Crossflow 140 update - jetting questions and jet sources

[Steve2ManyBoats]

Re-jetted my '82 stock crossflow 140 from 67s to 70s. Way too rich. Stumbled all over the place and the plugs and pistons were quite wet. Very high winds kept me from a sustained WOT run to see if I'd cured my burn down problem.

I did a deeper search of the archives and I'm beginning to think that I may have a power pack that is multifiring. Someone found a similar problem on a crossflow V6 with one lean hole that no amount of fuel could cure. They surmised that they had a power pack that was multifiring and flashing off some of the fuel pulse before combustion, keeping that cylinder way too lean. I'm going back to the 67s and swapping packs (my motor has 2 packs, one for wach bank) to see if the hot piston problem follows the pack. If so, I know I've nailed the problem.

Couple of questions:

1. On a crossflow, when does the motor come on the high speed jets? My idle is still fine, but with the 70s, at anything over 1,800 RPM, the motor is way too rich, stumbling all over itself.

2. Any good sources of jets? BRP "stealership" wants $7 a piece. Sounds like a lot. A cheaper alternative source would be great.

Thanks to those of you who have helped, I think I'm zeroing in on the problem.

Many thanks...Steve2ManyBoats

[EMDSAPMGR]

I was not aware of double firing issues on the older twin-pack engines. Thought this issue was related to the looper V6's that had a single pack.

[Steve2ManyBoats]

EMDSAPMGR - Please set this post:

http://forums.screamandfly.com/forums/showthread.php?t=116857&highlight=chernobyl

Morgan's 6-C describes a problem on a crossflow V6 that sounds like my crossflow V4 problem. Had you heard of this problem? Do you think I might be on the right track?

Thanks for the help.

Steve.

[Morgan's 6-C]

Re-jetted my '82 stock crossflow 140 from 67s to 70s. Way too rich. Stumbled all over the place and the plugs and pistons were quite wet. Very high winds kept me from a sustained WOT run to see if I'd cured my burn down problem.

I did a deeper search of the archives and I'm beginning to think that I may have a power pack that is multifiring. Someone found a similar problem on a crossflow V6 with one lean hole that no amount of fuel could cure. They surmised that they had a power pack that was multifiring and flashing off some of the fuel pulse before combustion, keeping that cylinder way too lean. I'm going back to the 67s and swapping packs (my motor has 2 packs, one for wach bank) to see if the hot piston problem follows the pack. If so, I know I've nailed the problem.

Couple of questions:

1. On a crossflow, when does the motor come on the high speed jets? My idle is still fine, but with the 70s, at anything over 1,800 RPM, the motor is way too rich, stumbling all over itself.

2. Any good sources of jets? BRP "stealership" wants $7 a piece. Sounds like a lot. A cheaper alternative source would be great.

Thanks to those of you who have helped, I think I'm zeroing in on the problem.

Many thanks...Steve2ManyBoats


Just noticed this thread, and with the little information given, it seems much like what I found with the V6-235.

In that case, replacing the pack for the affected cylinder (#4) after several meltdowns and trying everything else, proved to be the lasting fix.

Since this seems to be an ongoing problem for you, I assume you've marked the flywheel and checked timing using each, (or at least the problem) cylinder. That's a good place to start.

Also I would assume that since you're experiencing issues on one cylinder, and are looking at fuel flow or power pack, that you've checked and got good compression there, and that there's no idle or shift-into-gear sputtering problems. ...... Those problems would point towards a reeds/crankcase sealing issue which would cause your lean-out at higher rpms.


Good luck sleuthing it out,



Darlene

[Steve2ManyBoats]

The motor has two fresh pistons and all fresh rings. Compression after 10 hours of break in is 120 per hole, right on the money.

The timing was set at 5,000 rpm under load at 26 degrees BTDC, 2 degrees less than factory spec to give me a cushion while I figure out this problem.

One piston spit aluminum and a second scuffed origially which prompted the rebuild.

Idle ie excellent and off idle is perfect. I just have one hole (bottom starboard) that keeps trying to overheat and spit aluminum. Going richer just bogs the thing down.

My V4 has two power packs, one per bank. I assume that your V6 has/had two power packs, one per bank too.

I've tried to detect a multifire problem by marking the flywheel, but using the timing light in daylight does not show a multifire problem. Could the secondary spark, if there is one, be too weak to pulse the timing light? Did your multifire problem show up on a timing light?

Appreciate your post and help.

Thanks...Steve.

[Morgan's 6-C]

The motor has two fresh pistons and all fresh rings. Compression after 10 hours of break in is 120 per hole, right on the money.

The timing was set at 5,000 rpm under load at 26 degrees BTDC, 2 degrees less than factory spec to give me a cushion while I figure out this problem.

One piston spit aluminum and a second scuffed origially which prompted the rebuild.

Idle ie excellent and off idle is perfect. I just have one hole (bottom starboard) that keeps trying to overheat and spit aluminum. Going richer just bogs the thing down.

My V4 has two power packs, one per bank. I assume that your V6 has/had two power packs, one per bank too.

I've tried to detect a multifire problem by marking the flywheel, but using the timing light in daylight does not show a multifire problem. Could the secondary spark, if there is one, be too weak to pulse the timing light? Did your multifire problem show up on a timing light?

Appreciate your post and help.

Thanks...Steve.


I never saw any multi spark with a timing light, it's useless to look for it that way. The timeframe is so short, you'd need a scope to see it, so I never expected to see it by eye with a timing light. It's possible that it may manifest itself as a slightly blurry appearance when you check the timing with the light connected to the problem cylinder plug wire, but there's no certainty of it.

What you do want to check, is the timing on that cylinder. Mark your flywheel with the problem piston at TDC, then measure over and put a tic mark at 26 BTDC. If the timing shows up as more advanced, it could be the pack, or the other timing related components. Check them, but I'd bet it's the pack.

For the price of a pack, (about $100 at the time) I'd have saved Hundreds of $$$ in 2 subsequent rebuilds (not to mention down time) if I'd replaced the damn thing at the get go.

The V6 had 2 packs, port and starboard.



Darlene

[JWTjr.]

You need to mark TDC for each cylinder on the flywheel and run the engine at all rpm levels with the inductive pickup connected to each plug wire. You should see a steady flash for each wire only on that cylinder's timing mark. If you see multiple flashes, other cylinder's marks (for example, you see cylinder #2 when you are connected to #4) or you see the mark moving back and forth, you have a power pack failure. Replace them if you see any of these oddities.

JT

[SportJ-US-1]

The packs are differnet. The V-6 uses the 3 cylinder pack and the V-4 uses the 2 cylinder pack. They are not triggered the same. Also the V-6 pulses are 60° apart and the V-4's is 90°. You won't have the same result happening even if you had a double fire happen because of the 30° difference in the pulses. I have heard of the double fire, just never in the V-4.

[Morgan's 6-C]

The packs are differnet. The V-6 uses the 3 cylinder pack and the V-4 uses the 2 cylinder pack. They are not triggered the same. Also the V-6 pulses are 60° apart and the V-4's is 90°. You won't have the same result happening even if you had a double fire happen because of the 30° difference in the pulses. I have heard of the double fire, just never in the V-4.


Good point about the difference in pulse timings. It would put any cross (double) fire at a point where it would be hard for it to burn off the incoming charge. OTOH.......

If the SCR in the pack that fires that coil is firing as the voltage rises across it to a high enough threshold, instead of waiting to fire for the trigger signal at the gate, that would manifest itself as advanced timing on that cylinder. .... A very real possibility.

One other thing to ponder, are the little rubber hose pices that squeeze into the water passage around the cylinder to control the water flow all properly installed?



Darlene

[Forkin' Crazy]

This is off topic, but I like you avatar, Darlene! :D

[Morgan's 6-C]

This is off topic, but I like you avatar, Darlene! :D


Me Too,

It expresses so well, exactly how I feel, while having a "blonde moment".



Darlene

[Steve2ManyBoats]

I followed the advice from Morgans-6-C and tested both powerpacks. Both were steady and fired all four cylinders apparently normally, however, I scored two new Sierra replacement powerpacks (for a bonus price in eBay - $20) and replaced both packs anyway. PROBLEM SOLVED!

Took it out on the river today and beat the pi$$ out of it. Numerous WOT runs with chopped throttle plug checks. With the stock jets back in (67's), plugs are fine, teps is fine, piston tops look OK and no more spitting aluminum.

Thanks to all (especially Morgans -6-C) for the advice and help. Nice to have the motor back but it's kind of weird that a powerpack can go bad, fail only at WOT, be virtually undiagnosable, yet be able to take a piston out.

Doesn't leave me with a warm, fuzzy feeling.

Thanks...Steve.

[Morgan's 6-C]

I followed the advice from Morgans-6-C and tested both powerpacks. Both were steady and fired all four cylinders apparently normally, however, I scored two new Sierra replacement powerpacks (for a bonus price in eBay - $20) and replaced both packs anyway. PROBLEM SOLVED!

Took it out on the river today and beat the pi$$ out of it. Numerous WOT runs with chopped throttle plug checks. With the stock jets back in (67's), plugs are fine, teps is fine, piston tops look OK and no more spitting aluminum.

Thanks to all (especially Morgans -6-C) for the advice and help. Nice to have the motor back but it's kind of weird that a powerpack can go bad, fail only at WOT, be virtually undiagnosable, yet be able to take a piston out.

Doesn't leave me with a warm, fuzzy feeling.

Thanks...Steve.



One of the best methods of troubleshooting is to replace the possible/suspected "problems" with "known good" units and see if the problem gets solved. For a shop with spares in inventory, it's not such an issue, but for a guy in his garage, it could get expensive.

As most of us have learned from experience, electronics seem to defy logic with the variations in failure mode that they can exibit.

With power packs and ignition systems, as RPM increases, often times ,so do voltages. A pack may behave just fine at RPMs where you can check it with a timing light, but under high RPM and load, it'll break down and fire prematurely.


Glad you were able to score a good deal on the replacements,



Darlene