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TheWebDude
01-25-2008, 01:25 PM
Owner of a '84 Stars 'n Stripes with 351 Ford engine. No powerslot.

Better wrenches than I will ever be have had a devil of time diagnosing what is causing a "miss" at high/top end. Starts up, idles great, runs well at lower rpms, but once you hit skiing speeds(55K and 58K aka 34mph and 36mph, it misses and coughs. The problem then starts out at even lower rpms the warmer the engine gets.

We've tried a number of things and have ruled out:

carburetor
plugs
plug wires
rotor
electronic ignition module
distributor cap
coil
fuel pump
fuel line
timing

Voltage checks out. (I have an older model Perfect Pass speed control device on it, and the system is sending enough voltage to run it).
Besides, I believe the issue crops up whether or not the Perfect Pass is engaged.

Compression is ok in all eight cylinders.

My ace wrench (a nationally rated tournament driver who has worked on the boat since it was owned by the previous owner) has probably also tried a number of other things I've failed to mention here -- like checking out the electrical path leading to the ignition and such. I think the dang thing is starting to give him nightmares.

Yeah, I know, time for a new boat, but sheesh, it's a fine old ski boat and there aren't that many moving parts on such a model (not like today's).

He's also been through the fueling system a number of times and things check out there.

We are contemplating pulling the distributor from a working engine and seeing if that does anything. Wondering if anyone has any other suggestions.


If your browser is equipped with the Flash player, you can watch a video of recent lake test here (http://www.bayvideo.com/news/dangboat.html).


For more gory details:

The Troubled MasterCraft (http://inmotion.typepad.com/wed_rather_be_skiin/2007/08/the-troubled-ma.html)
and
The MasterCraft repair blues (http://inmotion.typepad.com/wed_rather_be_skiin/2007/08/mastercraft-rep.html).

Any ideas for a fix are welcome and thanks very much

-TWD

JLeuck64
01-25-2008, 02:07 PM
Dang!
That's a bummer.
It would be real cool if you new someone that could hook up some of the more common test equipment during a lake test. Early on during the video it sounded like the engine started to labor when the secondaries were opening up, would be nice to now what the fuel pressure looked like. But, you guys have probably been through all that.

Later on as she heated up it started craping out at a lower RPM, and it sounded like a cylinder dropping out electrically. Would be nice to hook up a scope to watch both the Primary and Secondary ignition during this time. It could also help to identify a worn timing chain and/or distributor as you were suspecting. If that stuff is not available and you have known good ignition parts to swap, give it a try. Don't forget the coil too...

Mechanically, if you could hook up a vacuum gauge it could help to diagnose some of the off the wall stuff like weak or broken valve springs. There is a pretty cool animated vacuum gauge website here

http://www.users.bigpond.com/ergoff/OTHER.HTM

kurtr
01-25-2008, 03:21 PM
What is the tach doing when the engine misses? Is it steady or does it bounce around? I have seen tachs be the cause of random misses, can your expert disconnect the tach before or during a test drive? It is my understanding that if the tach is steady the distributor is consistently firing the coil. If the tach is bouncing around I would start looking into the ignition system for the reason for the bounce. Your engine cannot instantly change rpm a tach that is instantly changing 500 to 1000 rpm would seem to be some type of problem in the ignition system.

Footin
01-25-2008, 03:25 PM
I would pull the cap and rotor and see if there are metal shavings anywhere under there. The bushings in the distibutor wear sometimes any cause the shaft to "bounce" around.

Footin
01-25-2008, 03:26 PM
Also there is a pick up screen inside the tank. It may be clogged.

the legend
01-25-2008, 05:11 PM
This might sound basic, (ignore if already checked) but i had a 35th Anniv. in the shop w/ the same issues and found that the ignition switch was loosing the ignition voltage just long enough that it caused all sorts of misses. I had several runs out on the lake with the customer with all different loads, non loads, hot,cold,ect. I found the problem when I shut the boat off and tried to restart when I noticed the starter sounded like it was delayed. I replaced the ignition switch and the problem was solved. I did not read the whole thread so I hope I haven't repeated anything someone else already said. Also check the connections @ the battery, make sure they are tight.Owner of a '84 Stars 'n Stripes with 351 Ford engine. No powerslot.

Better wrenches than I will ever be have had a devil of time diagnosing what is causing a "miss" at high/top end. Starts up, idles great, runs well at lower rpms, but once you hit skiing speeds(55K and 58K aka 34mph and 36mph, it misses and coughs. The problem then starts out at even lower rpms the warmer the engine gets.

We've tried a number of things and have ruled out:

carburetor
plugs
plug wires
rotor
electronic ignition module
distributor cap
coil
fuel pump
fuel line
timing

Voltage checks out. (I have an older model Perfect Pass speed control device on it, and the system is sending enough voltage to run it).
Besides, I believe the issue crops up whether or not the Perfect Pass is engaged.

Compression is ok in all eight cylinders.

My ace wrench (a nationally rated tournament driver who has worked on the boat since it was owned by the previous owner) has probably also tried a number of other things I've failed to mention here -- like checking out the electrical path leading to the ignition and such. I think the dang thing is starting to give him nightmares.

Yeah, I know, time for a new boat, but sheesh, it's a fine old ski boat and there aren't that many moving parts on such a model (not like today's).

He's also been through the fueling system a number of times and things check out there.

We are contemplating pulling the distributor from a working engine and seeing if that does anything. Wondering if anyone has any other suggestions.


If your browser is equipped with the Flash player, you can watch a video of recent lake test here (http://www.bayvideo.com/news/dangboat.html).


For more gory details:

The Troubled MasterCraft (http://inmotion.typepad.com/wed_rather_be_skiin/2007/08/the-troubled-ma.html)
and
The MasterCraft repair blues (http://inmotion.typepad.com/wed_rather_be_skiin/2007/08/mastercraft-rep.html).

Any ideas for a fix are welcome and thanks very much

-TWD

454Prostar190
01-25-2008, 05:36 PM
On a Ford truck that I had with a 302, the cam lobe that operates the fuel pump wore to the point that it didn't push the lever on the fuel pump down far enough for the fuel pump operate to it's full capabilities. The truck would surge at WOT because the carb bowls were emptying and then filling because the fuel pump wasn't keeping up. I think that I put an electric pump on it rather than a new cam and it fixed it.

learjet2230
01-25-2008, 05:47 PM
Guys, this looks/sounds like fuel delivery issues to me. Sounds like the engine is actually running lean (air leak), or not getting enough fuel. I would check these, it doesn't appear or sound electrical to me.
Check fuel pressure
Check fuel vent (clogged vent does that at high speed only)
Check Fuel tank screen (if there is one)
Is the gas fresh (no water)
Check the secondaries on the carb....run with the engine cover off and see if they open during a full throttle run. If the secondary diaphram is not holding good vacuum they may be opening and closing causing the surge. Let us know. I'm very interested.

BrianM
01-25-2008, 06:01 PM
distributer would be the next thing I checked. Swap it with a known good one.

TRBenj
01-25-2008, 06:12 PM
Guys, this looks/sounds like fuel delivery issues to me. Sounds like the engine is actually running lean (air leak), or not getting enough fuel. I would check these, it doesn't appear or sound electrical to me.
Check fuel pressure
Check fuel vent (clogged vent does that at high speed only)
Check Fuel tank screen (if there is one)
Is the gas fresh (no water)
Check the secondaries on the carb....run with the engine cover off and see if they open during a full throttle run. If the secondary diaphram is not holding good vacuum they may be opening and closing causing the surge. Let us know. I'm very interested.
While my first inclination would be to say that its a fuel issue, the absolute first thing you MUST DO is put a timing light on it. Check the base timing (idle) and full advance (which should occur by 3k RPM).

Assuming the timing checks out, move on to fuel. It seems like the problem starts surfacing right around the time when the secondaries kick in (3600-4000 RPM). How long has the problem been happening? You said the carb was rebuilt- did that coincide with when the problem surfaced? You said you checked the fuel line and the screen at the tank. Did you verify that the check valve on the pickup wasnt clogged or broken?

88 PS190
01-25-2008, 06:37 PM
distributer would be the next thing I checked. Swap it with a known good one.

Its an interesting idea, I've seen a distributor with some wear in its bushings show up on an oscilloscope and you could feel it miss at higher rpm. Couldn't see any issues with timing, and replaced many ignition items before discovering the cause and repairing the distributor.

Wasn't quite like that, but it was in a 4 cylinder.

Cam lobe for fuel pump is an interesting thought, wouldn't the pressure be low at all rpms? Or is the pressure fine but the volume lacking at speed?

TheWebDude
01-27-2008, 12:42 PM
Guys: These are all great suggestions and I will pass them on to my ace wrench. (who's not a huge Web feller to my knowledge)..

I y'am kicking myself for not having posted here ages ago. We'd probably have the "dang boat" running by now.

We do have a good distributor we can swap and that's what we were thinking of doing this coming week and will post further after that.

To answer some of the questions I know the answers to:

What is the tach doing when the engine misses?: We've disconnected the tach and the problem persists

Ignition switch? (That could very well be the issue, as I recall replacing it with a "cheapie" ages ago. ) However, I also recall that we bypassed the switch via a "hot wire" and the problem persisted.

We will check the cam lobe as well.

We've put a timing light on it at idle, but will check to see that we've put one on "at load."

Thanks again, very much!

-TWD

TheWebDude
01-30-2008, 10:22 PM
So guys, I did promise an update, but it is not much, as my "ace" has to undergo knee surgery this Friday and our latest lake test has been postponed to mid. Feb. until I return from some travels in a few weeks.

Just to carry on with the fuel pressure issue: we ran it with a pressure gauge attached (from the tank, I believe) and there was a bit of a wobble or drop, but it was difficult to tell what was causing it.

So, in addition to our idea to swap the distributor with a known good one, we are also going to put a clear fuel line on to the carb from the tank, to see if we can eyeball what is going on.

:(

learjet2230
01-31-2008, 08:18 AM
So guys, I did promise an update, but it is not much, as my "ace" has to undergo knee surgery this Friday and our latest lake test has been postponed to mid. Feb. until I return from some travels in a few weeks.

Just to carry on with the fuel pressure issue: we ran it with a pressure gauge attached (from the tank, I believe) and there was a bit of a wobble or drop, but it was difficult to tell what was causing it.

So, in addition to our idea to swap the distributor with a known good one, we are also going to put a clear fuel line on to the carb from the tank, to see if we can eyeball what is going on.

:(
You need to check pressure down stream of the pump. Does that boat have a pump in the tank?

dichdoc
02-05-2008, 10:28 PM
My 84 did the ignition switch thing too. Miss at speed at random times ski with an electrical engineer who traced it to the switch in about 3 minutes with a meter. TB

TheWebDude
03-27-2008, 03:16 PM
BrianM wins the refrigerator! We tried running it a second time with the fuel pressure gauge hooked up to the fuel line running from the tank, and also used a clear (see-through) line in the fuel chain.

There was no noticeable surge in fuel in the line, or on the pressure gauge. Having been through every inch of the fuel system, we ruled it out.

That left us with the distributer, which we stole from my brother's Nautique (don't tell him ;) -- and, neither of us had any great expectations we'd get anything other than the same old same old...

Lo and behold, the cough and sputter went away!

As the final test was conducted on Good Friday, I concluded that my guy had raised my boat from the dead ;)

The only questions I would like answered now, if someone could please...

1) Why didn't we think of this sooner?

2) What is it about the bad distributor that screwed things up?

Thankee kindly for all the input!

bturner2
03-28-2008, 08:33 PM
I had a 89 TriStar that had a simular miss that got worse as the day went on. It turned out to be the ignition switch. I found it by accident when I bumped the key while it was running. I was actually able to stop the engine by shaking the key while it was running. I know it sounds crazy but that's what happened.

sbuell
03-31-2008, 01:51 PM
Short of replacing it is there a good way to determine if I have issues with my distributor? I seem to have a very similar issue. I have been through pretty much everything else already listed here. If I do need to replace does anyone have a source for just the distributor. Through all of this I have replaced everything that already comes with the new one from skidim.com (electronic ignition, cap...)

TRBenj
03-31-2008, 02:27 PM
That left us with the distributer, which we stole from my brother's Nautique (don't tell him ;)

The only questions I would like answered now, if someone could please...

1) Why didn't we think of this sooner?

2) What is it about the bad distributor that screwed things up?

Youre lucky that your brother's distributor dropped right in. CC did not install conventional LH distributors into very many of their Ford engines. They primarily used RH engines (different dist gear) until '89, and they started installing distributorless ignitions in '91. You got lucky there.

Like I said in my first post:

the absolute first thing you MUST DO is put a timing light on it. Check the base timing (idle) and full advance (which should occur by 3k RPM).
You always need to check timing (both base and full advance) when diagnosing an issue like this. For a stock Ford 351w, timing should go from ~10deg to ~34deg at full advance, which should occur by 3,000 RPM.

It sounds like the weights/springs werent advancing properly, resulting in high RPM problems. Try taking it apart and see how freely they move.