I recently pulled and reinstalled my '96 LT1-was running fine but had some oil leaks and 125k miles so I wanted to do plugs and wires as well. I ended up also replacing the cap and rotor with a Standard Motor w/ brass terminals, water pump w/ coolant temp sensor, NGK coil on, as well as 4 new Denso O2 sensors.
Upon reinstall I can't get it to start. It will crank over but will not run. I have a service manual but am a bit of a novice doing this kind of trouble shooting. I started on the "cranks but does not run" troubleshoot chart. I have a basic scanner so can't do some of the things the chart asks. Here's what I've done:
- No codes
- Fuel pressure is 41lbs and used noid lights to verify injectors are getting signal to pulse
- Spark tester indicates there is spark at the plugs

The FSM says now go to the "hard start" diagnostics. That just leads me to ignition diagnostics. Here I've run in to a problem:
1) I have spark at the plugs. That leads the FSM to tell me to inspect the cap and rotor. I didn't want to drain all the coolant I just put in as well as take off the water pump yet so I'm testing the other components as well just to make sure.

2) When I probe the connector for the ICM and I get to the step "connect a test light to B+ (I assume this is positive battery terminal?) and probe terminal C" it lights up. The chart says "repair ICM ground circuit". If I have a problem with the ICM ground how am I getting spark to the plugs? That ground is part of the three terminal ground on the bellhousing stud. I pulled the grounds and all three terminals look fine-no fraying or loose terminal.

I have probed the Opti harness and it checks out fine.

I'm just not sure how to repair this ground that looks fine. How can I have spark at the plugs but not have good ground for the ICM?

 

I would suspect some sort of grounding issue as well. Even if there was some sort of hugely out of time issue (ie somehow opti was forced on), I would expect a backfire or something.

Perhaps a weak/poor ground is not allowing the coil to provide sufficient spark. That ICM check *may* be spot on. Perhaps even the injectors are not properly firing. Check the main engine ground etc…you should be able to test the resistance of the various grounds as well. You obviously have enough ground to “crank” though.

Perhaps the new coil is actually DOA….easy check to swap back to the old one if you have it.

The other option is a flooding situation. Check the FPR vacuum hose for fuel, check the oil for fuel…if clear try starting with foot to floor.

This is an odd one, but a lot was disturbed based on pulling the motor and the parts replaced.

 

I don't think any flooding has happened but it didn't occur to me to pull a plug to check. No fuel in the vac line and doesn't seem to have gas in the oil. I'll try putting it in flood mode though just to see.

The ground test at terminal C seemed pretty conclusive the ground wasn't totally grounding. Could be loose which is why I have some spark but not enough to run the engine. They're clean but I'll clean them up and reattach to see. There is nothing to indicate either the ground terminals or the ICM plug are not good to go which is what I don't get. Based on the wiring diagram that ground is stand alone-it doesn't run in to any other grounds in the harness.

I have tach movement when I crank as well as injector pulse. The opti harness checked out ok so I would think the opti is good. Unless of course the new cap n rotor don't have the right tolerances for a good spark. I tried to save myself time in the future by replacing the coil and cap/rotor but I'm wondering if it had the opposite effect.

 

I’d try swapping the old coil back in…easy and you know it worked

 

Unfortunately I chucked it months ago-this has been a long project. I can pick another one up though just to see.

 

If you get past these other troubleshooting tests (grounds, coil, fuel etc): Did you replace the timing chain? What work did you do to the motor when you pulled it? Have you run a compression test?


Also make absolutely sure your wires are in properly. I wonder too if it’s possible to put the rotor on incorrectly/backwards? You’d be getting spark but 180* (?) out of time?

 

I didn't remove the timing chain-just replaced the cover gasket and seals. I didn't take off the heads and have no reason to think compression was affected. All in all I did gaskets on the timing cover, oil pan, and intake.

I put new plug wires on as well. I'm certain they're routed properly and fully clicked on to the plugs and cap. Doesn't hurt to check again though. Same for the distributor to coil wire. I don't believe it is possible to put the rotor on backwards. I have seen people report they didn't have the rotor either fully seated or tighted down and that caused a problem. I followed all the FSM procedures and torque specs.

 

Ok - don’t mean to keep throwing ideas at you, but after following all of the standard troubleshooting…if you have injectors pulsing, fuel pressure at the rail, compression and spark (at the right time)…maybe last thing is to check is the fuel itself…make sure there is no water in the bottom of the tank…pretty outside chance but….

You could also try spraying some starter fluid into the intake to see if it kicks…again to verify fuel 100%.

 

So I opened the oil filler cap and thought I smelled a little gas. Then the dipstick and I’m pretty much certain there’s gas in the oil.

I had left the factory injectors in even though I had new Bosch 3s-the install instructions recommended 15 min idle so I figured I would just wait till I had fluids in it to then swap out the new ones.

I ended up installing the new ones after a few failed tries starting-I was thinking maybe they stuck closed and no fuel was getting in. I had read some posts where cars sat for a while and they stuck closed on ppl. Perhaps mine were stuck the other way?

So my plan is to change oil and filter, crank the car in flood mode and then see what happens. Should I also be changing the plugs I just put in?

 

So, I've able to do some more testing/diagnostics. The engine was definitely flooded so I changed the oil out and started it in 'clear flood' mode. It kinda (I guess) cranked better but still barely sputtered and didn't run. It does sound like it's closer to starting. Verified there's spark with a spark tester on a couple plugs but not all. Going to pull the plugs as well and see how they are.

Then I tested the coolant temp sensor in the water pump-I don't have a scanner per FSM directions so I pulled it and did an ohm test in various water temps. Checked out ok so that shouldn't be the problem.

Here's where it gets interesting-at this point I went all the way in and pulled the front apart to check the cap and rotor. I used a Standard Motor w/ brass terminals. It was all put together correctly but the rotor has a groove worn in it from the inside of the distributor cap. I searched all kinds of threads and didn't see this on anyone else's rotor. I'm guessing that is not helping create good, consistent spark. So, I'll get another cap and rotor, compare, assemble with distributor off the car and see what that looks like.