Hi all,
Well, I assume it is the strombergs. I've just bought a 1974 144 (genuine one owner) and yesterday drove it home. About 850km (525miles) in pretty hot weather most of the way, pulling a small trailer with a spare motor etc plus a trunkfull of other spares. Over 30C pretty much all the time.
It starts cold very easily and idles smoothly. When hot, e.g. after refuelling, it nearly flattens the battery trying to get it to start. Turns over a lot of times, a very hesitant catch if I'm lucky, then it very lumpily idles until it finally catches properly. Then it runs fine.
PO said he had the carbs rebuilt about 4 years ago. It's certainly running rich - you can smell that and the plugs were pretty carboned up when I pulled them at home. Replacing them with new NGK BP6HS made no difference to the hot start. I haven't yet checked timing or points gap, but it is running well. They are next on the list.
Idle is also pretty eratic. Idles as high as 2000rpm or so low that it stalls. Generally idles high when very hot.
Any quick fixes here? Or just hunt in the parts cupboards for some SU HIFs that I think are there somewhere and forget the strombergs.
All help is most welcome.
Regards
JohnH
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JohnH, Sydney, Australia

John. Remove needle and seats and carefully inspect for fine lint or dirt creating no seat condition, or better still replace seat assemblies. Most hot start flooding points leaking seats. Check ignition first.

This ain't a quick fix, and there's not necessarily any one thing wrong. Most of what you describe sounds like the normal behaviour of old Strombergs.

The only thing you really need to check, is simple. Pull the four screws holding the top cover on each carb, and lift the top. Fear not, it's quite a simple device and it won't drop piles of parts on you; there's only one big spring to keep track of. So. Have a look. Are the diaphragms in good shape? A leaking/split diaphragm will cause absolute havoc. Next, lift the air valve out (lift by the center), and check that the whole carb isn't filled with black ickiness from backfiring or dried fuel, smile if it's fairly clean, then put it back together, and assure yourself all is well. Four screws per carb, and you've checked the diaphragm which is the only real achilles' heel of the Stromberg.

If you check that and don't find a problem, smile and resign yourself to enjoying the benefits of fine British carbs of the 1970s.

Having put over 200k miles on a pair of Strombergs, I can assure you that the hot start problem is normal: Strombergs do that, even when the float is adjusted and the mixture is correct, even when the hot start valve is working, even fresh off a tune-up.

Brand-new Stromberg-equipped Volvos, reviewed by major magazines, exhibited this problem. I can send you the reviews if it will make you feel better. It's completely normal for the type and the more you try to "fix" it the more frustrated you'll get.

When starting a hot Stromberg vehicle on a hot day, put the acccelerator to the floor and hold it until she starts. The flood condition will clear quickly and the engine will start after about four seconds of cranking. If THAT fails, THEN you've got to lean out the mixture.

Rich running is also fairly normal, though I can't stop you from trying to tune it. Basic problem with tuning it leaner: the dashpots that enrich the mixture for acceleration NEVER hold their fluid, so after you've topped the dashpots you'll run well for a few days and then you'll go lean on acceleration. You see where this is going. If you want long-term drivability, and you don't want to fill the dashpots constantly, you just tune it a little rich and live with it. Every Stromberg Volvo I've ever seen was like this.

Idle issues are hard to fix once the butterfly shafts have worn a bit. Air will leak in, and rather than causing a stumble it'll cause a high idle. Because you're running rich, remember?

Fluctuation is pretty normal at high temperatures. It will go away when the weather cools down a bit. There's a certain temperature at which the suckage begins, somewhere around 30-35C. Below 25C, they're pretty good.

Once you get your Strombergs perfectly repaired and tuned, the amount of time they will continue to run asymptomatically will be measured in weeks. Sorry. My car was professionally maintained by a dealer and would do all this stuff within a couple weeks of getting it back, every time.

Don't get me wrong, the Strombergs did make the car go and they never let us down. And they were honestly pretty fantastic in cold weather -- every winter they ran great, started promptly even when we had to dig the car out from under six feet of snow, and so on. Great for cold. They just didn't like heat.

If you want a vehicle with Strombergs in it that idles smoothly, doesn't run rich, and doesn't flood on hot days, simply place the Strombergs into the trunk of a vehicle with those running characteristics.

Nothing wrong with continuing to run a Stromberg-equipped car. Just remember: KEEP IT FLOORED when you start it hot!

Weird. I ran a stromberg carbed 164 for years in Riverside California where it gets to be 110 for weeks at a time. Never had any hot starting problems with mine.

When I first got the car I took the carbs apart, as you say, and found that the diaphrams were intact and all the moving parts were operating well but the 2 springs in the carbs were totally different and 100% funky. I think in a fit of madness I took the spiral "springs" out of a pair spiral bound notebooks and put those into both carbs.

Also, I took out the little valve thingy on the side (the bimetalic thingy) and adjusted them both so they both opened and closed about the same amount when in both hot and almost boiling water.

That car ran like a champ. I foolishly pulled the strombergs and put on SUs instead -- not a mistake I'd make again. It ran fine with the SUs but was down on power and got worse mileage.


My guess is either terribly broken carbs or ignition problems. Only one of my dual SU volvos ever had starting problems *not* related to the points or other ignition problem. (that was terribly poorly balanced SUs on a 122)

I'm leaning towards something inside the carbs needing fixing. I've checked the timing (10BTDC at idle going to about 35BTDC at I'm guessing 2500rpm)), dwell (52degs - a little low, but probably not critical) and brand new BP6HS gapped to 28thou. I haven't checked the valve clearances. They might be tight because I couldn't hear any tappet sounds.
I'm away from the car for the next 6 weeks or so and will check all the above again, do the valves and finally pull the carbs to bits when I get back.
Thanks for all the help.
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JohnH, Sydney, Australia

So long as you've also checked to make sure the coil's making a nice fat spark then yes -- the carbs could well be the issue. The diagnostic tree on these cars starts with the ignition first but I have seen poorly running B20 cars with fuel system problems...

The CD175 carbs are pretty nice carbs, in my opinion, at least if they're operating 100% correctly, and I get the impression that they've got such a bad reputation that people rarely bother to actually sort them out.

Because they're common on all sorts of british cars, I suspect there is still good support for them -- take them apart and replace anything obviously wrong (IE they should be identical between the 2 carbs so if the springs are different, replace them both, the bimetallic strips should operate freely and have about the same range of motion at the same temperatures between them (I used a pot of hot water).

I don't think the damper oil makes much difference -- I usually used 3in1 or sometimes automatic transmission fluid of some unremembered specification... simple motor oil is probably the safest. The oil in the dashpots acts to enrich the mixture when accelerating -- the heaver the oil the slower the piston moves up and thus the higher velocity the air going through the carb -- causing more fuel than "normal" to get into the mixture.

They don't have some of the SU HS6 problems like leaky throttle shaft bearings and such. They do have the flaw of having more than 4 moving parts...

Hi,
You are right: great cold starting, but hot is a real issue. I sure take longer cranking than 4 seconds, much longer and many times. It's a tribute to the battery that it isn't dead by now. Since the first posting I've checked timing, valve clearances and dwell. All ok. So it sounds like the mixture is too rich and this is confirmed by the condition of the plugs and the smelly exhaust.
I haven't yet checked the diaphagms. The PO had them replaced in 2007, so I'm hoping they are ok. I'll check them next time I'm with the car.
How do I lean off the mixture? I've read Haynes etc and can't find anything about it. I can find the idle screws (on the shafts) and something also called an idle adjustment (on the side of the carbs above the temp compensator). Is this the mixture screw? I set them to 2 full turns out, like the book says, and adjusted them up to a full turn either way. I couldn't tell any real difference.
Thanks for your help. I won't get another chance to play with the carbs until March because I'm about to come to the US for a few weeks.
Regards
JohnH
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JohnH, Sydney, Australia

Tuning Strombergs is not a commonly addressed subject but British car circles tend to know them well; your local MG or Triumph mechanic will probably know those carbs better than your local Volvo mechanic does.

The obvious caveats apply, of course: don't mess with the mixture until you've fully sorted the ignition and valve adjustments...

I had a California-spec vehicle so I didn't have full control of my mixture, as California had some special pollution requirements. On most vehicles a special tool is required to adjust the mixture. There's an air bleed screw on the side of the carbs, but you would be well advised to mess with that only when you've got access to someone who knows Strombergs.

I've got the green book for it, which includes the complete factory instructions for tuning the carbs. I'll be happy to scan those pages for you when you get back. You'll be surprised at how useless they really are. But they might come in handy, you never know.

Again, you opened the throttle all the way, and held the pedal solidly on the floor the whole time while cranking, and the car didn't start after ten seconds with the throttle wide open? No choke was used? If all this is true, something's up. Don't even mess with "mixture adjustments" until you're past that stage; the mixture adjustments don't do a whole lot on these carbs and a gross problem like that is likely to be something more obvious, like a stuck air piston or a clogged air filter or a punctured diaphragm.

Anyway, revive this thread when you return and I'll scan the relevant pages for ya.

Have you adjusted the float? I wonder if the fuel level in the fuel bowl is too high and expanding during "hot soak" thus flooding the engine.

But yes, get your ignition system in order before trying to make carburetor adjustments.

I had the same problem and wound up going with a weber....BUT I later noticed that there is a "hot start" valve on the strombergs....i never messed with it cause they are still sitting in a box in the attic but that is a place you might start looking at to see if it is functioning properly. Check out this link for more info

http://www.autozone.com/autozone/repairguides/Volvo-Coupes-Sedans-Wagons-1970-1989-Repair-Guide/CARBURETED-FUEL-SYSTEMS/Carburetors/_/P-0900c152800641cf

dean