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quick question. When I'm tuning my carbs and setting idle, I often get them to a point where they are idling great, but when I rev the motor with the throttle linkage, the idle drops and acts like it's being "retrained" for a second or so, then the idle revs up fully. I get this condition frequently as I try to get the carbs synched and the idle set down to 900. I suspect that it might be starving, but the subsequent high rev has me confused. Plus, when I set the carbs any richer, it tends to diesel when I shut the car down.
I realize that this is probably pretty basic, but it's been bugging me that I can't say what going on for sure.
B20E with Dual HIF6 carbs (both fully rebuilt) BAL needles, o-ring thottle shaft seals, smooth throttle plates, extra vacuum port plugged.
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They will do that when they don't have (enough) oil in the dashpots.
--
George Downs Bartlesville, Heart of the USA!
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Considering how much time I've spent tinkering with my carb - pulling, adjusting, putting back on - I've keep the dashpot oil pretty well topped off with Marvel Mystery Oil. After reading some of the other SU Carb posts, I replaced the oil most recently with much heavier 30wt. Trouble is, that stuff is so viscous, I couldn't get the the dampers in, so I removed the circlip and took off the lower end of the dampers. Is that an especially bad thing?
I'm not sure if the throttle response is still poor with the heavy oil in there. I seem to think it improved. The weather went cold again, so I won't be until tomorrow that I get back to check the car.
In the off chance it is not the oil, what other problems could cause that sort of throttle behavior?
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RJ;
You have NO enrichening when you dissable the enrichening function by removing the one-way valve! ...then you I don't care what oil (or molasses) you have in the dashpots...because it doesn't matter! Remove your air filters and watch the dashpots shoot up when you blip the throttle...no different than if you remove the dashpot screws...no damping = no enriching = your symptoms
You have dissabled the enrichening function (by removing the circlip and the brass cylinder) which is what that assembly IS...and by doing that, then installing it with molasses for damping fluid, you have NO dampening whatsoever therefore no enrichening...and that explains your symptoms...
Please understand that things are usually the way they are for a good reason...if they didn't need that valve, it most assuredly would'nt be in there...and shouln't be removed without a well considered reason for removing it...
Cheers
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Eeah... Yes. Sage information as usual.
I'll accept your explanation for the form and function of the dampers. Nice to know and easy to reassemble - funny that it function wasn't covered very well in my SU carb manuals... My air filters have been off for over a month as I was tracking down a new return throttle spring for #1.
However, you missed a *crucial* bit of info in my post. This problem was occurring BEFORE I put molasses in there and removed the damper assemblies. It is actually responding better right now...
So, what WAS causing a lack on enrichment when I had everything stock?
Too lean a mix? When I richen it I get crappy mileage (<15) and the car diesels on shutdown - that usually means way too rich.
Thanks for the info.
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Hmmmm....could it be as simple as the colder, denser winter air causing a lean stumble upon throttle opening?
I generally find that three flats rich in the winter, back three flats leaner takes care of seasonal averages.
As far as responding better now...given the fact that I don't think you have ANY enrichening going on, I'd certainly expect a lean stumble unless you were REALLY rich to begin with! I'd start by restoring the dampervalve function and going back to ATF or MMO...
...as far as "checking" for enrichening...just for the fun of it...if you have the filters off anyway, and open the throttles somewhat quickly, you would expect the daspots to rise somewhat slowly (damping oil dependent) and you would noticably see the additional stream of atomized fuel enrichening the induction stream. Again, this is a momentary, no load (rotational inertia load only) condition, so a road-test is always a good idea...
...are your needle shoulders flush in their mounts?...
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Already cleaned restored to original dampers and MMO. Didn't see any ATF around. Have to check the other volvo's trunk. Pistons move freely with topped-up fluid
It was already dark when I was fidding with it, so it was hard to see what was happening, but I found that the carb were acting ultra-lean and refusing to idle w/o choke. I reset the jets to top and lowered them two two full turns of the screw (remember that these are HIFs so 1 flat = 1/4 turn). Also, these have the temperature compensation feature.
Anyway, they'd idle after I richened them a could turns, but testing #2 with the little lift pin kills the motor immediately. Thathas been a consistent problem in getting these carbs tuned up and almost always happens regardless of how rich #2 is.
I was getting cold so I gave up came inside before trying again tomorrow.
About your "shoulder" question. the needles are flush, but the jet bearing sits around 1/16" below the bridge of each carb. They've never sat flush with the bridge. I've asked about it before and been told that it's no big deal - still looks a bit "wrong" to me... The jet itself will adjust all the way to the top
Is it possible that this could be a float-starvation issue? I checked both when the carbs were off for repairs and they are matched, but my "power tuning" book didn't give me any direction on setting the float levels so maybe I screwed it up there?
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I'd go richer than two turns down, personally... My car's just a b20b and I run 2.5ish down in this colder weather we're having. Then again, my car probably doesn't mind being richer than yours as it's tired and whatever else, who knows.
Might try going another 1/4 of a turn on each, just because. I don't think it'll solve your "problem", but it's probably worth doing anyway. On my car, after driving on the highway and then letting the car drop down to idle speed it dips to lower rpm before working its way back up to my idle speed. Sometimes almost dies. Maybe because I'm a little too rich? Who knows. I currently have a synthetic blend of ATF in mine, and I do NOT recommend it. It isn't thick enough when cold to provide the amount of enrichening that non-synthetic would give. In theory anyway. And I seem to be experiencing that in actuality.
--
Kyle - 142, 145, and 244! - Oregon Volvo Tuners?
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If the engine dies when #2 lift pin is hoisted, then #2 carb is providing the predominent amount of correct fuel amount or mixture. It is either an unbalanced #1 carb, a overly rich #2 carb set at high throttle opening (leaks?), or a fuel supply problem with #1,like float height and check valve problems.
IIRC, the best way to check this is to remove the carbs and hold upside down. Set the gap between float hinge the same ~1/8 in, then squirt fuel into the check valve to see if it flows. This depends on which floats you're using. Some plastic ones are not adjustable.
Hope this helps
--
'89 245 sportwagon, destroyed by hit & run driver, RIP. '04 V70 2.5 T Sportwagon, 12k mi and '91 245 5-speed, 209k mi, replaced the '89
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It does help some thanks. I was able to get the car going again and avoid the richening problem when I open the throttle. Now it is idling and running okay, but it still dies if I play with the #2 lift pin. I've tried alternately richening and leaning out #1 and have kept both idles balanced with a unisync. The richness of #1 does not seem to be producing anything other than consistent death when I play with #2's lift pin. Weird.
Since it is running okay now, I'm not sure I want to fiddle with it much more but this weird behavior from #1 really bugs me. #1 is the only one of the two carbs to have the choke mechanism, so it is very important that it be doing it's job.
A couple of things could be contributing to my issue. First, the #1 carb was rebuilt with a later style SU23 kit that included an "improved" fuel jet with a straight pickup tube. The rear carb was rebuilt with an earlier style SU23R kit that had the more standard 90 degree elbow in the jet pickup.
Second, the fuel pump I have is a new "Volvo" pierburg fuel pump from "West Germany" (NOS?). Anyway, it puts out way too much fuel pressure which hits the forward carb first. I have an inline FPR but it's an off-the-shelf aftermarket device that has its own quirks.
I'm not sure of either of these two factors are really causing me trouble, but I wanted to ask for opinions.
Thanks
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If the engine dies when #2 lift pin is hoisted, then #2 carb is providing the predominent amount of correct fuel amount or mixture. It is either an unbalanced #1 carb, a overly rich #2 carb set at high throttle opening (leaks?), or a fuel supply problem with #1,like float height and check valve problems.
IIRC, the best way to check this is to remove the carbs and hold upside down. Set the gap between float hinge the same ~1/8 in, then squirt fuel into the check valve to see if it flows. This depends on which floats you're using. Some plastic ones are not adjustable.
Hope this helps
--
'89 245 sportwagon, destroyed by hit & run driver, RIP. '04 V70 2.5 T Sportwagon, 12k mi and '91 245 5-speed, 209k mi, replaced the '89
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If you couldn't get the dampers in, that means the oil is too thick and
the cure is not to disable them. I think 10W or 20W oil is what most
manuals call for and it has always worked OK for me.
--
George Downs Bartlesville, Heart of the USA!
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I have a 240 and just noticed the thread, I also have a 78 Triumph and use ATF, as do many other Triumph owners, as the dashpot oil, seems to work fine. I have a single Stromberg Carb.
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I will second this. A synthetic ATF or light oil is best, especially in cold climates. Most of us have a dribble leftover from the OD tranny's in Volvo's. Use this oil.
Singer Sewing Machine oil is also good.
--
'89 245 sportwagon, destroyed by hit & run driver, RIP. '04 V70 2.5 T Sportwagon, 12k mi and '91 245 5-speed, 209k mi, replaced the '89
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One other benefit, to those mentioned above, ATF is relatively Cheap, compared to good motor oil, 3in1, or oils labeled as "Damper oil"
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What ever became of the throttle plate valve, did you stick with HS6 plates or return to HIF plates? It sounds like too much air, not enough fuel...
I could see how if the HS6 plates were covering the HIF idle valve they could still be made to work responding to engine vacuum and idle ok. But, the lack of vacuum drawing metered fuel from the bypass valve because the piston is already up might make it hard for the momentary enrichment from idle to acceleration, there's isn't adequate time for the emulsification to occur in the right proportions. What are your needles again?
In any case that's just a thought. A couple days last winter the 122 wouldn't start w/ 30wt in the dashpots. Went back to ATF for a couple of weeks, and all was well 'till it warmed up again.
Have a blast, -Sean
--
1966 122s, 1970 142s, 1974 142e... Blue is beautiful
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