right im going to do a compression test on my car to see if ive got a bent valve, causing the over fueling, but whats the size of the hole that you screw the spark plugs in to?
General compression test
- Thread starter 99sei
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General compression test
OP
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wont it cause a smell of fuel to come out the exhaust though?
thats what im getting, as the fuel isnt getting burnt.
thats what im getting, as the fuel isnt getting burnt.
99sei said:
How does the car run?
Checked all the plugs are sparking?
Checked HT leads?
Etc...
If you are doing a compression test, all the kits i have ever used had a selection of threads on the pipes, so it should'nt matter what the plug size is, there should be the correct pipe in the kit.
OP
OP
ok cheers baildey
jamie - all new plugs and leads, changed the coil pack.
it runs ok then will get a little miss fire another 20 secs later the same
jamie - all new plugs and leads, changed the coil pack.
it runs ok then will get a little miss fire another 20 secs later the same
OP
OP
cleaned and put back in, will try another this week. cleaned it with a baby wipe, would that have been ok?
think i might have killed the cat with the constant overfueling though
think i might have killed the cat with the constant overfueling though
Cleaning wouldnt have helped if its broken!
Cat may be dead yes.
Bear in mind that the lambda is only switched into the ECU once it starts in closed loop operation (once the engine reaches certain conditions)....so that initial 20 secs of ok running may be open loop (usually overfuelled to heat up the engine), then it may go rough as the lambda is switched in, and found to be dodgy.
Also, the lambda probe failing doesn't cause the ECU warning light to come on....
Cat may be dead yes.
Bear in mind that the lambda is only switched into the ECU once it starts in closed loop operation (once the engine reaches certain conditions)....so that initial 20 secs of ok running may be open loop (usually overfuelled to heat up the engine), then it may go rough as the lambda is switched in, and found to be dodgy.
Also, the lambda probe failing doesn't cause the ECU warning light to come on....
OP
OP
got a compression test done today and.....
no compression at all HG has gone
would this have caused the smell of fuel?
no compression at all
HG has gonewould this have caused the smell of fuel?
That can't be right, if it has no compression at all it won't run, and head gaskets don't normally cause catastrophic compression loss, that's burnt out valve, broken rings holed piston territory. If one pot has no compression put a bit of oil down the bore. If you then see compression its rings, no change it's valves.
OP
OP
we tried plugs 1 3 and 4 no compression in any
we took the spark plug out, put the compression thing in and fired it up. is that what you do?
it runs, can get good power out of it when on the road. but emissioins are too high and the smell of petrol from the exhaust.
we took the spark plug out, put the compression thing in and fired it up. is that what you do?
it runs, can get good power out of it when on the road. but emissioins are too high and the smell of petrol from the exhaust.
you don't fire it up, no. Pull the HT leads off remove the plug of what you're testing, and put the tester in. turn it over on the starter a few times, the tester should record the peak pressure reading.
If you had no compression in 3 out of 4 cylinders, it wouldn't run.
If you had no compression in 3 out of 4 cylinders, it wouldn't run.
99sei said:
PMSL, The procedure is to check with the throttle wide open. You remove all the plugs from the engine, pull the connectors off the coil packs so the coils aren't firing. The person turnung the engine open holds the throttle wide open. Then test the compressions one by one. You should get readings within 10% of each other on all 4 cylinders. The compression reading itself isn't that important, within reason, mainly because the gauges tend to be inaccurate. You do want conformity however.
Pete
Malin Dixon
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You don't need to open the throttle if the plugs are all removed. There won't be any significant manifold suction as the air can enter down any of the spark plug holes.
You can leave the throttle wide open if you want, but as it spings closed it can be inconvenient.
You can leave the throttle wide open if you want, but as it spings closed it can be inconvenient.
OP
OP
so is it remove all the plugs or just one?
open tb or closed?
open tb or closed?
Malin Dixon
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The normal compression test is with all the plugs out. It doesn't matter if the throttle is opened or closed. By having the plugs out, the engine turns over faster, and you flatten the battery less, and air can get in so that you don't need to open the throttle.
I had never heard of the compression test with the engine running before. It could be useful, but even the web page describing the procedure says to do a normal test first.
I had never heard of the compression test with the engine running before. It could be useful, but even the web page describing the procedure says to do a normal test first.
Malin Dixon said:
How can air get in by having all the plugs out? The valves are still operating so there isn't suddenly some way for a cylinder to suck air in through another cylinder's spark plug hole!
custard said:
That's not a normal compression test, in fact the article describes it as "this test is an accurate if slightly esoteric and time-consuming test of cylinder breathing"
This http://www.pumaracing.co.uk/comp.htm is a sensible description of what Kris should be doing.
