L300 Glow Plug issues (cold start issues)

daisy

daisy

New Member
Hey folks. I'm currently troubleshooting a cold start issue where the relays are no longer clicking-on with ignition. The van can only be started after cranking for 3 minutes straight, smoking out my neighbours or jumping the busbar from the battery (no idea if I'm damaging anything by doing that)

Things I've tried:
  1. Checking and cleaning wires and connectors for corrosion from the #1 and #2 relays to the busbar
  2. Replacing glow plugs (Thought it was worth a shot as I'm pretty sure it has the originals in it and I found some for $25/piece at my local auto parts shop)
  3. Testing for voltage at the busbar during ignition (Getting zero reading. I probably should have done this first but i'm pretty new to electrical stuff)
Nothing has solved this yet. My next thought is to pull out the relays and test them using the methods described in the service manuals:
1545683452284.png

Question:
If I discover that my problem is one or both of the glow plug relays, does anyone know where to source them? I managed to find two 4D56 glow plug relays from CCA, one "blade type control" and another "screw type control". But they don't have a lot of info about them. I'll likely call CCA after the holiday and update this post with my findings.

Another route I've seen people go is installing a bypass switch to manually heat the plugs. I'd consider doing this but I worry there's more reason for the relays to activate the glowplugs than just for starting the engine that I don't know about. Also, I haven't found many good DIY instructions for doing this on an L300 and I'm not super experienced with electrical stuff.

Assumed glowplug relay bypass design:
  1. install a12v line from battery to the dash
  2. install a push button switch in the dash you have to hold in so it doesn't accidentally get left on
  3. install an inline fuse (that matches the amperage the glow plugs need?)
  4. install the 12v line directly to the busbar
If anybody has any insights into my problem and questions, feel free to chime in. I'll post whatever outcome I have here for future folks who may be experiencing the same thing.

Cheers, happy holidays!

Cody
 
Hmm. My thoughts:

-the glow plug ECU uses the resistance of the glow plugs to determine their temperature. So far only genuine Mitsubishi MD092392 or aftermarket NGK 2161 are known to work with the ECU.
-The temperature sender in the head (the 2-pin one, just behind the top radiator hose), like some kids, can go bad when it's of voting age. Part number MD050214. About $30 for a generic replacement.
-The glow plug ECU can fail internally from burst capacitors or from overheating from failed relays: FAQ on Delica.ca here.
 
I installed my bypass pretty much as you describe. But I used it to trip the glow relay rather than power the busbar directly. If you use it to power the busbar directly you will need to use MUCH heavier wire and switch.
The relays are basically interchangeable but one has a screw terminal and the other has a blade terminal. One of them should be good, if not both... I think the chances are more likely that they are fine and it's the ECU/control that is the issue. To test them just run a 12v wire to the center terminal and see if they click/activate. If they do, then that's the one you want to run your bypass wire to.
Number 1 is the 12v relay and I believe it is the one with the spade type center terminal. I just slipped the jumper wire into the plug along with the spade terminal... not as secure as the screw terminal connection; and it will probably oxidize over time because it's not a proper solder connection, but it works fine. If the 12v relay is bad, you could just use the 6v system. It's safer for the 6v glow plugs, but it is waaay slower. If I was just going with a bypass then I would use the 12v relay (assuming it's good) and 12v glow plugs.
 
sk66 said:
I installed my bypass pretty much as you describe. But I used it to trip the glow relay rather than power the busbar directly. If you use it to power the busbar directly you will need to use MUCH heavier wire and switch.
The relays are basically interchangeable but one has a screw terminal and the other has a blade terminal. One of them should be good, if not both... I think the chances are more likely that they are fine and it's the ECU/control that is the issue. To test them just run a 12v wire to the center terminal and see if they click/activate. If they do, then that's the one you want to run your bypass wire to.
Number 1 is the 12v relay and I believe it is the one with the spade type center terminal. I just slipped the jumper wire into the plug along with the spade terminal... not as secure as the screw terminal connection; and it will probably oxidize over time because it's not a proper solder connection, but it works fine. If the 12v relay is bad, you could just use the 6v system. It's safer for the 6v glow plugs, but it is waaay slower. If I was just going with a bypass then I would use the 12v relay (assuming it's good) and 12v glow plugs.
Click to expand...

Just read this thread, which sounds like the same issue im having. based on this, Im wondering if i might have an issue with the ecu since my Bypass was running to the good relay. Do both relays need to be functional to get power to the glow plug rail?
 
Just reading through this. That's for all the info everyone!

My controller varies the amount of time between clicks depending if the engine is warm or if I've just run the glow plugs. So it sounds like the glow plugs are working.

However, it takes a LOT of cranking the engine to get it started when below maybe 5 deg C (40 deg f ish maybe). This is course is then accompanied with lots of white smoke from all the fuel it injected while cracking it over.

Anyone experienced this?

I'm wondering if it's possible my glowplug are heating up, but somehow not getting fuel/air to the hot part? Is that possible? Could they be encased in carbon or something?

Any chance anyone knows what resistance range the glowplug controller is looking for? Alternately, what voltage it's looking for? Thinking I could use this to verify my controller is working.
 
Kyle_GP said:
'm wondering if it's possible my glowplug are heating up, but somehow not getting fuel/air to the hot part? Is that possible? Could they be encased in carbon or something?
Click to expand...
Not likely...

Kyle_GP said:
Thinking I could use this to verify my controller is working.
Click to expand...
Just test for voltage at the glow plug rail... it should be ~ 10v while powering the plugs.

Hard start is common when air is getting into the fuel... could be IP seals (front shaft seal seems to be pretty common), a crack in a rubber line, etc.
 
I like to test each glow plug out of the vehicle using a direct voltage source. Verify if you have 6v or 12v plugs. In approx 10 secs they should smoke and glow. This verifies proper operation along with checking the bus bar for voltage. If you choose to remove the glow plugs, first spray some penetrating oil on the threads as it would really suck if you break one. If all this is good, air in fuel should be checked with some clear hose in place of the fuel hose and observe if any bubbles present. It is very possible that the injection pump needs seals and or rebuilt.
 
I have had this same problem for years but I recently kind of overcame it. I have a manual plug button set up but what really helped was now I pushed the accelerator to the floor and then pull back a few inches. Then run the plugs for 5 seconds on the 6-volt setting and it starts right up. I have to back up on the accelerator a bunch so it doesn’t spew out exhaust all over the guys working on the house nextdoor. I’m wondering if all these years I just wasn’t giving it enough juice.
I have also wondered about an air leak though. I did replace a seal on the ip when I installed a new head. I also replaced one fuel line - I’ve been too lazy to do the rest. Not sure what other tests I could do to look for an air leak but I haven’t ever seen any fuel pooling anywhere.
 
sk66 said:
Not likely...


Just test for voltage at the glow plug rail... it should be ~ 10v while powering the plugs.

Hard start is common when air is getting into the fuel... could be IP seals (front shaft seal seems to be pretty common), a crack in a rubber line, etc.
Click to expand...
That's really helpful, thanks!

I'll try to see if I can switch to clear fuel lines and see any bubbles. I'm guessing if I don't see any bubbles then the next likely candidate is my infection pump?

That wouldn't be ideal, but I guess it's an opportunity to go to the higher pressure pump and injectors from the D4BF.

Anyone ever find a successful transplant of the electronic IP from the DB4H? Looks like it could be a Bosch VP37, which would be available all over due to VW using them in a number of their engines.

It would be great to have the ability to tune the pump from a laptop and have control over timing and a more defined fuel map.
 
Last edited:
Kyle_GP said:
That's really helpful, thanks!

I'll try to see if I can switch to clear fuel lines and see any bubbles. I'm guessing if I don't see any bubbles then the next likely candidate is my infection pump?

That wouldn't be ideal, but I guess it's an opportunity to go to the higher pressure pump and injectors from the D4BF.

Anyone ever find a successful transplant of the electronic IP from the DB4H? Looks like it could be a Bosch VP37, which would be available all over due to VW using them in a number of their engines.

It would be great to have the ability to tune the pump from a laptop and have control over timing and a more defined fuel map.
Click to expand...
Actually... Anyone ever looked at adding a couple sensors and using one of these? It could be really great for tuning the engine if it was possible without being really difficult to setup.

www.allturboshop.nl

Diesel ECU for VP37 EDC fuelpump | allturboshop.nl

A diesel engine controller for engines equipped with a Bosch M-type EDC electronic diesel injection pump, such as Mercedes Benz OM605 and OM606, as well as VP37 injection pumps found on lots of different cars. Package contents: electronic control unit 6 pin mini-fit jr connector 8 pin...
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