No start on 54-1173

[Gary t]

History
My car has been starting and running great then a few days ago I was out  and it started missing on the highway. When it was missing the tach was all over when it smoothed out the tach settled down.
I returned home and at slower speeds it seemed OK, put it away and a few days later I tried to start it and no go. There was no voltage on the coil found a loose wire on the ignition switch now I have voltage on the coil but no start.
There is fuel at the carb with  accelerate pump, now what to check?

[mylesofsmyles]

Okay, so there's power to coil, but sounds like no spark?

Can you work your way back from plugs, wires?  Maybe you're getting spark but a bad rotor/cap isn't distributing?  Points okay in distributor?

[bjthomp]

I've had a tach go berserk and traced the problem to points that were not opening far enough. I now keep the points at the high end of the gap setting spec. and regularly check the lube on the follower block.

[jbcollier]

Please tells more about what you are running.  Stock Renault engine, or?  Points or Electronic?  If electronic, what system?  Stock coil?  Anything else not stock?

[Gary t]

It is all stock I think.
Points are set 0.018.
This is going to be a journey as I have none lotus things but I will be fitting car work as I can.

[Clifton]

Spark when cranking? If not I would check your positive at the coil again and negative coming through tach to dist. check points if they're clean.

[jbcollier]

First, buy yourself a test light with an incandescent bulb.  They apply a small load to a circuit and are much better for troubleshooting than a digital multimeter which applies literally none.

go to the engine

lift off the distributor cap

Are the points open?  (If not, put the car in fourth gear and nudge it back and forth until the points are open.  Put it back into neutral.)

turn on the ignition

Do you have power at the white wire at the coil?

Do you have power at the white/black wire at the coil?

Do you have power at the points' insulated connection?

Let us know the answers to the above three questions and we'll go from there.

[Gary t]

Thanks John
I had done those checks using my antique Simpson 240 but this morning I built a proper test light.
I found voltage where I expected to find it  (with the light)
I get a nice  fat spark off the coil lead when I manually open the points.
Next I plan to remove spark plugs maybe after supper.

[jbcollier]

A nice fat spark is great.  Now we know the wiring is fine, coil works, etc.  I would next test the spark at the plug.  If there's a problem then, check the cap and rotor for shorts to ground and the ignition wires for connection break or high resistance.

Sometimes everything tests great but it still runs poorly.  Spark voltage requirements are very low when testing in the open air.  Voltage requirements rise dramatically as cylinder pressures rise (load).  So again, high resistance in the ignition wires and shorts to ground with the cap and rotor.  Also condensers can work well at cranking speeds and break down at higher speeds and loads.  Ignition coils can also fail as voltage requirements rise.

[Gary t]

I needed to make a remote  crank switch  in order to crank the engine  while attending a spark plug, that is done but I am too lazy to hook it up tonight.  Plug 1 looks about as I expected.
I know about  cylinder pressure effecting the operation  of spark plugs,  in another life we tested aircraft plugs in a test set where we could apply pressure up to shop air pressure. They would occasionally work fine at ambient but fail at pressure.

[Clifton]

I needed to make a remote  crank switch  in order to crank the engine  while attending a spark plug, that is done but I am too lazy to hook it up tonight.  Plug 1 looks about as I expected.
I know about  cylinder pressure effecting the operation  of spark plugs,  in another life we tested aircraft plugs in a test set where we could apply pressure up to shop air pressure. They would occasionally work fine at ambient but fail at pressure.

Cylinder pressure can be 1,000 psi at wot. Testing at 120-150 psi won't show much unless it's beyond bad.  If it's a plug or spark miss in general it will usually show up with increased load, wide open throttle. If it's missing at cruise and not worse at wot it may not be spark.

[Gary t]

I'm not really thinking plugs as it was running fine when I switched offbut a few days later no start.  But who knows.

[Gary t]

The reason I returned home was intermittent total missing and tach jumping all over.  I thought it was a ignition supply fault.  At idle in the driveway it was running fine.

[jbcollier]

Does it have a white wire at the coil?  If yes, then try this.  Go for a drive until the problem appears.  Now disconnect the white wire and run a jumper from the battery to the coil.  Problem solved?  Then you have an issue upstream from the coil (connection, ignition switch, etc).  Problem unchanged?  It's an issue with a condenser, coil, distributor, etc.

[Gary t]

Hi John no it will  not start I had some time this morning so rigged my remote crank button and yes I have spark at the plugs. When I crank  I get  occasional sharp barks from exhaust and occasional puffs at the carb but not a bark.
It has gone from what looked like a manageable DC fault to this what looks like all the plug wires are on the wrong plugs while sitting still in the garage