LS1LT1 Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
213 Posts
Discussion Starter #1 (Edited)
1994 Corvette:
Hi, I'm having a problem with my optispark distributor code 16. My MSD optispark failed so I replace it with a RichPorter optispark distributor, yesterday I installed the new opti and it did not work, code 16, so I thought I may have gotten a bad opti distributor, I returned it and got another new Richporter opti, installed it today and it still doesn't work and I'm getting code 16. My question is, is there anything else that could cause a code 16, the wiring is good, grounds are good, have correct voltage to/from ecm. Does anyone know what I might be overlooking or are there some other component tests I could complete or did I probably get another defective opti unit....if I did at all? I'm not sure on how to proceed so, any advice will be appreciated. I attached a short video of the attempted/conditions of no start.

Could the coil, computer, VATS or anything else cause code 16.

The ICM is new.

VIDEO:
1994 Corvette Optispark Distributor Problems - YouTube
 

·
Registered
Joined
·
213 Posts
Discussion Starter #3
Opti, opti harness and connections to the computer are about the only things it could be. The computer is looking at the opti and nothing else to determine a code 16. I didn't list the computer, since it would be a rarity, but could happen.
Shucks, i traced the wires/harness from the opti harness to the main harness back to the computer and everything is sealed and looks good. So, it looks like it's either the opti distributor or the computer. Being that this is the 2nd new opti, what are the chances that I got 2 bad optis in a row....I guess it could happen? I'm thinking, maybe I should buy/try a new computer...heck, I'm not sure at this point $$$.
 

·
Registered
Joined
·
6,377 Posts
Is the end of the opti harness at the opti corrosion free? Did you meter the leads there? I know you are getting the code 16 and you clear it and it comes back, but yet you are getting spark. Perhaps the code is a bit intermittent, because if the code were solid, you shouldn't get any spark or fuel delivery. What started the whole scenario (as in why did you replace the opti in the first place)?


This wouldn't have anything to do with the code, but are you confident the opti is indexed correctly? In the video, it seemed it was trying to run at times.


[edit] nevermind-I got the story from your post on LS1tech.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #5 (Edited)
Is the end of the opti harness at the opti corrosion free? Did you meter the leads there? I know you are getting the code 16 and you clear it and it comes back, but yet you are getting spark. Perhaps the code is a bit intermittent, because if the code were solid, you shouldn't get any spark or fuel delivery. What started the whole scenario (as in why did you replace the opti in the first place)?


This wouldn't have anything to do with the code, but are you confident the opti is indexed correctly? In the video, it seemed it was trying to run at times.


[edit] nevermind-I got the story from your post on LS1tech.
Yea, this issue has been a headache for awhile. Awhile back i installed a Comp Cam , 1.6 rockers, beehive springs, port & polished heads and a 58mm TB. Car started right up after cam install and ran great but, I didn't get the computer tuned, my buddy Otto owned a GN race/repair shop close by and he was going to tune the car but, he went out of business so, I never got the car tuned and I didn't drive the car often but, I did put somewhere between 500/700 miles on it. I planned on getting the tune done but, these problems started to happen. The car was running great then one day it started to have a cold start problem but, started after a few minutes of cranking. The car ran great after the difficult cold start and would start back up easily, only had a problem starting if the car sat over night. There were no codes at that time but a week later it coded it out and it gave me a TPS fault so, I changed the TPS sensor and the car still had the cold start problem. I wasn't sure what to do so, I brought the car into a local garage and had them look at it, they said the car was getting a low resolution signal. They said it would be pricey to repair because they would probably end up changing parts until the problem is fixed....I could do that so, I drove the car home. So, with the low resolution problem I figured it was the MSD opti, I replaced it with a cheap Richporter unit and still got a code 16 so, I figured I got a bad unit and returned it and the parts store gave me a new Richporter opti an I'm still getting a code 16. Not sure on how to proceed. Could be the opti or maybe computer....I don't know of any good LT1 mechanics in my area. So, I'm stuck on deciding whether I should call PCM for Less and get a new mail order tuned computer or return the opti but, what are the chance of getting 2 bad opti's in a row??

What did you men by indexing the Richporter opti?? I thought it could only go in one way with the slotted spline.

yep, I'm posting in 3 different forums, this one, LSTech & corvette forum.

this is a video of the cold start issue from last week, I didn't have a code 16 at the time:
CORVETTE FORUM HELP - YouTube
 

·
Registered
Joined
·
6,377 Posts
...

What did you men by indexing the Richporter opti?? I thought it could only go in one way with the slotted spline.

...
It is supposed to go on correctly one way. However people manage to put them on wrong all the time. Yes, the tab can be forced to go where it is not supposed to.
 

·
Registered
Joined
·
89 Posts

·
Registered
Joined
·
6,377 Posts

·
Registered
Joined
·
89 Posts
Its the opti. Put a GM or Delphi opti on it and i bet it fixes it. Cheap opti's are junk. Just my .02,
 

·
Registered
Joined
·
213 Posts
Discussion Starter #10
This video taught me way more than I used to know about the opti. It is actually a buick training video but it is the same thing.

Buick Know How: LT1 Optispark (ABITS) Distributor Operation and Diagnostics - YouTube


Sent from AutoGuide.com App
yea, I watched that video a few times in the past and re-watched it again last night after I read your post. My problem has to be the cheap opti, I'm getting the correct opti harness voltage:

A = ~5vdc
B = ~5vdc
C = 12vdc
D = ~0 - 0.1 ground

So, I'll return this opti again, I will probably dish out the extra cash and upgrade to the AC Delco or maybe send in the MSD to be rebuilt.
 

·
Global Moderator
Joined
·
13,431 Posts
Before you go get another opti, I would try another pcm. Even though lt1 pcm's rarely fail, if you had a spare you could swap it out in a couple of minutes to eliminate or confirm the pcm as a suspect.

Craigslist has them fairly regularly, or use this salvage yard search engine
Car-Part.com--Used Auto Parts Market You can search your state, region, or entire country, as yards on search engine ship parts all the time.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #12
Before you go get another opti, I would try another pcm. Even though lt1 pcm's rarely fail, if you had a spare you could swap it out in a couple of minutes to eliminate or confirm the pcm as a suspect.

Craigslist has them fairly regularly, or use this salvage yard search engine
Car-Part.com--Used Auto Parts Market You can search your state, region, or entire country, as yards on search engine ship parts all the time.
Yea, it's good/wise to have a extra PCM laying around for just such an occasion. I need a tune anyways so, i was thinking of getting a new computer with a tune on it from PCMforless. My reasoning for bad opti was that the opti harness was getting the correct volt readings, from my understanding, if those readings are correct then it should be the opti so, even if the harness readings are correct there could still be an issue with the pcm...it's just not showing any symptoms or issues and/or are there other diagnose checks that I'm not aware of at this point? One thing about this opti odyssey I'm learning a lot about the LT1 and luvin it! Just wish it wouldn't cost so much...no way around that! live & learn. I appreciate all the help/suggestions from everyone....thanks.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #14
I attached a video of the car starting today along with the fuel pressure drop:

Optispark Starts....sort of? - YouTube

Well, it's getting better but, it also getting worse. I was fiddling around with the car this afternoon and it STARTED and ran nice and smooth!! It needed a some cranking but, it started. When the car started the check engine light went off and while the car was running I used the scanner and checked for codes and the scanner stated "no faults found" but, soon as I shut the car off and scanned it again the code 16 was there, I erased it but, it came back or never went away, I wonder if it is a history code that for some unknown reason won't erase....anyone ever hear of this?? Prior to me starting the car I was messing around with car ground wires, i wiggled a ground wire under the brake booster and the car started, could be coincidence? I'll have to inspect all the grounds tomorrow, I think there are 5 or 8 in the front section of the car....anyone know which wires plugging into the computer are ground wires or a wiring/plug schematic? So, at this point I'm still not sure if it's the opti, grounds or computer but, the plugs/ground wires in the engine harness all read grounded. I'm gonna do my google research and hopefully find the needed info and if anyone wants to give some free advice, I'll appreciate it.

Also, the ASR service light is on, I have to research this, can this effect the motor in any way? My scanner doesn't read these code so, I'll have to grab a scanner for this or try the paper clip technique.

Also, I noticed my fuel pressure wasn't holding when the key was on but, not started. The fuel pressure instantly bled down. This could cause hard starting. The fuel pressure stayed at 45lbs while the car was running with no issues. On a vette the fuel pump is easily accessed, open fuel filler door and remove a couple hoses and bolts and it pops right out. I changed it last year but, I pulled it out today and clamped the return line and the system held the fuel pressure. Any ideas as to where the leak might be??
 

·
Global Moderator
Joined
·
13,431 Posts
Since all the GM service manuals in 4th gen section are for f-bodies, I suggest going to BBB Industries- Premium Alternators, Starters, Power Steering Products You can download most of your 94 corvette wiring diagrams there. They should have ground distribution, power distribution and pcm engine control diagrams there.

Our member GaryDoug has made an obd1 scan program for 94 & 95 cars. It reads regular codes, does running sensor scans, and reads abs and traction control codes.

However, I'm not sure if program will work, or not on a corvette, as it was made for f-body. But, I would pm GaryDoug and ask him as he knows way more about his program.

Find the obd1 scan program in 4th gen section.

About your fuel pressure. Since when car runs pressure is good, but when key on prime pressure falls, pressure regulator would seem to be ok. I would look for a leaking injector, or bad check ball in the fuel pump itself.

When you do a key on prime, fuel pressure regulator should be closed and not letting fuel get into return line for trip back to tank.

Fuel pump inlet uses the fuel pump check ball to prevent fuel returning to tank via inlet fuel line. Without the check ball in the fuel pump, the second the pump shut off, pressure would quickly bleed off as fuel returned to tank via inlet fuel line.

So if check ball isn't seating correctly fuel will bleed of, the speed of which depends on how bad the defect is.

But you should check for injector leakage as that can bleed off fuel pressure also. Injector leakage would change your air/fuel ratio when engine is running. Doing a running sensor scan should let you know how air/fuel mixture is doing.

However, you should still remove fuel rail and do key on prime to see if any fuel is leaking from injectors.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #16
Ok, I'm gonna tackle that issue soon, I have a Aeromotive fuel regulator and i rebuilt that when I installed the new fuel pump last year. I might install the stock regulator to see if the system holds pressure and if so, I'll rebuild the regulator again, the rebuild kit is cheap, so no big deal.

As far as the opti goes, earlier the car started a few times and ran pretty good/smooth. I went inside for dinner and when I returned to the garage I tried to start the car and it wouldn't start! I have absolutely NO spark at both the plugs and coil, I checked volts on the opti harness/wiring and everything is good, checked coil/icm volts/wiring and everything is good and no ground issues...oh,also checked all fuses and they are good and the code 16 fault disappeared from the system....no faults found?? Back to square one but, this time no spark and no system faults...what to do?? Probably bring back that crappy richporter opti and get the AC Delco, no way around it! Then, call around for a new computer with a tune. Man, this has been giving me hell!!
 

·
Global Moderator
Joined
·
13,431 Posts
Have you taken icm to be tested? It could be bad. Sometimes a fault won't make a code come up. So when testing at the icm connector, you were getting the 1-4 volt AC signal when motor was cranked?

Also, is your car an automatic trans? If yes, trans harness shares power with coil and icm. Something in electrical part of trans, or wiring, or connectors could be drawing power down to coil and icm causing no spark.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #18
Have you taken icm to be tested? It could be bad. Sometimes a fault won't make a code come up. So when testing at the icm connector, you were getting the 1-4 volt AC signal when motor was cranked?

Also, is your car an automatic trans? If yes, trans harness shares power with coil and icm. Something in electrical part of trans, or wiring, or connectors could be drawing power down to coil and icm causing no spark.
Yep, the ICM is new and I only check the leads to the ICM/coil check according to the GM shop manual, I didn't know about the actual ICM check while cranking...not mentioned in the manual or I didn't see it. i will definitely do that in the am....that's a good find!

It's a manual trans.
 

·
Global Moderator
Joined
·
13,431 Posts
Icm harness connector B is the one to check for 1-4 volts AC while cranking. Hopefully vette has same pin outs as f-body.

shbox.com has opti testing instructions, which I got this from.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #20
Icm harness connector B is the one to check for 1-4 volts AC while cranking. Hopefully vette has same pin outs as f-body.

shbox.com has opti testing instructions, which I got this from.
The ICM harness plastic connector is lettered, so should be a easy test plus, I have the GM shop manual for reference. I was reading the shop manual late last night and it stated that a blown A/C fuse could cause a no spark situation, I never checked the A/C fuses, so that will be one of the first things I'll look at today. wish me luck!
 
1 - 20 of 22 Posts
Top