non start issue

[georgeramos]

On my friends 124 Sport coupe 2liter

We have spark
We have fuel (well the throttle is working and spraying fuel to the carbs)
Cam timing marks aligned to the pointers simultaneously #1 is at TDC AND timing mark on crankshaft pulley aligns with its pointer simultaneously we rotated the dizzy so the rotor pointed to #4)

When we crank motor and use timing light the pointer does not align within the light.

No start

Cranks, occasional backfire (one VERY loud) but no start at all. Almost seems like fuel but it is definitely getting to the carbs.

This is the FIRST time the new dual carbs have been attempted.

Any thoughts? Thanks!

[RRoller123]

Sounds like somehow you may be at TDC on the exhaust stroke, not the compression stroke. Should all be set up at TDC on #4 cylinder, on its Compression stroke.

Any chance exhaust and Intake cams are swapped

[So Cal Mark]

without fuel you won't have a backfire. It's time to check basics; rotor is aligned with the cylinder on compression, distributor is set to fire at 10btdc, firing order is correct

[georgeramos]

We verified #1 at tdc with a straw while cam marks were aligned, crank mark was aligned and rotor was facing #4.

Ive read a bit about the dizzy being 180 degrees out but do not understand how that could be possible. Is that possible in what we have done?

Thank you

[georgeramos]

Would you mind elaborating on how we might be on the exhaust stroke instead of the compression stroke? How would we check/verify that?

Thanks again

[RRoller123]

You would watch the action of the valves ON NUMBER 4 CYLINDER. They both will be closed, i.e. you are in the portion of the cam cycle just after the #4 Intake valve has closed, and the #4 Exhaust valve has not yet opened. If you set this up on cylinder #1, but timed the ignition to cylinder #4, then you are firing on the overlap portion of the cam cycle, and igniting un-burned air-fuel mixture with both valves open, hence the bad backfire.

I made this chart to help understand Mark's 274FI cam when I was installing mine. You want the ignition point for #4 cylinder to be just to the left of the 0-deg TDC point at the center of the chart (~10-12 deg BTDC). I had the same thing happen, and blew the intake hose right off of the AFM with a backfire. Keep the hose very loosely tightened down by the hose clamps until you are sure it is all correct!

Hope this helps!

[georgeramos]

My friend insists that the cam is set to the marks so that TDC on #1 and #4 is the exact same thing.

We checked with a straw on #1 and set ignition to #4. In his mind and he has confirmed this with several other people those are the same...

I am very confused as I've fortunately never had to deal with this at this level.

I am posting a new question about this same issue...fuel related

[AFRetired]

It's not fuel related, you need to make sure #4 is timed for ignition just after intake valve closes TDC. each piston hits TDC twice in four cycles. You're on the the wrong TDC for ignition

[georgeramos]

But if the cam marks are both aligned along with the crank mark on the pulley and the rotor points to #4 (all simultaneously) can you still be rimed to the wrong tdc?

[blazingspider]

Pull the cam box covers. When #4 is at TDC and on the compression stroke, the camshaft lobes for #4's valves should have their base circles riding on the buckets and their pointy little noses sticking up and slightly angled toward the center of the motor. Now pull the distributor cap and ensure that the rotor is pointing toward the #4 contact. If not, pull and rotate the distributor so that it does.

Good luck

[RRoller123]

+1. I think that is it. Igniting on the overlap portion of the cycle is likely the cause of the backfire.

[RRoller123]

But if the cam marks are both aligned along with the crank mark on the pulley and the rotor points to #4 (all simultaneously) can you still be rimed to the wrong tdc?

Yes!

Pull the cam box covers as suggested and watch the valves as they rotate and catch them just as Blazingspider suggests.

[FiatMac]

But if the cam marks are both aligned along with the crank mark on the pulley and the rotor points to #4 (all simultaneously) can you still be rimed to the wrong tdc?

This could be the case if someone timed the cam shafts on the #4 cylinder instead of #1. This would require the ignition to be timed on the #1 cylinder to get a running engine (distributor timing would be 180 degrees from normal). By pulling a valve cover as suggested above you can determine if this is the case. If this is the case you can either time the ignition off of #1 (easy), or correct the cam timing (a little more involved).

[So Cal Mark]

perhaps the cam pulleys are on the wrong cams

[seabeelt]

Number 1 and number 4 are not the same thing as far as timing goes. Yes they are both at the top of a stroke, but one is at compression and the other is at exhaust. From the write up your problem is obvious. You are setting the timing #4 to fire on the exhaust stroke of that cylinder, when it should be firing on #1 compression stroke. Simple fix. pull the dizzy, and rotate until you get it aligned with #1 and you should be all set., As far as checking for the correct stroke you are on, two methods. pull the plug #1 if that is what you are using and see when you get compression by putting your thumb over the hole and feeling for when it tries to push your thumb off - need two people for this. Second more reliable is to pull the cam covers and rotate the engine and look for when the intake valve just closes on the up stroke (with your straw) - check timing marks, check crank pulley - aligning marks and pulley by rotating engine. Engine is at tdc compression #1. insert dizzy with rotor pointing to #1 plug distributor point. Reinstall cam covers. (you get oil all over the place if she fires up with no covers on) Give it a crank