Author Topic: Jazz 1.4 compression test  (Read 5207 times)

Jeffyjazz

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Jazz 1.4 compression test
« on: August 04, 2017, 08:09:28 AM »
Anyone know what psi I should get in my jazz cylinders

Going to test it tonight but not sure what figure I'm looking for and can't find it online

Jocko

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Re: Jazz 1.4 compression test
« Reply #1 on: August 04, 2017, 09:31:59 AM »
Main thing is that they are all about the same. Minimum of 142 psi with no more than 28 psi between highest and lowest reading. (Haynes manual - page 2A-1)

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #2 on: August 04, 2017, 02:01:33 PM »
Does it say what the psi when it's new

Just to gauge how much I have lost.  Obviously all being the same is ideal unless they are all rubbish lol

I'm still trying to figure out where my mpg has gone I'm back down to 39-40mpg again and I only do motor way runs

I get about 270miles out of a tank does that seem low

Jocko

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Re: Jazz 1.4 compression test
« Reply #3 on: August 04, 2017, 03:28:39 PM »
Compression doesn't drop off with age, to any great extent. The rings form the seal and they wear, along with the bore, but continue to form the seal until such time as they fail. In fact, if you re-bore an engine and fit new rings, it  actually takes a while to form a good seal. The compression improves as the engine gets a few miles on it. Another reason for poor compression is burnt exhaust valves. If you find a low reading, squirt some engine oil into the bore, then run the test again. If it jumps up to normal it could be the bores/rings. If it stays low it is usually the valves. A blown head gasket can also give a low figure but usually accompanied by other symptoms. Two low cylinders, next to each other, is often the head gasket blown between them. Modern engine really have to have been thrashed to lose compression due to bore wear. That or poor oil/servicing and millions of cold starts.

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #4 on: August 04, 2017, 03:51:53 PM »
 ::)test the first cylinder and it had 125psi took the test out and it left the end in the sparkplug hole

So not attempting the others as I basically had to destroy the threaded insert getting it out.    Plugs  are a very bright white colour so it's like it's running lean so who knows

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #5 on: August 04, 2017, 04:04:38 PM »
It doesn't use oil and it's always pretty clean when I change it so I didn't think it would be rings as I'm guessing that would soot the oil up

I'm not trusting that pressure reading as I'm not convinced the thing was in tight enough.   Will try it again when I have someone else to use the push in and hold type

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #6 on: August 04, 2017, 04:06:11 PM »
Here's one of the plugs.   The gap is probably a bit on the large size but I've got a new set for next weekend

[attachment deleted by admin]

culzean

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Re: Jazz 1.4 compression test
« Reply #7 on: August 04, 2017, 04:28:19 PM »
By the look of the body of that plug (as well as the gap) its has been in for a long time.  Modern cars do run lean and it is not unusual for ceramic to be white (if plug is correct heat grade for engine it will run hot enough to keep ceramic free of carbon, if ceramic does get coated with carbon it can track the spark down to plug body rather than bothering to jump the gap),  the plugs I recently took out of my Civic and wifes 1.4 GE were same colour as yours. 

As Jocko says it is unusual for a modern engine to lose compression through ring wear,  burnt valve can be down to badly adjusted tappets not allowing it to close properly (when an exhaust valve closes normally heat that the valve head has absorbed from the hot gas rushing past during exhaust stroke gets passed from valve head to seat and into water cooling, without this cooling the valve quickly gets too hot).   If your tappets are too quiet its a worry,  a bit of noise from tappets is not a bad thing.
« Last Edit: August 04, 2017, 05:06:36 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

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Re: Jazz 1.4 compression test
« Reply #8 on: August 04, 2017, 04:30:32 PM »
That plug looks a perfect colour. A nice light tan. Poor mpg with no change in driving habits is usually a sticking brake. Either that or a fuel leak.
I remember hearing a celebrity (I cannot remember who) telling a story about a neighbour who bought a new Jag. For the first year the celebrity and the next door but one neighbour, kept adding extra petrol to his tank (before the days of locking caps). Every time one of them went to the filling station, they would bring a gallon back, and after dark stick it in the Jag. The guy was always boasting about the fantastic mileage he was getting from his new car. After a year they stopped doing it, and suddenly his petrol consumption dropped to what you would expect. He had the car back to the main dealer about a dozen times before they admitted to him what they had been doing!

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #9 on: August 04, 2017, 06:09:48 PM »
Perhaps a fuel leak,    It passed its mot last week and emmisions were passable the HC were high but still in spec

I put The plugs in April last year so they have probably done 22k miles so probably due a change. They do look quite corroded though in that time

It's a mystery as it's the mpg has been slowly declining for the last 2 or 3 years so something is wearing or getting worse
« Last Edit: August 04, 2017, 06:12:23 PM by Jeffyjazz »

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #10 on: August 04, 2017, 06:30:34 PM »
That's it's emmisions

Excuse the sideways image

[attachment deleted by admin]

sparky Paul

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Re: Jazz 1.4 compression test
« Reply #11 on: August 04, 2017, 07:44:04 PM »
Nice sandy coloured plugs.

High hydrocarbons, especially with gradual deterioration, I would have a check for inlet manifold leaks, if you haven't already. Check vacuum pipework, brake servo, inlet manifold gaskets, but it's not a big leak you are looking for, so check thoroughly. Sounds backwards, but it's called 'lean misfire', where excess air between metering and inlet valve causes incomplete combustion.

It could also be compression related, is there anything else which makes you think this is a problem?
« Last Edit: August 04, 2017, 08:03:17 PM by sparky Paul »

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #12 on: August 05, 2017, 05:12:47 AM »
Nothing else is wrong with it,  i do about 24k miles a year and it never misses a beat

It's just with the mpg in this state It's becoming expensive

sparky Paul

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Re: Jazz 1.4 compression test
« Reply #13 on: August 05, 2017, 07:21:24 AM »
Anything that causes incomplete combustion, i.e. compression, ignition or fuel mix problems, will dent mpg.

Compression or ignition problems are more likely to come on suddenly, and are more likely to cause noticeable misfires and rough running - although two plugs per cylinder could mask any spark issues. Vacuum leaks can go unnoticed as it can just lean the mixture off a little. If you are running out of ideas, it's worth having a squirt around the inlet manifold with some carb cleaner or easy start, see if you can affect the idle speed.

Have you had a plug out of every cylinder, are they all the same colour? You're doing the right thing trying rule stuff out, but as Jocko says earlier, it pays to check the common problems like brakes binding, good spark, etc..
« Last Edit: August 05, 2017, 07:44:13 AM by sparky Paul »

Jeffyjazz

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Re: Jazz 1.4 compression test
« Reply #14 on: August 05, 2017, 09:16:40 PM »
I think the old girl
Is just tired out she's on 140k miles


My civic type r has just hit 170k still on original clutch!!!

Hondas are just great

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