Heat difference in heads

[rdeyoe]

Re: Heat difference in heads

Thanks guys. Really appreciate all the input. I'm pretty good with auto motors and have some time on aircraft turbines too, but this is just a big weed-eater motor....and my garage floor has 4 non-running weed-eaters sitting on it. Hate to get this one wrong!

@dazk: yeah, that big chunk on #1 has me a bit worried. Since I have to get a new gasket in there anyways, might as well go with a different head too. It may be 'good enough' to run, but I'd rather that all the cyls are balanced. Got a lot of $ tied up in machining and parts (actually, my girl does...she's the money, i'm just the hands), might as well do it right. I only have about 10 minutes of run time on it now, hate for something to let go now.

@dasel: I was hoping i had them wrong too. I'll do the head and gasket this weekend, try to get some run time on it and check the timing again, then go after the heat issue.

 

[rdeyoe]

Re: Heat difference in heads

@dasel & dazk: Just a quick question: I've heard of the "lean sneeze" backfire....i'm wondering if my backfire could be caused by that polished #1 cylinder. I don't have pics of that cyl. after i did the cleanup, but that plug looked different,...perhaps hotter than the other three. Maybe just shining up that head is causing the 'sneeze'? Trying to source a head and gasket now. But it strikes me that most of the head pics i've seen are textured and maybe polishing (even slightly) like you would do in a hot rod head (to get more flame front) is bad for these 2-cycles. I did the carbs last year. They weren't bad to begin with, but they've gotten a good cleaning, orifices wired out, chemical cleaning on all the dirty parts and float levels set. I'm pretty confident that they're feeding well, so i'm not leaning toward a lean sneeze. Even with the limited time the motor's run, there seems to be plenty of oil smoke, and wet plugs on shutdown. "Sneezing" doesn't seem to be an issue, with all this in mind to me. Could one cylinder firing early make it run backwards?

 

[rdeyoe]

Re: Heat difference in heads

Hey dasel: I made a stand to hold some old plugs in and bolted it to a ground on the engine. Turns out that I only have spark on one cyl. The number 3 seems to be the only one firing. Going to check all harnesses and such. I've searched around here, but I can't seem to find a troubleshooting procedure. There's a lot of component replacement in the manual, but no real troubleshooting either. Anyone good with these ignitions?

 

[daselbee]

Re: Heat difference in heads

I find it a stretch for that V4 to run on only one cyl. Are you sure of what you are seeing? For a good troubleshooting step by step procedure, go to

http://issuu.com/cdielectronics/doc...t.xml&backgroundColor=000000&showFlipBtn=true

and find the OMC section, there will be a section that pertains to your ignition. I would suspect wiring first, since you had it all apart.

Also, if using old spark plugs for testing, be aware that this method does not verify/guarantee spark quality. You need to have that spark jup a 7/16 gap with a good strong blue spark, and a sharp snap. Ten dollar adjustable tool avail. at the auto parts store. Or make one.

This is what I use.

http://ehardware77.ecrater.com/p/3274031/ignition-spark-plug-tester-tool

 

[rdeyoe]

Re: Heat difference in heads

More interesting news. After checking all connectors and such, I got 2,3 & 4 firing. I indexed the cyls on the fly wheel, and cranked it. I suddenly had 2 and 4 in reversed order, by the light! ACK! I only traced the orange / blue up to the point where it went into some insulation. After much tugging and pulling, I did find the 2-4 coils were reversed...you were right!

I'm still having issues with 1 not firing though. When I bought the boat, I noticed that someone had butt-connected that coil wire outside the connector...or maybe it was just cut, I can't remember now. I re-spliced it, but no joy. Checked the voltage from the power pack...nada. Pulled the power packs and switched them, still no fire on 1 (so power pack is ok. I pulled the four pin connectors from the packs and did ohm tests. Terminals A to B and A to C give ~33 ohms on port side. A to B on stbd is ~33 also, but A to C is infinite. Is this cyl one? This is testing back to timer base, so maybe I have a bad timer base? I checked the blue / white wire in C all the way back to the base, no breaks. Could the #1 fire at all with it's coil not plugged into the power pack? I was pretty sure it was firing before, I've had the timing light on it to set idle timing.

Thanks for all your help....I have the 2-4 coils switched correctly now, and I think that if I get #1 firing, I'd be golden. I'm feeling pretty certain the timer base is going out, maybe sporadically.

 

[daselbee]

Re: Heat difference in heads

Now you are making progress. I cannot tell you which terminal provides trigger signal for #1 cylinder, but maybe they are color coded.
On the V6 (mid-90s loopers) the timer base has 2 four pin connectors coming from the timer base. They have terminals A, B, C, and D.
There is a color code to them, and it follows just like the orange/blue - orange/green discussion above.

Only it differs slightly. The trigger signal for the top cyls on a V6 is a blue wire. The trigger signal for the bottom cyls is a green wire. It only differs for the middle cyl in that it has a purple wire there.

So why am I going on about this? Maybe the trigger wires on your timer base are blue and green. If so, you know which cyls they apply to.

 

[rdeyoe]

Re: Heat difference in heads

I think they are the same. The A terminals are white on port side, white / black on stbd. The B terminals are green (port) and green / white (stbd) and the C terminals are blue (port), blue / white (stbd). I'm surmising that the lack of resistance between the white/black and blue/white indicates the top coil (#1) trigger circuit and hence, no fire there. Must've just gone bad. I'm going to try to source a timing base and try that.

Started raining in NW Tn today, so I've got some time to work on it, but it feels that it's getting closer. Been getting frustrated with it, but I think once I straighten all the small stuff out, she'll run pretty well. Will keep ya'll posted...

 

[rdeyoe]

Re: Heat difference in heads

Just an update. Got the timer base in. The resistance values were better than my old one....and the #1 cyl is firing again. Put the power packs back to their rightful positions again, new (used) timer base in place and got fire on all four now. Filled up the test tank and (after some battery issues...old batter with no crank amps), primed up (fixed some large fuel leaks at the pump feed line), she fired up! Idle was a little high, so cranked back on the carb linkage a tad, checked timing and adjusted. Checked head temps (after assuring the right coils are in the right plug..duh!) and head temps are ~135 stbd, and ~128 port....close enough, i figure. The head gasket leak i thought i had is just the thermostat hose leaking that way...may have to change the hoses...they all leak quite a bit. Adjusted timing to 4* at idle. Still starts a bit hard cold, but when warm it's a one shot deal. Going to take it to the river next weekend. Just wanted to thank you dase for your insight. It's running on all four now. The river run will tell more (and I'm sure more tuning) but, for now it looks decent.

I took some compression readings too between runs and the port side is 115 on both cyls, the stbd is 105 on both. Not bad, but I'm thinking that side head still needs to be changed out. Also, the #1 cyl is getting more carbon than all the rest. Running hotter? Doesn't sound crucial, but i'm going to keep my eyes open for a head.

Thanks to all the experts here...appreciate all the help.

 

[rdeyoe]

Re: Heat difference in heads

Got her on the river this weekend. Started very nicely, after about three cranks....better than it ever has actually. Had six on the boat, but we were just going to do some river cruising and break-in. The idle was at 650-700 and pretty smooth. We headed out and had a misfire condition on something....felt like it was running on two cyls. Got the hood off and checked plug wires and all ignition connections. Didn't really find anything, but on the run back, it just fixed itself (?). Did about 10 minutes going from 1000 to 2500 for a few seconds and back. Then about a half hour getting to 3000 for thirty seconds and back down to cool. Then about another half hour getting to plane (~3500) for thirty seconds, with bursts to WOT. Runs really strong and smooth. There is an issue at full WOT where it feels like carbs are emptying after 15 seconds or so. I replaced the fuel pump last year and a leaking fuel line last week. The line has a sharp 90 degree bend in it, maybe kinking. I'll pull the fuel pump and check again.

Warm starts are just a bump....barely have to crank at all and she fires straight up. We probably got a good couple of hours on it at all rpms. It's very torquey. It's getting out of the hole well and up on plane pretty quickly for this boat (19' Viking Deck boat...not exactly a small craft). Probably stronger than I've ever felt it to be.

Came home and flushed, checked plugs (#1 still looks to be a bit hotter than the others) and did a compression check. #1 and #3 are about 130 psi, #2 is about 145 and #4 is around 140, sounds like the rings are sealing to me. I think after some tuning in the fuel pump and lines, the WOT problem should go away. Could be that we didn't fill the tanks completely too....will do that next time.

All in all, considering it a success so far. Hopefully, with a bit more break in and some good care it will last a while.....