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Ke70 4K-C Fuel Efficiency


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Hey guys, just a few quick questions.

 

During summer time, my car was doing pretty well fuel wise, wasn't focusing on the exact Km's on a full tank, but I'd say around 400-450km on a full tank, normal driving.

 

Now I barely get over 350ish km to a tank in the winter, normal driving as well. I drive 3-5km/ph under the speed limit always, so it's not a heavy right foot case. It also doesn't run very nicely till its warmed up, but I guess that's sorta normal with an old car

 

I filled up a full tank, drove 25 minutes and back in normal/ little traffic, and I had 3/4 of a tank left. Just doesn't seem right anymore. I checked all vacuum hoses (They're all fine) and checked for leaks, and took a few photos. I think there's a tiny leak at the fuel pump, but It could just be oil.

 

Also in the picture of the carb, with the choke fully closed, the right hand side valve is open? I thought when the choke was closed, it closes that too. When the chokes on, it opens it? Unless it's meant to be like that.

 

What could it be?

 

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You need to start calculating your litres per 100km.

 

So fill it up, reset the trip meter, drive around until you've done say half a tank. Full it up again, not the kms travelled and litres to fill it up. And do the math.

 

Better to give the engine a once over if you suspect bad fuel economy. Check spark plug gap, reset timing, give the carby a clean with carby cleaner, check air cleaner etc.

 

You don't have a sump full of fuel do you?

Edited by ke70dave
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You need to start calculating your litres per 100km.

 

So fill it up, reset the trip meter, drive around until you've done say half a tank. Full it up again, not the kms travelled and litres to fill it up. And do the math.

 

Better to give the engine a once over if you suspect bad fuel economy. Check spark plug gap, reset timing, give the carby a clean with carby cleaner, check air cleaner etc.

 

You don't have a sump full of fuel do you?

 

Cheers i'll check all that stuff out, probably end up replacing the plugs, they're only about 5,000km's old which is the worrying issue. As for the sump thing, I just thought fuel might've been leaking from the pump? Oil most likely from an old gasket or whatever, but yeah hopefully it all works out.

 

How many litres per 100km should I be getting approx.?

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Hi Oliver,

Hmmm ! Rings a bell. Once had something very similar occur years ago, and turned out, it was as Dave suggested above. A perforated diapham in the fuel pump, was allowing fuel through to the lower side of the pump & into the sump. Unlike the press metal can fuel pumps on some Rollas, yours is the diecast model, that can be dissembled easily.

 

Not a very hard job to take the fuel pump off & dissemble & check. I'd be doing that before anything else, as the drop in fuel economy was sudden, if I read your post correctly.

 

Cheers Banjo

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I'd say you should get between 6.5 and 7.0L/100km at 95kph on the coast, and use a L/100km more around town, unless the choke is on all the time. Push the choke off as soon as you can each morning.

 

The embarassing thing is that if you're getting 10L/100km you're better off fitting a newer 2L motor! Our Pulsar SSS does that, as does the Altezza's 3SGE.

 

Don't worry about the spark plugs, they'll do much more than that, but check points and timing. They retard the timing as they wear and that knocks a lot of performance off. It does sound like a fuel leak somewhere. If the pump diaphram is OK, check for a tiny fibre/dirt in the needle/seat that might be running it with a high fuel level.

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Cleaned the plugs, tried to adjust the valve clearances, didnt do a very good job, made the exhaust 0.33 instead of 0.30 but I will re-do it soon.

 

I tried to do the timing with a very dim light, I couldn't get it to 8 degrees without it stalling and running poorly, I adjusted the idle speed when it was about to konk out to keep it running, but when I drove it, it drove poorly. I have it at like 15-17 degrees now which is way off, but it runs perfectly? Not sure why.

 

Also bought a brand new fuel pump and that seemed to have fixed the leak out of the gasket area, even if I didn't need a whole brand new pump, its better to have one just incase.

 

If both things don't work, what's next? Anything to do with the gauge itself? Can't find any other leaks. Or do I just buy a new car (Don't really wanna do it)

 

Cheers for all the help guys, appreciate it.

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What you did with the idle is correct, as you adjust timing you have to adjust the idle. K motors seem to like more advance than factory, but since I fitted the electronic dizzy and re-did the advance curve mine is back on 19deg idle. So long as it doesn't 'pink' it is fine.

 

What were the plugs like?? ..and the points gap??

 

Ignore the guage, just run it from full tank to full tank and count the Km. I ran the 4AGE to dry over the weekend, carrying a 10L of fuel, and we got 680km from the 50L, so 7.3L/100km

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What you did with the idle is correct, as you adjust timing you have to adjust the idle. K motors seem to like more advance than factory, but since I fitted the electronic dizzy and re-did the advance curve mine is back on 19deg idle. So long as it doesn't 'pink' it is fine.

 

What were the plugs like?? ..and the points gap??

 

Ignore the guage, just run it from full tank to full tank and count the Km. I ran the 4AGE to dry over the weekend, carrying a 10L of fuel, and we got 680km from the 50L, so 7.3L/100km

 

My plugs were black last week, cleaned them all up shiny again, made the spark gap 0.8mm and then checked again yesterday, back to black, I'm talking full sooty black, some have spots of white which from what i've read is too much heat? I seriously don't know what to do anymore haha, I could send it to a mechanics for a tune up overall, but I'd rather do all the work myself and that way I can learn too.

 

Wowee 680km is insane. What should I be getting approx. per full tank KM wise? Just so I know if it really is stuffed.

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If the plugs go black its just running too rich.

 

The fuel level is too high I'd say as a starting point. Fuel is flooding into the carb through the needle & seat, so everything is fine except it dribbles out of the jets into the carb constantly.

 

You could have a garage put a mixture sensor up the exhaust to confirm its running rich, or take the top off the carb and measure the depth of fuel in the bowl. Then you'll need someone with a stock carb to compare it to. ..or buy a new needle & seat and fit it anyway.

 

The 600km back to home in the Hoonicorn showed that a 4K does the same as a 4AGE when driven at the same speed! Its usually cheaper to run by a L/100km or so, but I also drive slower...

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Ok cool, would that explain why it barely starts in the morning till i spray some fuel in the carby, then half way to work it starts to flood (?) I broke down and had to walk the rest of the way to work today so I really wanna get the issue fixed, I never touched the mixture on the carbi, only the ignition timing (which I stuffed up) and the valve clearance, which sorta made the ticking louder.

 

What should I do? I need the car on Saturday, so my only other option is to leave work early on Friday (Tomorrow) and see if a workshop can fix my issues haha, how much should I expect to fork out? I've never taken it to a workshop. Thanks again for the help altezzaclub.

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