[alex sol]

I have three glow plug controlunits.

original came with car
second came with motor swap
third bought from ebay

all three wouldn't get the car to start esp in the cold weather in Toronto.

i pulled the intake manifold and removed all six glow plugs, tested and they glowed with a second... then grounded to the fuel rail area, then hit the start button, slight delay, squiggle (pig tail) shows up, no glow action... tried six more times, charged up battery to full, no better


sooo.. i bloody hot wired the thing.

I had six spare glow plug ends and rigged up a six way parallel trigger that runs off the starter positive and then into a momentary spring operated on/off switch so it never gets forgotten in the 'on' position, ran the wire under the hood and in thru the driver's side door (couldn't find an easy way to run a wire through the firewall) and now just sits on the dashboard (temporary permanent fix) and it's too cold to mess around in my garage even with a 1,500 watt space heater..

plugged in, replaced the intake manifold and fired up... successful bypass!

no more head scratching or wondering if the D will start each cold morning...

[alex sol]

on the less colder days say above freezing, i'd need to crank 10-12 times and then sputter then start and major smoke show... hope this fix will make that experience a thing of the past....

[Owen81]

That is cool but I'm not sure how long they will last that way, the quick start glow plugs are activated with a PWM signal and not straight DC. It says multiple times in the shop manual not to activate them outside of the engine, and any current tests (straight DC) could damage the heating elements.

The preheating stages are determined by coolant temperature and battery voltage, are both of these reading correctly?
If so, I would check continuity of the control unit harness, including the ground and the engine ground as well. Something is amiss...

[lnxguy]

You've got an issue on your hands, why not fix it instead of a bandaid solution? You should have no problems starting that car no matter how cold it gets. I've had zero issues starting as cold as -36 (ambient).

[robnitro]

Full voltage on the plugs will shorten their life dramatically. From what I've read, they're rated for 7 or 9v but can use 12v for a quicker heating up, but not for long.

[rtd2]

Check your ground strap. Mine was corroded and caused starting issues. It's easy to test and cheap to replace.

[ptpending]

you can open all three ECUs and see that silver wires under clear gel are broken
so you need to buy NEW glow plug ecu and your problem will be fixed
you'll also need to check ground wire between engine and body, it can corrode in countries with real winter
335d m57 engine known to be sensitive to glow plug function and good battery to start in winter cold, while m47 and n47 can start with dead glow plug