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Volvo B21 Engine Tips


A few useful tips on the B21A engine

From club member John Holmes

I have a few tips and some information for other members based on my experience of owning a 244GL with B21A motor (carb not FI) since 1980, the same car and driver throughout.

1. Fusebox corrosion problem: I find the following works perfectly and simply:

a. treat it as a regular service problem

b. keep the solution dead simple

c. rotate and line up all the fuses so that the trough with the link in it faces you and they are therefore all at the same angle (also very useful for sighting the links when checking for a blown one, especially at night with a torch)

d. every 6 months/6000 miles rotate each and every fuse through the same small angle - I find a mere 10 degrees is quite enough - this will re-establish a good contact between the fuse and holder

e. afterwards check that all fuses are again at the same angle - you can easily spot the missed one - it's at the wrong angle

f. an very easy way to rotate these fiddly little things is to gently press against the fuse trough with one finger tip and then rotate your wrist, hand and finger in the desired direction. Don't try gripping them with your finger tips - they tend to jump out and disappear down that 'black hole' behind the spare fuse storage box!

2. 'Pinking': if your B21A pinks on light throttle openings and you've checked the fuel grade, the timing, the advance/retard etc. then try the following illogical test: WEAKEN the carb setting. Yes, I said weaken. Why? In the distributor's advance/retard system the carb vacuum and the centifugal weights both advance. You can't blame the weights, so you need less vacuum advance. Vacuum isn't present at the distributor at idle but appears rapidly thereafter as the throttle is opened. If the mixture is weakened, you'll put your foot down a bit further to get the same 'go', the vacuum is reduced, the spark is less advanced and the pinking may go away, as it did on my 12-year-old B21A when I finally worked out what was happening a few years back. Illogical isn't it?! I also fitted a Broquet catalyst first but it didn't help (see more later). Once I'd found the cure I was able to change to 2-star (unleaded) without light throttle 'pinking' returning.

3. Fuel pump leakage: if your breather plumbing or the flame trap are clogged then the increased crankcase pressure can cause all sorts of symptoms, many of which have been mentioned in recent issues. My own problem was that the mechanical fuel pump started to dribble 'gunge' out of the small (drain?) hole on the lower part of the pump casting. I had visions of diaphragm failure slowly leaking petrol into the sump, but it was only engine oil being blown out by pressure which in turn was caused by a clogged flame trap up on the cam cover.

4. Fuel consumption: the Broquet catalyst - sorry, but for me it didn't reduce pinking nor increase the mpg. I have logged every tankful since 1144 miles up to now (161k miles) and have achieved an overall grand average of 6.717 miles per litre (30.54 mpg). At present it is doing nearer 7.04 mpl (32.0 mpg). I have this data in an Excel spreadsheet and have analysed it for possible long-term effects such as age (mpg is slowly but steadily improving), for climate (there's a noticable annual cycle) and for carb settings (no detectable difference). Even a Mobelec electronic ignition unit at 13k miles (when 2 years old) and a Broquet unit at 87k miles (5 years ago) made no discernable difference then or since. Nor did a change to unleaded fuel. Another big variable of course is the type of driving - the mpg on each tankful has a variation that is pretty clearly a 'Normal' distribution, which to those of you who understand these statistical things, means there's no dominant single source of variation in the mpg figure.

5. Battery voltage indicator: here's a simple and very sensitive voltage meter for those with just a little electrical capability - take a 50 microamp meter (I used an RS one that's a edge-reading type and fitted it into a blank switch panel in 'switch alley' above the heater controls) and a 10 volt zener diode (any power rating) and a 100K resistor (any power rating) . Wire all 3 items in series directly across the battery. What happens is that there's no current flow below 10 volts, and above that there's a flow of 10 microamps per volt. The meter will effectively be reading 0 to 5 volts between its scale limits, which equates to 10 to 15 volts at the battery terminals. Since the current taken is so tiny you can leave this circuit permanently connected, which is convenient and very useful, especially in winter when you can see immediately the heavy loads drawing the alternator and battery down. The only problem you're likely to get, apart from duff components, is if the meter reads full scale all the time - don't panic - you 've just got the zener diode the wrong way round. Incidentally this device once saved a friend from blowing up his battery when his 144's regulator failed at maximum charge rate - the battery voltage went off the top of the scale immediately. If the meter has a clear plastic case you can add a small panel lamp outside the meter case to illuminate it at night - just wire the lamp onto one of the existing panel lamps above (eg the clock) or below (eg the heater controls).

6. For the more electronically adventurous I have circuits for both a wiper speed control and a wiper delay variation control I've made and fitted. Please let me know if you think anyone will be interested and I'll write and draw these up. Apart from a clutch replacement, front suspension arm bushes, and front discs (all in the last 15k miles) my 244GL has been DIY serviced by myself. I did have a 144 for a couple of years before buying this one. I admit I preferred the 144 except for the 244GL's overdrive, sunroof, height-adjustable leather seats and the (RHD) driver's footwell vent. I must be getting soft!


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