Lotus Elan

S4 Starting problems

PostPost by: Craven » Sun Sep 10, 2017 4:12 pm

Pre engage starter solenoid can take around 10 amps, if you are seeing appox 1volt drop across the switch this equates to a contact resistance of 0 .1 ohms.
Last edited by Craven on Mon Sep 11, 2017 12:09 am, edited 1 time in total.
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PostPost by: nmauduit » Sun Sep 10, 2017 6:38 pm

I've revisited the 1st page of that thread realizing it has been going on for a while now : just to be sure, has the starter been tested with a known good battery, or with a second known good battery added in parallel via jumper cables (possibly directly at the switch, with a solid ground at the engine) ? How old is the battery ? If the battery itself is also 12.7 or 12.8 that may not be a lot (I would rather rule that out before going anywhere else).

What I understand from the last comment is that the symptom is the starter not cranking at all (i.e. not even very slowly or just a little) : that is no power at all to the starter motor then, so it is not an issue of switch contact resistance like I mentioned earlier today (if battery and all electrical contacts are good that could lead into checking the starter itself - incidentally as was suggested by someone on the first page).
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PostPost by: collins_dan » Sun Sep 10, 2017 10:58 pm

It actually is a new one and both the old and new one are doing the same thing, which made me wonder if connecting the other wires to it was causing the voltage drop. Dan
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PostPost by: nmauduit » Mon Sep 11, 2017 8:08 am

collins_dan wrote:It actually is a new one and both the old and new one are doing the same thing, which made me wonder if connecting the other wires to it was causing the voltage drop. Dan


as said just above, the advantage of trying to jump start from a known good battery directly from the switch and engine is that you don't go through all the wiring (possible oxidation at chassis contact in the trunk, on inside the wire...).

You did not confirm on battery age and condition: with this kind of symptoms that is the first item on my checklist.

Can you confirm what are the actual symptom : starter motor not cranking at all (just a click) OR starter motor very slow or just doing a bit of a turn (possibly with headlight or interior light dimming a lot) ? I was understanding the first from recent posts, which would point to a starter solenoid issue (not excluding an other problem, but I would try to clear up the starter solenoid issue second, that is after the power supply and wiring is known faultless)

good luck !
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PostPost by: collins_dan » Mon Sep 11, 2017 4:33 pm

The starter was not fully engaging, just a click of pinion not fully engaging. If the car is rocked in second, then it would engage and start. Thought it was a starter issue, so replaced. (Starter is the pre-engaged kind, so solenoid is in the starter.) Problem continued. Tested voltage at the starter, from battery it was fine, from ignition under load, it was low. Battery was old, so replaced. Problem was reduced but not eliminated. Tested ignition switch under load and found that was the problem. Replaced switch. Again, problem reduced but not eliminated, which brings us to current. Both old and new switches are fine when bench tested, but lose a voltage when tested under load. My question is what could be causing this? Could it be a ground issue? How is the ignition switch grounded? Through the steering column? It is an S4 with the ignition switch on the column. Thanks, Dan
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PostPost by: mbell » Mon Sep 11, 2017 6:37 pm

Hi Dan,

I have to admit I've lost track of all the history background to this but I don't think bench testing the switch with a multi meter disproves it as the fault.

The relevant thing here is ohm's law, V = I * R. I.e. the voltage drop across the switch will increase with current, so a small resistance with high current can cause a significant voltage drop across the switch. Which could be cause of the fault

You also have to consider that the measured R value by your multi meter may not be the R value when the switch is engaged. The multi-meter measures R using low voltage/current. The electro/mechanic effects of putting a large current through the switch could result in much higher resistance than measured, causing a bigger voltage drop across the switch. So the only real way to know the switch is ok for sure is to measure the voltage across the contacts with the starter engaged.

Outside of that are you sure there isn't a mechanic engagement problem? Having to rock the engine suggests the pinon is getting stuck and not cleanly (dis-)engaging.

The earth of the starter system is via the engine, this is another area where a poor connection may read ok with multi-meter but cause a voltage drop at higher currents (e.g. starting). So cleaning the current earth and maybe adding a second test earth connection would be worth looking at.

Cheers,

Mark
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PostPost by: collins_dan » Mon Sep 11, 2017 7:31 pm

Thanks, Mark. When I pulled out the old starter, the pinion looked perfect, but it has been a lingering question for me as well due to the rocking making it work. As to the earthing, I have checked and cleaned the earth in the trunk/boot and it looked good and has been cleaned up. I have looked at the engine earth and it also looks fine, but has not been removed and cleaned, is that what you are suggesting? Thanks, Dan
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PostPost by: mbell » Mon Sep 11, 2017 7:40 pm

Yes, check/clean the engine to chassis earth connection. I'd also consider adding an extra one for testing and just to be sure, as can be tricky to get good connection. Or if you can the problem use jump lead.

If it consistently needs rocking in 2nd to release when it happens that would suggest mechanical issue rather than electrical to me. Could only throw wild guesses at what it could be thou!
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PostPost by: collins_dan » Mon Sep 11, 2017 9:58 pm

Thanks. Both the starter and ignition switch have been changed. The starter is definitely only getting 11.3 of the 12.7 volts, and that can be traced back to the spade that the starter wire is connected to. I did some reading on pre-engaged starters "The first contact supplies a low current to the motor so that it turns slowly - just far enough to let the pinion teeth engage. Then the second contacts close, feeding the motor a high current to turn the engine." Seems like my problem is the motor is not turning the pinion so that the teeth engage. To me it seems that the current is insufficient as the pinion is not being damaged, and others on the forum have stated that 11.3 is insufficient. Also, if the battery is fully charged, I have no issue. I appreciate your help. Very frustrating. Dan
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PostPost by: mbell » Tue Sep 12, 2017 1:23 am

I think most pre engage starters use a solenoid that pushes the pinion into the flywheel ring gear. It also has the switch that engages the starter motor once the pinion has extended far enough to be engaged with the ring gear.

So possible faults:
1) in some positions the pinion is not extending far enough to engage the switch and trigger the starter motor, basically a mechanical fitment issue

2) the electrical system isn't providing enough power to push the pinion into the flywheel ring gear and trigger the starter motor for some combinations of positions of pinion and ring gear.

I am not sure what voltage is consider good or bad for the solenoid, would have thought your about border line. Where are you connecting the earth connection for taking that measurement?

If engine block then it could be a sign or poor engine earth. If some where else then the starter might be seeing if less voltage due to earth. Basically, checking/testing the engine earth would be my next step.
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PostPost by: Orsom Weels » Tue Sep 12, 2017 6:10 am

Dan, with the old bendix type starter motor, the pinion engages the ring gear from the rear, & the ring gear teeth are chamfered that side to aid engagement. With the pre-engaged starter, the pinion engages the ring gear from the front, & as the twin cam was not designed for use with a pre-engaged starter, the teeth are not chamfered on that side, so some times they will not line up to allow clean engagement. This can prevent the solenoid moving far enough to make the electrical connection. Rocking the car in gear simply moves the ring gear a touch to allow clean engagement of the pinion. It may not be your problem, but I would say given your symptoms, it's worth a look. With the voltages you are seeing, the engine should turn over, at worst, it would be a bit slow.

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PostPost by: 2cams70 » Tue Sep 12, 2017 6:56 am

Turn the ignition on to the "run" position. Leave it on. Make sure car is in neutral with handbrake on. Connect a heavy duty jump wire direct from the battery +ve terminal and tap it against the solenoid coil terminal on the pre-engaged starter solenoid. Make sure you tap it against the terminal on the power side of the solenoid and not the ground side otherwise you will be in for a shower of sparks if nothing worse.

If starter turns over normally and engine starts using this method fit a separate 30A relay to alleviate the ignition switch and associated wiring from the heavy solenoid current draw. Problem solved.

If starter solenoid still clicks check the ground side of the solenoid coil for earth continuity otherwise it's a starter motor out for checking job. Make sure the starter motor securing bolts are tight too.
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PostPost by: nmauduit » Tue Sep 12, 2017 7:42 am

The 3 above suggestions all make sense - 11.3V is not a lot at the starter, and I would still first make sure that proper voltage and current is offered to the new starter for it to crank : big, fat and good quality jumper cable from a good battery on one side (possibly hooked up to a running car).

2cams70 wrote:Turn the ignition on to the "run" position. Leave it on. Make sure car is in neutral with handbrake on. Connect a heavy duty jump wire direct from the battery +ve terminal and tap it against the solenoid coil terminal on the pre-engaged starter solenoid. Make sure you tap it against the terminal on the power side of the solenoid and not the ground side otherwise you will be in for a shower of sparks if nothing worse.

If starter turns over normally and engine starts using this method fit a separate 30A relay to alleviate the ignition switch and associated wiring from the heavy solenoid current draw. Problem solved.

If starter solenoid still clicks check the ground side of the solenoid coil for earth continuity otherwise it's a starter motor out for checking job. Make sure the starter motor securing bolts are tight too.


This kind of test can also be done without turning the ignition on (so that the engine won't start since it won't have ignition), even without spark plugs to help it turn but that should not be necessary since on occasion the engine starts and all is fine : you hook the ground up to the engine and

if you hook up the the hot side of the jumper cable to the input of the switch you'll have 2 batteries in parallel, and you can try the starter from the key like you usually do, except that you should have more current capability at the starter (you can check the voltage drop when cranking, it should be improved from 11.3V)

if you hook up the the hot side of the jumper cable to the output of the switch you'll get the starter cranking directly on the second, known good battery (that of the running car) - do that from a handy stance and with a firm hand as it will generate sparks when the manual contact is getting established or removed (I would not do that with fuel fumes nearby, in a crammed closed garage and leaky carbs without an air filter)

if the starter always cranks in one of the 2 above tests with a known good battery helping or replacing the main battery, I would pursue the electrical route (clean up all connections from battery to switch if not done already; battery condition : hook the jumper cables from the second battery to the main battery and check if it starts every time, and if so swap batteries...)

if the starter behaves just like before (doesn't crank) with the second battery hooked up, I would take a good look at mechanical issues (starter mounting and alignment, play at the starter ring, etc. possibly looking at operation from underneath with an helper while you look through the bell housing hole after removing the can cover - then take out the starter and bench test it)

good luck !
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PostPost by: 2cams70 » Tue Sep 12, 2017 9:49 am

No need to run a second battery in parallel if you know the battery you have is in good condition. I always fit a relay on old cars as standard practise. I doubt the ignition switch and wiring was ever properly designed to handle the current draw from a pre-engaged starter solenoid. Most likely it was only designed for the solenoid associated with an inertia starter. The inertia starter solenoid draws much less current because it does not also have pull the starter gears in to mesh as it does with a pre-engaged starter solenoid.

If it's got a pre-engaged starter do your wiring and ignition switch a favour by fitting a separate started relay if not already so equipped.
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PostPost by: nmauduit » Tue Sep 12, 2017 10:28 am

2cams70 wrote:No need to run a second battery in parallel if you know the battery you have is in good condition.


indeed, if the present battery is good for sure, then one has to go further down the list of verifications... having a extra source of current and possibly voltage increase would only help if a component is borderline (contact oxidation, relay/solenoid sticking with old grease or dirt etc)

Since the symptom is intermittent (iirc at times it would crank just fine, and at times only click), I'm afraid it will be necessary at some point to give a close look at the potential mechanical issues (alignment, wear ...).

I have installed a pre-engaged starter on my S4se, without modifying the wiring : hot wire from the battery to the starter switch which is controlled by the key, then the output of the switch goes to the starter and solenoid together (that shortens the length of hot cable running along the car ... and looks just like stock from above). My battery is a LiFePo that outputs 540A max under 13.7V, and the switch is just fine. When on occasion I have cranked for a minute or two (I should not, I know... I don't do it anymore) what goes hot (could be above 60?C) is the lead connection at the battery and the cable nest to it.
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