Compression Results and Plug condition?

[Donald Terrell]

I have a 1988 Sunbird Corsiar with a GM 4.3ltr V6 and OMC cobra drive. I removed the plugs, the number one had something wet on it but they all looked good. Compression was 160 to 170 without putting any oil in cylinder. Is that good? I am trying different things because my engine is running real bad on the lake. Idles okay but when I try to throttle up it bogs down and I have to work the throttle just keep it running and it barely runs. I have rebuilt the carb. Although it passed a fuel volume test in the driveway I am in the process of checking the antosiphon valve. I have found no water or trash in the gas removed from the water seperator. The wires look good, distributor cap clean, points opening and clean. Checked the ESA because that is how it is running like the ESA may be stuck on. I have other post, just started this one to get feedback on my compression results. Thanks!!!

 

[Bondo]

Re: Compression Results and Plug condition?

Sure Sounds like a Fuel Delivery Issue,.......<br /><br />I'd go Back to the Carb.........<br /><br />A Carb. Kit is a 50/50 Shot,... At Best..........

 

[Donald Terrell]

Re: Compression Results and Plug condition?

The carb rebuild went well. The only thing I am concerned about is the two idle mixture screws. I counted the number of turns(2 1/2-3) which it took to bottom them out, then I installed them the same number of turns. What about the compression results? I think the numbers are good between 160-170, but I don't know what they should be, I can probably answer this with my manual. Thanks Bondo

 

[Bondo]

Re: Compression Results and Plug condition?

Originally posted by DonWon:<br /> The carb rebuild went well. The only thing I am concerned about is the two idle mixture screws. I counted the number of turns(2 1/2-3) which it took to bottom them out, then I installed them the same number of turns. What about the compression results? I think the numbers are good between 160-170, but I don't know what they should be, I can probably answer this with my manual. Thanks Bondo

Your compression #s are Fine,..........<br /><br />A Shop Tach,.. Or a Vacuum Gauge are the Best tools for setting those screws,......<br />But,......<br />A "Good Ear" can get Pretty Close,..........<br /><br />At a Warm engine Idle,...start with either 1 of them,....turn it In till the engine drops, or sounds less smooth,... then turn it out till it does the same thing,..... then back in,.... Now settle that 1 just short of in the middle,......<br />Do the same thing with the Other Screw,.......<br />Then back to the 1st Screw,....and to the other,...etc.....<br /><br />When you get them balanced,.... <br />Go back,+ reset the idle to 650rpm,......<br /><br />Good Luck,..........It sounds like your Gaining on it,..................

 

[Don S]

Re: Compression Results and Plug condition?

Don't allow the engine to just idle all the time during the adjustment. Disconnect the throttle cable from the carb, and after adjusting, give it some throttle to "Clear it's throat" and then see how it idles. Readjust, throttle up, let idle, Readjust, throttle up, let idle, Readjust, throttle up, let idle. Do this many times until your results are right. If it doesn't happen, then something else is wrong.

 

[Donald Terrell]

Re: Compression Results and Plug condition?

Okay, But I will have to build a wrench to turn them with, the thermo housing is directly in front of them, they are very hard to access. But would these being off make my boat run so badly? When looking at the antisiphon valve I noticed something on the right side, looking backwards, behind the riser that looks like some kind of ballast for lack of a better word. It looks like a voltage regulator? I don't suspect it, I just wondered what it was. It is not shown in the Clymer book, but I have ordered an original OMC service manual and may buy a Seloc brand also.

 

[TilliamWe]

Re: Compression Results and Plug condition?

just spit ballin here: was the "wet" on the plug water? Guys would a bad maifold do any of this? Or if it was that bad, he'd be hydrolocked at initial start up, wouldn't he? like i said, just spit ballin!

 

[Donald Terrell]

Re: Compression Results and Plug condition?

It was the number 1 plug which seemed to have a little oil on it. I just received the original OMC service manual, so I will keep at it. I have one of those devices that attaches to your plug, then you attach your plug wire to it. It has a light in it which flashes when the cylinder fires. Does anyone know about these?

 

[Haut Medoc]

Re: Compression Results and Plug condition?

Timing light?....JK

 

[Donald Terrell]

Re: Compression Results and Plug condition?

No it's not a timing light, although I need to buy a new timing light. It's a small device that has a boot to fit over the plug, then an enclosed light then a nipple which the spark plug wire boot fits onto. I guess it replaces pulling the plug out and grounding it to see if it sparks. I have never seen one of these until I bought a box lot at an auction and it was in there. I tried it on a car, kinda neat, but I am not sure that if it flashes it means for sure the plug is sparking or just that fire is getting to the plug. I need some help on another topic I have going about the correct service manual for my boat and why the last letter of my model number is an A? There is more info on that topic if anyone could go to it and read it. Thanks!! Everyone

 

[Don S]

Re: Compression Results and Plug condition?

There are spark testers that work that way, they have a glass tube that the spark arcs through so you can see the spark, but it's not a light.<br />Could that be what you have?<br /><br />

 

[Donald Terrell]

Re: Compression Results and Plug condition?

THAT'S IT!!!!!! DONS I wonder how reliable they are? If it's lighting(sparking) does that mean that for sure plug is firing.

 

[Don S]

Re: Compression Results and Plug condition?

You posted at the beginning that the distributor cap and wires and points all LOOKED good. How long has it been since the engine was tuned up completely. New Cap, Rotor, Points, Condenser along with NEW sparkplugs (NOT Champions). Then you need to set the point dwell with a dwell meter, and then reset the timing. When the engine is running also check the advance timing to be sure the advance is working.<br />You can also do an OHMs test on each plug wire, and see if the ends are shiny. If they are corroded, replace them.<br />After all that, then start carb adjusting. The best way to check the plugs to see if they are firing is to pull them out of the engine, hook a plug wire to them and ground the base. Crank the engine and see if the plug is firing. If one doesn't fire, try it on a different wire to determine if it's a plug or wire problem.<br />You may also have a vacuum leak, hook a gauge to the intake manifold. You will have to remove the pipe plug and install a hose barb fitting for the vacuum gauge.