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1996 Sunsetter running poorly when hot


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mexicoke

So boat's been back in the water for ~2 months and seems to have developed a running issue when hot. Boat has the 320 Indmar, port injection engine. 

On the first startup of the day, starts instantly, runs and idles great. 

Once warm, it runs well above an idle, but at idle, especially in gear, it's noticeably rough. It also will take a good 3 count to start once hot. There's also a distinct fuel smell when standing on the swim platform with the engine running. 

 

Things I've checked: 

Fuel Pressure is ~42psi, key on engine off, ~38 at idle, ~43psi WOT. This seems withing spec

When hot, the ECU believes the engine is 159F. This data was capture via https://www.themalibucrew.com/index.php?/forums/topic/52012-lets-talk-mefi/& (thanks to everyone who contributed over there, especially, @GaryDoug for the MEFI2 tool). It shouldn't be over fueling based on that temp feedback. 

 

I'm a little stumped and out of my knowledge base at this point. Any suggestions? 

 

 

 

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What parts have you replaced and when?

for example 

electrical: cap rotor wires plugs icm

fuel: pump✔️ Filters? Cleaned throttle body? Fuel injectors serviced ?

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mexicoke
12 minutes ago, Bozboat said:

electrical: cap rotor wires plugs icm

fuel: pump✔️ Filters? Cleaned throttle body? Fuel injectors serviced ?

Plugs, wires, cap, and rotor were replaced last July, ~40 hours ago. 

It is getting about time for plugs, seems like I should at least pull a couple and check if they are wet. 

Fuel filter also was done in July, nothing else has been changed recently. 

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A leaking fuel injector may be causing an overly rich condition.  See if the fuel pressure drops quickly with the key on and engine off.

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mexicoke
6 hours ago, csleaver said:

See if the fuel pressure drops quickly with the key on and engine off.

I should have mentioned that, fuel pressure was rock solid, key on engine off, for ~10 minutes. 

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I had something similar issue with my former 99 Moomba outback (carbureted). When I turned on the blower The problem was much less noticeable. Then I replaced the vent hoses in the front that connect to the bilge and that helped as well. I assumed it had to do with build up the fumes in the engine bay after running for an extended period of time. 

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Check the condition of the ignition components (cap, rotor, spark plugs, wires), check the ignition timing, and perform a compression test.

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electricjohn
Posted (edited)

Take a good, deep look under your distributor cap and/or try another coil.

Edited by electricjohn
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mexicoke

Looks like I have a few more places to look. 

Sunday/Monday I'll head out and do some more diag work. I'm going to just change plugs, it's close to time anyway. Then I'll inspect the distributor cap and rotor contacts(might just replace). I'll ohm out and inspect the wires and coil. 

I'll dig out a timing light and check timing. (It's been years since I've used one of those, I think I have one somewhere)

I'll bring my scope+clamp and do a relative compression test too. 

Anything else to check?

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17 hours ago, mexicoke said:

Plugs, wires, cap, and rotor were replaced last July, ~40 hours ago. 

It is getting about time for plugs, seems like I should at least pull a couple and check if they are wet. 

Fuel filter also was done in July, nothing else has been changed recently. 

Spark Plugs should be good for awhile 

as electricjohn mentioned replace the coil, get a spare ICM, work on eliminating electrical concerns,  still possible that you have fuel injector issues due to the rich fuel smell 

you may have multiple unrelated issues 

sounds like electrical but then their is the raw fuel smell  

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mexicoke
3 hours ago, Bozboat said:

sounds like electrical but then their is the raw fuel smell  

The raw fuel smell, great cold start, and poor hot start really seems like a rich condition to me. But I'm kinda out of ideas and ways to test them. 

Doing an ignition service isn't a bad idea, I'm just not sure it's my issue. 

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Posted (edited)

When do you get the raw fuel smell

 

maybe replace the idle air controller and the throttle position sensor.  Real mechanic would check them with ohm meter, I would replace both because they are not expensive, they are likely 20 plus years old and while you have the tools out why not.  The IAC made a difference on my 99.

Edited by Bozboat
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I wouldn't throw parts at it until you get the throttle body clean.  Use some spray cleaner and get everything inside clean.  You can open the throttle do get the edges of the butterfly and down in the side passages.

I would suspect a spark miss or sticky injectors before the IAC or TPS.  In fact, you can test your TPS since you have a MEFI reader.  If the values are smooth and follow the throttle, it is good.  The ICM that @Bozboat mentioned is the low-hanging fruit as I see it, because it is also cheap but known to be heat sensitive.  If you check yours or replace it, make sure it has plenty of thermal paste underneath.

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41 minutes ago, justgary said:

I wouldn't throw parts at it until you get the throttle body clean.  Use some spray cleaner and get everything inside clean.  You can open the throttle do get the edges of the butterfly and down in the side passages.

I would suspect a spark miss or sticky injectors before the IAC or TPS.  In fact, you can test your TPS since you have a MEFI reader.  If the values are smooth and follow the throttle, it is good.  The ICM that @Bozboat mentioned is the low-hanging fruit as I see it, because it is also cheap but known to be heat sensitive.  If you check yours or replace it, make sure it has plenty of thermal paste underneath.

What he said 

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mexicoke
13 hours ago, Bozboat said:

When do you get the raw fuel smell

I smell fuel when at idle hot and cold, I assume this is normal when cold based on the water temp sensor.

I did have one more question, if anyone knows: Does the Monsoon 320 with MEFI2 use a manifold air temperature sensor? Looking back at the log files from the MEFI2 tool, I see that sensor is pegged at 300deg/5volts. 

I'm becoming suspicious of my IAC/TPS. I'll bring my meter. 

I'm very against using the parts cannon, much prefer to test and verify issues rather than shotgunning parts into something. You guys have given be lots of test points, thank you! I'll report back. 

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43 minutes ago, mexicoke said:

I smell fuel when at idle hot and cold, I assume this is normal when cold based on the water temp sensor.

I did have one more question, if anyone knows: Does the Monsoon 320 with MEFI2 use a manifold air temperature sensor? Looking back at the log files from the MEFI2 tool, I see that sensor is pegged at 300deg/5volts. 

I'm becoming suspicious of my IAC/TPS. I'll bring my meter. 

I'm very against using the parts cannon, much prefer to test and verify issues rather than shotgunning parts into something. You guys have given be lots of test points, thank you! I'll report back. 

I think the air temperature sensor is for big block applications only.  You should not smell raw fuel when the engine is running, even when cold.

Again, test your TPS with your scan tool.  And the parts cannon only works if everything in the intake is already clean.  Putting a new IAC into a filthy throttle body doesn't make sense, especially if that was the problem and your IAC was good already.

If your plug wires are more than ten years old, just change them.

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mexicoke
24 minutes ago, justgary said:

Again, test your TPS with your scan tool. 

I will, I'll also bring my meter so I can read values at the sensor itself in case there are any discrepancies. Don't want to replace a sensor if there's just a corroded wire, that won't help. 

24 minutes ago, justgary said:

Putting a new IAC into a filthy throttle body doesn't make sense, especially if that was the problem and your IAC was good already.

I'm going to check/clean it. That would obviously be the cheapest and easiest thing to fix. I don't have plans to fire new parts onto anything until I verify they existing ones are bad via testing. 

I'll check the ICM too, not sure I'll be able to determine if there's an issue there though. I'm not sure if that's the best way to test. Any tips?  

Plug wires are less than a year old. 

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Posted (edited)

Most ICMs have a small white paint dot on them that will turn yellow when the module has been overheated.  That is probably the easiest way to determine if the ICM may be causing a problem and if further testing is needed (testing procedures are in the MEFI 4 manual).

Edited by csleaver
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electricjohn
6 hours ago, mexicoke said:

I smell fuel when at idle hot and cold, I assume this is normal when cold based on the water temp sensor.

I did have one more question, if anyone knows: Does the Monsoon 320 with MEFI2 use a manifold air temperature sensor? Looking back at the log files from the MEFI2 tool, I see that sensor is pegged at 300deg/5volts. 

I'm becoming suspicious of my IAC/TPS. I'll bring my meter. 

I'm very against using the parts cannon, much prefer to test and verify issues rather than shotgunning parts into something. You guys have given be lots of test points, thank you! I'll report back. 

I am almost positive there is no MAT input to the MEFI on your engine. My MEFI-4 does not use one. MEFI only looks at MAP for baro and ECT for temperature during cranking.

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Posted (edited)

I have learned a few things today

First, you guys really know what the hell you're talking about. Especially, @justgary, @Bozboat, and @electricjohn. I have officially been humbled. 

Second, when the salesman holds up the list of items just serviced, verify it, all of it. Engine had a supposed full service last July when I purchased, the things I looked at looked brand new(plugs, wires, oil, trans fluid, belt, impeller), the things I should have inspected (cap, rotor) we're in really poor shape. It's embarrassing how bad they were, but here's the picture anyway.  

spacer.png

 

The whole distributor is in pretty poor shape, I'm planning on saving it, but replacement has crossed my mind. The screw heads for the ICM were completely gone. 

spacer.png

Found one of them under the cap. I'd never seen a failure like that before. 

k8jY5NP.jpg

 

The distributer survived removing the ICM, however the ICM did not. Because I couldn't remove the screws, I just cracked it to be able to lift it off. Not a real loss, had clearly seen better days and had the "yellow dot" as described @csleaver

voPhuya.jpg

 

I then removed the remains of the "studs." Little oil and some vice grips. They were very brittle but with a little back and forth complied. 

rue4eVg.jpg

I would have fired the whole thing back together, but it was getting late and the autoparts stores nearby didn't have all the parts needed. I didn't feel like driving 2 hours round trip again.

 

In case anyone cares, my TPS worked perfectly per my scan tool, I did clean the throttle body and IAC but they were pretty clean, not perfect, but not bad. So yea, looks like this has been a spark issue the whole time. 

So I'm going to order a new ICM, rotor, and cap. The standard AC Delco ones are acceptable here right? I'll also need the ICM screws, anyone know what size they are? 

On Wednesday or Thursday I'll clean up the distributer with some scotch bright and a little solvent, reassemble, and test. 

Huge thankyou to everyone who's helped so far. 

 

 

 

Edited by mexicoke
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I'm not sure what size the screws are for the ICM, but they should be easy to source from most automotive stores.  It is important to use thermal grease when installing the new ICM.  Normally, there is grease and instructions included with most replacement parts.

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Posted (edited)
13 hours ago, mexicoke said:

I have learned a few things today

First, you guys really know what the hell you're talking about. Especially, @justgary, @Bozboat, and @electricjohn. I have officially been humbled. 

Second, when the salesman holds up the list of items just serviced, verify it, all of it. Engine had a supposed full service last July when I purchased, the things I looked at looked brand new(plugs, wires, oil, trans fluid, belt, impeller), the things I should have inspected (cap, rotor) we're in really poor shape. It's embarrassing how bad they were, but here's the picture anyway.  

spacer.png

 

The whole distributor is in pretty poor shape, I'm planning on saving it, but replacement has crossed my mind. The screw heads for the ICM were completely gone. 

spacer.png

Found one of them under the cap. I'd never seen a failure like that before. 

k8jY5NP.jpg

 

The distributer survived removing the ICM, however the ICM did not. Because I couldn't remove the screws, I just cracked it to be able to lift it off. Not a real loss, had clearly seen better days and had the "yellow dot" as described @csleaver

voPhuya.jpg

 

I then removed the remains of the "studs." Little oil and some vice grips. They were very brittle but with a little back and forth complied. 

rue4eVg.jpg

I would have fired the whole thing back together, but it was getting late and the autoparts stores nearby didn't have all the parts needed. I didn't feel like driving 2 hours round trip again.

 

In case anyone cares, my TPS worked perfectly per my scan tool, I did clean the throttle body and IAC but they were pretty clean, not perfect, but not bad. So yea, looks like this has been a spark issue the whole time. 

So I'm going to order a new ICM, rotor, and cap. The standard AC Delco ones are acceptable here right? I'll also need the ICM screws, anyone know what size they are? 

On Wednesday or Thursday I'll clean up the distributer with some scotch bright and a little solvent, reassemble, and test. 

Huge thankyou to everyone who's helped so far. 

 

 

 

I learned everything about my boat here. When it comes to mechanics, others are way smarter about this stuff. 

Today I learned about the yellow dot. My wife is wondering why I just exclaimed “yellow dot.” 

I have replaced the ICM years ago when it failed,  but the “yellow dot”...now adding  that to my checklist
 

  I replace the cap and rotor every 3rd year. It always looks worn, I average 30-40 hours a year, they don’t last long, I don’t know why, maybe it is my set up. Regardless, I have found the marine version lasts longer than the automotive version. I buy them at Bakes.  

Edited by Bozboat
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14 hours ago, mexicoke said:

First, you guys really know what the hell you're talking about. Especially, @justgary, @Bozboat, and @electricjohn.

Mostly we learn slowly, but we have seen these same questions many times after hanging around here for a while.

@csleaver is the one who really knows what he is talking about.  He usually waits for us to cram our collective feet in our mouths, then gently pulls them out for us.  A big thanks to him for helping out!

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1 hour ago, justgary said:

Mostly we learn slowly, but we have seen these same questions many times after hanging around here for a while.

@csleaver is the one who really knows what he is talking about.  He usually waits for us to cram our collective feet in our mouths, then gently pulls them out for us.  A big thanks to him for helping out!

then, at the point where we should have absorbed sufficient knowledge, we're old enough that we are not able to remember who said what when.

i know a lot but can't remember it.

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Well, I've got an update and it's good news and bad news. 

I swapped in the new ICM, used lots of heat transfer paste, replaced the screws (size is 3.5x0.6m, 25mm length, Napa wanted $11 for 2 screws, got 50 for $5 from Fastenal, if you need some let me know), new cap and rotor installed too. 

Boat fired right up as always. Unfortunately when hot, I was still having issues, on a hot restart had the same long crank and somewhat rough idle. Rich smell was pervasive when sitting on the platform. 

While sitting at anchor, drinking a beer, I started a little investigation. Pulled the flame arrestor, disconnected the throttle cable and held the butterflies open, with my ear right next to the throttle body I can hear a slight hissing and it reeks of fuel. This is key off sitting for ~10 minutes. I asked my wife if she could hear it too(tinnitus sucks), she could. 

So, I'm 99% sure I have a leaky injector, just don't know what one. Any ideas how to find it? Look at plugs? stick my bore-scope down the intake? Just pull them all and get them serviced? 

What I don't understand is I tested the fuel pressure and didn't see it drop over 10 minutes key on engine off. I cannot remember if that was done cold or hot, so could be a temperature sensitive injector, but that's a guess. 

Thanks as always. 

 

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