Won't start after HG change

Hi all,

I've just changed the head gasket on my K Series 1.8 and now it wont start. I have spark and I have fuel so I tested the cam position sensor and that's where I'm out of my depth.....

A bit of history, the guy I bought it off sold it cheap because the head gasket had just been done but was still overheating (there was a garage receipt), I assumed it was something easy like an air block and thought I got a bargain but no it has been a mare from the start, (I had an MGF for years so I've done this before).

Before I changed the head gasket I had coolant in the oil, a leaking water pump seal and all sorts of dash lights coming on. Hawk eye diagnosed a temp sensor and O2 sensor. There was a host of other jobs that needed doing to, exhaust mid section, track rod ends etc but nothing that would affect the ignition.

When I stripped it I found the guts of the thermostat had been removed and the gasket hadn't actually been changed it looked like someone had just torqued the head down another 180 degrees and it was in a right state (old type) but at least the head was flat so no skim needed. I put in the MLS head gasket and reassembled with all the new parts in the kit. I had a lot of problems getting the new Cam Belt on, when everything was set to the marks the belt was about half a tooth out so I couldn't get it tight down the front edge without turning the crank about 2 or 3 degrees, I don't know what the tolerance is so I don't know if this is significant.

Anyway, there is pressure in the fuel rail, I used the Hawkeye to test the injectors and they all work, I have spark in all four cylinders I also did a live test on the cam and crank sensor and got "cam sync lost". I tested the cam sensor but I'm not sure if A, I'm doing it correctly or B, its actually duff. I have permanently live in the live feed with and without the ignition on, earth is OK with continuity to the battery and the body, when I test the resistance the multi meter flashes 1984 briefly (I don't know if it should flash or stay on?). When I turn it over I have a permanent 11.9v from the middle wire again I don't know if this should be permanent or it should pulse?

I think I've checked all the obvious stuff, fuel trip switch etc but I'm no expert by any stretch of the imagination. Any and all advice is most welcome

David Moore said:

Cam Belt on, when everything was set to the marks the belt was about half a tooth out so I couldn't get it tight down the front edge without turning the crank about 2 or 3 degrees, I don't know what the tolerance is so I don't know if this is significant.

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It's not uncommon for the cam timing to be 1/2 a tooth out. If it is out, I set the cam advanced and not retarded.

Are you 100% sure the timing isn't 180° out? Did you lock the crank in the timing position? Did you make sure you have the correct cam pulley pins in the correct location slot for the cam it's fitted too?

Yeah pretty sure, I had them all marked up before I stripped them. I'm going to take the cover off again tomorrow so I'll double check

Yup, I'm a Muppet thanks Nodge, no idea why I did that its not the first HG I've changed on a K series but yeah 180 degrees out.

However, (isn't there always a however....) it fired up OK but it idles really lumpy, I've checked all the loom connections, there's no drop in coolant and I've cleaned out the IVAC but it hasn't made a difference. The idle is up and down but mostly down at about 700 rpm and the engine is rocking the whole car until I rev to about 2000 rpm, but after I've revved it it drops and almost cuts out. I'm going to disconnect the exhaust section by section tomorrow but that's the last thing I can think of. The only other thing I can see as an issue is there seems to be a lot more slack in the accelerator cable than there was before, I've tightened it up to almost end but it still seems loose to me.

Hopefully you can point out something else that's nice and obvious and make me look even dafter

When I did my first K series HG I refitted the exhaust cam wrong with the tag in the position for the inlet cam. Have you checked they are correct?
As for being half a tooth out I found the best way to fit it was to get the two cams in correct position with no cam lock, fit the belt around the crank held on with clothes pegs then while holding the belt tight turn the inlet cam back just enough to get the belt on, then tighten the cam against the belt and fit it round the exhaust cam.
Once it is on the cams correctly it's fairly easy to work onto the other pulleys. IIRC I think I had the tensioner very loose while doing it.
I think it took me a few goes to get it right and this might not even be the best method but it worked for me.
You do need to have (or make) a cam turning tool though.

Yeah I double checked all that after Nodges post. Its still rough.
I've swapped the cam position sensor but I'm still getting the same readings and the Hawkeye is still giving "Cam Sync Lost" in live data although testing it with a multi meter it looks like its doing what it should. I've started stripping the loom down looking for a short but that's going to have to wait till the weekend before I can have a proper go at it.

The only other thing obvious I can see is the IVAC, I've cleaned it out but I can't move it by hand, I'm pretty sure I could move the MG's when I did that one but it was a few years ago....

Have you sorted the half tooth out issue yet? If both cams are half a tooth out it's because one is a whole tooth out.
This is a good photo showing the locating pins for the inlet and exhaust cams. I once fitted the inlet cam with the pin in the exhaust position but in my case the car refused to start. Trouble was I couldn't see the issue until I took out the cam pulley bolts as they cover the pins.


The other thing is the crank, did you take the pulley off to set it correctly. Some folk try to use the marks on the pulley but they can be out quite a bit. Best take the pulley off and use the two marks on the crank to line it up accurately.
As for the idle control valve try squirting a load of carb cleaner or similar into it while the engine is running.

Thanks Alibro, I didn't check the crank pulley to be honest, I'll double check that at the weekend to. Camshaft pulleys are set correctly, they are currently both central and the crank pulley about half a tooth advanced (maybe a fraction less). Even if it is a timing position problem the cam sensor not reading is still concerning.