Idles great, runs great, then starts acting up.

[Uraijit]

Alrighty guys,
It just never seems to end. I've found another issue that I can't quite figure out. My engine will idle all day long with no issues. Give it throttle, it goes right on plane with no hesitation. All gauges read great. Temp is fine.

When cruising (3000-4000 RPM), it will run fine for several min. Then it will just lose power for 1/2 second, and immediately regain full power for 1/2 second, then lose power, then get power. It will keep this up for about 3 seconds, and then continue running great for 3-5 more min.

I can't do anything to cause the problem. I can turn nice and hard, fast accel/decel, go through rough chop. None of this will cause it. It's totally intermitent.

Can't figure it out. It's got fresh dry fuel, and a new water/fuel separator. The coil and spark wires are all clean and tight. It seems like a loose connection SOMEWHERE, but I can't think of where to look.

Also, when we first started the boat up, the battery was very low. I don't know if it's related, but a parasitic drain coming about at the same time as this issue seems likely to be correlated.

Any ideas?

* 5.7 liter Chevy engine
* Points ignition, timed to 8 deg BTDC
* Quadrajet 4 barrel carb
* Mechanical Fuel Pump

 

[jerryjerry05]

Re: Idles great, runs great, then starts acting up.

The drain is probably a clock or radio.Put in a battery switch.Or put in a dual batter/switch combo.That way you will always have a hot battery.
Next time your out unhook the tach and run without it.Then the next thing might be to look at the coil and condender.Jerry

 

[Uraijit]

Re: Idles great, runs great, then starts acting up.

No clock, no radio. This seems to be a new problem. The battery's never drained before. It's only a few weeks old too.

I pulled the battery cable, and tested. Looks like there's a .28 amp draw somewhere. Over a quarter amp seems significant!

The draw appears to be on the main wire which goes to the starter, and then piggy backs over to the main solenoid.

 

[Uraijit]

Re: Idles great, runs great, then starts acting up.

Nobody?

 

[Limited-Time]

Re: Idles great, runs great, then starts acting up.

Have you tried running on a remote tank??...........................I'd check the anti siphon valve................it sure sounds like a fuel supply/delivery issue.

 

[Uraijit]

Re: Idles great, runs great, then starts acting up.

My boat has two tanks. I switched over to the other tank when I took it out yesterday, to test that theory out. The engine started running hot before I could put it through the paces and see if it would happen again.

I'm so frustrated with this boat right now...

Any ideas what could be drawing .28 amps with the key off? There's no clock, no radio, nothing that should be drawing any current that I can think of...

 

[driller80545]

Re: Idles great, runs great, then starts acting up.

I would disconnect hot wire from ignition switch and check for amp draw. The surging you are experiencing could be indicative of a bad switch. Remote chance, but easy to check.

 

[JustJason]

Re: Idles great, runs great, then starts acting up.

I'm assuming your using a multimeter....
so please don't make an *** out of you and me

disconnect your alternator and see if it goes away....

and..... i betcha don't have a battery switch.... correctamundo??

 

[Uraijit]

Re: Idles great, runs great, then starts acting up.

Correct, no battery switch. I can get a switch, but that just seems like a band aid fix. I'll probably end up getting a switch anyway, but I'd like to fix the actual problem as well, rather than covering it up.

 

[Limited-Time]

Re: Idles great, runs great, then starts acting up.

For your current draw issue I'd hook the meter up and start pulling fuses.................next I'd move to the non-fused "live" wires...............its gott'a be one of them.