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Runs fine, for a while, then fades/quits

KAG

Contributing Member
1984 Crusader 270 (but put in rebuilt long blocks about 6 years ago). Converted to electronic ignition.
Boat sat on hard during 2016, 2017 and 2018 (but started and ran for a bit in 2018).

Started okay and ran fine in yard (2019).
Launched (late July, 2019), started fine, drove across harbor, started to stall, but would restart. After a while wouldn't restart. Next day started, ran for while, quit.
Suspected contamination was clogging fuel filters. Changed filters. Ran okay for while. After about 10 minutes at cruising speed it quit. Thought maybe gas really bad and it clogged another filter, so changed again. Ran for a while. Swapped fuel hoses (so engines running off filter usually used by other engine). Problem seemed to transfer to other engine. (this test now suspect) Decided had to be fuel. Replaced filter again and ran both engines off other fuel tank. (other engine running fine so figure that tank and gas okay). (Note: fuel tanks pumped out in 2015 so all gas, except any residual that didn't pump out, is new.) Ran fine for about 15 minutes at 1000rpm, then another 15 minutes at 2900rpm, then quit. After half hour restarted, ran for about an hour at 1500rpm, then quit, wouldn't restart. Next day started but couldn't do extensive test.

Because they were old and I was desperate, replaced carb and coil.

Engine started, ran for about 20 minutes, including about 15 at 2900 rpm. Then quit. (Quitting usually involves loss of rpm over course of minute or so, total failure to rev back up, then stalls). After half hour started again but only ran for about 10 minutes at about 1200 rpm (wouldn't restart). After another half hour started again, ran for about two hours at 1000rpm (then I shut off as we were back. (We went on a trip, about 25 miles each way, this was the return home, didn't try to increase speed during those two hours, preferred to get as far as possible with two engines rather than risk losing one even though at slow speed).

Next day: started, ran about 15 minutes at 2900rpm, then started to quit. Switched hoses. Problem stayed with same motor so not filter (at least main one, there is a smaller one mounted to engine, replaced earlier but only first time). Have only been using one tank so both engines getting gas from same tank. Other engine running fine so fuel itself not problem.

Seems to be getting better in that it will sometimes go longer if speed kept low, but still won't go for extended period at cruising speed.
I put electric fuel pump in gas line (between filters) as a way to test if fuel pump (mechanical) was bad (although wouldn’t mechanical fuel pump be good or bad, not work for a while then need to rest?). Figured it would also pull gas through filter if it was partially clogged. Does not seem to make any difference.

I was going to try to test fuel flow at carb but don't have a way to do that without it going all over (hot) engine. Is there a gizmo that can be put at the end of the fuel line at the carp to measure gas pressure or flow? I did back the fitting off, gas came out, seemed to be under pressure which suggests no problem with the pump.

Only thing that makes any sense to me is clogged filter, but hose switch seems to eliminate that. (plus multiple new filters, which should still be clean since using other gas tank.) I don't know of anything else that affects a motor during use (other than sometimes a coil, but replaced that already). Any suggestions appreciated.


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check the filter in the carb...under the fuel line nut?

are you sure it's a fuel starvation issue? Q&D test is to look down into the primary bores and depress accelerator pump plunger - if fuel squirts from the accelerator pump nozzles, fuel is in the float bowl....and a timing light is a decent test to ensure spark is occurring...
 
check the filter in the carb...under the fuel line nut?

are you sure it's a fuel starvation issue? Q&D test is to look down into the primary bores and depress accelerator pump plunger - if fuel squirts from the accelerator pump nozzles, fuel is in the float bowl....and a timing light is a decent test to ensure spark is occurring...

I am not sure of anything, it just seems like a fuel problem (most other problems are more consistent). Next time I am out will try the Q&D test to see if there is fuel there, but assume there will be if it will idle.
It will usually at least sputter so there must be spark, and obviously a spark the times it will idle (even though it won't rev up).
It can't be the little filter at the end of the fuel line as a new one came with the new carb.
 
never huts to verify anything....especially if you aren't positive definite....


you say you are running on one tank - separate pickups for each engine?
 
You might want to check your tank vents and make sure that they haven't become blocked. Another thing you can do to eliminate the tanks would be to unhook them and attach an outboard tank to it with fresh fuel. If it stays running then you will know its your tank.
Best of luck with the search.
 
If you didn't from the beginning of the ignition conversion take the time to wire a dedicated 12v wire to new system. Points systems tend to have a resistor built into wiring to prolong the life of the points. Using power from old system can result in intermitting operation.
 
If you didn't from the beginning of the ignition conversion take the time to wire a dedicated 12v wire to new system. Points systems tend to have a resistor built into wiring to prolong the life of the points. Using power from old system can result in intermitting operation.

There is an external resister. I followed the directions for installation of the electronic system. Do you have a wiring diagram of how you think it should be wired? I was under the impression that these systems either work or they don't. If they do malfunction on an intermittent basis would/could that result in it running but only at lower rpm? The electronics were installed years ago and worked fine for years (which doesn't mean it couldn't have gone bad).

As to gas and tanks: There are two gas tanks, two valves (either engine can be run off either tank) - but I don't remember if there is a split in the hoses or two separate pickups in each tank. I can't say the tank isn't the problem since I don't know what the problem is but I don't see how it could be the problem since I have the same issue regardless of which tank I am running off and the other engine runs fine off the same tank I have been using since the third filter change.
 
If the conversion has been working for years, your issue is unlikely tied to your issue....and following the instructions provided is always a wise choice.

"Two valves" is a bit vague......accurate configuration of the fuel system will help ID potential issues.

It could be the fuel is fine, but the problem engine has a pickup tube a bit deeper than the other and there's crud in the tank that gets sucked onto the screen thus starving the carb of fuel....shut the engine off and the vacuum dissipates and the crud drops off....could also be crud in the anti-syphon valve.....
 
Might put a volt meter on the coil just to ensure input voltage is not dropping off. Shorting tach, CB, ignition switch, wire junctions etc. have all been known to partially fail as circuits warm up. Interesting caper.
 
To clarify the fuel supply set up: There are two tanks. Hoses runs from each tank to a valve (maybe two hoses from each tank, one to each valve or, less likely, they split, have to look next time I am out (boat is anchored out in harbor)). The valve allows you to switch between port and starboard gas tanks (or off). The "out" from each valve goes to a filter, then to an engine. So, unless you disconnect and switch the hoses, the port valve serves the port engine, starboard valve serves starboard engine, but both can take gas from either tank. Since the problem occurs whether I run the (starboard, problem) engine off the port or starboard gas tank (and the port engine runs fine) I don't think it is the gas or pick up from the tank.

One thing that I forgot to mention but Mulletwagon's post reminded me off: the tach has been bouncing around a bit at low rpm, e.g. it will bounce between 800 and 1000 rpm even though the actual engine speed seems pretty steady. I don't know if that is a clue or unrelated quirk.

I spoke to someone local who suggested the inner wall of the gas hose could be collapsing. Doesn't seem like that could be it since it won't rev up even in neutral (which doesn't require much more gas), but will likely replace the hose (which is fairly new) so I can cross it off the list. Will also check for voltage changes, but probably can't do until the weekend.

Thank you to everyone for your input and suggestions.
 
I would say the tach is a clue....especially if it started wandering when the fade did.....

On the troubleshooting, I'd be inclined to pop the distributor cap on the starboard engine and make sure it is clean on the inside and make sure the rotor is serviceable. While the cap is off, make sure the advance mechanism is working and the shaft isn't 'loose'. then run it until the fade comes in....Mullet's volt meter check would be go to hook up as well. It could be as simple as one of the connections on the ballast resistor has corroded and fails to pass enough current once it gets hot. If you have somebody to help drive the boat, while its running, you can do the wiggle test on the wires feeding the ignition and the main harness connector, too...
 
Everything looks good inside distributor (cap). Cleaned all connections (e.g. starter, coil, ballast resistor). Started, ran (for less time than usual), died. Tried bypassing ballast resistor (wire with allegator clips on both ends), started, ran for two to three minutes, died. Was alone and it was breezy so couldn't check voltage while running.
New symptom (maybe result of new carb?): seems to surge. As advance throttle not much seems to happen, then hops up 300-400rpm, especially at higher speed, e.g. seems to hop from 2600 to 3000 rpm with minimal throttle change. Could be unrelated.
 
a clip on timing light is one of the easier ways to verify you have spark.....still haven't seen where you reduced the issue to loosing fuel or loosing spark....
 
Have eliminated electronic ignition as potential source of problem.
ignition control nodule has been suggested, but I can't find one. Likely this engine (1984) would have it? Suburbans from that year apparently did but I can't find one, or any unaccounted for wires.
Hope to have a crew tomorrow so I can do better spark testing.
 
Add a fuel pressure gauge to the line, don't worry that it's "over the 'hot' engine." You need to figure out if you have fuel pressure, while it's stalling. It's not enough that you have fuel pressure when you try to start it up. You need to make sure you have proper fuel pressure while it's running.

Secondly, an electronic fuel pump installed may not solve the problem, if you're forcing too much fuel into the carb it'll stall just the same as starving it.

Third, I'd replace the mechanical fuel pump. It seems like the last fuel supply gremlin that you could be having.
 
Still working on it.
bypassed fuel pump and used electric one. Still problem.
finally found enough adapters to use fuel pressure gauge. Holds steady around 4lbs, even while motor dying.
used in-line spark tester. Sometimes looks different (almost steady rather than flicker) but difficult to judge, because sparks dies when motor does. Hard to determine cause from effect.
reasonably confident is electric, not fuel.
Have replaced coil and swapped electronic ignitions between motors. There isn't much else to the system. Distributor?
 
Loosen, clean and reattach all grounds (both ends) associated with the ignition or tachs. Swap wiring to tachs so that left reads right and vice versa to rule out internal problems.
 
I cleaned connections on engine before, but will repeat and do all (including battery switch and battery, although not likely a problem since other engine runs fine). Will also swap wires to tachs but am wondering what "internal problem" could be revealed by this?

I will have to check (not likely until weekend, we are expecting some weather) as to what distributor is on there. For some reason the engines have different ones and I forget which is which.
 
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You believe the problem is electrical in nature. It has been reported on this forum that a failing tach can sometimes cause apparent ignition problems. If true (I have not seen this one myself) and if it applies to your system (perhaps only MEFI systems), then switching wires to the tachs is a simple way to eliminate that possibility. You did report that one tach was "bouncing around" That is all the suggestion was meant to do. To clean and retighten all ignition related wires you would have to take them off anyway.
 
a 'bad' tach typically impacts the older distributor ignitions.....where the tach lead connects to the same coil terminal as the 'breaker' initiating the spark....
 
Did you ever find the issue? I just purchased a 85 grand sport that has the same issues as you're describing. But I noticed my fuel guage on the starboard side bounces along and when I go to use my trim buttons I loose power. I'm looking at a electrical issue but I went through the same steps as you did with the fuel issue.
 
No, never did figure it out. No clue what to do next so haven't touched the boat this year, just sitting on the hard. I feel like it must be something simple, but can't think of what else to change/test. Only thing I can think to do is replace the engine or dump the boat.
If you figure it out or have any suggestions I would be glad to hear it.
 
No, never did figure it out. No clue what to do next so haven't touched the boat this year, just sitting on the hard. I feel like it must be something simple, but can't think of what else to change/test. Only thing I can think to do is replace the engine or dump the boat.
If you figure it out or have any suggestions I would be glad to hear it.


I have a 1985 Gibson with Crusader 270's. I have the exact same problem. It is also sitting on the hard. I've put so much time and money into it and it's done nothing but cost me the time and money. I've been on this forum in late 2019 I believe. You can look it up. If you want to contact me I will be more than glad to let you know what I've done. It is still not repaired. Maybe we can help each other. Please let me know if you would like me to contact you.
 
I had the exact issue and after going thru all of what you have done (and $$$) I finally found my problem. I was the anti-syphon valve located on top of the tank, the fuel line connects to the anti-syphon valve and the runs to filter, then to the carb. There is no filter in the tank. Pickup tube sits near the bottom of the tank, fuel is sucked up and through the anti-syphon valve before any filter...poor design I'd say and easily clogged. Hope this helps, let us know. BTW anti-syphon valve is less than $10
 
WJK55: Thanks, something else to check, if I can find it. I don't recall seeing one but access to the tanks is limited. I doubt it is the valve since I have two tanks, the problem occurs regardless of which tank I am using and it seems to be getting fuel, but will verify.

I actually, after leaving it for a year, have just started working on the boat again in hopes of using it this year. Since the motor runs and only has an issue after running at higher speed for a while, I will have no way of knowing if I have fixed anything until I have the boat put in.

QUESTION: Does anyone know of a way to simulate running the engine with a load (i.e. like it would be when going 15kts) when it is on the hard?
Thank you.
 
...just my two cents on the anti siphon valves....on my boat the anti siphon valves are threaded into the back side of the tank selector switches.Screenshot_20190727-172507_Firefox.jpg....this is what mine looks like...
 
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QUESTION: Does anyone know of a way to simulate running the engine with a load (i.e. like it would be when going 15kts) when it is on the hard?
Thank you.

not without pulling the engine....

if you think its tank related, for troubleshooting purposes, you could use an outboard tank...but you have to understand the risks involve and mitigate them...
 
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