4a. Won’t start after full rebuild. Any ideas what to check next pse?

[Bfg]

13 hours ago, Steven Whitaker said:

I just spun the engine over without ignition on holding a piece of paper loosely over the carb mouths and there’s virtually no pull.  See video.  Maybe a bit on the front carb.  Does that point to valve timing?  Thanks

Sorry, I cannot see the throttle mechanism being operated, but without the throttle's butterfly being open there will be next to no air flow through the carburettor or at the mouth.  

  

As Keith says "the vacuum advance isn't connected so there is an open tube at the carbs which will allow air in".  Perhaps incorrectly, I had assumed you would have blocked this off as you have the crankcase breather vent.

Pete

 

[Bfg]

11 hours ago, Steven Whitaker said:

Thanks Mike.  I’ve just removed the inlet manifold and found that the mating face is not flat as per the photos.  Would this be enough for it not to run.  I’m thinking that the draw / pull on the vacuum stroke will pull air from least path of resistance, which could be the gaps as shown?  I shone a torch from behind and can see a millimetre gap.  Tnx.

  

Yes, this extent of flange distortion would weaken the mixture to such an extent - the engine would not start. 

Having corrected this with emery paper on a broad flat plate - I think you are very close to having a running engine  ..assuming of course the manifold to carb flange, and each of the carb's flanges were also checked and corrected for flatness.

Well done ..  a credit to your perseverance.

Pete

 

p.s. As a word of warning to others ; the inlet manifold to cyl. head flanges need to be both free from local distortion (as was evident in Steven's photos) and at the same time trued to the same plane as each other (..to sit on the machined-flat face of the cylinder head).  The broad emery paper flat plate Steven used achieves this, whereas if flange distortion is filed flat individually then one flange may be out of plane with / at a slightly different angle to the other. This equally applies to the exhaust manifold flanges.

 

 

Edited November 23, 2023 by Bfg

[Steven Whitaker]

2 hours ago, Michel Higuet said:

Pity he pic is not horizontal but on pic 1 as I already says previously the pushrod of inlet cyl 2 is/seems lower than those on cyl  1 but I measure from the cork as reference and maybe it is more compress in front of cylinder 1... 

Hi.  Both valves on cyl 1 are closed with clearance at the tdc on the photo.  Thanks.

[Bfg]

13 hours ago, Steven Whitaker said:

Just checking valve timing.  It seems ok?  All at tdc showing valve positions.  The pic with both valves closed with clearance under tappets is at tdc and rotor arm pointing to cylinder 1 on comp stroke which I think is correct..   So can I rule out the valve timing being wrong?

  

Yes, this is the correct valve timing at TDC for #1 cylinder.  The rotor arm is directed at the distributor cap's #1 plug lead ..and the points are on the cam lobe, which (with 0.015" points gap) visually corresponds to (static) ignition timing of 4-deg BTDC being very close to correct.

Pete 

[Steven Whitaker]

13 minutes ago, Bfg said:

Yes, this is the correct valve timing at TDC for #1 cylinder.  The rotor arm is directed at the distributor cap's #1 plug lead ..and the points are on the cam lobe, which (with 0.015" points gap) visually corresponds to (static) ignition timing of 4-deg BTDC being very close to correct.

Pete 

That’s good.  Thanks Pete.  I’m at a loss with this now.  

[Steven Whitaker]

1 hour ago, Bfg said:

Sorry, I cannot see the throttle mechanism being operated, but without the throttle's butterfly being open there will be next to no air flow through the carburettor or at the mouth.  

  

As Keith says "the vacuum advance isn't connected so there is an open tube at the carbs which will allow air in".  Perhaps incorrectly, I had assumed you would have blocked this off as you have the crankcase breather vent.

Pete

 

I think the throttles were open for the paper test but I had better do this again.  I was getting bit tired by this point and can’t remember if the springs were on or not, holding the butterfly’s closed!!!  As you say, it’s important to breath..  thanks.

[Nigel A]

Been following this with interest and fingers crossed it finally starts.

I’m confused though about how you can hold the choke fully out, hold the throttle half open and operate the starter with only 2 hands?

keeping my fingers crossed 

Nigel

[Steven Whitaker]

Hi Nigel,  It’s not easy.  Left hand on the solenoid button and right hand pushing choke fully down and opening throttle with a finger.  Need a glove on the right hand as it gets a bit painful after several hours……….

[Steven Whitaker]

1 hour ago, Bfg said:

Sorry, I cannot see the throttle mechanism being operated, but without the throttle's butterfly being open there will be next to no air flow through the carburettor or at the mouth.  

  

As Keith says "the vacuum advance isn't connected so there is an open tube at the carbs which will allow air in".  Perhaps incorrectly, I had assumed you would have blocked this off as you have the crankcase breather vent.

Pete

 

Thanks, I’ll block this off too then.

[Nigel A]

Hi Steven

sounds like you need a helper and someone with you to bounce ideas off.

i see you have followed Mick’s advice and put some fuel directly into the cylinders..

have you checked again that the plugs are definitely sparking?

Nigel

[Nigel A]

Hi Steven

meant to say that I would definitely find a way to wedge the choke fully out so you are able to operate the throttle and starter properly 

Nigel

[Steven Whitaker]

3 minutes ago, Nigel A said:

Hi Steven

sounds like you need a helper and someone with you to bounce ideas off.

i see you have followed Mick’s advice and put some fuel directly into the cylinders..

have you checked again that the plugs are definitely sparking?

Nigel

After putting fuel in the cylinders late last night and not getting a murmur, I turned the lights off!  I did think about checking the spark again, but I’d had enough of the old girl.  I went and had a quiet beer instead.  

[Nigel A]

That’s always my solution to an unsolvable problem 

[Steven Whitaker]

On 11/22/2023 at 9:08 AM, rcreweread said:

You say it fired a few times but when you pulled the plugs, they weren't wet - there should have been evidence of fuel on them if you squirted some fuel in through the carb mouths -I would try a bit more fuel squirted into the carbs, or put a little squirt direct into each cylinder but don't overdo it or you will flood the plugs.

One other longshot - if you have the original cast exhaust manifold fitted, make sure you haven't fitted the gasket to the down pipe 90 degrees out because it will fit in any orientation but get it wrong, and it blocks the gas flow by approx 50% which will cause back pressure

Cheers Rich

Ok, thanks.  Gaskets are all good. 

[keith1948]

Resistance across + and - terminals of coil 3.0 ohms. Resistance between either one of those and central contact 10,000 ohms on my spare unused standard coil.

I use NGK BP7HS plugs with 0.025 inch gap. You have checked spark using one of plug leads to engine and got a good spark. What happens if you connect a plug lead to a plug you have removed from engine and check spark across plug gap by holding plug body onto engine? If all plugs show a spark with this test then you have probably eliminated plug/coil issues. In one of your tests you put fuel into engine directly and replaced plugs and nothing. So either plugs not sparking or no fuel.

Check points gap is 0.015 inch (dwell angle 57 deg if you have a dwell meter). Static timing 4 deg before TDC on my car (others can be different but mine is standard engine).

Might be worth turning over engine in the dark and looking for sparks tracking around plug leads to where they shouldn't eg tracking to each other or bits of engine. A friend of mine had problems because lead between coil and top of distributor was shorting out to underside of bonnet. Make sure plug leads and lead from coil do not touch each other or anything they shouldn't.

Check you have continuity between -ve connector that goes to terminal on coil to the spring on the points. Disconnect lead from coil for this test. When points are open there should be continuity between end of lead that goes on coil -ve and the spring arm for the points. When points are closed then you should have continuity to distributor body. You have 2 spade connectors, a wire from the connector on the distributor body and one from the condenser which then connect to the breaker spring arm. Several areas where you might have a loose or dodgy connection or broken wire.

If all the above are ok then I think you will have eliminated electrical issues although might be worth changing the condenser. Time then to look closely at carbs and why you don't seem to have fuel getting into engine. You have probably by now eliminated unwanted air leaks. Start with float chambers. Is there fuel getting to them ok and do the float valves move freely? Check float height. Others have suggested that your gravity feed might be an issue although I am tending to think you might have a blockage or incorrectly set jets on the carbs. It's some time since I worked on SU's (I have Strombergs). Do the pistons in the carbs move up and down freely. They should fall with a clonk (unscrew dampers to check this). If they don't then jets not aligned properly. 

I'll leave others more familiar with SU's to advise further. If you connected your fuel supply via the mechanical fuel pump then you would eliminate gravity feed questions.

Keith

 

 

[Michel Higuet]

Until now one problem is found, the HT coil  (1.5ohm for a 6 volt coil with ballast or 3 ohm for 12v.)  The plan of inlet manifold is not flat but there was no test to prove it give an impact... For the rest I wait until I will know the values of the vacuum in the manifold and compression in the cyl. Until now I presume their will not be ok. When will it tested with a good HT coil?

In Dutch "Meten is weten" give in English  "to mesure is to know".

[twostrokekid]

7 hours ago, keith1948 said:

..."I'll leave others more familiar with SU's to advise further. If you connected your fuel supply via the mechanical fuel pump then you would eliminate gravity feed questions"

If the engine does start up you will give the empty fuel pump a hard time as the rubber diaphragm is not designed to run dry. It will cycle continual full deflections up and down rather than the usual damped micro deflections biased against spring pressure when the pump is full. You might be better off removing it and blanking the hole in the block off rather than risk tearing the diaphragm.

 

 

 

[keith1948]

11 minutes ago, twostrokekid said:

 

If the engine does start we will all be popping the champagne corks!

Keith

[twostrokekid]

1 hour ago, keith1948 said:

If the engine does start we will all be popping the champagne corks!

Keith

I'll be looking for a bright star in the east!

[Steven Whitaker]

1 hour ago, keith1948 said:

If the engine does start we will all be popping the champagne corks!

Keith

I’ll be buying a round when it does!

[Steven Whitaker]

10 hours ago, keith1948 said:

Resistance across + and - terminals of coil 3.0 ohms. Resistance between either one of those and central contact 10,000 ohms on my spare unused standard coil.

I use NGK BP7HS plugs with 0.025 inch gap. You have checked spark using one of plug leads to engine and got a good spark. What happens if you connect a plug lead to a plug you have removed from engine and check spark across plug gap by holding plug body onto engine? If all plugs show a spark with this test then you have probably eliminated plug/coil issues. In one of your tests you put fuel into engine directly and replaced plugs and nothing. So either plugs not sparking or no fuel.

Check points gap is 0.015 inch (dwell angle 57 deg if you have a dwell meter). Static timing 4 deg before TDC on my car (others can be different but mine is standard engine).

Might be worth turning over engine in the dark and looking for sparks tracking around plug leads to where they shouldn't eg tracking to each other or bits of engine. A friend of mine had problems because lead between coil and top of distributor was shorting out to underside of bonnet. Make sure plug leads and lead from coil do not touch each other or anything they shouldn't.

Check you have continuity between -ve connector that goes to terminal on coil to the spring on the points. Disconnect lead from coil for this test. When points are open there should be continuity between end of lead that goes on coil -ve and the spring arm for the points. When points are closed then you should have continuity to distributor body. You have 2 spade connectors, a wire from the connector on the distributor body and one from the condenser which then connect to the breaker spring arm. Several areas where you might have a loose or dodgy connection or broken wire.

If all the above are ok then I think you will have eliminated electrical issues although might be worth changing the condenser. Time then to look closely at carbs and why you don't seem to have fuel getting into engine. You have probably by now eliminated unwanted air leaks. Start with float chambers. Is there fuel getting to them ok and do the float valves move freely? Check float height. Others have suggested that your gravity feed might be an issue although I am tending to think you might have a blockage or incorrectly set jets on the carbs. It's some time since I worked on SU's (I have Strombergs). Do the pistons in the carbs move up and down freely. They should fall with a clonk (unscrew dampers to check this). If they don't then jets not aligned properly. 

I'll leave others more familiar with SU's to advise further. If you connected your fuel supply via the mechanical fuel pump then you would eliminate gravity feed questions.

Keith

 

 

Thanks for your help Keith.  I’ll process it and have another session on Saturday morning.  Cheers.

[Steven Whitaker]

6 hours ago, Michel Higuet said:

Until now one problem is found, the HT coil  (1.5ohm for a 6 volt coil with ballast or 3 ohm for 12v.)  The plan of inlet manifold is not flat but there was no test to prove it give an impact... For the rest I wait until I will know the values of the vacuum in the manifold and compression in the cyl. Until now I presume their will not be ok. When will it tested with a good HT coil?

In Dutch "Meten is weten" give in English  "to mesure is to know".

Thanks.  I’ll check again on Saturday morning.  Cheers.

[trchris]

Just been reading through this post and can’t find any mention,unless I’ve miss it , have you compression? You need to go back to basics if you’re bypassing the carburettors and have a spark and assuming the valve and ignition timing is correct it should fire and run on the fuel you’ve poured into the cylinders. Even with badly adjusted carburettors it will still try and fire/run albeit spitting and coughing 

Chris

[Bfg]

On 11/23/2023 at 3:24 PM, Michel Higuet said:

In Dutch "Meten is weten" given in English  "to measure is to know".

or just perhaps "Meten is verzanden in cijfers"  ?  ..which is a google translation of  'to measure is to get bogged down in numbers'  

I don't mean to offend. It's just that a four-stroke internal combustion engine will run within an extremely broad ranges of variables. It may not start and run as smoothly as one might like, nor might it pull strongly at a certain rev range, or else it may have brilliant or absolutely appalling fuel consumption, but it will start and run if those variables are within +/- 10 or 15 percent of what the books says they should be. And that is all that's needed to address the question being asked 'why is this engine not starting.?'  Tuning of those parameters can happen after the engine runs.

Blah, Blah, Blah.. Just a few of the variable parameters include ; a broad spectrum of camshaft profiles, the camshaft's / valve timing which conceivably work within a range of +/-  10 or 15 degrees from optimum. Ignition timing offers a similarly broad spectrum ..as well we know from an auto-advance mechanism going from 0 degrees to 15 or more degrees advanced.  Or perhaps the different types of valves. Then, as is being discussed, are the coil's resistance and voltage, wiring continuity, the points gap and the dwell angle, and the ramp profile of the cam which opens those points ...if at all there are mechanical, rather than magnetic or optical, or whatever. Each again have a broad parameter within which they will work. And then there's an enormous spectrum of spark-plugs being made for thousands of different 4-stroke engines. We might otherwise measure and number crunch with the above '&/or scenarios' ; the upper and lower range of acceptable (for starting) compression ratios, the variables in combustion chamber shapes and their porting. What effects ram pipes and turbos and super-chargers has, and of course the degree of back pressure from / through the exhaust. And/or again the mix of the fuel itself, which if I recall may range from something like 20:1 to 7:1 fuel-air and still fire.  But of what octane ? indeed what fuel additives or planet-saving spirit fuel or gases, Nitros to LPG, agricultural and static engine paraffin-like fuels to that especially formulated for use in the extremes of drag racing. Talking of extremes we must not forget to factor into our analysis both temperature &/or humidity, richness of oxygen or nitrogen in the air versus airborne salts, minerals and dust particulates.

No, okay let's stick to the TR engine, as otherwise I could go on & on, and on.  Yeah, I know - I already have.  But my fear is that ; to adopt "to measure is to know" each and every &/or possibility of any particular TR4A engine (..with this one we've barely discussed its rebuild specification, &/or possible variables in its carburation &/or ignition) - might only lead to wholesale number crunching ..and ongoing analysis.

Is not an actual figure, for each cylinder's compression (at what engine revs ? ) on an engine that's not yet been bedded-in, and apparently lacking its dose of fuel mix, almost irrelevant in its exactness.? 

Surely it's much easier and quicker to do as Steven has now done, which was to have a quick look at the rocker arms at TDC on #1, together with a peek at the points to check (within acceptable parameters) both the valve and ignition timing.  And then to stick one's finger loosely over the plug hole as the engine spins ..to gauge (from experience) the extent of sucking and compression.  Again all he needs to know is ; whether they are within reasonable parameters for the engine to start ?

It seems to me that these simple tests, without gauges but done already, have narrowed his investigation down to ;  a) fuel-air mix,  &/or  b) quality of spark.

Regarding  a).. it comes down to  i) fuel not being fed, or  ii) it not sufficiently being picked up and drawn into the engine.  Taking the fuel pipe off the carb and turning the tap on checks the flow ..while a whiff of it will confirm its fresh petrol (no laboratory analysis ought to be necessary). And fingers spanning over the carburettor's mouth, with the throttle open, as the engine is turned by a freshly charged battery - checks for the latter. 

Diagnostics is really that simple.

Regarding b).. quality of spark.. Elimination of failure in ignition components, like the plugs, points and its insulation, condensor and wiring, HT leads, and Low tension supply and its polarity (all of which are easy to check) narrows the possibilities down to.. the coil.

I'd reason - Steven is very close to having a running engine. 

Pete 

p.s.  I confess - in all my years of home mechanics, I've never once measured the resistance of a coil.  I have however had cause to swap coils out though ..after following the process of elimination.

 

 

Edited November 24, 2023 by Bfg

[Rob Salisbury]

And another thought is that with all the low rev churning on the starter motor any cam /follower lube applied to the rebuilt engine will have been wiped off leaving near metal to metal contact, at least pour some fresh oil down each pushrod tube to help.