Hi guys

Have another issue that's come up with regards to the glow plug/ preheating light. Like most diesels I know you have to wait for the coil light to go out before starting but a while but the light stopped coming on completely after repeatedly jump starting the car when it had a faulty battery.

The battery was replaced but the coil light never comes on. It was the summer then and I always waited a few seconds before I started it and it started and ran perfectly. It's getting cold in this part of the world now and she's struggling to start. And on start up the coil light flashes for a while (not more than a minute) before going off again, this didn't occur in the summer.

There's no warning lights on the display about the glow plugs, there never has. I have diagnosed it so I don't have any codes either. It's an 07 1.9 jtd. I'm thinking it's a relay but your advice would be appreciated before buying a part I might not need.

Hi Mate,

have you the possibility to check for power coming to the plugs / plugs continuity ??

Regards, Bernie

Bernievarian said:

Hi Mate,

have you the possibility to check for power coming to the plugs / plugs continuity ??

Regards, Bernie

Click to expand...

Hey Bernie

As in check for continuity I the cable that runs from the really to the plugs?

Sorry using my cell phone.. am are you suggesting I check the continuity in the cable running from the relay to the glow plugs

Hi,

no, I meant continuity of the plugs themselves, check with an ohmeter, hopefuly found all ok so we can eliminate that part of the equation.

- do you have fuses @ the battery + connector ? -> verify / replace (F7 - 50A)
- depending model of car (age), this fuse could have migrated to main distribution box
- power from battery reach the preheating relay box ? -> verify / restore connection
- the relay itself is protected by a fuse in the body computer (under the dash) -> verify / replace (F59 - 10A)

That's about it for the preheating circuit checks; the lamp on the dashboard is lit by the dash controller thru the CAN bus...

Regards, Bernie
-

Bernievarian said:

Hi,

no, I meant continuity of the plugs themselves, check with an ohmeter, hopefuly found all ok so we can eliminate that part of the equation.

- do you have fuses @ the battery + connector ? -> verify / replace (F7 - 50A)
- depending model of car (age), this fuse could have migrated to main distribution box
- power from battery reach the preheating relay box ? -> verify / restore connection
- the relay itself is protected by a fuse in the body computer (under the dash) -> verify / replace (F59 - 10A)

That's about it for the preheating circuit checks; the lamp on the dashboard is lit by the dash controller thru the CAN bus...

Regards, Bernie
-

Click to expand...

Thanks Bernie

I've checked everything short of the glow plugs themsevels, they're a little difficult to get to. I did run a scan on it and the preheating unit came up. Fiat emailed me a quote on glow plugs instead of the unit itself.. until then I plan to run the glow plug circuit through a switch that I can actively switch on and off to get them to temperature in the morning, as I understand it it shouldn't be a problem? It's only temporary as I have a feeling the unit will be beyond my means..

How much did fiat quote you?

Glow plugs difficult to get to ?? Remove the air box and there they are ! They're the very first thing to check when cold starting issue (difficult start)! Don't waste your time playing with a switch (BTW you'd need a high current one !!), test each plug individually instead, you can unplug them, use a 12V halogen bulb (50W house lamp) to hook the plug directly to battery positive; if the bulb lits, the glowplug is ok, if not it's dead... If they're all good, then it's probably the preheat unit that's bad, OR the coil fuse @ body computer. Could not source preheat box diagram so can't tell you which pin is the relay coill or if there is any electronic inside (which I doubt) ; anyway, you said the box came up with the actuator test (I guess) so there is little other option... check the plugs and tell us...

Regards, Bernie

AND, as usual, if someone here helped You understand -or better- fix your issue, hit the thanks icon @ bottom right, it's free and make us feel helpy ;-)

Bernievarian said:

Glow plugs difficult to get to ?? Remove the air box and there they are ! They're the very first thing to check when cold starting issue (difficult start)! Don't waste your time playing with a switch (BTW you'd need a high current one !!), test each plug individually instead, you can unplug them, use a 12V halogen bulb (50W house lamp) to hook the plug directly to battery positive; if the bulb lits, the glowplug is ok, if not it's dead... If they're all good, then it's probably the preheat unit that's bad, OR the coil fuse @ body computer. Could not source preheat box diagram so can't tell you which pin is the relay coill or if there is any electronic inside (which I doubt) ; anyway, you said the box came up with the actuator test (I guess) so there is little other option... check the plugs and tell us...

Regards, Bernie

AND, as usual, if someone here helped You understand -or better- fix your issue, hit the thanks icon @ bottom right, it's free and make us feel helpy ;-)

Click to expand...

Hi Bernie

I'm sure you've been told this before but you're an absolute legend!! Thanks for the help.

So I don't have a test light but I kind of made one got a head light bulb and a attached wires to each of the terminals.. connected the one wire from the light bulb to the positive terminal and the other end from the light bulb to the top of each glow plug.. on 3 out of 4 of them the light bulb lit up..

Firstly is this an appropriate technique and secondly and more importantly will the faulty glow plug be causing this fault?

Hi StormN (sorry no Firstname...),

thank you for the compliment, but I'm far from being as you say and certainly not the only one ...

The "bulb method" is a good one to detect open or resistive (bad ground) circuits, but obviously it can't detect short to ground failure !
The best way is to use a multimeter or at least an ohm meter. A shunt Ameter is also helpfull to verify huge loads (such as glowplugs / rear defrost ...)
As for the fault: one single glow plug should not prevent the engine from starting, but could have damaged the control box if the initial failure was a short to ground. Anyway, the control box need to be checked. What kind of equipment have you at hand ??

Regards, Bernie

Hi Bernie

Thanks anyway.. I've got a multi meter and tool box with most spanners and sockets. Is there a way to test the control box as well?

Yes, there is, let me check for pin numbers and I'll be back with the procedure...

Thanks mate

Hi, couldn't find the internal diagram of that controler :-(

Anyway, here's how I would verify it:

- remove it from its bracket (need to remove the steering oil tank on LH cars, don't know about UK)
- locate the connector which goes to the plugs, remove the other !!
- on the last, you should have 4 wires; pin 1: plain black, 2: grey/red, 3:blue/black and 5: grey/blue
- VDC between 1 & 3 should be 12V (ish) with key ON (pin 1 @ ground)
- the two other pins receive/send-back signal from/to the ECU, no clue here what they are :-(

No clue weither it's a mechanical relay that's build in or a SolidStateDevice so I can't give a verification procedure :-( But obviously, you should get 12VDC positive at the four glow plugs outputs WHEN the preheating is supposed to occur.

That's about all I can do, unless I find some time afternoon to remove mine (from a 1.3mjt90) and see what's inside ;-)

Good luck, Bernie

ps: tell us whatever you found...

Got a few more bits of info from eLearn, see pic...
Also from visiting other sites (europarts) it is almost sure there is a timing circuit (electronics) AND a mechanical power relay !

Regards, Bernie

Thanks Bernie will try it out tomorrow

Hey Bernie

here we go..

So at the preheating unit theres 2 connectors; one from the vehicle ecu (will call it Cable 1) and the other that runs from the preheating unit to the glow plugs (will call it Cable 2) and theres also a 12V line bolted onto the unit directly from the battery.

Cable 1 had the following readings:
Pin 1: Ground
Pin 2: 3.47V
Pin 3: 12.32V
Pin 4: 11.46V

On connecting Cable 1 back into the preheating unit and removing Cable 2, all 4 pins on the preheating unit read 12.49V...

I cant make sense of this but hopefully you can. Also all readings were taken with the key in the ON position, when preheating would be occurring. Also i have a Check Glow Plugs Warning on the display.

Hi StormN (still no firstname...),

On connector "1" (actually B)
pin 1 & 3 : should read 12VDC; seems ok
pin 2 & 4 : still no clue what's going on here; one is the command signal FROM and the other the feedback TO the ECU
BTW: this connector should have 5 pins...

All pins on connector 2 are internally hoocked together so the normal reading with preheating in operation should be 12 VDC(ish) : seems ok.
The check glow plug warning is because the circuit detects NO power thru the glow plugs, since they are disconnected... Could you confirm that there is no 12VDC on connector 2 (actually C) AFTER the preheat has timed out ?
- re-connect all
- key ON, preheat warning should not pop-up
- after 8sec the preheat light should switch OFF
- leave key ON, disconnect connector 2, should have no VDC on box outputs...

If al this is ok you should be fine replacing the bad glowplug...

Regards, Bernie

Hey Bernie

yes its pin 5 and not 4, 4th pin is open/not there..

Just did as you said, after 8 seconds theres a click sound from the unit and the VDC reads 0V at all four outputs.

However when everything's connected all I get is a flashing preheating light and I still get the check glow plug display.

May i add Bernie, before the flashing and the colder weather, i never got the preheating light indicating preheating is occurring for those 8 seconds.

Regards

Nelson

Hi Nelson,

the controler checks what current goes to the 4 glowplugs; if one gets open, less current is drained so the controler would tell the ECU there is something wrong (via one of the signal wires, pin 2 or 5), the ECU will then tell the dashboard to flash the glowplug light... Looks that's what your car is doing.
You should replace the defective glowplug and your preheating circuit should be back to life as normal. Be carefull those glowplugs are extremely brittle !! You've be warned ;-)

- have the car in your garage
- stop the engine
- gain access to the glowplugs (remove air-box)
- let engine cool down completely
- spray WD40 or your preferred unseizer stuff on the plug thread
- leave it for the night
- next morning you should be able to remove it WITH THE RIGHT TOOL ...
- install the new one (copper unseizing paste on the thread is a good idea)
- reconnect wire(s), re-install air-box
- ignition ON, pre-heat light should pop-up at dashboard for 8sec
- if so you're done !!

Regards, Bernie