New Motor Wont Start! Help!

[AmericanZ28]

So after about 60 miles on the new motor, it started sputtering at around 3k+ rpm, and then suddenly died on me. I tried to restart the engine but nothing. It didnt even try to start. It turns over fine, but absolutely no thunder. I checked the fuel pressure and saw 43 psi at the valve. I pulled the two front spark plugs on the driver side and put them againts the header bolt to ground them and they both had spark but was very dim, and looked weak considering it was dark.

The car didnt throw any codes, and the only thing I did different this time I drove it was to take out the ABS Fuses and replace the O2 sensors. The ICM has 11.53 volts on one side and -11.53 volts on the other side of the connector. I reused my old Optispark (10k Miles, OEM), and MSD Coil. The ICM is probably the original one from 96. Before this, the car would start and idle fine when cold, but would either idle poorly or turn off after it warmed up and was restarted. I have the MSD 8.5mm Wires that are 8 years old and have about 40K miles. Car currently has 117K miles. If it was the Opti, or connector, would it still spark? Im lost Any ideas?

[raroZ28]

http://shbox.com/1/4th_gen_tech2.html#opti_test

See what that proves.

[Joe 1320]

There could be several things. What I would do at this point since you say there is spark, is spray a few shots of starting fluid into the open TB and give the key a twist. If the engine fires up and dies, you have a fuel delivery problem....... you may have pressure, but something isn't telling the injectors to open and allow fuel delivery.

If it's a no spark condition, here is an ignition troubleshoot proceedure.

Here is a igniton diagnostic to be run while the car is in a no start condition, do this once you've ruled out the fuel pump (check pressure and volume) .

Step 1. Connect a spark plug tester to a spark plug wire and
check for spark while an assistant is cranking the engine.
Check each plug independantly. this checks for open
spark plug wires. Spark in one or more than one wire
indicates the problem is in spark plug wires or optispark.
If no spark exists, go to step 2.

Step 2. Check for spark at the coil wire with the spark tester
while cranking the engine. A spark indicates the problem
is in the distributer (optispark). If no spark go to step 3.

Step3. Perform check on ignition coil.
a: Unplug coil electrical connector and check pink wire for
12v. If power go to b.
b. using ohmeter low scale, hook up the leads to the
primary terminals on the ignition coil. Should indicate
very low resistance. If not, replace coil.
c. Using the high scale, hook up one lead to the primary
terminal, the other to the secondary terminal. Should
not read infinite resistance. If it does, replace coil.

Step 4. Disconnect the ignition module connector and with the
key on, check voltage at terminals A and D on the harness
side of the connector. (pink/black and white/black wires)
If under 10 volts check for faulty circuit from the ignition
module to the coil or check for grounded external coil
circuit. If 10 volts or more, change the voltmeter to a/c
scale and measure voltage on terminal B while engine is
cranking. (white wire). If 0 volts, Have ECM checked. If 1-
4 volts, with the key off, disconnect the module
connector. Install a LED type test light on the positive
battery terminal and probe terminal C on the harness side
of the connector (black wire). The light should illuminate.
If not, check ground wire in the harness to the module. If
the test light is on, go to step 5.

Step 5. Remove the coil wire from the coil and ground it to the
frame. Connect LED test light into the optispark harness
connector red wire terminal C. The harness connector that
you will use is located on the passenger side of the
engine up near the fuel rail. You will need to insert a back
probe pin into terminal C. If the test light flashes when an
assistant cranks the engine, the optispark is suspect. If
no flashes, replace the ignition module.

If the above tests results are correct and there is still no
start, it is tough to to tell the difference between a
faulty module or optispark. Module = Cheap$$, optispark
=moderate $$$.

[blackthunder50]

I had a similar issue after installing a new opti and all of the other elec. stuff. During the install I weakened one of the wires that went to the ICM. When driving a few thousand miles later it started breaking up really bad and then wouldn't start. The wire split and was held together by the insulation. Check for any wires that might have been loose in the connectors or snapped.

Good Luck!

[AmericanZ28]

Thanks for the in-depth diagnostic guide Joe! I will try this out tommorow morning. I have a new IC Module to try, but if it doesnt work after I install it, I cant return it. Also, do you know if the colors on the connector are the same as the earlier LT1's? I've read that there are some differences. Im assuming your guide is for 96/97 cars since yours was a 96.

Thanks for the tip BT! I will definately check that.

[AmericanZ28]

Ok, tested voltage at the connector and had 11 volts at both ends. Checked the white wire while cranking and saw 2 volts AC. Plug to coil has 11 volts as well. Tried spraying starter fluid into the TB and nothing! I replaced both the IC module and Coil, and checked for spark on 2 other cylinders. Both had a bright spark, but still no thunder. I checked compression on 2 cylinders, and had 160 psi on both. I take it its time for an OPTI?

[Joe 1320]

Perhaps. I tend to test the spark coming out of the opti rather than at the plugs if i suspect the opti. I keep a few known good spark plug wires and use one to test each output of the opti cap. That's a little easier than getting to each spark plug. Spark on two cylinders doesn't really say much other than you have spark on two cylinders. It would be more helpful if it said "I have spark on only two clyinders" or "No spark on the other 6 cylinders. The same thing is going to apply to a compression check. However...... the fact that there is compression is good. That might rule out a mechanical timing issue. Comparing all cylinders usually tells you what you want to know in terms of health of the motor. I'm guilty of shortcuts too. That starting fluid trick is a shortcut. If the motor won't fire, it's not from fuel........ that's really what the starting fluid is. So a no fire at that point means no spark or so weak that it won't fire. It points directly to the ignition or it's management barring any mechanical timing issues like a broken timing chain or jumping a tooth. At this point it's a good GUESS that it's the opti, it's helpful to know if the rest of the 6 cylinders are a no spark. If they turn out to have spark, obviously you'll have to look elsewhere.

[Kevin - Blown 95 TA]

Also check all your engine grounds since a 20,000V spark needs a good ground path.

[AmericanZ28]

OPTI DEATH! I took off the opti off and heard loose parts rattling. I took it apart and the rotor was completely off. The odd thing Joe, I had spark on cylinders 1 and 3. I picked a random cylinder on the passanger side, (cyl.4) and checked it for spark and it had spark. I dont know how, considering both screws had worked their way out on the rotor.

So after finding a place that had the distributor in stock (Reman. Optics w/ lifetime warranty, and new cap and rotor; $327 w tax) I got it in, buttoned everything up, cranked the engine over, AND NOTHING! Now I had no spark at all! I hooked up a jumper to the battery as it was beginning to turn slow, and it FIRED!

However, soon after it warmed up, I took it for a ride around the block and it started idling roughly when I came to a stop, and eventually shut down. It wouldnt start back up unless I gave it a little gas. Is this now an Idle Control Valve issue? Can I just compensate by adjusting the set screw at the TB? I returned the new IC Module since I still had spark, and re-used the original.

Kevin, I checked the ground cable and even scuffed up the paint on the ground strap that goes from the body to the coil bracket. The multimeter also reads low resistance from any part of the engine to the battery. According to MSD, their coil produces 40,000V

[raroZ28]

maybe you got another bogus opti?

Shoulda went OEM from thepartsladi on ebay. I got my opti in 2 days for 255 shipped, might take an extra day since you're in cali.

Could be a bent valve.

Check the compression on all cylinders. I had a similar issue, see my youtube video's, just search carlosg815.

I went back and forth for days. It would idle like crap, when I'd stop it would shut down and not start, etc... I couldn't figure it out, I kept suspecting opti, icm, timing, bad Madz28 tune, etc. The ignition system tests kept coming back great. I waited 3 days before I broke down and did a compression check.

Did a compression check, 7 cylinders down, all were good, then when I got to cylinder 8 I got nothing. Hooked up the air compressor and pumped some air in there, sure enough, my exhaust was whistling out the back. Bent exhaust valve on that cylinder. Pulled the head, went to a machine shop and got a standard 1.6 ss valve and had the valve replaced in about an hour, and was back in business.

Not sure how the valve got bent, my timing wasn't off or anything. I KNOW it wasn't bent when I bolted everything up. Maybe I over-revved it, or maybe my valve lash wasn't set good (i had never done it, had my neighbor who's an engine builder set it for me), but I bent it after having the car put together for 5 minutes.

[Z Ya Later]

Alright, time to get my feet wet again on this Tech stuff. lol

I know they're pricey, but I'm going to make this recommendation anyways. If you have the money and want a good Opti, I recommend the Dynaspark. It is definitely a solid unit, and I base this not only on the experience I have with my unit but from what everyone else has said about theirs as well. They are not cheap, but worth every penny IMO. I hope you can get her back up and running soon.

Love, peace and chicken grease. lol

[AmericanZ28]

Raro, did you car only idle rough after warming up, or did it do it cold?

Z, Im getting close to that point where I might break down and just head that route. Injuneer swears by it, and many others support it. How many miles do you have on it?

[Z Ya Later]

Z, Im getting close to that point where I might break down and just head that route. Injuneer swears by it, and many others support it. How many miles do you have on it?

I don't know the exact mileage, but I know I've got a few thousand at least. Craig and I put it in last year, so I would est. around 8-10,000 mi. The nice thing is that they're rebuildable for less than $100 if they ever fail...at least, that was the last figure I heard. Plus its pretty much the only Opti upgrade you can do without knowing "a guy". lol

[Rob B (shoebox)]

... Injuneer swears by it,

I have never heard this from Injuneer. You better doublecheck that.

A genuine GM opti is normally your best/cheapest bet. Most people have been well satisfied with optis from thepartsladi on Ebay. They seem to be legit units.

[AmericanZ28]

I have never heard this from Injuneer. You better doublecheck that.

A genuine GM opti is normally your best/cheapest bet. Most people have been well satisfied with optis from thepartsladi on Ebay. They seem to be legit units.

Woops. I dont know why but I read right past that and assumed it was the Delteq coil per plug system. Sorry Injuneer. I had never heard of the Dynaspark, but based on their website and Zs testimonial, it looks like the best bet.

With regards to the unit I bought, it looked very solid and identical to the OEM. I know looks can be deceiving. I bought it because I was desperate to get it out of my parents home as it's taking up space.

Moreover, do these symptoms point to the opti? Is the opti that prone to heat soak that it would only fail after warm up, and not idle?

As a sidenote, my cats still begin to glow toward the back after warm up, and there is a wierd smell coming from the exhaust when I rev the engine.