Crank no start

[tomloans]

Today, the motor ran for a bit and was making the same noise noted below in the video. I started to test for a spark and after the last test which was fine, the motor started to just crank with a back fire every second or so. Plugs are all wet. Fuses at the starboard side are fine so coils are not bad.

I put in the old spark plugs which were clean and same thing. I had an extra tracker valve and I swapped that as well in case my eyes were not seeing a tear in the one that had just 8 hours on it. It appears I have no spark or the motor is severely flooded.

Sure could use a miracle or someone willing to sell me a 2021 V8 250 Pro XS.

Here is what it sounded like before it stopped firing up...

[Bryanmc57]

I wonder if that compressor finally let go....

[tomloans]

I wonder if that compressor finally let go....

Bryan, I just cant believe the compressor let go after about 100 hours on it. Anything is possible of course but it didn't show any signs of wear at all. I updated to the newer version about 100 hours ago. It looks like fishing is out until February when my service guys are available. This one I just cant figure out.

[Another Distraction]

Did you remove belt and review compressor?

[tomloans]

Yes a number of times and even sent a video Don. It is solid. I know the signs as I have changed one out already. In my last case with the compressor going out, it was very subtle horizontal movement and a little more noisy than most. Currently this one is perfect ( knock on wood ). I actually slept on this and I think it may have been that I started the motor so many times as I was checking for a spark that my battery went low and maybe the ECU reacted to it. Put the battery on a charger and I am going to try again today and will report back.

I just can't imagine why there would be no spark on most of the cylinders all at once. This is the only thing I can think of. Will report back.

[kris_tx]

did you check kill switch?

[tomloans]

Kill Switch is good. Here is what I have after battery fully charged ( wasn't the battery ). Crank, no start ( not even a sputter ), end cranking and big backfire. Repeated twice.

[EuropeanAM]

Need to physically CHECK spark with a spark tester. Also need to verify there are no FUEL VAPORS inside the engine cowling.

Verify fuel pumps run when you turn the key ON.

Air and Fuel Pressure Tests next. You'll have to get results from a Glycerin-Dampened gauge set:

At 3 seconds of cranking:

At 6 seconds of cranking:

At 10 seconds of cranking:

[Bryanmc57]

Question Don... Not for complete diagnosis but wouldn't a set of AC gauges with the low side connected to the air schrader confirm air pressure when cranking? I know they're not the glycerin dampened gauges but they would show whether or not there was pressure in the air rail no?
ges

[tomloans]

OK so here is what's going on now. I have a backfire every time I crank for a few seconds. I literally checked all 6 coils to see if there is an issue with them using the service manual chart and a ohm meter for résistance. This takes some time because there are 5 prongs to test against each other and against the output as well. All six are perfect. I used an old timing gun to see if I have a spark and I have a flashing signal from the gun. I replaced all six spark plugs with known working and clean plugs prior to.

I hear the pump running and fuel sprays out of the starboard side when I press in the Schrader valve. The spark plugs are wet and I am getting a backfire.

I also check the ohms at the crankshaft sensor as well to see if that is not working. 350 it was perfect.

Am I simply heavily flooded? Is the spark weak?

I am going to put a pressure gauge to the Schrader valves and see what I get. It is an AC gauge as that is all I have. Maybe it might give some insight.

Finally in the manual it states that the PCM can short with a bad coil in some instances and it states to check the resistance between Pin C24 and Pin B1. Well mine has no resistance at all which states according to the manual the PCM is bad. But how can it be bad if I have a spark and fuel. It pointedly states that if the PCM was bad I would have no spark from the coils. Plus my Rinda Diagnostic tool is connecting and reading the PCM perfectly.

Why is there no coughing if flooded. This has been quite a challenge. Thank goodness it has been raining but I really want to get this fixed before next week. Fishing!

Thank you all!

Tom

[tomloans]

So using a simple tire gauge which locks when reached the maximum. I had 31 on the port side and 46 on the starboard side steady almost right away and it held there. Fuel pressure would hit before I even started cranking so the fuel pumps appear very good. But 31 seems very low considering I believe it should be 80 on the port side and about 90 on the starboard side. But maybe it is different when the engine is not running.

[EuropeanAM]

If you have spark, the PCM's ignition driver circuits are functioning.

No substitute for correct gauges. Use the right tool and identify the problem, or not and not. Honestly is that simple.

Side question: How full is your REMOTE (boat) oil tank right now?

[tomloans]

How full is your REMOTE (boat) oil tank right now?

1/2 full

Also I have parts on order to be able to screw oil filled gauges into the Schrader valves and hopefully get correct readings.

This is very strange that I have wet plugs, spark, yet no coughing at all. Just a backfire after cranking for more than a few seconds. Anyways thanks for your help fellas. I will run the fuel/air pressure tests and be back with you all.

[EuropeanAM]

Good deal on the oil tank.

When you have reliable info from verifiable gauges, we should be able to narrow it down.