Fuel question

[Maisie]

I run a 1985 1600 S series engine Maestro, which has the following problem:

It normally runs on LRP. For a few months, it's started on the 2nd turn over or so, but then stuttered to the point of almost stalling 2 or 3 times before it runs smoothly (but at quite a low idle). It's had no power to pull up hills or awya from a standing start. I was stuck for petrol to get home the other day, and found myself at a garage with no LRP, so I put in some unleaded, and it seemed to start and get going better, and seemed a lot more powerful and faster. I've just repeated the experiment with Optimax and it seems again quicker, but not as good as the unleaded. I'd like to keep it on LRP to keep the valve seats OK - does this fuel "experiment" tell me anything about how to go about tuning the car to make it run better on LRP? It is likely to be rich, lean, or what?

[HiRich]

I have no idea to be honest, though I would suggest taking a look at your spark plugs, and the spark they are able to generate as well. The symptoms are as likely to be about quality of spark and/or timing as they are about mixture.

And if you didn't realise, one tank of lead-free will not have caused any obvious damage.

Sorry to have wasted your time...

[Dave Brand]

One tankful of unleaded won't do any harm. Your valve seats will have lead (or substitute) deposits on them which will protect them for several thousand miles (the so-called 'lead memory'). I'm not sure if this applies to LRP, but when leaded petrol was still available common wisdom was that on tankful in three or four of unleaded was sufficient to prevent valve seat damage.

I suspect that the adjustments you need may be to ignition timing rather than to carburation. Rather than messing about trying to find the optimum settings, why not use unleaded/Optimax with a lead replacement additive?

[spearce]

It seems that LRP is worse than useless for competition purposes (and isn't going to be available for much longer anyway). If you can't get proper leaded 4 star, better to use unleaded + additive than LRP. I've been using unleaded (optimax if I can get it) for several years with no probs.

[Maisie]

I know I won't get any damage from 1 tank, and it's been suggested that I should use Optimax + lead substitute, which could be an expensive habit! Oddly enough, though, the fuel economy on Optimax was a hell of a lot better than I expected. I can't fiddle with the ignition timing as it's all done by a fuel ECU under the dash Will try spark plugs - it's time the poor bugger had a service anyway.

[KC]

You should check your fuel filter. It sounds like your car may be starving for fuel. Its common for cars with a partially clogged fuel filter to start a little rough and go on to idle, but the filter will keep the car from running at speed becasue it just can't get enough fuel.

[noise boy 2]

This question was adressed by Car Craft a while back, and as I recall, the feeling was that running unleaded in a car originally designed for leaded fuel would not be a problem until long after the engine was in need of a rebuild, as the wear due to the lack of lead was so infentisimal (sp?) that it would take forever for the valves to recess into the seats far enough to cause a problem. Robert

PS Found a reference to this at this link, it's a motorcycle magazine, but the principals are the same, the info is about halfway down the page.

http://www.motorcyclecruiser.com/tec...ust/index.html

[medler]

I agree with Noise boy2 thoughts on the subject. When leaded fuel was replaced with unleaded there was a lot of discussion in classic car circle about what using unleaded would do. It seems that for most engines it would take a long while to effect the valve seats, unless being used for competition. Also vehicles with alloy heads already have hardened valve seats, so should not be affected by using unleaded. The main change between leaded and unleaded was the reduced octane rating as most classic cars were using 4 star leaded, so the only modification was to change the timing to run with the lower octane rating.
If the problems with your car are just with LRP, have you been getting it from the same place? It could be that it has been badly stored. Did you use standard Unleaded or the higher-octane stuff?
I agree with the advice of changing fuel filters and a service, then maybe start using unleaded and lead substitute every few tanks if you want some peace of mind.

[Bluebottle]

We had a bad experience with LRP before we even knew about it- the pumps were still labled as delivering leaded petrol, the result was a gummed-up carb! Unleaded with additive was cheaper than LRP untill the tax on LRP was changed to bring it into line with unleaded.

Which reminds me.... why is leaded petrol (still available at a selected few places) not taxed as a low-sulpher fuel when it is actually zero sulpher?