts: 1,334
Likes: 225
Update: Yesterday , I cleaned the terminal connections on the OPTI, IAC, coil, ICM, and idle speed motor. Used spray contact cleaner, followed by a bit of dielectric grease. Tried to start it, and same as before, no start, with brief partial firing as the key was released. I then pulled the connection at the OPTI in and out several times in a row, hoping to improve the connection. Next attempt, it fired up and ran well. Shut it off, and tried to start it again this morning. It cranked for about a second, then fired up and ran smoothly. It’s hard to see the terminals inside the OPTI connector, but they look to be a bit dark, not shiny. I’m thinking that may be where the intermittent issue is. I do have a new wiring harness that goes from the OPTI to the connector on top of the intake manifold. I may try that harness to see if it helps. If anyone has other suggestions, please let me know! Thanks!
John
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
It might even be where the wire enters the connector, and not just the terminals. I would definitely replace that harness. Just make sure they're keyed the same. I've heard some try to replace the harness, and the connector wouldn't go in because of the connector having a different locating key.
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Update
Weather was nice today, so I decided to take the 95 to run an errand. It started up pretty normal. I let it idle for a minute, and it seemed a little rough, but would rev up OK. Started down the street and it began misfiring pretty significantly. Turned around and brought it back to the garage. I guess the next step is to try doing some diagnostics before planning to install my new OEM Opti. I’m pretty certain it’s ignition related, by the way it’s behaving. Any tips on how to narrow down the possible issues?
John
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
When my opti entered its death-throes (lasted about 3 minutes, I didn't make it back to the house, it quit about a mile short.) I noticed several things:
> The tachometer was very erratic. Jumping all over the place.
> The Service Engine Soon light came on. (It had set C/H 16)
> While waiting for the tow truck, the only code was H16.
Re Code 16: DTC 16 is the low res pulses that are used for ignition. The 16 and 36 (Hi Res) DTCs use the other to check themselves. If one pulse is present without the other, the appropriate DTC sets. When checking codes, the engine is not running so there are no reference pulses from either high or low, so the DTCs can't run. 16 and 36 will therefor always be History codes. When my opti died (it never started again) I could clear the H15, verify that no codes existed, crank it, and H15 would reappear. This convinced me that the 31 year old opti had **** the bed. I replaced it with a Petris, and it fired right up. So far (a month and 500 miles), so good.
Others' experience may be different.
> The tachometer was very erratic. Jumping all over the place.
> The Service Engine Soon light came on. (It had set C/H 16)
> While waiting for the tow truck, the only code was H16.
Re Code 16: DTC 16 is the low res pulses that are used for ignition. The 16 and 36 (Hi Res) DTCs use the other to check themselves. If one pulse is present without the other, the appropriate DTC sets. When checking codes, the engine is not running so there are no reference pulses from either high or low, so the DTCs can't run. 16 and 36 will therefor always be History codes. When my opti died (it never started again) I could clear the H15, verify that no codes existed, crank it, and H15 would reappear. This convinced me that the 31 year old opti had **** the bed. I replaced it with a Petris, and it fired right up. So far (a month and 500 miles), so good.
Others' experience may be different.
I started it up in the garage just now. It fired up and seemed to run smooth. No erratic tach movement, nor CEL. Revved up easily. Held at 2000, and 3000 RPM, with no misfiring. It seems to be load related, which might indicate the coil? ICM? Any ideas on how to troubleshoot?
Thanks,
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
I ran the car in the garage with the lights out, looking for possible plug wire arcing, but there was no signs of any sparks. I held the throttle up around 2000 or so, and there was a slight roughness, but nothing major. Still thinking it’s ignition related. I hate to throw parts at it, but I’m thinking of trying a new ICM, and possibly a new coil before I dig into the Opti. Suggestions appreciated.
John
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
When you checked for codes, and "none were found", was that with a paperclip and the Service Engine Soon light? If = yes, do you know how to use the onboard diagnostics to pull History codes?
The SES light method doesn't show history codes, but if the previous rough running episodes set a code, they should be in memory as History codes. The onboard diagnostics can retrieve them.
If you don't know how to use the onboard diagnostics (speedo LCD and fuel and trip buttons) ask. It's pretty cool, and a powerful tool.
The SES light method doesn't show history codes, but if the previous rough running episodes set a code, they should be in memory as History codes. The onboard diagnostics can retrieve them.
If you don't know how to use the onboard diagnostics (speedo LCD and fuel and trip buttons) ask. It's pretty cool, and a powerful tool.
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
A: You can't trust it. You have to keep driving it with the knowledge that it may stop running altogether, and plan accordingly. (No trips out of AAA range from the house.)
B: You do need to keep driving it so it will act up again. When it does, you now know what to pay attention to: Tach, SES light, and look for H codes in Module 4 in the onboard diagnostics. Hopefully, it will quit for good and not re-start. Then you can find it.
When my 92's opti died, it had hiccuped a couple of times on previous short errand trips; I knew something was up, but there were no codes. About the 3rd trip since the first occurrence of "I wonder what that is?", it ran really shitty for about 3-4 minutes then quit for good. It was simple to conclude that it was the opti because it never fired again.
B: You do need to keep driving it so it will act up again. When it does, you now know what to pay attention to: Tach, SES light, and look for H codes in Module 4 in the onboard diagnostics. Hopefully, it will quit for good and not re-start. Then you can find it.
When my 92's opti died, it had hiccuped a couple of times on previous short errand trips; I knew something was up, but there were no codes. About the 3rd trip since the first occurrence of "I wonder what that is?", it ran really shitty for about 3-4 minutes then quit for good. It was simple to conclude that it was the opti because it never fired again.
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
I drove it up and down my street just now. Definitely missing. Even backfired a couple of times when I free revved it a little. Idle is rough, like one or two cylinders missing off and on. Still no codes or erratic tach signal. Could it be just the Opti cap and/or rotor? I guess I would still need to pull the water pump and crank pulley to access the cap, correct?
John
John
Heel & Toe
Joined: Jan 2023
Posts: 15
Likes: 3
From: Alameda County Ca.
Cranks but won't start
Hi, I suggest that you go to YouTube and search using the phrase "cranks but won't start" and of Course information about your car. "corvette"
Lots of good stuff on YouTube.
Lots of good stuff on YouTube.
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Latest updates
Replaced fuel pump and got good pressure at rail, along with good hold pressure after pump stops. Car started but still running rough. Long story short, determined #2 plug was bad. Replaced plug, engine started and ran smoothly. Tried to stat again, and same issue as original one, engine will crank, but no start. After cranking for several seconds, it will sputter briefly when key is released. During cranking, confirmed Spark at one plug, and fuel pressure at rail, and injector pulse at one injector. With injector pulses and spark, I’m thinking it’s not the Opti. What is the next likely culprit? ECM? VATS? Also, there is no tach movement while cranking. Any suggestions?
Thanks,
John
Thanks,
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Yet Another Update - Still No Start
I watched a YouTube video with a 94 Vette display the same condition as mine, that is it would crank for 10 seconds without starting, then sputtered when the key was released. He found the ground strap was dirty under the battery to the engine block. So, I pulled my battery and cleaned the connections. Unfortunately, no change whatsoever. I also went through the FSM diagnostics somewhat, checking continuity for the Opti harness and voltages at the computer connections. Everything seemed ok. The diagnostic tree for no start ended up with either a bad wiring connection to the Opti, or the Opti itself. I’m getting ready to just ‘bite the bullet’, and change the Opti. Still interested in anyone’s thoughts on other things to check first.
Thanks,
John
Thanks,
John