Hi all. I have to admit I am at a lost to why my engine will not start after a rebuild. There is good compression on all cylinders as this can be felt when turning the engine by hand. There is also spark at the plugs. I have also checked both valve and ignition timing a number of times together with Tappet clearances. I have changed the petrol in the carb float chamber. The engine turns over on the electric starter reasonably quickly but almost stops when it gets to firing point then quickens again once past this point only to slow again at the next firing point. I have checked all plugs and they are wet after cranking.
Is it a possibility that the engine is not cranking quickly enough to start. If so could I disconnect the starter and ignition circuit from the starter and temporary connect these together in order that the ignition runs on 6 volt whilst putting 12volts to the starter in order to turn the engine faster.
All suggestions are welcome as to possible causes as to why it will not fire up.

John Mason

Location: Nottinghamshire

John
This screams ignition timing,it should fire on the handle,so cranking speed isn't an issue.You say that you have a good spark,and that you have checked the timing, are you certain that the spark is, or just before TDC? Remove all four plugs, and lay them on the cylinder head,switch the ignition on and turn the engine over by hand, establish when a piston is on its firing stroke and that the plug fires at or just before TDC.
With petrol in the carb and a spark at roughly the right time there aint no reason why it wont fire.
J

Location: As far east in Kent as you can get

Hi john.

Is it not trying at all to start.

Or is it trying but won't start.

Tony.

Location: HUNCOTE on the pig

Location: Nottinghamshire

Thoroughly check that your plug leads are all sound and that the cap and rotor arm are faultless.
Check also that the manifolds are tight and its not sucking In Extra air to dilute the fuel mixture.

They always start eventually , except if you've not fitted the timing chain/ distributor to the right marks, if you had the engine fully stripped.

Best of luck and hope it starts soon

Regards
Bill G

Location: Scottish Border

As I get older I have developed a habit of putting the leads on the wrong plugs...the A7 will run with two leads switched, just.

I am not for a moment suggesting that you are similarly afflicted but I don't half feel an idiot when I realise what I've done.

Location: Fishbourne near Chichester

When you first told us that your engine wouldn't start in Brian Hutchin's thread a couple of weeks ago both Alan Fairless and myself suggested a tow start had worked for us in the past when we've had 'new' engines that didn't want to play. Have you tried it?

Also, in your first post you report: "The engine turns over on the electric starter reasonably quickly but almost stops when it gets to firing point then quickens again once past this point only to slow again at the next firing point."

That suggests it's thinking about starting but can't. Just the sort of thing a tow might overcome.


Steve

Location: North Yorkshire

If your valve timing is right and firing order is correct try turning the distributor while you pull the starter. It should at least cough somewhere in the first 10 or 15 degrees of rotation which will give you encouragement and a point to note the distributor position...

Location: N W Kent

You have my every sympathy John, at least mine has been persuaded to run and even to allow a couple of test runs of about 3 miles each.
I have terrible problems getting the engine to run and keep running. I suspect the float chamber level and am looking at that at the moment. When running the engine pops and bangs for a bit but then settles down.
I still have a screeching noise at times despite a new set of brushes in the dynamo and a check on the bearings in the (rebuilt) dynamo but the bearing is a new sealed one and seems to be ok.
I must agree with others that ignition timing is probably the key to our problems but its not easy getting to a satisfactory starting (no pun intended) point to make final adjustments.

Location: Near M1 Jtn 28

Sounds like too much advance - the starter is fighting the piston having fired too early and trying to run backwards.

S

I always find compression stroke. Aim the timing mark for the ole pressure take off. Set the dizzy so the bit on the points is just about to go up the cam to open.

If it doesnt fire (usually does), retard it a smidge and it will.

Then fine tune with the dizzy

Sometimes a new engine will have no compression. This makes it difficult on two fronts.

It is hard to figure out the compression stroke. And poor compression leads to a small bang. So its hard to start.

Im with the others. Give it a tow

I had a similar problem recently with my 29 special. Having dismantled the engine to cure an oil leak I noticed a lot of backlash on the camshaft gears, so I sorted through my bag of bits and found two that meshed closer.

Although I eventually got the engine to fire, it would not run smoothly or pull well. like yours it had good(ish) compression. Working on the premise that I started with an engine that worked and now it didn't and the only thing I'd changed was the camshaft gear, I assumed I'd set the new gear with the timing marks misaligned. So I pulled the cover off and checked - dots aligned. I then got out the valve/cam/crankshaft diagram - whatever the proper name for that is - and compared the valve openings/dwells with the pistons. They were slightly out.

I then compared the fitted cam gear with the one I had replaced. The keyway/dots angle was about 170 degrees different! I always thought they were identical, although matched pairs. Obviously not. So, did you fit a new gear?

Rick

Location: Deepest Norfolk

Location: Farnham

Location: Nottinghamshire

Reading back through the comments, I realised that in fact I have changed something.
Trying to remove the nut on the front of the crankshaft I foolishly stopped the crankshaft from turning by jamming a piece of brass in the timing gears with the result that the crankshaft gear was damaged.
I obtained a replacement gear and fitted it being careful (I thought) to get the gears in the correct place for meshing.
I need to check that out but am working on another possible problem, namely that the fuel level in the carb bowl may be too low.
The engine has started on a number of occasions but died after a second or two.
Instead of continuing to hijack Johns posts, I think it might be better to start a new one called 'Rebuilt engine refuses to start and/or run'.

Location: Near M1 Jtn 28

I have recently sorted out a bit of a brain teaser on a rebuilt engine. It started briefly but then would not restart, various popping etc. Re timed it and it fired but refused to run, rechecked timing fuel etc. decided on a push start, fired up for a second or two then stopped. Another push, kept seeming like it wanted to go, then no longer firing almost like the timing kept going out and then being correct again. The owner told me that he had replaced the dynamo distributer assy as a unit and the car had run perfectly well prior to the rebuild. However on removal of the distributer the drive gears were totally knackerd, after fitting a new gear in the end of the dynamo and swapping out the distributer the problem was solved. Just goes to show you can never make assumptions that something is correct or in good condition unless you have carefully checked it yourself.

Location: Auckland NZ

PROGRESS REPORT. Today Saturday 23/4/16. I have managed to get the engine running although I had to use spray easy start. She ran well firing on all four although on a rather fast tick over. I can now be assured that both valve and ignition timing are ok although possibly a little fine tuning may be required with the dizzy once warmed up. I obviously still have some minor problems with the carb or manifold leaking air but at least I know where the problem lies.

THANK YOU EVERBODY FOR YOUR TIPS AND ADVICE.


John Mason

Location: Nottinghamshire