Sad motor - what to check next?

[gmacrae]

Two clean plugs, humm that would definitely buck. I think that would point to ignition or water leak. If you shined a lite up in the bored while turning did you see any stains in a bore?

What i could see of the bores looked great, but I couldn’t really see much... A water leak would have to come via the headgasket right? Leaking into 2 cylinders would be unlikely... The ECU only runs 3 injector drivers (1+2, 3+4, 5+6), so if one was faulty if could hold both injectors wide open and flood those cyls. I think the clean plugs might’ve come from 3+4...that’s the latest theory anyway... still struggling to get my hands on the required tools and time (leakdown tester, noid lights or scope to check the injectors)...

[gmacrae]

Ok I got myself a (cheap) leakdown tester, and it says all cyls are 5-10% (each piston about 10mm below TDC)



Problem is, when I wound each cylinder down to around BDC it only showed each to be at 60% (in the "moderate" range). Instructions it came with said to "calibrate" the tester by winding the regulator up till the leakdown gauge is at 0 (by which time the pressure gauge reads about 29psi), then plug it into the plug hole hose. I would've liked to test each at 100psi like everyone has suggested but even 50psi would cause the leakdown gauge to be pinned way above its range. Frustrating!

So I pulled the heads off to have a proper look - all the bores look shiny and smooth. Definitely no evidence of a ring scuffing anything up. The only thing that looks out of place is a pinhole in 2 of the bores (pictured is #5, but #4 has a similar hole in the same spot)

Hard to see how this could be caused, or if its worth worrying about?




Here are the underside of the heads - all looks about right to me?



If this all looks ok, I'm just going to order new CCMS reeds, get a small amount milled off the heads at a local auto engine shop, and put it all back together. Any suggestions of a safe amount to mill the heads? I always run 98ron/93mon.

Would love any feedback you guys can sling my way!

[Motv18]

3, 5 look washed pretty good, from the intake port.

So much seems to test good, the pool of fluid worries me some but appears to be fuel oil even though dark.

I hate are doing it over the net, but it starting to look like a peeing injectors ( vapor goes boom, liquid might just burn and miss) will test normal since it’s a mechanical issue with the jet. That much carbon build up I could see the injectors getting crusty.

[gmacrae]

3, 5 look washed pretty good, from the intake port.

So much seems to test good, the pool of fluid worries me some but appears to be fuel oil even though dark.

I hate are doing it over the net, but it starting to look like a peeing injectors ( vapor goes boom, liquid might just burn and miss) will test normal since it’s a mechanical issue with the jet. That much carbon build up I could see the injectors getting crusty.

Yeah 3 and 5 do appear a bit washed, i gather they are the 2 clean plugs... I had the injectors out a few months back to replace all the orings and they were clean as a whistle, but may as well get them cleaned and flow tested for sure. The rest of the crankcase is surprisingly clean, it looks like new in the front half.

Can anyone recommend a safe amount to have the heads skimmed? A little more compression would be good as I always run good gas, and I'd like them resurfaced for reinstalling anyway

[Capt.Insane-o]

It's filthy rich.

[nitro_rat]

the pool of fluid worries me some

Sorry, I couldn’t resist quoting that...

[gmacrae]

Ha. Yep cheers fellas. Filthy rich it is. Cleaning/flowing the injectors tomorrow.

Have CC'd the heads, they're stock 38cc, milling 4mm off should take them down to about 35cc - this isn't going overboard, right?

Also, I am OK to re-use the stock headbolts @ 35ftlbs as I've seen in here? Understand the stock 30lbft+90degrees is a bad idea for used bolts...

[gmacrae]

OK injectors were fine but are nice and clean now anyway. Motor all back together with new reeds, stuffers, 34cc heads, same problem still. Starts fine but is still super rich. At idle my multimeter says all 3 injector drives are at ~80% duty. Definitely looking like the ECU... (well called Capt!)

Anyone got a cheap Brucato they wanna sell me?? Damned if I can afford full retail right now!

[gmacrae]

Looks like I've got this motor running great, after a long winter of cursing and swearing at it! Will update with all details soon

Quick question, with no modules on the motor, consensus seems to be 25 degrees max timing on a 2.4 - that's what you guys would recommend? marks only go to 24

[Capt.Insane-o]

Light boat, good gas 25 is fine.

[KIRCHNER]

[QUOTE=gmacrae;3031275]Hi guys, wondering if you might be able to help me diagnose this old girl, motor is a Merc Laser 220

I was coming home across the lake the other day, started perfect, came out of slow zone, put the foot down, got on plane as per usual, then after about a minute cruising at about 4000rpm the revs dropped about 1000rpm, continued running though, then as i backed right off it started kinda bucking (would be the best way to describe it)... It taking it real slow to the nearest beach @ 1000rpm it would continue to buck, with the occasional sneeze. The bucks/misses would often cause it to stall outright. Start back up straight away and carry on at 1000rpm, bucking, sneezing, stalling. Got towed the rest of the way back.

The bucks would send thru the gearbox and initially made me think the gearbox had crapped itself. Have since drained the gearbox and there were no metallic bits in there, oil looked fine.

Have also tested compressions thinking maybe a ring picked up, but all are 120-125 after 2 seconds cranking (all plugs out) and come up on the gauge quickly.

New spark plugs installed (they were quite old) and its still not happy. Will run/idle ok but gave a solid backfire once (exhaust) and is running pretty rough/weak

Timing light shows all cylinders are firing.

Plugs show all are getting fuel/wet.

Gave it new coils/leads/switchboxes/stator last year, triggers about 7 years ago.

Reeds maybe the culprit?

Where would you guys say to look next? It is an old motor and i've had a pretty good run, but hopeful she's not dead yet, after seeing the compression numbers...

Thanks for looking

Gene[ HEY its ART same motor mine got so bad cant even start, fuel pouring into case black sludge, smoked, &quit i think its over.

[tunnelmike]

Thanks for the update. Mike.

[gmacrae]

HEY its ART same motor mine got so bad cant even start, fuel pouring into case black sludge, smoked, &quit i think its over.

Ahh **** sorry to hear Art! Did you ever try another ECU? Mine seems to have a new lease on life. I'll write up everything that happened in here tonight so ya'll can have a good laugh at me! Well I've learnt a lot at least so I can't complain

[KIRCHNER]

YEAH new acu it did nothing except empty my wallet! elect pump runs longer than usual when i turn ign on. pressure @ 40 lbs. fuel dumping in fron somewhere, not vst. cranked with pump wire off and got some life and backfire. good spark good comp timing spot on my exhaust looks like texas oil well gone bad. cant start now. i took .060 off heads for 32.5 cc. ART

[gmacrae]

YEAH new acu it did nothing except empty my wallet! elect pump runs longer than usual when i turn ign on. pressure @ 40 lbs. fuel dumping in fron somewhere, not vst. cranked with pump wire off and got some life and backfire. good spark good comp timing spot on my exhaust looks like texas oil well gone bad. cant start now. i took .060 off heads for 32.5 cc. ART

I noticed mine (with the ACU) ran the EFI pump on when I disconnected the head temp sensor - possible you have a break in the head temp sensor circuit? That'll dump a lot of fuel in. Check continuity from the 2 sensor bullets right back to the ECU plug?