Engine start voltage dip & glow plugs questions

CaptnALinTiverton

xT1N Westfalia
I have voltage dip getting worst. AM battery 3 months old is suspect since everything else has been replaced in the past. Last time, ECU etc. blanked but ignited while glow plug light flashed before running. I'm having battery changed but concerned about glow plugs coming on after voltage dip again. Some say glow plugs not needed in summer. My questions are, can glow plugs coming on during ignition hurt positions? I suspect now cause I guess they do no get that hot. Secondly, if I remove F5 at battery to make me feel better about possible damage until problem is sorted, will that make starting slightly harder and will the ECU light CEL because glow plug current didn't happen when commanded? Where is Dr. A when you need him? AL
 

Pnwsquid

Active member
I have voltage dip getting worst. AM battery 3 months old is suspect since everything else has been replaced in the past. Last time, ECU etc. blanked but ignited while glow plug light flashed before running. I'm having battery changed but concerned about glow plugs coming on after voltage dip again. Some say glow plugs not needed in summer. My questions are, can glow plugs coming on during ignition hurt positions? I suspect now cause I guess they do no get that hot. Secondly, if I remove F5 at battery to make me feel better about possible damage until problem is sorted, will that make starting slightly harder and will the ECU light CEL because glow plug current didn't happen when commanded? Where is Dr. A when you need him? AL
This might be a better topic for the T1N forum, you'll get significantly more eyes.
 

autocamp

un-Airstream'ed & un-Dodged NAFTA JC
Humm! A seasoned EE with advanced education cannot figure this out.:rolleyes: Must be a mind bender of an issue. I am still learning how to wire a duplex outlet with GFIC so not to risk killing myself.
 

autostaretx

Erratic Member
What does a voltmeter say your battery *and system* voltages are dropping to?
I recently replaced my battery, but before i did i tested my 2005 Sprinter to extreme low levels ... it would dip down just below 10 v (so 9.8) as a system voltage during starting ... but it did start. (just about as quickly as with a new battery).
I didn't specifically look at the glow plugs, but if i did an "instant start" (not waiting for the coil to go out), the coil remained on the expected time. (which is/was short)
The glow plugs draw 65 amps when cold, then that drops to about 30 amps as they heat up.
How long they stay on depends upon the ambient (and perhaps motor block) temperature.
They can stay on for 30 seconds or more *after* ignition on cold days.
Instead of unplugging them, why not just turn the key to Start after only a couple of seconds hesitation in the Run position?

Voltmeter (and clamp-on current metering) can reveal many things.

--dick
 

grozier

Active member
Glow plugs come on regardless of temperature I think. They might also do “afterglow” when running to improve emissions. Do not worry about them.

Based on your symptoms I would check all grounds, including the main block-to-frame ground. (Didn’t you have the engine out once or other major engine work?)

Good luck and keep us posted.

Ted
 

CaptnALinTiverton

xT1N Westfalia
Thanks autostaretx and Ted for replies. Voltage usually drops to high 9s even with another new battery. I suspect that the MB battery is best and wet cells are stronger for cranking. The stated symptoms only occurred once: engine was warm after driving and shut down for maybe 10 minutes, turned key and waited for plugs to go off, voltage dropped on crank and instruments went blank, ignition caught and started, instruments relit with plug light on again then off. So this raised the question of plugs on causing damage after starting. I had good connections, new starter two years ago, double ground strap and new aftermarket battery installed three months earlier. Since I was away from home and suspected the new battery and a repair shop was two blocks away, I ordered another brand battery there and after weekend, it started normally and drove to shop. Battery load tested ok but voltage was on the low side. I know that sounds like over reacting but I had more fun planned and a deadline to get home. So this was not the click, relay block or connection symptoms.

So reason for post was to share experience with others, vindicate my bad battery suspicion and ask about possible harm from plugs being on after engine running.


AL
 

autocamp

un-Airstream'ed & un-Dodged NAFTA JC
I apologize for my poor reading incomprehension. I comprehended wrongly you were asking for help to diagnose the voltage sag problem. Only now that I realized you were doing a victory lap that the first MB battery that you opine is the best, but turned out to be defective, but you pin pointed the problem and rectified with a replacement battery.

Hmm! Glow plugs being on after engine started causing damage is a foreign idea that never occur to me.
 

grozier

Active member
Do you have anything unusual on the “coach” side of the vehicle? If you still have the 12V AC unit, remove the big fuse along the inside of the left fender to eliminate that system.
 

autocamp

un-Airstream'ed & un-Dodged NAFTA JC
Ted does have a very good point that should be checked and it is not immediate apparent even its existence. Get yourself a clamp meter capable of measuring DC current. It will save you hours of time to find where the currents are going, and if your battery is being charged, and how much.

IMG_7117.jpeg
 

CaptnALinTiverton

xT1N Westfalia
No issues on the coach side; I made a controller circuit that controls the isolation relay and that only engages when the alternator spins up due to the D+ line controlling the coil feed. Also autocamp, no need to apologize. I wasn't specific about the battery types. Here is the scoop: I've always used OEM MB wet cell batteries. I got the urge four months ago to try AM (After Market) Exide maintenance-free (really AGM I suppose but I've never heard start batteries refered to as AGM, just maintenance-free) because a friend did the same. Then when I had that "voltage drop out" start experience away from home, I took advantage of local shop for fear the Exide failed to deliver those CCAs. The shop put in a NAPA maintenance-free equivalent as well so I'm trying it out for now. I just have a gut feeling that the MB wet cell is better because I have always found them to die a slow death rather than suddenly thereby preventing you from being stranded as you know when they are starting to go bad. Perhaps this is all ridiculous assumption but it would be interesting to hear if others have formed similar opinions.

Thanks, AL
 

autocamp

un-Airstream'ed & un-Dodged NAFTA JC
AGM = Absorbent Glass Mat. Majority of maintenance free car batteries are AGM. Maintenance free battery is a broad category which implies you don't need to check for battery fluid and replenish it.

You missed the point that Ted and I tried to point out to you of a potential current path that you may not be aware of. The big cable with the series 150A fuse do not go thru the isolation (I prefer to call it combiner) relay under the driver seat. It goes straight to water boiler compartment where the switch mode power supply and the big relay for the AC resides. Could you have a sizable phantom current leak on that path? It may be worth checking.

I am under the impression the Sprinter's isolation relay is design only to close after the starter cranking, which means it serves well to cut in safely to charge the house battery bank when the engine is running.
 

autostaretx

Erratic Member
I am under the impression the Sprinter's isolation relay is design only to close after the starter cranking, which means it serves well to cut in safely to charge the house battery bank when the engine is running.
The MB relay only kicks in *when the alternator is running (generating charge)*
So it actually waits a few seconds after the actual engine start (about 4 seconds in my T1N)
(if you have a voltmeter attached, you can watch the step-up in system voltage at any starter-battery-fed 12v socket)

If you have the Ek1 option (as most US Sprinters do), the "D+" terminal is the same "OK to connect" signal.

--dick
 

autocamp

un-Airstream'ed & un-Dodged NAFTA JC
The MB relay only kicks in *when the alternator is running (generating charge)*
So it actually waits a few seconds after the actual engine start (about 4 seconds in my T1N)
(if you have a voltmeter attached, you can watch the step-up in system voltage at any starter-battery-fed 12v socket)

If you have the Ek1 option (as most US Sprinters do), the "D+" terminal is the same "OK to connect" signal.

--dick
Thanks. With all the German vehicles with house batteries that I have inspected the combining relay coil is energized by the alternator field coil power supply. I infer in the Sprinter is is switched on by one of the smart module. I believe the one in our Westfalia is the same as Sprinters with the aux battery circuit in the passenger seat box.

It perplex me why the Captain needed to do the D+ modification.
 

CaptnALinTiverton

xT1N Westfalia
I acknowledge all that you both said but the cable to the air conditioner (Kersner) relay (which I replaced with an equivalent relay) uses the D+ line as well so that relay will not energize as well until alternator is up. You both are right in that if the D+ comes on during the starting, the Kersner could energize and short out the starting circuit. I have prevented that by running the ground side of that relay through the air conditioner switch in the roof (replaced by a DPDT switch) so the AC would have to be switched on by this switch as well for the relay to kick in. Asside from that impossibility in my case, I don't have any visible discharge issues in the starting circuit.

Thanks,

AL
.
 

Kajtek1

2015 3500 X long limo RV
I would advice to "invest" in battery testers as 9 volts on GP alone means serious issues.
I have 2
1st is 50 am load tester,
2nd is "Solar" tester who using electronic circuit and voltage spike determinates CA.
Between the 2 I can tell not only battery CA but also longer-term capacity.
I rather buy cheaper flooded batteries as I don't drive on the walls and have no need for AGM.
The latest Bosch battery rated at 1000 CA, tested 1320 amp when new and 1200 amp after 2 years. Not bad for $100 expense.
 

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