Misfire on multiple cylinders

[Steve B.]

This still sounds like an ignition issue if the spark is weak and plugs are fouled. That coil output isn't making it to a plug like it's supposed to. The only other things I am thinking of are plugs themselves. Can you verify which ones you stuck in there? And how were they gapped? Did you check timing yet?

Steve B.

Edited August 9, 2020 by Steve B.
more questions..

[Newcomer]

This is the second set of plugs MR43LTS gapped at .045.  I haven't determined that the spark is weak.  I have tried two coils.  It appears all cylinders are misfiring.  Timing light slowly blinks on #1 wire, and very random or inconsistent on other wires.  Does it sound like the pressures are ok with the fuel pressure regulator?

[Newcomer]

The engine is not running good enough to check the timing.  I can see the timing mark, and it is advanced but the light is not blinking on this plug enough to verify the timing.

[Steve B.]

Hmmm. Yes, that pressure sounds just on the low side, but shouldn't cause the engine to misfire like that. Is the boat new to you? And a little more basics, is the system voltage around 14.2 when it's running?

Steve B.

[Newcomer]

Boat is new to me, and not very well maintained.  Been one thing after another. Voltage is around 13 and increases with throttle to maybe 13.5 or so on analog gage.

[Newcomer]

Does this 2001 wakesetter allow for a scan tool to be hooked up?  If so where do it plug into?

[UWSkier]

1 hour ago, Newcomer said:

Does this 2001 wakesetter allow for a scan tool to be hooked up?  If so where do it plug into?

Yes but not an automotive scan tool. There's a plug right above/around the fuel pump. 

[justgary]

Test your timing light on your car to make sure that it isn't the problem.

I would not mess with the fuel rail if it isn't leaking.  Don't do extra work until you get the engine running correctly.

You do not have cats in your exhaust.

Remove the cannon plug near the starboard rear of the engine, make sure it is clean, and very gently spread the male contacts before you reconnect it.  Next, remove and clean the ground connectors at the rear of the starboard head and the port head.  Now do the same thing for the battery, alternator, and starter connections.  You want to make sure that the ECM has no excuse for having low 12V power input.

If it still won't run better, remove the ECM cover at the rear of the engine and pull the long connectors and very carefully inspect them for corrosion and pushed/bent pins.  Be slow and methodical so you only have to do this once.  When you are sure that both sides of each connector is good, reconnect them and try the engine again.  While you are in there, post a photo of your ECM, or look at it and compare online to see if you have a MEFI2 or MEFI4 ECM.

[justgary]

After thinking about it a little more, a bad temperature sender can cause the engine to run very rich.  Find both temperature senders and carefully clean the connections.  Heck, you might as well do the oil senders while you are in the mood.

[Newcomer]

Here's the latest.  Battery is fairly new and charged.  About 14.5 volts across the battery when running.  Checked the ECM appears to be MEFI4 with the connectors straight up.  Removed these connectors, inspected, no bent pins, no corrosion, very clean.  Cleaned ground connections at motor.  Cleaned temp sensors/senders terminals.  Removed the engine harness round cannon connector.  It looked clean with silicone dielectric on it.  What I did notice is that it's not keyed.  How do you tell if this is in the correct orientation?  I take it that instrument indications probably would not work if this connector is 180 out.  It is not fully pinned, only using about 7 pins. Strange that it is not keyed though. I removed the vacuum at fuel pressure regulator, it has vacuum but there is no change to engine when it is disconnected.  I checked the timing light, works on another vehicle.  I can put it on any plug wire on the boat and the light indicates erratic firing.  At times #1 and #5 are flashing very slow.  When #1 is flashing enough to verify timing, the mark is before tdc.  This engine only has small timing tab with one notch.  Timing seems ok, although wanders slightly probably because running so bad. A few wires seem to fire fast mostly normal, and other wires are very inconsistent.  Compression was 150 on all cylinders.  I switched around a couple of plug wires, no change.  I used a different wire in place of coil wire, no change. Can TPS be a problem?  What are the thoughts next?

Edited August 9, 2020 by Newcomer

[UWSkier]

I'd recommend building a cable and getting the MEFI software from this thread. 

 

Here is a sample output from my 2001 Indmar Monsoon. 

https://drive.google.com/file/d/1ysib4TE5qaBzJIld_1i0JTzcbngXpxfw/view?usp=sharing

[Newcomer]

Confirmed that there is very little spark.  Steve B. had it right earlier.  I ran the engine with a spare plug and put it on different wires to observe the spark.  There is barely spark, which is why the timing light is inconsistent from the wire induction.  They all seem to have consistent firing, but it is just barely visible.  Occasionally there is a white decent spark.  It does this on two different coils, one coil is new.  I checked the voltage across battery at about 1500 rpms is 14.5volts.  Checked voltage on the two coil connectors.  Purple wire to ground is 14.3v (gray connector). Brown wire to ground is same at 14.3 or so volts (upper black connector).  Voltage is while running at about 1500rpms .  Could this be two bad coils?  What are the relays for at the ECM harness?  Is it possible something is not getting turned on by the relays? Anyone know what voltage I should read across each coil connector? Gray connector has purple and gray wires, black connector has pink and brown).  There is certainly not enough spark to fire correctly.  Thanks 

[justgary]

The cannon plug should have an arrow on the outside of each housing to show you how to line it up.

Verify that your distributor cap is seated correctly.  I have seen one that had a little tab on it that kept it from seating flush with the distributor body.

Find the ECM data port and jumper terminal A to B.  Crank the engine.  It should run at a high idle with 10 degrees BTDC timing.  Verify the base timing with your light while you check to see if the spark is more consistent.

[Newcomer]

Not really a misfire, but a lack of fire.  Sounds and acts like a misfire, especially seeing the erratic timing light.  The spark is so weak, it is barely visible.  Where is the ECM data port?  Is it the diagnostic connector near the fuel pump?  Also, the timing tab is small and hard to see.  What is considered 10 degrees BEFORE?  And Thanks justgary.  

[Newcomer]

I also swapped some other wires with the new ones.  And used a plug wire in place of coil wire which is new to rule that out.  No change.  Still just barely a spark.  I will take a closer look at the cap and rotor.  Anyone ever had wrong cap and rotor making increase clearances or gap issues? This is a new set.  The original that was on it when I bought it was doing same thing. Does this engine have a cam sensor?

Edited August 10, 2020 by Newcomer

[UWSkier]

No cam sensor. There is one in the block but it's not wired up. Never heard of a rotor clearance issue. I like the ACCEL cap and rotor available at any O'Reilly. Brass contacts and good price. 

[Harderkev]

 I'm chasing a misfire on my '99 Monsoon also, but only when cold. Have you checked for corrosion on your distributor reluctor? Varying degrees of rust on each reluctor tip would account for overall weak spark and some cylinders behaving worse.

 It's the same concept as a lawn mower magneto rusting over the rainy winter months and not having spark in the spring.

[Newcomer]

Are reluctor tips the eight points off the shaft under the rotor?  I cleaned all of this when I changed out the ICM and pickup coil in the distributor. Good advice, I'll check them.

Edited August 10, 2020 by Newcomer

[Steve B.]

Hm, I think this is somehow a lack of a physical electrical connection. If it was just timing, a strong spark would still be there, just out of time. Coil, cap, rotor issue. I would plop a plug right on the output of the coil in open air and watch it. In other words skip the cap and plug wires. Then just spin it over. The engine wont like it much, but I think would be okay for a second or so. Of course as a CYA again, please have a fire extinguisher close by. Maybe even wear rubber gloves any time the key is on at this point. This girl wants to run. 

Steve B.

[Harderkev]

2 hours ago, Newcomer said:

Are reluctor tips the eight points off the shaft under the rotor?  I cleaned all of this when I changed out the ICM and pickup coil in the distributor. Good advice, I'll check them.

Yes. I wanted to get home and look at mine before responding. Took some 220 grit to the reluctor arms and pickup pins but didn't see much corrosion on mine.

 Spent some time cleaning and checking connections; one of the female connectors for the 4-pin distributor plug was misaligned so I bent it back into position. Found the rotor arm had < 1mm of end play in the rotor casting. Will be replacing my cap and rotor since the current ones are cheap aluminum contacts.

 I like Steve B's suggestion of checking the coil output. Have you checked for excessive distributor shaft play? Mine is snug side-to-side but will lift up about 3/16".

[Newcomer]

Great idea, Steve B.  I will give it a shot, should not be a fire hazard since straight from coil as no cylinder will have fire.  As far as the thought of lack of electrical connection, I believe there is a connection, since all plugs do fire just a very dim spark.  I have never seen anything like it where you have to put the plug in a shadow just to see the spark.  I believe this is why there is so little inductance through the wires to fire off the timing light.  With this in mind, the coil is getting the signal, just not enough umph.  I am now finding that I may have alternator problems with someone putting on a parts store rebuilt gm alternator on this thing and it's not wired like an original marine alternator should be. I wonder if all of this is related to the alternator.  This alternator is charging as I get 14.5v across the battery when about 1500 rpms.  I'll see if I can put my other post about alternator wiring here, and please provide some feedback.       

      2 hours ago, Newcomer said:

Hey UWSkier, I need some clarification on this.  You are helping me with another maybe related electrical issue/post.  I am getting ready to do this alternator upgrade to 2001 Wakesetter.  What I found is someone put a rebuilt car parts store alternator on my boat, cut the original wire harness and wired this rebuilt alternator to the flat style two wire gm connector.  The heavy orange original wire goes to the single terminal and then to starter, I get that.  The last person cut the purple wire and joined it to now white wire of flat connector.  The red wire from the flat connector is not connected to anything.  Then there is a black ground.  My question is since the original is gone, what was the original wiring.  I have an orange, purple, black coming through the original harness to the alternator.  If I use this upgraded alternator with the oval two wire connector, the purple wire connects to both?  Also, I'm reading related posts that talk of not being able to cut the engine off.  I tried this with this rebuilt alternator because some people put the sense wire back to the hot stud on the alternator.  I also could not cut the engine off, without pulling the coil wire, so the wire is not connected.  What was the original Indmar hookup for these three wires going to four terminations.  Please help, thanks

 

Edited August 11, 2020 by Newcomer

[Newcomer]

Harderkev, I like your suggestion also.  I will investigate further.  As far as end play, side to side is good.  I think up and down is about the same on mine.  I think this is normal and due to cam gear down below slightly rotating the shaft.

[justgary]

Do you have at least 12v at the coil? 

[Newcomer]

14 volts to ground at the coil.

[Harderkev]

Speaking of ground and what Steve B. said, have you checked resistance values of your coil ground leads? Maybe a high-resistance ground wire is causing the poor spark?