5.0 merc efi, fouling plugs, missing, and more

[livethedream]

Hi folks, hate to introduce myself by asking for help, but it happens. i'm new to the boating world and if its as addicting as motorcycling i'll be around here quite a bit to yack and push buttons.

so i'm moderately mechanical and bought a fixer-upper 2000 chaparral sse200. i'm trying to get it running and need some help troubleshooting. here's some background... it wasn't well cared for and sat for an unknown, apparently long, amount of time. the fuel in the tank was nasty yellow and some bits of debris in it and the fuel filter was rusty... given it and the tank had about 15% water. i siphoned out the tank, changed the filter and cleared the lines out and put fresh fuel in, then cleaned all the (fouled) plugs.

with that it started and seemed to run quite good on the muffs, but the next day it was miss firing and stalled and now won't restart.

i pulled the plugs tonight and did a compression test. i don't know the technical number of each cylinder but looking to the stern and down at the motor, they were:

..........stern..........
1 - 150 ...... 5 - 150
2 - 150 ...... 6 - 120 *
3 - 150 ...... 7 - 150
4 - 150 ...... 8 - 150

120 PSI is ok, but does mean something is wrong at cyl #6, or no?

Also, all the plugs were darkened again since cleaning them the day before, except cyl #3 looked exactly as it did when i cleaned it. Like there's no fuel going to it. That plug does spark when grounded though.

Tips on what to do next, or what's happening in there?

 

[Uraijit]

Re: 5.0 merc efi, fouling plugs, missing, and more

Just so you know. Your cylinders are numbered as follows:

-Bow-

1-----2
3-----4
5-----6
7-----8

-Stern-

Ideally, the cylinders should all be within 10% of each other. That lower reading shouldn't cause it not to run, but it should be examined further. Did you try putting 2-3 squirts of oil into the cylinder, to see if it brings the compression back up?

How's your timing?

I'm assuming this is a fuel injected system, being that it's so new?

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

I didn't, will try tomorrow but it wasn't my main concern yet. That dry clean plug bothered me more...

 

[Uraijit]

Re: 5.0 merc efi, fouling plugs, missing, and more

I didn't, will try tomorrow but it wasn't my main concern yet. That dry clean plug bothered me more...

Fuel injected?

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

yep, 5.0 L merc EFI, year 2000, MCM type

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

with this multiport fuel injection, 3 of the 4 cylinders being fed by the one injector are getting fuel, so is the only reason for the dry plug a broken intake valve? or, will that valve not open if it isn't getting a spark signal?

 

[Don S]

Re: 5.0 merc efi, fouling plugs, missing, and more

I assume you have the TBI (Throttle Body) as compared to the Multiport with an injector on each cylinder?
Do you have spark? Is the engine cranking over fast enough? Low battery and slow cranking will not start an EFI engine like it will a carbed engine. The ECM sees to low a voltage to allow it to start.
Have you looked at the cap and rotor? I would sure recommend NEW plugs, cap and rotor if they are over 2 years old, regardless the number of hours on the engine.

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

thanks Don,

yep there's spark at this plug when cranking. battery is a strong 12.4, cranks strong, no problem there.

it is the throttle body with 2 injectors at the top, each feeding 4 cyl's.

new plugs and wires will be done, but why no fuel in that one?

 

[Don S]

Re: 5.0 merc efi, fouling plugs, missing, and more

Also, all the plugs were darkened again since cleaning them the day before, except cyl #3 looked exactly as it did when i cleaned it. Like there's no fuel going to it. That plug does spark when grounded though.

Might want to do a leakdown test on that cylinder, you may be getting water in the cylinder which would basically be steam cleaning that spark plug.
When running, if you pull the plug wire off that plug, does the engine rpm drop and do you hear a miss?

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

the dry cylinder (#3) had full compression at 150 psi, so there wouldn't be a leak correct?

it's a different cyl (#6) thats low at 120, but will do a leak down on that one today.

 

[Tail_Gunner]

Re: 5.0 merc efi, fouling plugs, missing, and more

Plug's in a boat engine look terrible as compared to plug's in a car engine...no light tan at all...very dark and look fouled. I wish i had some pics i once took of a 1 yr old set... gruesome looking.

Have you peered into your throttle body while under power..the two injector's should fire a even circular mist...very uniform...and smack dab into somekind of plate... seems crazy but it works.. firing that atomized stream into the wall and watch it drip it that is..

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

i wish i could get get it under power. i'd like it to start and idle to begin with. lol

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

When running, if you pull the plug wire off that plug, does the engine rpm drop and do you hear a miss?

i wish i could get it running long enough to test that. for the short minute or two that it was idling (then stalled and wouldn't restart), the engine was missing. given the one dry plug at cyl #3, it would be safe to assume so far that that is the one needing attention... not getting fuel.

 

[Don S]

Re: 5.0 merc efi, fouling plugs, missing, and more

The leakdown test isn't to find a compression leak, but to find a coolant leak to the cylinder more of a cylinder pressure test than a leakdown test.
Best thing to do is remove a hose from the thermostat housing and hook up a clear hose and fill with water. Then pressurize the cylinder with the valves closed and see if any bubble come to the surface.
Sort of like shown in the volvo overheat tests in this link.
http://www.4shared.com/account/file/50572185/e88f1d89/Volvo_Penta_Overheat_Diagnosis.html

Have you tried putting the throttle to the WOT position and trying to start? That is the clear flood mode of starting.
Here is a link to the OEM manual for your engine you can download.
http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/24/24covr1.pdf

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

interesting, ok will try that today too.

i did try a wot start and it didn't help.

 

[Don S]

Re: 5.0 merc efi, fouling plugs, missing, and more

i did try a wot start and it didn't help.

Pour a little gas into the throttle body and see if the engine fires at all.
Have you done any fuel pressure tests yet?

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

thats on the list today too.

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

k, i didn't get nearly as much done as i hoped today but here's an update.

installed all new plugs - started right up but is still missing, then stalls from idle after about 30s to a minute. If i hold the rpm up around 2,000 it'll keep running but again, missing.

While it was running i took the spark arrestor off to see the injector spray and it looks really good. strong clean circle pattern. I wasn't able to test the pump but by the look of the spray i don't think its a fuel problem.

I have a cap and rotor coming and will do that tomorrow, but any other thoughts? Battery was fully charged at 12.8v and i'm now at a loss. I really really hate taking stuff to shops and paying $120/hr!

 

[Uraijit]

Re: 5.0 merc efi, fouling plugs, missing, and more

Did you get a chance to check your timing on it? If it's running, you should be able to check that now.

Did you try pulling that "dead" plug, and looking at it? If it's still not getting fuel, you may have an intake valve that's not opening.

 

[livethedream]

Re: 5.0 merc efi, fouling plugs, missing, and more

haven't checked the timing yet, i'll have to work thru the manual on that one.

but that previous dry plug was nagging my brain just now cuz i didn't get a chance to pull it before it started raining... so i took the chance of melting (i'm made of sugar) and just went out and pulled the 4 on that side and they all have a nice tan bake to them. now i'm really confused.