2.7 CRD (WG) Glow plug voltage (cold start issues)
 

Hi all,

Great forum. Located in Europe, but avid user of this forum, all be it passive. Have been putting all the info from the 2.7 CRD sticky to good use.

But now experiencing a problem that got me stuck. So I thought maybe AJOR can help!

Problem
Her in Europe nights are getting colder. At the moment around 6C. Up until now cranking for about 2 seconds, which was fine for us. But now cranking for more than 5 seconds and after that a rough idle.

Findings up until now

• glow plug fuses both fine
• tested glow plugs (GP''s) no. 1 through 4. I didn't want the hassle of removing fuel rail to reach no. 5 and figured that if 1 through 4 were ok, that the GP's would probably not be the problem.
• GP 1-4 resistance: all four measured 0.8 Ohm
• GP 1-4 voltage: ranging from 10.6 - 10.8 Volts
• Battery Voltage in rest: 12.02 Volts
• Battery Voltage when glowing: 11.70 Volts
• Battery MOPAR OEM part from nov. 2012, so not even 3 years old
• Rough idle clears after about 2 minutes
• no smoke of any colour coming from the exhaust

Questions

• Is the 10.6 - 10.8 Volts enough for the GP's to glow properly? Spec voltage is rated 11.5 Volts.
• Possible causes for voltage drop between battery and GP's (11.7 while glowing vs. 10.6/10.8 Volts measured at GP's)?
• Is the rough idle related, or a different issue altogether?
• What tests can I do with multimeter to verify the 2 GP relays are working properly?

Any hints / tips are greatly appreciated!

Thanks,
Marty

Haven't access to my files as on the road but battery is low and could be the culprit.
Not much experience with cold though, cold at my place is about 6 c.........

I'd say voltage is a likely issue. The glow plugs may still be knackered even though the resistance it consistent across all plugs.

From memory there are two circuits, I think 1-3 are on one and 4-5 are on the other, if one circuit is down this may create an issue.

Also have you checked for codes to see if there is an error report by the ECU?

Jason

Did u eliminate the case of air in your fuel system?
Indeed rough ideal is not a symptom of air but its neither a symptom of glow plugs

Will switch out relays to see if this has any effect, nearby ASD relay seems to be same type, so I have a "spare" to switch out.
Good test for relay, because using a bad relay in the ASD should kill running engine within a few seconds ;)

No codes are present when doing key dance. A fitting scan tool is still on the "to buy" list

As far as I can tell no air bubbles visible in fuel lines at telltale locations like fuel pump or filter.
Maybe far fetched, but rough idle could be symptom for glow plugs because they stay on, even after engine has started. This is to "help" in cold weather.
Although 6C is not that cold. It's going to get a lot colder the coming months. Thats why I'm keen on fixing it within 2-3 weeks.

Ok, update on aforementioned problem.

Had battery load tested. Was original MOPAR OEM battery with CCA of 800A. Under load it tested 644A and a voltage of 10.10V when starting. Alternator is OK with 14.2V.

So decided to change batttery because of decreasing CCA and cranking voltage beginning to get lower aswell (I was told that lower than 10V is when battery becomes a real problem during wintertime).

Put in new Exide 100 Ah battery with CCA of 900A. Next morning after reasonably cold night (7 C) problem still persists.... Ah well, at least we're starting winter with a good battery.

Switching out the glow plug relays with the ASD one (same relay) made no difference. Still pondering on low glow plug voltage though... 10.6V with battery at 11.7 while glowing, so where's the voltage drop going....

Ok, so next item on the list is fuel lines and o-rings. One fuel line (filter to LP pump) was recently replaced when putting in a new thermostat.
Two to go: new line from LP pump to HP pump and new line from HP pump to fuel rail. Thanks to the Everything CRD sticky no problem in sourcing these parts from MB shop.
Also changing the o-rings on the fuel pressure control valve and pressure sensor, both on opposite ends of the fuel rail.

Replacing fuel filter with a Mann filter at the same time last one was 10K km ago.
Will check fuel hoses to filter again, but they seem pretty new.

So will keep you posted if this resolved issue.

BTW: no rest with a JGC! At same time AC evap was found leaking, so will have to pull dash aaaaaargh.
Having some trouble finding right aftermarket evaporator and heater core for 2.7 CRD. But will start new thread on that one!

Marty