Low compression and high fuel consumption

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Re: Low compression and high fuel consumption

Post by Ollie »

No it's not drain I'm talking about. Without a thermostat your coolant system is always open. Making the car need to keep itself a lot warmer... You don't seem to understand what people are saying to you.
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Re: Low compression and high fuel consumption

Post by crteezy »

Yorindesarin wrote:
Sat Nov 14, 2020 4:17 pm
No it's not drain I'm talking about. Without a thermostat your coolant system is always open. Making the car need to keep itself a lot warmer... You don't seem to understand what people are saying to you.
Yeah sorry I'm still a new for these mechanical stuff... Previous owners may have removed the thermostat as a shortcut solution for the overheating on high rpms. My mechanic couldn't identify the reason for the overheating
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Re: Low compression and high fuel consumption

Post by 350matt »

OK this image may help as to why you should never just remove the thermostat ( on most engines)
thermostat Dual Poppet.jpg
as you can see if the stat is not there at all then you will be losing some flow from the pump back down the bypass, instead of going through the rad

if you don't have one then get a new one in there right away
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Last edited by 350matt on Sat Nov 14, 2020 10:09 pm, edited 1 time in total.
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Re: Low compression and high fuel consumption

Post by warpc0il »

Is fuel in Sri Lanka sold in US or Imperial Gallons?

8 mpg (US) = 9.6mpg(UK)
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Re: Low compression and high fuel consumption

Post by crteezy »

warpc0il wrote:
Sat Nov 14, 2020 9:32 pm
Is fuel in Sri Lanka sold in US or Imperial Gallons?

8 mpg (US) = 9.6mpg(UK)
Here we use litres and kilometres. My car is doing only 3.x kilometres from a little
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Re: Low compression and high fuel consumption

Post by goodeggbob »

A silly question maybe , but could your climate be a reason for removing the thermostat?
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Re: Low compression and high fuel consumption

Post by ChrisHolmes »

Without the thermostat the engine will take longer to warm up and will use more fuel. Then once up to temperature the coolant circulation will be less efficient for the reasons posted above.
As a first job fit a thermostat and see what effect that has.
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Re: Low compression and high fuel consumption

Post by crteezy »

goodeggbob wrote:
Sun Nov 15, 2020 8:21 am
A silly question maybe , but could your climate be a reason for removing the thermostat?
Yeah that's possible. But my one has an overheating problem when doing high rpms which other cars don't have
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Re: Low compression and high fuel consumption

Post by warpc0il »

I suspect that the thermostat was removed because the car had an overheating problem and someone thought that might fix, or at least mask, it. This was never going to work, for the reasons Chris says above.

You need to replace the thermostat and then work out why the engine is overheating in the first place.

It might be a problem with the coolant flow; blocked radiator, water pump, etc
or air flow through the radiator, missing seals around the radiator mount, or seized fans

Or is could be that a sticking brake is making the engine work much harder all the time, which would also be the explanation for the fuel consumption.

Is the car otherwise standard?
Is it running the original airbox?
Is the air filter clean?
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Re: Low compression and high fuel consumption

Post by crteezy »

warpc0il wrote:
Sun Nov 15, 2020 1:23 pm
I suspect that the thermostat was removed because the car had an overheating problem and someone thought that might fix, or at least mask, it. This was never going to work, for the reasons Chris says above.

You need to replace the thermostat and then work out why the engine is overheating in the first place.

It might be a problem with the coolant flow; blocked radiator, water pump, etc
or air flow through the radiator, missing seals around the radiator mount, or seized fans

Or is could be that a sticking brake is making the engine work much harder all the time, which would also be the explanation for the fuel consumption.

Is the car otherwise standard?
Is it running the original airbox?
Is the air filter clean?
Coolant flow - checked
Radiator - checked and cleaned
Water pump - checked
Fans - checked and replaced with series 2 fans
Airbox - original
Airfilter - replaced
Missing seals around the radiator // will double check this one
Sticking brake // need to check
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Re: Low compression and high fuel consumption

Post by 350matt »

fitted a thermostat yet?
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Re: Low compression and high fuel consumption

Post by Ben_r1 »

Maybe it’s a head gasket :lol:
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Re: Low compression and high fuel consumption

Post by crteezy »

Ben_r1 wrote:
Sun Nov 15, 2020 9:30 pm
Maybe it’s a head gasket :lol:
if it's the head gasket what can I expect? Any signs to identify if it's the head gasket?
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Re: Low compression and high fuel consumption

Post by Juey »

(There isn't a head gasket - that was a joke)
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Ben_r1 (Mon Nov 16, 2020 11:00 am)
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Re: Low compression and high fuel consumption

Post by Ben_r1 »

crteezy wrote:
Mon Nov 16, 2020 10:14 am
Ben_r1 wrote:
Sun Nov 15, 2020 9:30 pm
Maybe it’s a head gasket :lol:
if it's the head gasket what can I expect? Any signs to identify if it's the head gasket?
Sorry that was a cheap joke, but I can understand how someone not familiar with the car may not understand it as such, I retract my statement :oops:
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Re: Low compression and high fuel consumption

Post by crteezy »

Ben_r1 wrote:
Mon Nov 16, 2020 10:59 am
crteezy wrote:
Mon Nov 16, 2020 10:14 am
Ben_r1 wrote:
Sun Nov 15, 2020 9:30 pm
Maybe it’s a head gasket :lol:
if it's the head gasket what can I expect? Any signs to identify if it's the head gasket?
Sorry that was a cheap joke, but I can understand how someone not familiar with the car may not understand it as such, I retract my statement :oops:
That's ok mate. This is my 1st car and I've just bought it last month. I'm still a rookie for this mechanical stuff (especially for rotary) and I'm already suffering from this car. Help me to troubleshoot :crybaby:
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Re: Low compression and high fuel consumption

Post by AndyBrad »

I get about that mpg when doing really short journeys.

I must say its a bit of a difficult first car this. Youll have some fun.

The only way to find out if its got low compression is to get it tested. There are so many things that can cause the symptoms you are experiencing that its important to rule them out.

If its over heating you want to take a look at this in line with the ignition components. Before you start spending money. take the plugs out and make sure everything is pushed together ok. take a note of what the coils are and pop a picture up here.

Is it using coolant? when you say its running how what exactally is happening? is it straight away. Does it happen if its kept below 5k but for a long period of time? how long are the journeys your taking?
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Re: Low compression and high fuel consumption

Post by crteezy »

What do you mean by is it using coolant? Doesn't overheat below 5k. My longest journey so far was 200km and it didn't overheat. When driving normal it doesn't overheat. but when keep pushing hard like in the racing mode it quickly overheats within 1-2 kilometres.
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Re: Low compression and high fuel consumption

Post by 350matt »

Using coolant means the level in the header / radiator tank will drop over time / miles

if this is true 1st check you have no weeping hose joints , signs of damp on the engine or under the engine

if you don't then its an internal issue with a failed seal

and please fit a thermostat
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Re: Low compression and high fuel consumption

Post by crteezy »

350matt wrote:
Mon Nov 16, 2020 12:42 pm
Using coolant means the level in the header / radiator tank will drop over time / miles

if this is true 1st check you have no weeping hose joints , signs of damp on the engine or under the engine

if you don't then its an internal issue with a failed seal

and please fit a thermostat
Drove over 100km after refilling coolant and the coolant level didn't drop. So I'm guessing it's fine.
Did you mean a seal inside the engine? can it be a reason for high fuel consumption? If so what should be the next step?
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Re: Low compression and high fuel consumption

Post by 350matt »

If the coolant isn't dropping then great

next step is to fix the overheating
then worry about the fuel consumption

1st fit a thermostat
then do a compression test and possibly replace the plugs at the same time

let us know how you get on
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Re: Low compression and high fuel consumption

Post by crteezy »

350matt wrote:
Mon Nov 16, 2020 12:51 pm
If the coolant isn't dropping then great

next step is to fix the overheating
then worry about the fuel consumption

1st fit a thermostat
then do a compression test and possibly replace the plugs at the same time

let us know how you get on
In Sri Lanka, we don't have a place that performs rotary compression tests. I've done 2 compression tests using analogue tester in 2 places and in the 1st one I got around 6 bar each rotor (cold engine) and the 2nd place I got 5 bars /70 psi each rotor (hot engine). So I'm guessing it must be something in between and the compression isn't good. Already replaced plugs and coils. I'm suffering from late starts as well. Sometimes it takes forever and sometimes it starts fine (still late).
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Re: Low compression and high fuel consumption

Post by ChrisHolmes »

crteezy wrote:
Mon Nov 16, 2020 1:01 pm
350matt wrote:
Mon Nov 16, 2020 12:51 pm
If the coolant isn't dropping then great

next step is to fix the overheating
then worry about the fuel consumption

1st fit a thermostat
then do a compression test and possibly replace the plugs at the same time

let us know how you get on
In Sri Lanka, we don't have a place that performs rotary compression tests. I've done 2 compression tests using analogue tester in 2 places and in the 1st one I got around 6 bar each rotor (cold engine) and the 2nd place I got 5 bars /70 psi each rotor (hot engine). So I'm guessing it must be something in between and the compression isn't good. Already replaced plugs and coils. I'm suffering from late starts as well. Sometimes it takes forever and sometimes it starts fine (still late).
Check your spark plugs and also look at the underside of the ignition coils for cloudy spots on the insulation which is a sure sign of them breaking down.
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5bar is certainly an acceptable compression result so unlikely to be causing the the starting issue but only a rotary tester will show up each faces compression.
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Re: Low compression and high fuel consumption

Post by crteezy »

Checked Plugs and Coils and they are fine. So does it mean a 5 bar compression doesn't cause a late start issue? I'm gonna check my battery tomorrow morning. If the battery also good what should I check next? Starter motor?
Last edited by crteezy on Mon Nov 16, 2020 5:02 pm, edited 1 time in total.
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Re: Low compression and high fuel consumption

Post by ChrisHolmes »

How did you check the coils?
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