5.0GL-H mixture adjustment / manual

[skydiveD30571]

VP 5.0gl-h with stock 2bbl Holley carb. list # 75034, date stamp # 2276

I learned the hard way yesterday what the difference is between setting idle mixture on the driveway vs. in the water . It sure sounded good on the hose, drop it in the water last night and trouble right off the bat.

I'm still battling an idle/start problem on this engine. Trying to set the idle mixture correctly to help with warm starting. It idles nice and steady, but warm starts (5 minutes or more) are trouble. It's not a hard start, it turns over really quickly actually. But it doesn't seem like it catches too well. For example, if I shut it off, wait a few seconds, then start it again, it has a nice strong start where rpm's rev up then drop down to a solid idle speed (just like a modern car). After waiting a few minutes then trying, it kind of stutter starts like it barely catches. Then rpm's come up but not very high and the idle lopes up and down (about 700rpm - 400rpm) until I give it a little throttle and return to idle. Then it's nice and smooth.

I called Holley, and they have absolutely no information on the carb since it's a "proprietary Volvo model" :facepalm: I looked in the service manual, but according to the volvo penta website, it says to use the 5.0gl-a/b/c/d/e manual for the -H engine. There are no carb specs for the -h engine, and I know they're different than the rest since my stock power valve is a 10.5...higher than the latest listed engine the gl-d/e. I'm guessing Volvo hasn't updated any manuals to inlclude the -h version, but I'd appreciate it if Don or anyone else familiar with manuals could comment. Also my float level is less than parallel while inverted, but I have no hesitation or any other problems outside of a loping idle after a warm start. So I'm not sure if that's right either. Any ideas guys? I'm at a loss here.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual



Also, I noticed that I do not have the manifold adapter or gasket (#1 and #5). I have the regular base gasket #6 and the 2 barrel carb sitting on that. Does it affect anything to not have the 2bbl to 4bbl adapter on? It seems like this is stock but I'm not sure.

 

[Maclin]

Re: 5.0GL-H mixture adjustment / manual

If you have a 4bbl manifold then the 2-4bbl adapter is needed. If you can bolt the 2bbl carb directly to the manifold using all four bolts/studs then you have a 2bbl manifold and the adapter is not needed. I am thinking the top of your manifold does not look like the one in the drawing. If it does look the same, two long oval openings, then I am not sure how a 2bbl could mount to it without the adapter.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

When I removed the carb, I removed the #2 screws so I think the adapter stayed on the carb when it all was removed. My bad, thanks for clearing that up.

Still can't find the factory specs for my carb. Not in manuals, Holley has no idea, Volvo won't answer technical questions, not a single dealer or mechanic around here knows the answer (and why would they? There isn't an updated manual for my engine). What a pain. I guess I'm gonna spend the weekend tied to a dock messing with it until I get it right.

I understand to have it in the water in gear. Throttle cable disconnected. Engine warm. My ear is not tuned enough to do it that way, and I don't fully trust my tach gauge, so I plan to use a vacuum gauge. According to drawings, there is 1 full manifold vac port on a 2bbl 2300.... for the pcv valve. Pretty sure the choke vac tube is connected to ported vacuum. I'm guessing I need to use the pcv one. I tried pulling the pcv hose off the carb during idle and the engine revved up pretty good. Setting the mixture like this doesn't make sense to me. You'd essentially be setting the idle, then when the pcv hose is attached again it'll be too lean with the added intake air, right? So should I use a T-fitting on the pcv hose?

I'd like to get this set this weekend since I've been fighting it all year.

 

[Senior B]

Re: 5.0GL-H mixture adjustment / manual

Lets talk Carb adjustments on the world famous 2 barrel Holley 2300. These adjustments, to me, are best done when the Choke has warmed and is fully open. There are 2 types of adjustments: Idle mixture and Idle speed. Mixture being lean or rich and speed being rpm. You can do this easily on muffs for both, and fine tune "in gear" idle speed on the water if need be. On these carbs, there are 2 idle mixture screws. They are located on each side of the carb metering block which is right behind the front float bowl. The screws are hidden behind plastic sealing caps that are easily removed. When you access the adjustment screws, turn them Clockwise all the way in till they just seat. DONT TIGHTEN THEM! Then back them out 1 complete turn. Next start up the boat and adjust your idle speed screw to have you at or slightly above 800 rpm. I have mine @ 825. Now the spec for the initial adjustment screws is 3/4 to 1 turn. We initially turned then out to one. Turn each one in/out about a 1/4 turn till you get the smoothest idle. If your using a vaccum gauge then till you get the best reading. Mine is between 3/4 and 1 on each side. Your idle speed may need to be tweeked after your done. With mine idle set at 825 rpm in neutral, my idle speed is 650-700 in gear in the water when the engine is warmed up. If initial start up and right in gear at the ramp, when power unloading off the trailer it will surge a bit @ 500 rpm till it warms up. For this reason I most always do a short 5 min run on muffs in the drive way before I leave. Hope this helps.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Thanks Senior. I plan on using a vacuum gauge. Currently I have the idle mixture adjust to about 3/4 on both sides and idle was smooth. I'm trying to tweak it just a little for better starting characteristics. When you mention the surging idle during initial startup until it warms up, is that caused by a rich mixture since the choke still isnt fully open? I frequently have a surging/loping idle at startup anytime it has set for 5 minutes or more. Give it just a touch a throttle and return to idle and no more surging. Hopefully that's just a sign of an idle mixture thats too far on the rich side.

 

[Senior B]

Re: 5.0GL-H mixture adjustment / manual

It could be rich a mixture but I have found that since I put my Idle speed a little on the high side that it has pretty much cured that minor issue I had on warm start up. You could also see if your choke is set on the cold side and starts to close shortly after shut down.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Update:

Well the attempt to cure this problem was unsuccessful. If anything, I discovered the problem is not the mixture but something else.

I used a T-fitting on the pcv hose to read vacuum. Let it warm up in the water, then starting adjusting the mixture. I found where rpm/vacuum drops off due to a rich setting, and also where it drops off due to a lean setting. In between these 2 points, there is no apparent change in engine rpm or vacuum so tuning was difficult. Now for the interesting part.

Manifold vacuum was definitely low, and occasionally unstable. Here's what I noticed:

1) At startup, vacuum was slightly less than 15", and not steady. Every 2 seconds or so it would dip down to about 14", and come back up to 15. There is also alot of short needle vibration.

2) Over the next 1-2 minutes, vacuum would continue to dip down but the average would slowly rise. It would top out about 16".

3) Once at 16", sometimes the dip down would stop and it would remain constant besides the vibration. Other times it would still be erratic. I can't give a definitive description because the needle movement rarely ever did the same thing.

4) Mixture tuning had a very small effect on vacuum, maybe .5" difference, inside the range between too rich and too lean.

5) I've also got an intermittent "tapping" noise coming from the block. It's apparent about 75% of the time at idle and only at idle.

I'm thinking it's not a mixture problem. This spring I remember checking the vacuum and it was a steady 17.5". I know low vacuum indicates a vacuum leak normally, but what else can cause that? I tried pulling plug wires off the cap one at a time to see if a cylinder is missing. After the 4th one I was tired of getting shocked so I quit. Is there an easier way to do this? So to sum it all up:

Sluggish start after sitting more than a few minutes
loping idle until given throttle then it returns to normal
low erratic manifold vacuum
runs great outside of idle. No hesitation or loss of power
Occasional tapping noise coming from block at idle
New plugs/wires/cap/rotor at beginning of this season

Any ideas anyone??

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

bump

 

[sqbtr]

Re: 5.0GL-H mixture adjustment / manual

http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

Think I'd start with a compression test

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

That's where I plan on starting after another search for a vac leak. And a timing check. My vacuum readings were too inconsistent to really determine what was going on. The closest one I've seen is in the service manual that says "a slow float between 14 and 16 indicates bad ignition component" except it starts at 14 and very slowly and erratically rises to 16. Not really a float.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

I got 4 good boating days in this weekend which helped me see how the engine is behaving.

Cold start is great. Every morning I give 1 pump and set the throttle at about 1/4 and it turns over in less than a second. After warming up, bringing the throttle back gives a nice steady idle.

No acceleration or running problems at all.

If turned off more than about 1 minute then turned back on with throttle in neutral, engine turns over but has trouble catching. sloppy idle with rpm consistently bogging from 400-700rpm and will not clear on its own. Increasing rpms to 1000 for 5-10 sec and returning to idle results in nice steady idle.

Eventually I began doing warm starts by opening throttle about 1/8-1/4 throttle. Fires right up in under a second. I leave it there at 1000rpm for 5-10sec then return to idle where it is nice and smooth. Doing this helped me enjoy the weekend and not worry about it, but it is a pain to explain to the driver while in the water. And I want it to run as good as possible.

Sometimes in the evenings, when idling returning to a fallen boarder, the idle had the same bogging action. Same steps to clear it.

No black smoke indicating flooding or really rich idle. Mixture screws are both out about 3/4. I noticed late one evening after sitting for ~20min to air up a tube, I was behind the boat when it was started. I noticed a small puff of white smoke or steam. Not sure which one it was. It was small and laid low which could explain why I don't see it from the drivers seat. Not sure if this always happens or just that one time.

So my question still remains:

What is causing this issue during idle after startup? When the throttle is increased to 1000rpm for a few seconds to clear it up, how can I find out if its the extra fuel or extra air thats clearing it up? If the carb was slowly flooding after the engine is turned off (I checked the throat and there is no fuel drip from the bowl or jets) wouldn't it create black smoke from the exhaust also? As stated above, changing the idle mixture has no effect. If I knew what could cause this sort of thing I could know where to begin looking. Right now I'm just stumped. Thanks.

 

[Maclin]

Re: 5.0GL-H mixture adjustment / manual

That (still) sounds like a power valve with too high of a vacuum rating to keep it closed at idle. I can't remember where you were with that other than the VP proprietary thing, like what HG rating they said. If too high and the engine vacuum cannot keep it closed then the idle mix will be rich, that can make the idle vacuum even lower. If the PV is right on the edge then that would explain why idling slightly higher then coming back down would get vacuum high enough to close it, then stay closed once the idle mix is "thinned" out.

A Holley recommendation is measure highest vacuum at idle, then divide that by 2. In automotive applications the highest vacuum while idling in gear is what they use.

http://forums.holley.com/entry.php?430-Holley-Power-Valve-Tuning

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Holley said it should be a 10.5 valve and that's what is in there. On startup, vacuum now is usually slightly lower than 15" but raises to 16" over the course of a minute or so. It is not a steady vacuum either, with constant flutter and fluctuations of about 1" down as the bogging down occurs. Does a 10.5 valve start to open at 10.5", or is it fully open at 10.5 meaning it starts to open sooner?

I can't seem to find a 10.5 locally, so I think I'll order a new one. One more thing to eliminate.

 

[Maclin]

Re: 5.0GL-H mixture adjustment / manual

What is in there now? That is what I could not remember. I think your symptoms point to too high a PV rating on the PV that is in there now.

A 10.5 seems high, even in automotive apps, pretty rich setting. It takes at least 10.5HG to keep it fully closed. But if you have a higher one in there now then try the 10.5. If you have a 10.5 in there now then I would try an 8.5.

 

[Maclin]

Re: 5.0GL-H mixture adjustment / manual

sorry, just saw that you said it has a 10.5 in there now. I would try an 8.5 next unless you think the PV in there now is compromised.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Is there a way to check if the pv or gasket ring is slowly leaking after turning off the engine? If its a slight flood because of a fuel leak, its not enough to have soot or black smoke. I ordered a 10.5 pv and will order a 8.5 too. Ill try replacing the 10.5 first before changing to a smaller number since it accelerates great and I don't want to affect that.

I'm checking timing, water separator, and coil/alternator voltages tonight to hopefully eliminate that stuff.

 

[Maclin]

Re: 5.0GL-H mixture adjustment / manual

If it leaks just very little while the engine is not running then you will see vapors in the carb bores as the fuel hits the hot plenum floor in the intake, and you may even be able to hear the sizzle. If it leaks more than that while the engine is not running that raw fuel would pool up in one or more of the cylinders where an intake valve is open. Waiting an hour or so then looking at each spark plug to see if any are wet with fuel is the only way I know of to check that. If it did that though it would be very hard to start the next time, you would have to open up the throttle wide open and wait for several spark cycles before any wet fouled plugs would begin sparking. The engine would run very rough as one or more cylinders is not firing right away.

Your description of events indicates the condition clears pretty rapidly, and that is not usually the case if raw fuel is leaking while the engine is not running. A rich mixture (as in PV not closing at idle) with the engine running will make the engine run roughly but the plugs won't foul necessarily. Wet fouling means raw fuel has entered directly into the cylinder with no air, and that will not ignite and in fact can short the plug to where it has to almost dry out before it will fire. I do not think yours is doing that.

Did you find out what the tapping noise is or was? Could be a sparkplug wire arcing somewhere. You can see that best in the dark.

Has the boat always acted this way? Sorry if you have told us before. I am just wanting to think about what all could be related.

 

[skydiveD30571]

Re: 5.0GL-H mixture adjustment / manual

Tonight I replaced the fuel filter. Dumped the contents in a glass and after 3 hours there is no separation at all. Checked timing and it is spot on at 10deg. Of course there is no manual for the 5.0gl-h but the gl-d/e models called for 10deg so I'm assuming its right. Used some carb cleaner and went searching for a vacuum leak. Half a can later I'm baffled at where it could be if there even is one.

On all startups tonight the loping idle cleared itself within 30 seconds without any throttle input. Once stabilized, idle rpm didn't fluctuate much but the engine ran a little more rough than normal it seemed like. I did run it in the dark but did not find any sparks arcing. The tapping noise really resembles the sound of a diesel engine, just quieter. Like standing several feet away from an idling diesel truck. Very much the same sound and frequency.

A couple of odd things I noticed tonight:

1. While finishing up the girlfriend asked what this fast rattling sound was. I know its the pcv valve so I pulled it out of the valve cover to show her. The idle instantly cleaned up and sounded much better. Surprised, I turned the engine off and waiting 5 minutes to fire it back up. Start up was strong with no loping at all. Idle went to 600 immediately then slowly rose to 800. The difference in idle and start up quality was interesting...

2. The plug wire from the coil to cap that I have, original from volvo, is 1 foot long and has a resistance of 450ohms. The replacement I got from autozone is also 1 foot long but has a resistance of 5300ohms. Is there a difference in auto and marine wires or is something going on here? Of course the autozone wire doesn't fit the cap so I can't try it out.

 

[Maclin]

Re: 5.0GL-H mixture adjustment / manual

Regarding #2 point, Your readings sound pretty far apart, but truly the only way to measure high tension wires is a "megger" or MegaOhm meter. They produce high voltage and measure the drop.

Spark plug high tension wires come in "resistor" and "not so much resistor" types, the internal wire composition is the difference. The resistor ones do have more resistance by design, this is to allow just a little more spark-gap-arcing energy to the plugs. There should be some markings/text on the wires that give an indication if they are resistor wires or not. Coil and Spark plug wires should be the same type.

Regarding #1,
It is difficult for me to recommend "straying" from the OEM plumbing as it were, but if it was mine I would try some pre-PCV type setup. This would involve blocking the PCV barb on the carb, and changing the PCV out for a vent only type elbow at the valve cover (basically a gutted PCV) and routing the existing hose into or close to the flame arrestor where any crankcase venting would get drawn in.