Please help
03-13-2024, 06:42 PM
#1
Please help
So, I just got a 93 with LT1 on Sunday. Drove it home, no problems, parked it and went to bed. Got up next day tried to start, and it cranks but won’t turn over. The car has all kinds of new parts from what I was told and you can see the parts are all in new looking condition under the hood. Water pump, opti, ICM and coil, fuel pump and tank, fan motors. I bought a new ignition coil and ICM just in case and plugged them up and still nothing. Security light is not flashing either. Fuel pump sounds like it’s kicking on as well. I don’t think it’s getting spark.
03-13-2024, 08:30 PM
#3
Burning Brakes
Do you have any details on what brand opti or ICM was used? There have been lots of reported issues with bad new parts, including the aforementioned and fuel related parts such as pumps and sending units. So, since it’s easy enough, check for spark first by grounding out a plug and have someone crank. If there is spark, it does not necessarily mean it’s good spark or the timing is right. Check your fuel pressure with a gauge at the rail. If you don’t get up to proper pressure by bumping the key to on, or if you get pressure but it immediately trails off after the initial fuel pump cycle, you will know you’re leaking down somewhere (pump, injectors, fuel pressure regulator). Another quick thing you can do after you check for spark, is to pull the vacuum hose from the FPR and see if it’s wet with gas in there. It should be dry. From there, you need to start isolating ignition components and testing them. By chance did the PO give you multiple sets of ignition keys? If you used a different one, try the one that you drove home with. They have specific frequencies. It’s likely an issue with the installation of all those new parts or a defective new part. Given what all was just replaced, it sounds like they may have had a sitting and/or non running car and got it fired up prior to selling. The best thing you can do is buy the factory service manuals for your year. They are the key to diagnostics with these cars.
03-13-2024, 09:59 PM
#4
Do you have any details on what brand opti or ICM was used? There have been lots of reported issues with bad new parts, including the aforementioned and fuel related parts such as pumps and sending units. So, since it’s easy enough, check for spark first by grounding out a plug and have someone crank. If there is spark, it does not necessarily mean it’s good spark or the timing is right. Check your fuel pressure with a gauge at the rail. If you don’t get up to proper pressure by bumping the key to on, or if you get pressure but it immediately trails off after the initial fuel pump cycle, you will know you’re leaking down somewhere (pump, injectors, fuel pressure regulator). Another quick thing you can do after you check for spark, is to pull the vacuum hose from the FPR and see if it’s wet with gas in there. It should be dry. From there, you need to start isolating ignition components and testing them. By chance did the PO give you multiple sets of ignition keys? If you used a different one, try the one that you drove home with. They have specific frequencies. It’s likely an issue with the installation of all those new parts or a defective new part. Given what all was just replaced, it sounds like they may have had a sitting and/or non running car and got it fired up prior to selling. The best thing you can do is buy the factory service manuals for your year. They are the key to diagnostics with these cars.
03-13-2024, 10:39 PM
#5
Can’t I just put a spark plug on the end of the wire and try to crank and see if the spark jump?
You can. Just make sure to ground the metal body of the plug to something on the engine.
03-14-2024, 12:17 AM
#6
I also had some codes I cleared out from my dash. From my understanding those codes were stored codes that were never cleared from previous repairs because they started with the letter H. Those codes would pop back up with the letter C in front of them if they were still an issue, correct?
03-14-2024, 01:51 PM
#7
Last edited by PennyUnwize; 03-14-2024 at 02:37 PM.
03-14-2024, 03:06 PM
#8
Burning Brakes
Possibly but I don’t think so. As far as fuel pressure you need to check it with a gauge that plumbs in at the fuel rail.
03-14-2024, 03:34 PM
#9
Looks like my opti is shot. I got no injector pulse, and with what little battery life was left I could see a little spark from the injector coil to my test light.
03-14-2024, 09:24 PM
#11
Charge the battery, so you can continue with diagnostics.
Code 25 will not cause a no-start.
H-codes are VERY important. Many codes can only be "Current" when the engine is running. If a diagnostic routine that requires the engine to be running sets, it will show as a History when the engine is not running. Some important H codes in Module 4 are: H16 (Opti low res. Smoking-gun bad opti code) H36 (Opti Hi Res. Can't cause a no-start) H41 (Ignition control Module).
If you remember, what were the codes you cleared? Include the Module number, if you know.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~
Here's a simple check for Reference Pulses. You need to be able to hear the fuel pump run, so a quiet environment or a helper listening to the tank filler with the cap removed.
If = NO, Check for H16 as outlined above.
Code 25 will not cause a no-start.
H-codes are VERY important. Many codes can only be "Current" when the engine is running. If a diagnostic routine that requires the engine to be running sets, it will show as a History when the engine is not running. Some important H codes in Module 4 are: H16 (Opti low res. Smoking-gun bad opti code) H36 (Opti Hi Res. Can't cause a no-start) H41 (Ignition control Module).
If you remember, what were the codes you cleared? Include the Module number, if you know.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~
Here's a simple check for Reference Pulses. You need to be able to hear the fuel pump run, so a quiet environment or a helper listening to the tank filler with the cap removed.
- Turn key to RUN. Fuel pump will run for 2 seconds and stop. Leave key in RUN.
- Wait about 5-10 seconds. Crank the engine briefly. Just enough to turn the crank 1/4 turn or so.
- Listen for fuel pump to be running, and stop after 2 seconds.
If = NO, Check for H16 as outlined above.
03-14-2024, 09:27 PM
#12
Race Director
What do you mean cranks but won't turn over? Turning over is cranking. Is the starter motor spinning the motor or not?
03-14-2024, 09:38 PM
#13
03-14-2024, 09:53 PM
#14
Drifting
Prev owner on my current project put an Auto Zone Opti in. It was still clean as new when it failed. Just because it is new/replaced does not guarantee it is good.
03-14-2024, 10:08 PM
#15
Yea that’s what I’m thinking. Unfortunately I’m gonna have to get one from either the orange store or the green store. Looks like Petris is sold out and there’s no way I can afford an MSD one right now.
03-14-2024, 11:35 PM
#16
All those H3x codes in Module 1 can be set by low battery / system voltage.
Run my test for "Reference Pulses". It tells a lot about several things. If the fuel pump runs after cranking breifly, the ECM recognized reference pulses.
Another pretty simple check: Watch the tachometer while cranking. If it just sits on zero, there won't be spark. ICM or ECM. There could still be Reference Pulses, however.
I would wait for a Petris. There is no substitute, IMO.
Run my test for "Reference Pulses". It tells a lot about several things. If the fuel pump runs after cranking breifly, the ECM recognized reference pulses.
Another pretty simple check: Watch the tachometer while cranking. If it just sits on zero, there won't be spark. ICM or ECM. There could still be Reference Pulses, however.
I would wait for a Petris. There is no substitute, IMO.
Last edited by PennyUnwize; 03-14-2024 at 11:43 PM.
03-15-2024, 01:17 AM
#17
Drifting
Petris is worth the wait. that is route I went. One day of work and three days cleaning.
03-15-2024, 01:31 AM
#18
[QUOTE=IHBD;1607621787]
I’ll take the battery to get a recharge in the morning.
2 things I know for a fact, I get no tach jump when I try to start, and I do not have a code 16. The sys light was also blinking when I drove it home and the service engine soon light comes on when I try to start.
I was sure I had good voltage from battery, but now that I’m doing some reading 18 volts is apparently high for a battery.
18 Volts is high. I doubt you saw 18 V, if you did, check your meter. The 3x series codes in module 1 WERE history codes. They could have been fairly old, from a previous LOW voltage episode.
I had my neighbor listen for my pump and he said it turned on, but I’ll double check the length of time it’s on.
What you're checking for is that it runs again after a short crank. The actual time it runs doesn't mean anything. You wait for it to stop. A brief crank. Listen for it to be running a second time, then stops.
I know my tach didn’t move a millimeter when I tried to crank it either.
The tach gets it signal from the ICM. So no tach, no Primary ignition.
Also if I’m understanding correctly, I can’t get a code 16 unless I can get the car to turn over, correct?
If the engine cranks, and the low-res pulses are missing, it should set an H16 at cranking speed. (Lo-res pulses are what makes it run.) When my 92's opti shot craps, it quit and never ran again. I had an H16, no tach movement, and no fuel pump the second time after the 'brief crank'. Classic no reference pulses. I cleared the H16, cranked it for 5 seconds, the H16 came back. I replaced the 1992-dated Opti with a Petris.
"Turn over" is what it does with the key in START. "Starts, then Runs" Is what it is supposed to do / does after you release the key from START.
18 Volts is high. I doubt you saw 18 V, if you did, check your meter. The 3x series codes in module 1 WERE history codes. They could have been fairly old, from a previous LOW voltage episode.
I had my neighbor listen for my pump and he said it turned on, but I’ll double check the length of time it’s on.
What you're checking for is that it runs again after a short crank. The actual time it runs doesn't mean anything. You wait for it to stop. A brief crank. Listen for it to be running a second time, then stops.
I know my tach didn’t move a millimeter when I tried to crank it either.
The tach gets it signal from the ICM. So no tach, no Primary ignition.
Also if I’m understanding correctly, I can’t get a code 16 unless I can get the car to turn over, correct?
If the engine cranks, and the low-res pulses are missing, it should set an H16 at cranking speed. (Lo-res pulses are what makes it run.) When my 92's opti shot craps, it quit and never ran again. I had an H16, no tach movement, and no fuel pump the second time after the 'brief crank'. Classic no reference pulses. I cleared the H16, cranked it for 5 seconds, the H16 came back. I replaced the 1992-dated Opti with a Petris.
"Turn over" is what it does with the key in START. "Starts, then Runs" Is what it is supposed to do / does after you release the key from START.
2 things I know for a fact, I get no tach jump when I try to start, and I do not have a code 16. The sys light was also blinking when I drove it home and the service engine soon light comes on when I try to start.
03-15-2024, 02:19 PM
#19
Burning Brakes
All those H3x codes in Module 1 can be set by low battery / system voltage.
Run my test for "Reference Pulses". It tells a lot about several things. If the fuel pump runs after cranking breifly, the ECM recognized reference pulses.
Another pretty simple check: Watch the tachometer while cranking. If it just sits on zero, there won't be spark. ICM or ECM. There could still be Reference Pulses, however.
I would wait for a Petris. There is no substitute, IMO.
Run my test for "Reference Pulses". It tells a lot about several things. If the fuel pump runs after cranking breifly, the ECM recognized reference pulses.
Another pretty simple check: Watch the tachometer while cranking. If it just sits on zero, there won't be spark. ICM or ECM. There could still be Reference Pulses, however.
I would wait for a Petris. There is no substitute, IMO.
Another thing you need to consider, if the opti winds up being the problem, is if anything leaked on it or into it. The new opti might have been fine but the new water pump could have leaked or they didn’t replace the timing cover seals. If the seals are leaking, you are going to draw oil right inside the opti. If your diagnostics lead you to a failed opti make sure it isn’t because of that. It will be evident once you take the cap off. If you wind up replacing the opti, now is a good time to do those seals and convert to a vented opti like the 95-96 cars had. All available with Petris. This is a job you want to avoid redoing for a long time. And it would suck to put in what’s available now and do the job again a month later.
Even the Delco water pumps are Chinese now. About the only mechanical water pump I would put on nowadays is a flokooler. Made in USA, high flow, heavy duty, tight tolerances, billet aluminum turbine, no blow by, and no cavitation for $179. I’m torn between that an electric for my car.
Last edited by C4 Steck; 03-15-2024 at 02:26 PM.
03-15-2024, 04:20 PM
#20
Race Director
The number 1 water ingress point is the wiring harness. It isn't sealed, and so water will migrate right now the harness, past the pins, directly into the optical sensor.
If it was being prepped for sale, it wouldn't be surprising to hear that they cleaned the engine bay, and some water or cleaner got on the harness and killed the opti. Lots of people think covering the opti helps. It doesn't, the outside shell of the opti has a seal to prevent water getting in. The wiring harness is a direct pathway for water to get in.
If it was being prepped for sale, it wouldn't be surprising to hear that they cleaned the engine bay, and some water or cleaner got on the harness and killed the opti. Lots of people think covering the opti helps. It doesn't, the outside shell of the opti has a seal to prevent water getting in. The wiring harness is a direct pathway for water to get in.