Lotus Elan

S4 Slow Crank

PostPost by: Temmck » Sat Apr 16, 2022 10:48 pm

Working on putting an S4 back on the road after 30+ years of storage. Engine turned over by hand when I bought it but after restoring the carbs and fuel pump the engine turns over very slowly and sometimes not at all. I search the archives and the following is what I have tried:
- Battery: I am using the same battery that starts my Elise daily driver (575 CCA) with no problems.
- Bypass Battery Cable: I use jumper cables to apply voltage directly to the starting solenoid.
- Oil changed
- Compression is 165, 170, 165, 170psi
- Tried cranking with no ignition.
- Used battery cables from running car.
Tried all of the above with no change in slow cranking. I measured the voltage at the solenoid and the voltage drops to 5V when cranking. The cable from the solenoid to the starter gets hot when cranking so I'm thinking either the engine has a problem or the starter is bad. The engine spins freely with plugs removed. Is this the failure mode of the starter?
Appreciate any ideas or other tests to try.

Thanks, Terry
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PostPost by: mbell » Sat Apr 16, 2022 11:57 pm

Have you tried by passing the starter solenoid? (Connect jump cables to the starter terminal.)

Have you tested/cleaned the engines earth connection? It by padded it with jumper lead direct to engine?

Checked for good connections on the starter?

Imo It's either a not great connection or bad starter. So try to rule out the bad connections, if still isn't fixed then probably pull the starter for test/rebuild/replacement.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: Temmck » Sun Apr 17, 2022 12:31 am

I have bypassed the solenoid by connecting battery to the lead going directly to the starter but I have not gone directly to the starter yet.

I placed the battery negative directly to the engine block.

i will refresh the connection of the positive lead to the starter to see if that shows any improvement but probably not until tomorrow afternoon.
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PostPost by: ericbushby » Sun Apr 17, 2022 8:48 am

Hi Terry
You do not appear to have eliminated any weak or loose earth connections yet. Using your jump lead connect the battery negative terminal direct to the engine block or starter motor fixing bolt.
The 5 volt reading at the solenoid is suggesting volt drop in the wiring or connections, not a faulty starter motor. There should be 9 or 10 volts at the solenoid when cranking.
You could measure the volt drop between the battery negative and the starter motor body instead of a jump lead which might be easier.
Best of luck
Eric in Burnley
1967 S3SE DHC
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PostPost by: nmauduit » Sun Apr 17, 2022 2:10 pm

Temmck wrote: The cable from the solenoid to the starter gets hot when cranking so I'm thinking either the engine has a problem or the starter is bad. The engine spins freely with plugs removed.


depending what you call freely and slow, to me this would possibly point to a combination of issues to clarify...

If the cable does get hot in the middle (i.e. everywhere along its length) that means that either a lot of current is flowing through it, or that this cable itself is too thin or internally corroded which would raise its resistance (hence a larger portion of the electrical power would go into heating it rather than cranking) : you may try the starter direcly with a large jumper cable as suggested to clarify that (rather than on the solenoid output which leave a small length of original cable) - if the original cable rather gets hot on a specific point, this is where the unwanted resistance would be.

if without plugs it cranks at say 2 or 3 times the speed required for starting, since 5V (more than there would be with a starter short) while cranking and a lot of current would mean some electrical power is delivered : I would double check all 4 sparks are firing and in good condition, that the timing is good (and fuel etc...), then would try again after the direct attempt before swapping the starter.

PS: my Weber S4 does not crank fast (high torque modern starter...) in spite of a 13.4V LiPo battery, esp. if I come back to it after several months, it may have a bit too much static compression, still it seems that it's barely cranking cold, then goes a bit faster when opening the throttle, but it always starts when the sparks are clean (I pump a bit of fuel in it via the accelerator pump, depress the pedal a tad to help it gather speed, and help it at the pedal while warming up when it cracks, no choke)
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PostPost by: Temmck » Thu Apr 21, 2022 12:03 am

I cleaned all connections at the starter and placed the jumper cables directly on the starter with ground on the engine block - no improvement. The battery is still strong and turns over my Elise just fine. I'm starting to question my jumper cables.

At this point, I plan to refresh all grounds and wire terminals and place a new battery in the trunk and try again.
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PostPost by: nmauduit » Thu Apr 21, 2022 8:19 am

revisiting this thread it jumps out to me that if the engine cranked fast enough to measure the compression as stated (~170psi on all 4), it should crank enough to start if all else is fine (mainly fuel and spark). What carbs do you have ?

Also is with a known good battery and strong jumper cables directly at the starter (solid ground on the engine and solid power on the starter motor bolt where it comes from the solenoid) you get one cranking speed,you are not likely to go much faster on the original wiring loom (rather the opposite) : only thing I would think of if this is not the case is that a poor battery in the trunk is sinking the jumper battery in parallel when jumping (if applicable)...

So at this point I would double check spark (4 plugs and timing), fuel (fresh, fuel level in the webers if applicable, idle circuit or input gaze not plugged etc.), possibly trying to get a puff of smoke using a start fluid can to confirm timing.

Good luck !
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PostPost by: ericbushby » Thu Apr 21, 2022 8:25 am

Hi terry.
You have obviously eliminated all of the wiring and chassis connections now. There isn`t much left.
If you have a doubt with the jump leads then you can measure the volt drop from one end to the other. If the cables are similar then the volt drop should be about the same on both.
It does not matter how long the meter leads are as the current through the meter is negligible.
Check the battery voltage when cranking even though you believe it to be good and measure the voltage at the starter motor. With a 12 to 14 volt battery there should be 9 or 10 volts at the motor. The rest is lost as volt drop in the cables and due to the internal resistance of the battery.
I would consider these as final checks and then it is time to replace the starter motor.
Best of luck
Eric in Burnley
1967 S3SE DHC
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PostPost by: ericbushby » Thu Apr 21, 2022 9:08 am

Hi Terry,
Having just written that above, I realise that I could have been more helpful.
I have just checked those voltages on my S3.
Battery voltage before tests 13.6v

When cranking with no ignition
Battery voltage 9.8v
Solenoid to cam cover screw 7.8v
Neg. batt terminal to cam cover screw 1.5v this is the chassis connections
Pos. batt terminal to solenoid 0.6v main power cable volt drop

These readings are with a reduction gear pre engaged Powerlite motor drawing approx. 160 Amps
The battery is Type 063, 44 Amp/hour, 11 years old.
Hope this helps
Eric
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PostPost by: Craven » Thu Apr 21, 2022 11:12 am

If possible can you bump start or tow, get the engine running and see if you are in the same situation. There are conditions where the standard set up will not crank a ‘tight’ engine.
I don’t know the current drain of a stalled starter motor.
FWIW.
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PostPost by: bitsobrits » Thu Apr 21, 2022 12:02 pm

Have you verified your initial timing? If your distributor is too far advanced you can end up with a sort of 'lumpy' starter action (brief spin then grunt) as the engine cranks then tries to fire too soon.
Steve

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Elan S3 1967 FHC pre airflow

Formerly:
Elan S1 1964
Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
Europa S2 1970
Esprit S2 1979
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PostPost by: Temmck » Sun Apr 24, 2022 4:30 am

Thank you Eric, this data is very helpful. I will check them against mine.

Car has strombergs

All testing I have done is without ignition so timing is not in play yet.

Good idea on the tight engine. If I can’t get it started with the new battery, I’ll try to bump start it.

Just bought a new battery but I am now traveling so did t have a chance to try it out yet. Will report back when I get home next weekend. Thanks all for the continued assistance and ideas.
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PostPost by: Temmck » Wed May 04, 2022 3:55 am

My slow crank situation has been resolved.
I dropped in a new battery and the engine cranked over as it should. So my problem was two fold. One bad battery in the trunk and a bad set of jumper cables. Both will be discarded.
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PostPost by: tdskip » Sun May 22, 2022 12:38 pm

How is the car coming along?
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