Misfire on multiple cylinders

[Newcomer]

I have a 2001 wakesetter vlx that runs very poorly, uses excessive gas, smells of gas fumes.  It has the indmar gm 5.7 engine.  I have found that the engine is misfiring on multiple cylinders.  I have changed wire set, plugs, cap, rotor.  Replaced the knock sensor.  Checked fuel pressure is 45 on the rail.  I put a timing light on plug #1 to check the timing, and the light barely blinks.  So I changed to the different plug wires just to see what the light will do.  It is very erratic on any wire.  There is no consistency to the firing.  I don't know what to do next.  I have read about crank position sensors, cam sensors but I don't know if my boat engine has these.  I am unable to locate a crank sensor.  It has clean fuel, new fuel filter.  What should I do next?  I need some help.  Am I missing something obvious.

[saburkhart]

You’ve covered everything I can think of. It doesn’t make sense but I’ve seen a week battery do some strange things🤷‍♂️

[Newcomer]

Fairly new strong battery.  Pulled all the new plugs, they are all black and smell of gas.

[hunter77ah]

How is the flame arrestor? It kind of looks like a cold air intake if you aren’t familiar with it. 

[Newcomer]

Flame arrestor is clean, it runs the same whether installed or removed.  During troubleshooting I have it removed.

[Newcomer]

Is there any history of bad coil or ICM?  I read other posts about crank position sensor that have similar symptoms, but I don't know if this engine has one.  I can't locate a crank position sensor.

[Steve B.]

Yep, replace that coil and ICM. How is the gas?

Steve B.

Edited August 2, 2020 by Steve B.
added info

[Newcomer]

Gas is new, tank was previously removed and cleaned.  Is there any way to check the coil or ICM?

[Newcomer]

Anybody know whether the 2001 indmar 5.7 has a crank position sensor?

[justgary]

No crank sensor.  The ECM gets its timing from the ICM under the distributor cap.

When you replace the ICM, be sure to use plenty of thermal grease.  They are temperature sensitive, yet they live in a very hot place.

[Steve B.]

I just got an MSD coil from Summitracing, like $30. While you are back there I would just do it.

Steve B.

[Gary Pelletier]

Any codes?  Bad MAP sensor will cause a rich condition.  Another thought is the ignition control module ( under the distributor cap) - I’ve had them fail (it usually just dies though). 

[Newcomer]

No codes, or I don't know how to get codes.  There is no check engine light, or no indication on any gage.  I guess there is a way to hook up a scanner, but the only connector I can find is a single yellow wire near the ECM. There is another connector with fuses, the three fuses are good.

[justgary]

1 hour ago, Newcomer said:

No codes, or I don't know how to get codes.  There is no check engine light, or no indication on any gage.  I guess there is a way to hook up a scanner, but the only connector I can find is a single yellow wire near the ECM. There is another connector with fuses, the three fuses are good.

With weak spark, our money is still on the coil.  Next in line is the ICM.  Change the coil first and see how it goes....

[Newcomer]

Still at it and still scratching my head.  I have replaced the coil, the ignition control module, the pickup coil in the distributor.  Still has misfire.  I have removed all injectors and had them cleaned.  I changed out the MAP sensor.  Previously switched out the plugs, plug wires, and cap.  Fuel pressure reads 45 psi on the rail with ignition on, and about 38 psi at idle.  Anyone with ideas or solutions at this point?  Smells of unburnt gas, probably because of bad misfire.  Plugs are black and wet.  Seems misfire is multiple cylinders as I can put the timing light on any wire and the light is not steady or consistent.  What is the next step?  Thanks for any feedback.

[justgary]

What is the fuel pressure at cruise and wide open throttle?

[Newcomer]

I haven't checked the fuel pressure underway.  I have been hesitant to use the boat since it runs so poorly.  Didn't want to take a chance on further damage.  What pressure should I expect at WOT or cruise speed?  Thanks

Edited August 8, 2020 by Newcomer

[Newcomer]

Do these indmar engines have catalytic converters or something similar in the exhaust?  Is this something that can be checked?

[Steve B.]

Wow. Sounds like it is not a lack of fuel. Hate to ask, but no chance you have wrong wires on wrong cylinders? Don't think your engine has catalytic equipment. Does spark seem strong now that you replaced the coil? Now, I'm wondering about the quality of connection between the cap and coil. Your cap was a good one with brass  conductors?

Steve B.

[Newcomer]

Wires have been checked again, not miswired.  Did the same thing with the old set.  New cap and rotor, with brass contacts. Nothing changed with the coil, probably will put original back on. Number one cylinder seems to be the worst with misfire.  Timing light barely blinking at times, then speeds up.  But never consistent firing.  The even side (port) seems to have the most consistent firing when looking at the light.  That's why I was wondering about catalyst.  I just use the timing light as a reference for watching misfires.  I know it is generally just used on plug #1.

Edited August 8, 2020 by Newcomer

[Steve B.]

My only thought now is still a bad coil or coil wire. It may be new, but you should have a ton of spark. Do you have an old spark plug wire you can swap for a coil wire? Just to eliminate a faulty coil wire. We'll get you going !

Steve B.

[Newcomer]

Just checked the fuel pressure at the rail.  45 with ignition on, 38 at idle.  At cruising speed about 40, and WOT still about 40.  What is this telling me?  What would be a normal reading? There is vacuum with no obvious leaks, hose is in good shape.  Also, the mounting bolt at fuel pressure regulator bolts into the rail.  There is no sealing washer, just the bolt and flat washer in the mount.  This mounting hole goes into the rail through to the fuel interior.  Seems like the threads should have some sealant or a sealing washer.  What are the thoughts?  I will also swap the coil wire with another one.  Thanks maybe we are getting closer.

[SkiPablo]

2 hours ago, Newcomer said:

Just checked the fuel pressure at the rail.  45 with ignition on, 38 at idle.  At cruising speed about 40, and WOT still about 40.  What is this telling me?  What would be a normal reading? There is vacuum with no obvious leaks, hose is in good shape.  Also, the mounting bolt at fuel pressure regulator bolts into the rail.  There is no sealing washer, just the bolt and flat washer in the mount.  This mounting hole goes into the rail through to the fuel interior.  Seems like the threads should have some sealant or a sealing washer.  What are the thoughts?  I will also swap the coil wire with another one.  Thanks maybe we are getting closer.

just jumping in to follow.   What gauge are you using to test the fuel pressure?  I think i need to do that on my boat too.

[UWSkier]

You should use red loctite on the fuel rail bolt or it can leak. However, your fuel pressures are right around what they should be, perhaps slightly low. Should be 43ish at WOT. 

You can build a code reader for pretty cheap. Or for a little more you can build a cable to read from your ECM. 

[Newcomer]

SkiPablo, just using a standard fuel pressure gage that screws into the fuel rail. I also measured all cylinder pressures at close to 150 psi each cylinder, all really close.  UWSkier what info do you have on code reader?  All I see is one connector near relays with one yellow wire.  I see no standard connector for a scanner.  Where should I go from here?  Thanks for the input