272 Schrick cam wont start???

[hispeedimports]

Ok, this is what I have:

M20 2.5L

New rebuilt head with 272 degrees Schrick cam installed. I have spark, fuel, the engine turn but wont start or even attempt to start.

Someone told me that the timing could be 180 degrees off, but It does not make sense to me if the cam and crank marks are line up perfectly

Is it possible to have the timing off 180 degrees even if the timing marks are line up?

Need help, thanks in advance.

[jlevie]

Is it possible to have the timing off 180 degrees even if the timing marks are line up?

No. But since there is spark you could have the fuel supply and return lines crossed. Or have a large intake leak.

[Jaxx_]

timing as in... spark timing?

[hispeedimports]

No. But since there is spark you could have the fuel supply and return lines crossed. Or have a large intake leak.

I checked the fuel lines and they are correct, I removed the return line and a good flow of fuel is coming out.

Haven't check for intake leaks.

Thank you for your help.

[hispeedimports]

timing as in... spark timing?

He was talking about the block being 180 degrees off tdc from the head cam.

I had the motor at tdc before removing the head from the block, but wile the head was out I did turn the block crank a few times cleaning the pistons so before installing the head I turned the crank one more time to line the tdc mark with the mark on the timing cover.

So he was saying that I needed to turn the block a full revolution 360 degrees for tdc before installing the head.

[nando]

whoever told you that is a moron.

search for posts by jlevie. he's the M20 god - he's probably got an entire start-to-finish no-start M20 post somewhere.

how did you verify there was spark? I guess if you're getting fuel pressure, the crank sensor must be working.

[MR 325]

Just curious, what is your valve clearance at? If the valves are too tight that can keep it from running. Sounds crazy I know but it's happened to me personally.

[e30leigh]

what engine? l-jet or motronic? if its l-jet and its timed up without it being tdc #1. it will never start... if its motronic it will make a hell of a scene.

air leaks wont stop it from starting. it will just run like shit. but it will start.

the valve clearances could be an issue as said before.

could be that you have no compression also. does it sound like theres any restriction?
try a couple drops of oil down into the bores. it lubes the upper rings and gives you back compression.... if thats the issue. bt it will smoke like a bitch when it starts and needs to be kept with revs on for a while to clear it out. so it could be used to run in the cam at the same time lol. but youll need to make sure everything else is mint first.

[nando]

what engine? l-jet or motronic? if its l-jet and its timed up without it being tdc #1. it will never start... if its motronic it will make a hell of a scene.

no, motronic doesn't care. spark is *always* timed off the head, and it's batch injection so that makes no difference (even if it was sequential, it would still be timed off the head). TDC on the block is still TDC, it's not possible to be 180* off at the head or 360* off at the crank.

[e30leigh]

no, motronic doesn't care. spark is *always* timed off the head, and it's batch injection so that makes no difference (even if it was sequential, it would still be timed off the head). TDC on the block is still TDC, it's not possible to be 180* off at the head or 360* off at the crank.

its possible on l-jet. the dissy is run off a gear, which is run off the crank, so if its 180 out. it will try spark the wrong cylinders. and motronic cares. it has a reference signal for tdc so it knows to fire cylinder 1, and to work out exactly where it is on start up. if its 180 out it will do the wrong spark timing again. basically it will try to run the cylinders in the reverse order they are ment to. or there abouts. and that will never run.

i forget the degrees. it may not be 180. but if your tdc 6 and not tdc 1 then you have issues. if it is 180 degrees. then its going to give you issues. and i believe that it is 180 as they are companion cylinders.

and the fuel injection is only sequential at a certain point. i forget if its on start up, idle only, or once the car comes off fast idle, ie has started to warm up. i think its only on start up. and i know for sure the injectors are grouped 1-3 and 4-6 on motronic. as i was just working on one recently on a e28 watching the osiliscope patterns on both groups. so i know for a fact that they change from one to the other.



to check its right. on motronic. put the engine timed to tdc, check the reference lug is close to or right over the sensor,
on l-jet put the motor to tdc the same as before but check that the dissy rotor is pointing to the cylinder 1 spark plug lead terminal in the cap.
that will rule out tdc timing issues.

[jlevie]

An engine with a Motronic engine management system is in time if the crank hub mark is aligned and the cam sprocket mark is aligned. That has cylinder #1 at TDC and the timing notch on an M20B25, or flywheel slug on an M20B27, and distributor rotor in the correct position.

The DME fires the injector banks sequentially. Bank one is cylinder 1, 3, & 5 and bank is cylinders 2, 4, & 6.

[nando]

its possible on l-jet. the dissy is run off a gear, which is run off the crank, so if its 180 out. it will try spark the wrong cylinders. and motronic cares. it has a reference signal for tdc so it knows to fire cylinder 1, and to work out exactly where it is on start up. if its 180 out it will do the wrong spark timing again. basically it will try to run the cylinders in the reverse order they are ment to. or there abouts. and that will never run.

i forget the degrees. it may not be 180. but if your tdc 6 and not tdc 1 then you have issues. if it is 180 degrees. then its going to give you issues. and i believe that it is 180 as they are companion cylinders.

and the fuel injection is only sequential at a certain point. i forget if its on start up, idle only, or once the car comes off fast idle, ie has started to warm up. i think its only on start up. and i know for sure the injectors are grouped 1-3 and 4-6 on motronic. as i was just working on one recently on a e28 watching the osiliscope patterns on both groups. so i know for a fact that they change from one to the other.



to check its right. on motronic. put the engine timed to tdc, check the reference lug is close to or right over the sensor,
on l-jet put the motor to tdc the same as before but check that the dissy rotor is pointing to the cylinder 1 spark plug lead terminal in the cap.
that will rule out tdc timing issues.

motronic isn't sequential, it's never sequential. it might fire all 6 at once during startup, but otherwise it's paired 1-5-3 and 6-2-4. that's still considered batch fire.

[e30leigh]

An engine with a Motronic engine management system is in time if the crank hub mark is aligned and the cam sprocket mark is aligned. That has cylinder #1 at TDC and the timing notch on an M20B25, or flywheel slug on an M20B27, and distributor rotor in the correct position.

The DME fires the injector banks sequentially. Bank one is cylinder 1, 3, & 5 and bank is cylinders 2, 4, & 6.

i stand corrected. thanks for that. i struggle to remember sometimes when the majority of timing ive done recently has been on later model cars after 2000.
so wish i could work on m20s only though haha.

as for l-jet tdc #1 will need to be confirmed with the dissy rotor in the right position. Im sure of that.