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Great site you have here. I have been browsing the forum for the past couple of weeks and thought i'd finally join.
I bought my first car about 9 months ago after a proud volvo tradition in the family (a 1978 245L and a 1989 740GLE) - it is a 1972 142S with the twin stromberg carbi's. I am a complete novice mechanic but I am very eager to learn.
On that note ill get to the subject of the post. Car starts/runs great but recently i have noticed that it is 'stuttering' at high rpm (e.g. driving on a highway or up a large hill). In this situation it doesn't accelerate smoothly at all (whereas a month or two ago it was fine). I have recently had the points replaced along with the spark plugs and leads so i dont think its a sparking problem but i have my suspicions about the carbi's. As i said i am learning as i go but can anyone point me in the right direction?
thanks for your help,
evan
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Wow! Thanks everyone. I wasn't expecting a response that good. I have purchased a Haynes manual on eBay (as well as a few others) so i will read up on all the suggested problem areas before anything else and get stuck into it. I will keep you all posted on the results. Once again thanks for the help.
cheers,
evan
p.s. i have posted an image of my 'baby' in the gallery
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I don't what your fuel is like there, but here in Australia our fuel is crap. If I drive my B20 gently around for a month or two it will splutter & carry on when I try & give it a bit of stick. The cure for mine is to either throw a new set of plugs at it or just cane it a few times to clean the plugs.
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disregard my post saying it advances,it retards. I missed a gear on that one, now will check posts and take my medicine.
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Phils reply is right on, new points always have a bedding in period. As well as putting dwell angle out as they close up it also increases advance by opening points earlier which can cause plugs to misfire.
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If it only runs funny after you've had the throttle pretty far open for a little while (accelerating on the highway or going up a hill) then it possibly could be a partially bllocked fuel filter, possibly a failing fuel pump. Often they can pass enough fuel along to the carbs under partial throttle and idle conditions, but at full throttle or close they can't keep up - and after a certain number of seconds the fuel bowls in the carbs get low and the car starts running lean.
I had this happen fairly often on my PV after resurrecting it from its 15+ year 'slumber' as lots of little rust particles worked their way into the filter. I could have repeatedly flushed the tank (I did flush it once when reviving the car, apparently lots of particles only work loose when fuel sloshes around vigorously) but just replacing a $2 filter every month or two seemed easier. After about 2 or 3 filter swaps it all settled down and has been fine for a year or two.
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posted by
someone claiming to be Niel
on
Mon Dec 1 07:40 CST 2003 [ RELATED]
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The Strombergs also has a metal mesh filter in them. Mine had mud-like rust all over them as well as a thich layer of this gunk in the float bowl after 32 years, although the fuel filter was always replaced at servicing. You take off the carbs, turn them over, unto the screws and carefully remove the cover to reveal the float mechanism. Note: a new gasket is required. Unclip the float, and the little valve and filter sits in the corner where the fuel enters. While you're there, check the hight of the floats. It regulates the fuel level required for the fixed metering needle, unless you've got the earlier adjustable carbs. This info should come with a carburettor rebuild kit, which is very easy to fit. I've done the Strombergs on my '71 144S last year. Don't worry about all the extra gaskets in the kit, that's normal. Actually I think the kit came with a new mesh filter. But before you go this far, first check the ignition, which is what we all agree upon.
On another note, check the drive shaft universal joints (if you have not yet). I've gained at least 20% more power by replacing mine (e.g. 5% ^ 3 = 19%), not realising they were rusted in place and one was starting to eat into the fork... They were replaced in mid to late 70's, and it was only last month that my father told me there are grease nipples on them, which was not OEM and people usually don't check it. Al I've noticed was a mild clunk and upon inspection only one joint felt worn. Now take-off is so much better...
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The difference (I thiink) would be that when floored an ignition problem would immediately appear, where a fuel supply problem would show up only after a certain number of seconds (depending on how much fuel the engine needs vs. how much it is getting).
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I don't see a new distributor cap or rotor mentioned in your list of new parts. While you're in there rechecking the points, clean the inside of the cap, particularly at the top between the contacts. It can get carbon traces formed that cause a certain amount of shorting between the contacts. Sometimes they're hard to see. It wouldn't hurt to scrape the contacts clean with a knife, along with the contact on the rotor. Examine the rotor closely any cracks, etc.
Another possibility, although not a real common problem, could be that the condensor is going bad.
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posted by
someone claiming to be Niel
on
Mon Dec 1 07:12 CST 2003 [ RELATED]
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Or in my case the carbon contact in the center of the cap was completely worn down and the car would die once a day and start up perfect 5 minutes later.
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posted by
someone claiming to be Niel
on
Sun Nov 30 23:30 CST 2003 [ RELATED]
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Check the centrifugal advance stops. This is something I've actually read about only a few minutes ago on a motorbike site while searching for something else, so I'll just give the basic idea. With a timing light, set the timing correct for idle speed. Now rev the car and see that the timing does not advance beyond the double line mark (not sure if my 144 has that, it's midnight in New Zealand). This is the point where maximum centrifugal advance occurs. The distributor has metal tabs to stop the centrifugal weights from advancing the timing beyond a certain point. Over time these tabs wear, slowly increasing the maximum advance. But in your case I would suspect that it got bent (ever so slightly) when the points got replaced. Also, aftermarket points have weaker springs, and are more prone to floating at higher RPM. It is possible to drill out the rivit and fit 2 springs. Aftermarket points also wear faster, or it might have now just settled similar to how a new engine needs a tune-up after 1000km. Generally, OEM parts are much better quality than aftermarket.
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Hi Evan,
Well, if it ran fine a month ago, I don't think I'd blame the carbs right off, although I wouldn't rule anything out just yet. A worsening high-rpm miss under load would make me suspect the ignition first. It could be that your newly-replaced points are closing up -- they'll do that pretty quickly from wear on the plastic bit that rides on the distributor cam if the cam isn't lubed with a thin smear of light grease.
Pop open the distributor cap and turn the motor (adjustable wrench on the nut that holds on the lower pulley, if you can't turn it by the fan belt) so the points are as open as they can be. Measure the gap between the point contacts. It should be around .016", just a tad less than the thickness of a dime. If it's substantially less, that's very likely the problem.
Let us know how you make out -- it could be several other things, but that's where I'd start looking.
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Phil/Evan!
Most of these distributors have worn point cams so that you usually can't get
an accurate setting with point gap. A much better way is to use a dwell
meter and set it to about 60° dwell. Smaller point gap = more dwell.
On all of mine the resulting gap is quite a bit less than 0.016".
(With a new distributor it will be pretty close.)
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma
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They do wear a bit with time, It does pay to have a close look at the lobes to see if one is worn my than the others. To do this check the gap while you turn it to all 4 positions, also check for timing differences with the timing light between 1 & 4.
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On all of mine the resulting gap is quite a bit less than 0.016".
I've noticed the same thing on my Amazon.
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