77 240D Won't Start / No Crank - PeachParts Mercedes-Benz Forum

eric.e · #1 01-25-2016, 01:04 PM

Having what I assume is an electrical issue. Checked the battery, 90% charge.

Whenever I turn the key, glow plug light comes on... wait ... goes off, turn key, nothing. A small click from the engine, then nothing. I try the key again, this time no glow plug light, no gauges. Nothing.

Checked the fuses, all good. Checked the little relay fuse, looks ok. Glow plugs are newer (less than 1 year old).

What worries me is the no cranking. Could the starter have died? It's weird because it started fine the morning I last drove it, then the same evening, nothing.

Any ideas on where I should begin to try to diagnose this situation?

Maxbumpo · #2 01-25-2016, 01:08 PM

Really sounds like a dead battery to me, but could also be a dead starter (solenoid or starter motor itself). Put a volt meter across the cigar lighter contacts while attempting to crank, see what kind of voltage drop you get. Should not go below 10 volts I think.

Can you try to jump start the car? You'll need a good heavy-duty set of jumper cables, don't try with wimpy wally-world cheapo cables.

Can you take the battery to your FLAPS and have them load test it?

eric.e · #3 01-25-2016, 01:19 PM

I plugged the battery to my smart charger, and it read the battery as 90% charged at 12.3v.

If the battery were dead, would the meter read it incorrectly? I've never had an issue with the charger before...

jay_bob · #4 01-25-2016, 01:20 PM

Make sure your battery cables are secure. Remove and clean them. BTDT.

A bad connection will allow enough current for minor electrical loads but when you hit that starter, the resistance of the bad connection will not let the current flow through that allows cranking.

Air&Road · #5 01-25-2016, 01:28 PM

Take a tire tool or something and momentarily short between the two heavy nuts on the starter solenoid. It should spin the starter jus a little. After that try the key again.

Obviously, put it in neutral and firmly set the parking brake before doing this.

Hope this helps.

Maxbumpo · #6 01-25-2016, 01:28 PM

Quote:

Originally Posted by eric.e

I plugged the battery to my smart charger, and it read the battery as 90% charged at 12.3v.

If the battery were dead, would the meter read it incorrectly? I've never had an issue with the charger before...

Battery capacity diminishes over time, until it no longer has enough energy to start the car. A typical battery life is five years or less. 90% of a reduced-capacity battery may not be enough to start your car.

Batteries can also fail with an internal short, and that won't show up until a load is placed on the battery.

There should be a date code on the battery (month/year). If your battery is more than three years old, it is suspect.

eric.e · #7 01-25-2016, 01:34 PM

The battery was replaced this past August. I should think it is fine. I will try getting a jump start later.

Maxbumpo · #8 01-25-2016, 01:54 PM

Can you check the system voltage with a meter while attempting to crank? That will help isolate either a battery problem or a starter problem.

eric.e · #9 01-25-2016, 02:02 PM

What would be the best way to do that? My cigarette lighter has never worked. Also I just realized you are in Charleston SC as well. And I am realizing you have helped me before...

Maxbumpo · #10 01-25-2016, 02:06 PM

If you've got a multi-meter, and a set of test leads with alligator clips, clip the meter leads to the battery +/- and place it on your windshield so you can see it while you crank.

I think I passed you my cell before, last fall when you had starter trouble. Let me know if you need it again. I work in North Charleston, but can stop by downtown on my way home no problem. IIRC you live or work at a place downtown?

barry12345 · #11 01-25-2016, 09:26 PM

Some of your description is typical of a marginal connection. Usually battery connections but there are other places.

Basically once a heavy current is asked for the marginal connection just opens up more. The clue being you turn the key and get the glow plug indicator. Turn to engine crank and not much if anything. Turn the key off and go back to the glow position and there is no light.

The higher current heated the marginal connection up and it opened totally until it cools off again so you can repeat the same cycle. This is not an absolute certainty by any means but would be my initial search.

barry12345 · #12 01-25-2016, 09:31 PM

Quote:

Originally Posted by eric.e

The battery was replaced this past August. I should think it is fine. I will try getting a jump start later.

Flakey battery not totally impossible either.

Maxbumpo · #13 01-26-2016, 07:42 AM

Eric - please see PM - have to re-schedule.

Air&Road · #14 01-26-2016, 08:05 AM

Did you try jumpering across the starter solenoid?

If you are not confortable doing that do a voltage drop test. Use a digital voltmeter to first check for voltage at the starter motor terminal when someone hits the key. If there is nine or en volts or more there the problem is the starter. If there is no voltage there, check voltage a the primary voltage on the solenoid. If not 12 volts or so there when key is on, problem is in the switch and neutral safety switch circuit if it has a neutral safety switch. If there is voltage at sol primary, use the dvm across each section of the circuit. Begin with the battery post and battery terminal. If there is more than a tenth of a volt or so drop then clean the terminal. Do the same on the ground side. You ae making hese checks when the key is turned. Anywhere voltage is dropped other than the motor itself, is a potential problem.

All that said, if you have a hot battery and clean tight battery terminals, short across the two big terminals on the solenoid and see if he motor turns.

sleepstar · #15 01-26-2016, 03:00 PM

check the ground strap from the drivers front of the transmission bellhousing