5.0GL-H mixture adjustment / manual

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Back in May I replaced the wires when I did the cap and rotor. I went to a local Napa store and cross-referenced the volvo part number for the wire kit. The coil wire was about 1/2" too short so I kept the original on there and changed out the plug wires.

Im trying to figure out why removing the pcv valve from the valve cover would make such a difference. I don't think the valve allows any more or less airflow either way, so the only other thing would be the sucking force in the crankcase. Why would removing this vacuum make startup better?

I got to thinking last night about this. I read that a rise in engine rpm is usually a sign of a vacuum leak. I also have slightly low and erratic vacuum at idle that could support that claim. So with the pcv valve out, the starting engine rpm is 600 and rises to 800. But with the valve in it rises to 700. So maybe the engine is normally trying to start and run initially at 500rpm and struggles that low hence the loping idle, until the rpms rise and stabilize at 700 where it is comfortable? Maybe try adjusting idle speed so that rpms start at 600 and rise to 800 and see if it starts better that way? I realize this won't fix the problem but it could narrow down my search to a vacuum leak. Am I on target here?

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Tonight I went hunting for vacuum leaks again. Still haven't found anything. I pretty much soaked all 4 edges of the intake manifold as well as the carb base and carb and any bolt or valve around the intake.

Finally did a compression test and the numbers comforted me quite a bit:

165 175 180 185 170 170 180 180

Spark plugs all looked the exact same which I believe rules out an ignition problem with just one cylinder. All were black from the tip down to the 2nd thread. It was a dry thin black, not wet like a rich condition would give. Do spark plugs "erase" earlier signs? What I mean by that is, if an engine is set to idle rich for awhile, then is set to idle lean, after say 20 hours or so will the plugs show a lean condition or will they still look rich? I ask this because The idle was set pretty rich for a few weeks in June but I adjusted it back to spec (slightly on the lean side) about 20 hours ago. Could this show that maybe the carb does have a small leak causing the idle to be slightly rich despite the lean mixture screws? But not enough of a leak to flood it?

Measured vacuum again, this time not T'ed into the pcv hose. I tried it plugged iinto the pcv port with the valve removed. Vacuum was a steady 17" with soft fluctuations of about .5". Volvo service manual says to plug into this port but doesnt say whether to remove the valve or not, and that 14-19" in normal. I think its safe to say vacuum is good.

While playing around I noticed she idles really well and sound at 800rpm. Drop it down to 700 and it gets a little rough. Since the idle circuit is more sensitive with the lower speed, I suspect whatever is making the plugs look rich is adversly affecting idle performance below 800rpm.

 

[Silvertip]

Re: 5.0GL-H mixture adjustment / manual

Spark plugs take on their natural light to medium tan color on a properly set up carb only after a sustained high speed run and then engine shut down immediately (no idling whatsoever). If plugs are black and sooty at idle then there is an "idle" mixture problem. By pulling the PCV you essentially created a vacuum leak since the other end of that hose is below the throttle plates on the carb. Is nobody else concerned about the engine knock???? Bent push rods, worn rocker arms, rocker arm stud pulled partially out, a bad rod or main bearing, or a bad cam lobe can all make rapping noise. What is the oil pressure reading hot. The standard practice on warm start of a carbed engine when cars and trucks had a carb was to hold the throttle open a bit. That applies to outboard and I/O engines with carbs provided they don't have a "Quick Start" or "Turn Key" system. You proved to yourself that this technique works. However, when an engine is shut down for just a minute or so and it fails to start immediately and acts flooded in the process, you have a carb issue. There is a needle and seat issue, a porous casting, or something else going on. You should not need to replace standard parts with something else to mask a different problem.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Thanks for the comments Silvertip.

I was idling close to an hour before removing the plugs. Since thats where my problem is at, I wanted to make sure the black plugs represented my idle condition not a running condition over the weekend.

You're right about the vacuum leak. I moved away from the pcv valve. It ran better out only because it increased idle rpm which made it smoother. Bring the idle back down to where it should be and its rough like normal.

Oil pressure at idle is constant 40psi. After a long wot run on a hot day, I've never seen it below 20 at idle.

The engine "knock" like I mentioned resembles the sound of a diesel engine except much quieter and not always apparent. With the compartment closed it is inaudible, and with it open I tend to not even notice it while I'm working on something else. There is definitely an intermittent noise there, it comes and goes during idle and is not loud, but it is definitely there. Whatever it is apparently doesn't affect compression. I have never seen under a valve cover before so I would be lost trying to figure it out on my own.

While doing the compression test last night with the throttle wide open, a quick glance down the bores I noticed the manifold floor looked like it was glistening. This was easily 45 minutes after the engine was shut off. It was too dark to investigate and I didn't have a flashlight with me but I plan on doing this again and seeing if it was fuel possibly from a leak. Will the manifold floor ever look wet? It seems like it would be hot enough that fuel couldn't sit on it while running. I have checked before and there is no leak from the boosters and the throttle plates are bone dry so I don't believe it is a needle/seat or fuel pressure problem. I have a new power valve, power valve gasket, bowl-metering block gasket, and metering block-carb body gasket arriving today. The o-rings on the bowl bolts broke a long time ago so I need those replaced too. Would a local autoparts store carry those o-rings?

 

[Silvertip]

Re: 5.0GL-H mixture adjustment / manual

If you were to look very carefully into the carb bores from the bottom up, you would see that the throttle plates may or may not be tightly sealed against the bore. There would also be idle passages almost in line with the plates. So yes -- fuel can get past the throttle plates without wetting them. And yes, the manifold plenum can be dampened with excess fuel. Probably not with the engine running but certainly after shut down and a carb that dribbles. Unless you have properly set the float level I contend that is part of the problem if not all of it. A needle and seat that is not seating tightly is also possible. That's an easy check. Remove the carb, tip it upside down and let the fuel run out. Now blow (by mouth -- not compressed air) into the inlet fitting while holding the carb upsdie down. If air passes -- you have a float/needle/seat issue. If no air passes that says the needle and seat are fine but does not rule out float level that is not adjusted properly.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

I have checked float level before and it was actually lower than parallel to the bowl. As I stated earlier in the thread, the correct level is a mystery since neither Holley nor Volvo nor service manuals can confirm it. I chose not to mess with it since I have no driveability issues related to low float level. No sight plug on this model, it can only be dry adjusted. When I pull it apart to replace the power valve and gaskets, I will do the needle/seat check and confirm float level. I may even pick up another float just in case this one is slightly flooded. I have no idea how to tell if it is heavier than normal or not. Thanks again.

 

[Silvertip]

Re: 5.0GL-H mixture adjustment / manual

I have checked float level before and it was actually lower than parallel to the bowl. As I stated earlier in the thread, the correct level is a mystery since neither Holley nor Volvo nor service manuals can confirm it. I chose not to mess with it since I have no driveability issues related to low float level. No sight plug on this model, it can only be dry adjusted. When I pull it apart to replace the power valve and gaskets, I will do the needle/seat check and confirm float level. I may even pick up another float just in case this one is slightly flooded. I have no idea how to tell if it is heavier than normal or not. Thanks again.

You can check the float for saturation by placing it in a container of fuel. If it floats it is fine. If it settles into the fuel or sinks, it is definitely not good.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Thanks for all the ideas I feel like they'll lead me down the right path. This engine is 6 years old, still covered in red paint, and I'm the 2nd owner with this being the 2nd year I've had it. I can tell what's been tinkered with before and what hasn't. The carb had never been removed but the fuel bowl was pulled before I owned it. I'm not sure what was done in there or if they were chasing the same problem I am. One idle screw had also been adjusted but the other one had never been touched.

Do these Holley carbs come stock with the blue reusable gaskets or are those aftermarket? When I took it apart thats what was inbetween the bowl/meter/body. I've also read some hot rod forums about how Holley's have a tendency to leak, and mating surfaces can become warped from over-tightening. Is there a way to test this outside of trying a different carb? It could be possible that the OP over-torqued the bowl on and warped something.

Are fuel bowls interchangable? I sure wish this bowl had a sight plug in it since that would tell alot about what's going on in the carb.

 

[Senior B]

Re: 5.0GL-H mixture adjustment / manual

Brother, I've got to say that I think you're trying to Nuke this but it's your craft, your perogative and you are the Captain. The spec on the 2300 2 Barrel Holley hasn't changed much across the years from 2000 on. Wish I had access to my manuals but I'm a Navy guy on deployment at the moment. The float bowl is to be parallel to the top of the float bowl. Just turn the bowl over to check and adjust as nessesary. If the float is bad, you'll hear the fuel inside it if you take it out and shake it. If you take it apart, might as well put a re-fresh kit in it which will include new power valve, accelerator pump diaphram, float bowl needle valve and all gaskets. Screw Torque on the these is @11 ft pounds. I torqued mine to 135 inch pounds and it hasn't leaked a drop. My boat is a little older than yours, but I too have the 5.0GL, same carb set up with @520 hours. Runs like a top and always has, but my idle too, is a tad low and lopey on a hot start with no throttle movement. Give just a pinch of rpm for a couple seconds and it's smooth. Has been like that since 05 when I got it and after I rebuilt the carb this spring. I will close by saying "Have a blast on your fine running craft and enjoy your time on the water." Best of luck

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Thanks Senior I appreciate the input. I did enjoy our trip to Tablerock after I figured out how to hot start it consistently. First time all year I didn't have to worry about anything. But I know last year it didn't do this sort of thing, so my mentality is to run it and enjoy it on the water, and tinker around at home when I'm bored and try to figure out what changed. I do enjoy troubleshooting and repairing/learning about the boat, but only so much of it!

The service manual for the 5.0 GL's has float level for every version at "parallel to fuel bowl when inverted" so I believe you are right when saying that's where mine should be. I'm curious as to why someone adjusted it and what they were trying to fix. I have new gaskets and power valve now that I plan to throw in just for grins. Are these float ands needle/seats generic enough that the Holley section of the local auto parts store will carry the one I need?

Finally got a picture of her nice and clean. Added the tower myself this spring.

 

[Senior B]

Re: 5.0GL-H mixture adjustment / manual

The exact Holley re-build kit for mine and I would bet yours is the same was a 703-36. Got mine at my local Advance Auto Parts store for $22.00 The kit did not include the float. Believe you mentioned that your power valve was like a 10.5 or something? Stock valve for mine is a 4.5 by the book and that's what will be in the kit.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

I think you're right. Its still a Holley 2300 so that kit should work. I'm thinking Holley says they don't have rebuild kits because Volvo chose the power valve size and other adjustments. So they just let Volvo handle the specific rebuild kits. Summer is about over so it looks like I'll enjoy the last few weeks of good weather and do a rebuild over the winter when I have time to kill. Will report back soon with what I learn about leaks (or the absence of).

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Update:

Well I'm happy to announce that I am back where I started on this! That sounds like a bad thing but its not. It now starts/runs/idles great.

I cleaned the plugs, reinstalled them, and warmed the engine up. Over the next hour I started the engine a dozen times, listening for starting and idling characteristics each time and making small adjustments to idle speed/mixture. I turned both screws in (lean) 1/8 of a turn and now it hot starts beautifully. Nice and strong with no throttle. I tried turning them in another 1/8 and idle speed/smoothness dropped considerably. It goes to show ya how different engines can be! Most of what I read says engines like a slightly rich mixture to start but not this one. I waited almost an hour to start it again, nice strong start and no need to have the throttle open. Spent a good amount of time staring down the throttle bores with the engine off and throttle open and never saw any signs of a leak at all.

"Back to where I started" refers to how it was acting this spring. Starts good and idle rpm's settle out, then over the next 15 seconds the idle speed slowly rises 150 rpm and idle is a little rough but can be ignored. I tried adjusting the idle speed higher and lower, same increase. I think I can adjust this so that it ends up at a good speed, but curious as to what can cause that. Throttle cable is disconnected from carb linkage. As for vacuum leaks, I have spent atleast 3 hours now with carb cleaner, soapy water, and propane checking every corner wall and bolt of the intake manifold, valve covers, carb base, carb body, fuel bowl, etc and haven't found anything. This leads me to ask...can a carb have a sort of internal air leak that wouldn't be detectable from the outside? I'm not really familiar with vent passages and all that.