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Sputtering Supra Comp |
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psotama 
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Joined: 12 May 2005 Status: Offline Points: 1 |
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 Topic: Sputtering Supra CompPosted: 12 May 2005 at 11:14am |
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I have an '85 Supra Comp with a 351W. This spring replaced spark plugs, fuel filter and switched to electronic ignition (eliminated ballist resistor, did not replace coil). The engine runs and starts fine, but after being at higher speeds (~25-28 mph) the engine begins to sputters/surges. If I flutter the throttle sometimes is pulls through, but eventually it will bog down and stall. I confirm I have spark throughout the sputters (timing light flashing). Once the above systems occur, the engine eventually sputters at lower speeds, too. Could the culprit be bad fuel or water in fuel? I've added fuel additives for water, but doesn't solve issue. Any advice is appreciated. |
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BarefootOz
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Mr. Oz Joined: 22 July 2004 Location: United States Status: Offline Points: 23 |
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Posted: 12 May 2005 at 11:31am |
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Psotama,
I would go to the fuel pump next...  |
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Ski ya later,
Oz |
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CTSkier
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Posted: 16 September 2005 at 10:47pm |
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Psotama, Did you ever figure out what was wrong with your Supra? My '83 has the sames issues. So far I have verified that the fuel lines are clear, changed the fuel pump, carb, distributor (with electronic ignition), coil, fuel/water separator. Still, the issue persists. Tomorrow I'm changing the plugs and wires. I'm quickly running out of fixes. Help!! Sean
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GottaSki
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Joined: 23 July 2004 Location: United States Status: Offline Points: 116 |
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Posted: 17 September 2005 at 9:27am |
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Fuel pump is suspect, and is doomed to fail if original.but this is best checked first.... There is sometimes a cone shaped screen filter sandwiched within the fittings of the fuel tank's dip tube and 90 degree elbow. It clogs over 20 years and induce fits with owners and mechanics. Fuel starvation occurs at progressively lower speeds and shorter durations as it clogs. '80's centurians had them, perhaps yours does too. Yank it out and rely on your filter/separator cartrige for filtration. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Tommya
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Joined: 21 May 2007 Location: United States Status: Offline Points: 5 |
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Posted: 21 May 2007 at 5:30pm |
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I've got a similar problem with a 351 Ford in my 85 Centurian. That Elbow was old with high flow resistance (to check it, I just blew into it and could tell it was too much resistance--Yuck--gas breath). Since the symptoms are the same as "Postama" I was wondering if the resistance to flow could have weakend the fuel pump? One thing I did this weekend to trouble shoot it was to run it till the problem started and then I cool down the fuel pump by pooring lake water on it. The problem temporarily went away. But, Vaper lock would do this also. BTW, who makes a good inexpensive in line fuel pressure guage? I understand it should be about 5-7 PSI at at the carb inlet at idle is that right? |
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83Centurion
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Posted: 21 May 2007 at 5:57pm |
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Also consider the filter screen at the carburetor-some of the Holleys had either a filter screen or a small paper/plastic filter at the fuel inlet. If you've got it, I'd pull it and rely on a quality fuel/water separator filter. If you do not have a rigid fuel line you might also consider the condition of the fuel line itself-of course you're supposed to have a rigid line from the fuel pump to the carb inlet but often they've been replaced. I replace mine with a flexible and actually had a bit of a disagreement with the local CG safety guy over it-I replaced it with an aviation grade stainless braided fuel line and aviation grade fittings. The CG safety inspector said that wasn't satisfactory in a marine application-I had to agree to disagree with him on that point. |
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Tommya
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Joined: 21 May 2007 Location: United States Status: Offline Points: 5 |
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Posted: 22 May 2007 at 6:18pm |
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I'm ahead on that game. So far I've replace the elbo at the tank, cleaned the fuel sock, replaced the the 8' fuel hose, put a new water separator filter, replaced the solid fuel line and the carb inlet filter. That just about covers it. The only thing not replace in is the fuel pump. I really hate replace and pray debugging! Funny how it always comes down to "agree to disagree" and acceptance with saftey inspectors. |
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Beltfed
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Posted: 22 May 2007 at 10:14pm |
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If you’re saying the engine starts to lose power and eventually stalls does it need to cool down some before it will restart? You may want to do a compression check at the time of stall it’s possible that your valve seats have worn down, I know its sounds crazy but I had it happen on an 86 malibu 351 and what the heck a compression check cost nothing. |
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Despite the cost of living it’s exceptionally popular
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Tommya
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Posted: 23 May 2007 at 7:56pm |
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Yes, once the problem happens if I let it cool down it will idle fine again. I can get it to start but it will stall out quickly untill it cools down. I did do a compression check but the engine was not showing the problem at the time of check. I had 90-110 on the gauage, Nothing in the red. I Didn't know that the compression could change with temp so much? Good Idea, thanks!
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GottaSki
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Joined: 23 July 2004 Location: United States Status: Offline Points: 116 |
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Posted: 24 May 2007 at 10:12pm |
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Also check that the tank vent is clear and free, and that no mud wasp setup shop in there.
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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caliendog
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Posted: 29 July 2009 at 5:32pm |
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I have an '87 Supra Saltare and changed to the electronic ignition kit and had problems. Changed back to points and a condensor....problems solved ! Hope you saved your old parts.
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white shadow
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Joined: 29 July 2009 Status: Offline Points: 1 |
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Posted: 29 July 2009 at 6:05pm |
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I have '83 Ski Supreme and I am having the same problem. Put eletrictronic ing. on about 1 month ago. Vince @ DIM said regap pickup in dis. @ .006. They come preset @ .008 to .010. I am going to try this over the weeking. I will post Monday to let ya'll know what happened. I have checked all the stuff ya'll talked about and all seemed to be right! If this doesn't work I am going back to points & cond.
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manseau
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Joined: 12 August 2004 Location: Billerica MA Status: Offline Points: 7 |
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Posted: 29 July 2009 at 6:36pm |
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Did the problem start with the conversion kit?
I got two bad ones from the factory before I got the one that worked. An old timer told me years ago that most motive problems are electrical.
Thirty-three years of back-yard mechanics bare him out. Once you have exhausted all your electrical possibilities, measure your fuel pressure, it should fall between 5 and 12 psi for a carburetored boat, 100 to 500 psi for fuel injected depending on sophistication (CI, multi-port, DI etc) The ethanol alcohol may have caused other problems including loosening up the varnish that would normally have stayed put, then migrated into your carburetor. I assume you've changed your fuel filter at the beginning of the season; that serves double-duty as your water separator. Stabli and Starbright make a marine enzyme treatment for ethanol gas, but this can also free up the crud thats been slowly building-up in your fuel system over time. Your symptoms have been widely reported by users of motorcycles, chainsaws, lawnmowers and of course, boaters, but also airplane pilots. This ethanol has been reeking havoc everywhere. I just finished rebuilding my 1968 Mercury 350 outboard carb., that fixed that issue. This weekend I am going to tare-down my Holley 850, to see if that is what's causing my 83' SN 2001 hard starting and no idle. I've tried everything else, I'm fairly certain this is the issue here as well. I feel your pain. |
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compclen
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Posted: 29 July 2009 at 7:34pm |
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Me too on a 90 MC Tristar with 351 W. I solved mine with a carb rebuild, a filter- separator change, a fuel pump filter change, and cleaning the strainer at the tank pickup tube and pumping some sediment from the bottom of the fuel tank. Was the first time I have had fuel related issues in 12 years with this boat and several more with a SN that preceded it. I blame the Ethanol. I WILL be more careful about water in my transfer cans and using stabilizer this fall. Never used it before. Good luck with yours. Skiing is more fun than mechanicing.
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J. Patterson
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rkazmer
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Posted: 29 July 2009 at 7:57pm |
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Try finding mid-level grade gas (sliver at BP) that does not have ethanol in it. Sta-bil also sells a product for marine applications to counteract the effects of ethanol. May work for you. I have a 86 ts6m comp with all the upgrades and I use the fuel and sta-bil and my boat runs smooth.
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Morphix
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Posted: 30 July 2009 at 6:04pm |
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You might want to start simple, a lot of people are reading into this a lot and perhaps a bit too much and over-complicating things. Always remember, there are only a few things you need for combustion. Air, Fuel, Compression, Spark. So keep it simple, when your engine dies.... look for fuel, the way I do it is take a peek into the carb with the flame resistor(air filter) off. Make sure you see fuel when it's about to die, make sure that the engine responds when you pump the throttle and make sure you can see it being dumped into the carb. If so, chances are that it's not your fuel system-pump/line/filters etc.
If you have compression while its hot, well thats an easy one to look for. Use a compression guage.
You know you recieve air, obviously, unless your butterfly shuts or some thing, but you can look for that easy.
So that leaves the hardest one to detect/look for etc. Your electrical system. The fact that you switched to an electronic ignition without replacing the coil bothers me. I was always under the impression that when one replaces points and moves to electronic ignition, one must also switch to a matching coil for proper voltages etc. So, just out of my spite, id start with the coil.
I had a very similar problem but much more inconsistent when i had my old 1984 Supra Comp. Turns out it was an electrical short in a cable with a small cut in it that went to the distributor. I replaced my coil and switched from a points style ignition to electronic ignition which matches the coil and it ran perfect ever since.
I hope the info helps.
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manseau
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Joined: 12 August 2004 Location: Billerica MA Status: Offline Points: 7 |
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Posted: 04 August 2009 at 7:14pm |
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After all my trials, I should have listened to my own advice. Fortunately before tearing down my Holley, I checked all the ignition wires with an ohm meter and found a bad one! Problem solved.
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A government strong enough to give everything you want, is strong enough to take it all away.
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manseau
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Posted: 04 August 2009 at 7:20pm |
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Here in the northeast, all grades of fuel are 10% ethanol. The poorest rural communities were grandfathered for a short while, as were smaller airfields and some marinas, but everything now is 10%, I wish it wasn't true.
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A government strong enough to give everything you want, is strong enough to take it all away.
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Surfmeister
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Joined: 26 August 2009 Location: Knoxville Status: Offline Points: 1 |
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Posted: 26 August 2009 at 11:39pm |
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Had friend with an older Mastercraft. His problem was an exhaust leak. If the engine hood was off no problem. When the hood was down the exhaust choked the engine. He didn't notice the 'big hole'. Took about two seconds to hear the problem and spot it. Somewhat easy fix. just hard to remove the old exhaust hoses. Had similar symptoms with my Moomba and it was bad gas.
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