Lotus Elan

Engine Doesn’t Start

PostPost by: Tmac897 » Sun May 19, 2024 6:08 pm

Trying to fire up my rebuilt engine, but I haven’t gotten it to start. I know the whole spark / fuel routine, so that’s not my question.

I’ve got a new, fully charged battery, but the engine turns somewhat slowly. I only cranked it a few times, and only for a few seconds each try. Battery cables are noticeably warm, as is the solenoid and the starter itself. I disconnected the battery and went no further, as my automotive electric knowledge is rather thin, and I didn’t want to make a worse problem. Any guidance?

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PostPost by: mark030358 » Sun May 19, 2024 7:34 pm

Could be timing, but my bet would be the starter motor.

Try pulling the plugs and cranking again to see if it speeds up.

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PostPost by: gjz30075 » Sun May 19, 2024 7:39 pm

Maybe the engine ground strap (you put that back on, right?) is bolted to a painted part of the
engine or frame. With an ohm meter, check engine block to frame resistance. Of course, it
should be zero.
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PostPost by: Tmac897 » Sun May 19, 2024 8:11 pm

gjz30075 wrote:Maybe the engine ground strap (you put that back on, right?) is bolted to a painted part of the
engine or frame. With an ohm meter, check engine block to frame resistance. Of course, it
should be zero.


Ground strap is back on. Will check the resistance. Thanks.

Just checked - it is zero.
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PostPost by: Tmac897 » Sun May 19, 2024 8:22 pm

mark030358 wrote:Could be timing, but my bet would be the starter motor.

Try pulling the plugs and cranking again to see if it speeds up.

Cheers
Mark


I’ll try this tomorrow.
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PostPost by: HCA » Mon May 20, 2024 12:47 am

Tmac897 wrote:
gjz30075 wrote:Maybe the engine ground strap (you put that back on, right?) is bolted to a painted part of the
engine or frame. With an ohm meter, check engine block to frame resistance. Of course, it
should be zero.


Ground strap is back on. Will check the resistance. Thanks.

Just checked - it is zero.


Why have you put this thread in twice?

You say zero. From where to where do you have this reading? If wires and starter is hot, then no way can it be zero
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PostPost by: Andy8421 » Mon May 20, 2024 7:57 am

Given the high currents in the starting circuit, even a very small resistance will result in the starter not working properly. Although a budget multi-meter will spot something that has failed, you won't really be able to measure resistances low enough to make meaningful analysis of a marginal system.

Having said that, if the OP's cables, solenoid and starter are all getting warm, then there is clearly plenty of current getting around the system - so a high resistance somewhere in the circuit is unlikely to be the problem.

If the starter is not known to be good, then potentially that could be a problem, or alternatively the engine could be tight from its rebuild.

As a start, I would remove the plugs and confirm that the engine can be turned over by hand, and if all is good, see how well the starter spins the engine with the plugs out.
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PostPost by: 512BB » Mon May 20, 2024 10:15 am

This is how I start a newly built engine. First, I connect up good thick jump leads from an every day driver to the Lotus and run it at about 1500 rpm. With the plugs out, spin the engine over for about 10 seconds, then stop. I do that 3 times with a 30 second pause in between. That will fill the carbs with fuel. Observe the glass bowl on the fuel pump to see that it is full. Hopefully the oil pressure gauge will have registered some pressure by the third spin over, but I don't worry if it has not. Replace the spark plugs. Then about 4 presses on the loud pedal and go for a start. Usually requires more petrol so another 3 - 4 squirts and off she goes. Make sure oil pressure comes up within 10 -15 seconds. Disconnect jump leads. Check timing.

I run a new engine for about 10 minutes at 1500 rpm then shut it down for a good look around. Top up rad. Make sure that the oil filter is pre filled with oil before the start up and have some good fire extinguishers to hand at all times. I do not mean a 2kg one. A friend burnt down his garage and lost his S3 when the car caught fire on start up.

Good luck with it.

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