Finally got around to joining the 3rd gen crowd again after many years. I picked up a nice 89 IROCZ 350 that needs a little work to make roadworthy but has a great body still (a very hard find here in IL).

Anyways, after getting her home and fixing the VATS problems that she was suffering from (bypassed with resistor, bypassed starter motor relay, and turned off VATS fuel disable in ECM), she would crank but wouldn't turn over after firing up a couple times. Considering that she has been sitting for a while, I went for the first 2 well known culprits, the injectors and the igntion system.

I went through all the injectors and tested for voltage and resistance. All are getting proper voltage from the harness and all the injectors tested above 15 ohms for resistance.

Next I started checking the plugs, wires, coil, and distributor. The wires were garbage and dry rotted, coil didn't test properly, and the distributor was a corroded mess under the cap. So I put in a new remaned ACDelco distributor, new coil, new wires, and new plugs. Upon completion, she fired up first try without issue. Stopped and started another couple times to make sure, then took her out for a quick drive around the block to see how she runs, which is much better than before when I could get her started.

Thinking I have the issue solved, I park her in the driveway and leave her sit for the afternoon while I work on fixing the struts on a buddy's car. After we complete his job and I go back out to start up the Camaro and put her back the in garage, she almost fires up but then goes right back to cranking without turning over.

Since I was going out, I leave her in the driveway and start thinking about what else could be the culprit. After a couple days I go back out to see if I can get her back in the garage. She fires up first try and runs great. Very strange to say the least.

Anyone have any experience with something similar? I've done a few searches and about the only thing I could come up with after everything I've done would be the ECM. While she definitely needed the all new ignition I put in, I really don't want to spend $100-$200 on a new ECM if that won't solve the issue.

My TPI knowledge is somewhat limited, as the 3rd gen I owned many years ago as a teenager was an 84 LG4. Most of my knowledge is in the LT1, as I've had my 94 Z28 for over 15 years now. But anything that I can try I will, as this weird starting issue is definitely something I don't want come spring time when I can start driving my new 89.

 

My '90 formula did this exact same thing because of a dead/dying fuel pump or connection. Completely random, and sometimes it wouldn't do it for months. In my particular case, it was definitely a problem closer to the tank side; not the ECM or engine harness or even fuel pump relay.

Listen for the fuel pump prime. If I didn't hear it, sometimes I could twist the key back and forth between run & off until it primed. Then it would start and run fine. It never died while running.

 

I have the same problem too and everyone keeps telling me its my fuel pump not priming but even when i hear it prime it still wont start sometimes.

 

I don't believe the fuel pump is the culprit as I have put a fuel pressure gauge on the test valve and its always at 45-46 PSI when attempting to start or when it does start and runs. Fuel does not seem to be the issue on my car, as I can smell fuel in the exhaust when starting but not turning over. Also, once she does start she runs just fine without any issues now that I've replaced the entire ignition.

I'm going to have to do more digging as I haven't gotten much time to work on it yet but at this point I have to believe it is some weird electrical issue.

 

Well I finally got around to spending some time diagnosis this problem and its seems to get stranger with more information. The fuel pump is definitely not the problem and the injectors are firing. I decided to try pulling the codes even though no SES light, which gets me the error code 33 - MAP sensor circuit error (signal high indicating low vacuum). This doesn't make much sense for this year, as the 89 does not have a MAP sensor at all. No other codes are present, aside from the diagnostic mode 12 code.

I did some searching and apparently some other people have had this problem before, although there doesn't seem to be much info available as to what fixed the issue. I'm going to start going over all the vacuum lines to see if any are cracked or broken. If any one has fixed this issue and knows anything, please let me know.

 

Turns out that code 33 is actually for the MAF sensor on the 89, since it doesn't have a MAP. Replaced the MAF and then it started throwing a code 15 for engine coolant temperature sensor. After replacing that as well she fires up every time now and idles properly. Always fun trying to chase down multiple sensor issues.