240D no start, will not crank over

[AJD]

Symptoms:

When cycling glow plugs, the glow plug relay makes a whining/singing noise for maybe 5-10 seconds and then stops.

Car will not crank or turn over at all.

Tried jump starting but made no difference = battery is not the problem.

I replaced the glow plug relay with a spare, no differernce, same symptoms.

Any ideas on what wiring to check...?

Thanks in advance.

[junqueyardjim]

AJD, are you sure the battery is not the problem. If not the battery, then you have a bad ground problem. Do you have a meter to check the battery? Most Parts Stores will check it for free. Quick "jump starts" usually are not productive on a diesel. Tell us why you think the battery is not the problem.

[AJD]

I checked the battery with my analog meter. It seems to check ok. When I tried to jump start (which I assumed would not work before I even began), I let the jumper cables stay on for a few minutes with the donor vehicle running. This made no difference. The starter did not even crank a little bit.

My hunch is that it's in the wiring somewhere - I am just not sure where to start looking, and was hoping that someone may have had the "grumbly glow plug relay" symptom before.

Thanks,
Andy

[junqueyardjim]

And of course I have been wrong in my thinking often. But I don't think you have a battery. I think you need a battery. Now solve your problem the easy way. Glo plugs are not the problem. It is your battery. Pull it out, hitch hike to town or call a cabby, but get a real test on it. Take along enough money for a new one, about $80.00 to $100.00. Or call Mercedes for a "Free" on the road or in your driveway start. I think they will check your battery also, but it is free. Mercedes batteries are very high priced. But they will come to assist in your start problem.

[vstech]

could be the neutral safety switch, does your car have the jumper block near the battery on the fenderwell to short the starter?
also with your headlights on, do they dim when you hit the starter? what exact voltage does the battery read? what does it read when you turn the key to the start position?

[junqueyardjim]

No, 240D's don't have that handy little box. At least my 83 240D doesn't have one.

[Junkman]

Originally Posted by AJD

I checked the battery with my analog meter.

That is not enough information. 12.6 is a fully charged battery. Either you have it or you don't. Ign switch trips solenoid and starter cranks. That requires good ignition switch, wiring, battery and starter. If starter spins but engine doesn't crank, you need a bendix or perhaps to just clean and lube it.

Next step is to make sure that battery cables are clean & tight at both ends. You can measure voltage at the battery terminals them move 1 lead to the + cable terminal & measure voltage drop, then the neg terminal, then the neg ground end etc until you've been through the circuit including cable on solenoid. Voltage should not drop. Also check the junction box on the passenger side frame rail.

Next check small trip wire that runs from ignition switch to starter. Should be 0 volts with key to anywhere but start and full battery voltage with key to start. Take those measurements & report back. You may also want to google no crank for more details. Information is everywhere.

[vstech]

Originally Posted by Junkman

That is not enough information. 12.6 is a fully charged battery.

not quite true.
a FULL battery has 12.65v
a battery will maintain a float charge of over 13v with a good charger/alternator.
Open Circuit Voltage Approximate State-of-Charge at 80°F (26.7°C) Hydrometer Average Cell Specific Gravity Electrolyte Freeze Point
12.65 100% 1.265 -77°F(-67°C)
12.45 75% 1.225 -35°F(-37°C)
12.24 50% 1.190 -10°F(-23°C)
12.06 25% 1.155 15°F(-9°C)
11.89 or less DISCHARGED 1.120 or less 20°F(-7°C)

[TnBob]

A battery may read close to the proper voltage of ~12.6 volts but still have insufficient current or amp capacity to crank the motor over.

Hitting the start with the headlights on will give you a better idea but it sure sounds like a very weak or bad battery.

Did this just start or has the symptom been getting progressively worse ?

[AJD]

I will bring my DMM from work home tommorow and check exact voltage of the battery.

The problem has not been progressive and just started this afternoon. The car was driving fine earlier today. That's why my hunch is wiring somewhere or possibly the ignition switch.

[hockeyboysomers]

Do yourself a favor, take the negative cable off the battery and clean the negative post and cable clamp with some kind of abrasive.( brass brush, sand paper, steel wool) I've saved myself, and others from buying a new battery, with just this advice. For some reason a non conductive layer of corrosion forms on the negative post. I assume that because only a small area of the post is actually contacting the clamp, some current is getting through, but with the huge draw of the starting circut, not enough current gets through. Imagine if you had a small wire going to your starter and ignition circut. (speaker wire size) When you turn the key to the first position all of your dash lights would light. as soon as you hit the glow cycle position the wire would probably melt and you would not be able to start the car. For some reason this corrosive battery cable problem seems to happen most when it is damp, misty,and cool. Kind of like the weather we had here in the northeast on Wedneday this week. Check the cable, at least it's free. If it doesn't work move on to what the others have suggested. Good Luck, Dave

[chomptown]

My guess would be a bad ground also. So is the starter turning at all? That would be the next place I would check. Is it making the starter *click* sound?

[benhogan]

Check the starter relay. Follow where the big red wires (pos) meet (one from battery, and one from the starter). They meet at the starter relay.

You can try to jump it (connect the two) with a big enough wire. If the starter comes to life then the relay is bad.

However, I would check the obvious ones first like the battery and possibly a bad ground wire connection.

[Junkman]

Originally Posted by vstech

not quite true.
a FULL battery has 12.65v
a battery will maintain a float charge of over 13v with a good charger/alternator.
Open Circuit Voltage Approximate State-of-Charge at 80°F (26.7°C) Hydrometer Average Cell Specific Gravity Electrolyte Freeze Point
12.65 100% 1.265 -77°F(-67°C)
12.45 75% 1.225 -35°F(-37°C)
12.24 50% 1.190 -10°F(-23°C)
12.06 25% 1.155 15°F(-9°C)
11.89 or less DISCHARGED 1.120 or less 20°F(-7°C)

AND the details are all over the web. AND many volt meters have enough variance to not be able to accurately distinguish between 12.6 and 12.65. AND many of these old alternators have out put onthe low side. AND my SD starts easily with 12.2 unless the wiring is messed up or starter is bad which is really mostly wiring. Regardless, without measurements, we are only posing possibilities of which there are only a few.

With the engine in neutral and emergency brake set, use the end of your lug wrench to short the bottom terminal of the starter solenoid to the heavy starter motor terminal just below it.

When you short it, don't keep spinning it to start it, simply bump it, then try the key.