Glow Plug Relay Bypass
#1
10-26-2022, 11:22 AM
Glow Plug Relay Bypass
Hi, I have a suspect glow plug relay problem, if i test the relay on a relay tester it shows a pass with a green LED, if i turn on ignition on my 2007/2008 Grand Voyager the relay clicks but i don't think its doing any more than that, So my question is can the relay be bypassed temporarily so as to rule it out as the reason the car won't start, The relay in question is the Grey one situated front right of engine next to fan relays on UK vehicle. I have tried to get a new replacement but without success. Any help would be appreciated. The car is a 2007/2008 2.8 diesel Grand Voyager LX
All The Best
Steve
All The Best
Steve
Last edited by Taskmaster; 10-26-2022 at 11:40 AM. Reason: Fuller Description
#2
11-02-2022, 01:14 PM
suggest you rig a multimeter set on 20v DC range or DC if auto ranging on the output of the relay - if you're getting a 12v reading when ignition on then relay's OK. IF OK then check on first fed glow plug should get same reading - follow through to last glow plug. (Relay keeps the 'plugs live for quite a few seconds when ign. switched on (ambient temperature dependent)
I normally start mine straight away without waiting for the 'plugs to heat up.. at least down to 5 Celsius... around 40 F (approx).
I normally start mine straight away without waiting for the 'plugs to heat up.. at least down to 5 Celsius... around 40 F (approx).
#3
08-02-2023, 04:33 AM
Relay bypass
Old thread, I know, but for reference:
Assuming this is the VM Motori 2.8 CRD found in the 200? to 2007 models (you state 2008, which would be the new chassis and engines, right?), the glow plugs and the relay can be activated and tested separately. I would recommend you to measure a few things before you start to bypass the relay. Start by measuring the plugs and then measure to see if you get 12 V after the relay. Here is how:
First, locate the gray relay on the very left of the front crash bar (all positions as seen from the driver's seat). Just front of the battery, you will find the gray Omron relay with slightly larger connectors on the poles that connect when the relay is activated. My 2007 2.8 CRD has four other, black, relays to the right of that gray one. This relay connector does not have the standard red tab that prevents accidental removal of the relay.
Remove the plastic top cover of the engine (3 pcs. of 10 mm hex bolts).
To the front right (remember, from the driver's position), on the generator bracket (triangular, held by three bolts), you will find a connector with four relatively thick wires. These are the wires going to the glow plugs. Disconnect this.
In the loose connector, that was the front one, you should be able to connect your multimeter.
The part of the connector that is mounted to the bracket with a plastic clip goes to the plugs. This is where the coloured wires are. The other part of the connector goes to the relay and has four black wires. When turning the key to "ignition", you should read ~12 V here for 15 seconds, which is the duration that the relay stays on. After engine start, it will be on for another 2 minutes (measured in summer at about 20 °C).
While you have the connector loose, measure the resistance from the connector to the plugs. The four contacts each go to one specific glow plug.
#1 - Black, left cylinder, near the battery, behind the EGR valve (only present on 2007 I think)
#2 - Grey with black stripe, behind the inlet pipe
#3 - Red with gray stripe
#4 - Green with black stripe, behind alternator
Each should be close to 1 Ohm, or basically a short. (Lots of multimeters show 1-2 Ohms when you connect the test wires so a reading up to, say, 3-4 Ohms is OK). If any of these show no connection (or very high resistance), the plug is fried.
If you have 12 V in the connector when you should, the relay is working. If you have about 1 Ohm of resistance (basically a short) to all four plugs, they are OK.
Now, for the relay, mine was clicking but I had no output, just like yours. I did have 12 V in to the relay (red/black wire is 12 V feed, red/white goes to the plugs). Answering your question, you CAN connect the red/black and red/white wires via the relay connector, but I would advice against that. If all plugs are OK, you will have about 50 A here, so your average heavy-duty 1.5 mm2 wire will start to glow (almost, it will be very, very hot at least). You also risk ruining the relay connector. The relay is rated at 70 or 75 A and the "30" and "87" terminals are 9.5 mm, not the standard 6.3 mm. If you have no idea why they are so big and what 50 ampere means, don't mess with it!
If you still want to try it, use a wire that is at least 2.5 mm2 square area (AWG 14 in that horrendous US scale). If you use standard 6.3 mm cable shoes, make sure they're clean and connect one really properly first and then firmly connect the other one. Any hesitation will cause a poor connection and a lot of heat until it is properly in contact with the relay connector, causing fraying in the connector.
Now, the relay connector is the next part to examine. If this one is fried, it will not work properly, perhaps not at all. Replacing it is a daunting task as you need to make sure those 50-70 amps are handled properly. Any poor connections will generate heat and may even start a fire. I replaced mine and used even thicker cables and special screw terminal strips where both screws made contact with with both leads. I also checked the connections with a thermal imaging camera to make sure they were 100% good.
The last thing to check if all the above checks out is the voltage at the plugs. Many people start here, but it is messy, dirty and no fun at all. I very much believe that if the above is correct (plugs, relay, connectors), you won't have to go here. Measuring the voltage at the plugs is cumbersome to say the least. The plastic caps will hinder the measurement and they don't come off easily. If you feel compelled to measure here, I suggest drilling a small hole in the caps in order to be able to measure. This will void the weather protection offered by the caps, but it shouldn't be a big deal really. The alternative is to remove the caps one by one from the plugs, pry off the cover and reinstall the metal connector only. The metal connectors consist of two parts, the copper connector itself, crimped to the wire, and a metal "ring" that works as a tensioner for the actual connector. This "ring" is easily lost...
Assuming this is the VM Motori 2.8 CRD found in the 200? to 2007 models (you state 2008, which would be the new chassis and engines, right?), the glow plugs and the relay can be activated and tested separately. I would recommend you to measure a few things before you start to bypass the relay. Start by measuring the plugs and then measure to see if you get 12 V after the relay. Here is how:
First, locate the gray relay on the very left of the front crash bar (all positions as seen from the driver's seat). Just front of the battery, you will find the gray Omron relay with slightly larger connectors on the poles that connect when the relay is activated. My 2007 2.8 CRD has four other, black, relays to the right of that gray one. This relay connector does not have the standard red tab that prevents accidental removal of the relay.
Remove the plastic top cover of the engine (3 pcs. of 10 mm hex bolts).
To the front right (remember, from the driver's position), on the generator bracket (triangular, held by three bolts), you will find a connector with four relatively thick wires. These are the wires going to the glow plugs. Disconnect this.
In the loose connector, that was the front one, you should be able to connect your multimeter.
The part of the connector that is mounted to the bracket with a plastic clip goes to the plugs. This is where the coloured wires are. The other part of the connector goes to the relay and has four black wires. When turning the key to "ignition", you should read ~12 V here for 15 seconds, which is the duration that the relay stays on. After engine start, it will be on for another 2 minutes (measured in summer at about 20 °C).
While you have the connector loose, measure the resistance from the connector to the plugs. The four contacts each go to one specific glow plug.
#1 - Black, left cylinder, near the battery, behind the EGR valve (only present on 2007 I think)
#2 - Grey with black stripe, behind the inlet pipe
#3 - Red with gray stripe
#4 - Green with black stripe, behind alternator
Each should be close to 1 Ohm, or basically a short. (Lots of multimeters show 1-2 Ohms when you connect the test wires so a reading up to, say, 3-4 Ohms is OK). If any of these show no connection (or very high resistance), the plug is fried.
If you have 12 V in the connector when you should, the relay is working. If you have about 1 Ohm of resistance (basically a short) to all four plugs, they are OK.
Now, for the relay, mine was clicking but I had no output, just like yours. I did have 12 V in to the relay (red/black wire is 12 V feed, red/white goes to the plugs). Answering your question, you CAN connect the red/black and red/white wires via the relay connector, but I would advice against that. If all plugs are OK, you will have about 50 A here, so your average heavy-duty 1.5 mm2 wire will start to glow (almost, it will be very, very hot at least). You also risk ruining the relay connector. The relay is rated at 70 or 75 A and the "30" and "87" terminals are 9.5 mm, not the standard 6.3 mm. If you have no idea why they are so big and what 50 ampere means, don't mess with it!
If you still want to try it, use a wire that is at least 2.5 mm2 square area (AWG 14 in that horrendous US scale). If you use standard 6.3 mm cable shoes, make sure they're clean and connect one really properly first and then firmly connect the other one. Any hesitation will cause a poor connection and a lot of heat until it is properly in contact with the relay connector, causing fraying in the connector.
Now, the relay connector is the next part to examine. If this one is fried, it will not work properly, perhaps not at all. Replacing it is a daunting task as you need to make sure those 50-70 amps are handled properly. Any poor connections will generate heat and may even start a fire. I replaced mine and used even thicker cables and special screw terminal strips where both screws made contact with with both leads. I also checked the connections with a thermal imaging camera to make sure they were 100% good.
The last thing to check if all the above checks out is the voltage at the plugs. Many people start here, but it is messy, dirty and no fun at all. I very much believe that if the above is correct (plugs, relay, connectors), you won't have to go here. Measuring the voltage at the plugs is cumbersome to say the least. The plastic caps will hinder the measurement and they don't come off easily. If you feel compelled to measure here, I suggest drilling a small hole in the caps in order to be able to measure. This will void the weather protection offered by the caps, but it shouldn't be a big deal really. The alternative is to remove the caps one by one from the plugs, pry off the cover and reinstall the metal connector only. The metal connectors consist of two parts, the copper connector itself, crimped to the wire, and a metal "ring" that works as a tensioner for the actual connector. This "ring" is easily lost...
Last edited by VMdiesel; 08-02-2023 at 04:40 AM.
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