STD Tuning Engine why are the GPs on separate wires?

why are the GPs on separate wires?

why are the GPs on separate wires?

 
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bricktron
'77 240D

174
03-17-2017, 03:22 PM #1
i have an '85 GP relay with 5 outputs and 5 wires leading to the 5 glow plugs.

why aren't the GPs just wired in parallel on one big rail? would something bad happen if i replaced those 5 wires with one big one?


english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates




bricktron
03-17-2017, 03:22 PM #1

i have an '85 GP relay with 5 outputs and 5 wires leading to the 5 glow plugs.

why aren't the GPs just wired in parallel on one big rail? would something bad happen if i replaced those 5 wires with one big one?



english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates




03-17-2017, 04:02 PM #2
Depending on which plug fails, all following fail too... With separate wires you have only one failing and starting is still fairly easy. Up until ~'80 (IIRC), plugs were actually wired in series...

____________________________________

'88 300CD Turbo Coupé - OM603
DiseaselWeasel
03-17-2017, 04:02 PM #2

Depending on which plug fails, all following fail too... With separate wires you have only one failing and starting is still fairly easy. Up until ~'80 (IIRC), plugs were actually wired in series...


____________________________________

'88 300CD Turbo Coupé - OM603

Alec300SD
K26-2

32
03-17-2017, 04:06 PM #3
Old syle loop glowplugs were wired in series, but there is too much of a voltage drop when wired in series.
The connector wires would get very hot, and IIRC when one glowplug failed none would work.

With the 5 individual connections, you still get adedquate glow (most of the time), even with one glowplug burnt out.
This post was last modified: 03-17-2017, 04:07 PM by Alec300SD.
Alec300SD
03-17-2017, 04:06 PM #3

Old syle loop glowplugs were wired in series, but there is too much of a voltage drop when wired in series.
The connector wires would get very hot, and IIRC when one glowplug failed none would work.

With the 5 individual connections, you still get adedquate glow (most of the time), even with one glowplug burnt out.

NZScott
HX30W 73/44mm

398
03-18-2017, 03:46 PM #4
There is no reason not to wire the plugs off one connection, MB made individual wires to detect if a GP had burnt out with a clever GP relay.


Series plugs have nothing to do with an '85 car and should've stopped production 30 years ago....


1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km

1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD




NZScott
03-18-2017, 03:46 PM #4

There is no reason not to wire the plugs off one connection, MB made individual wires to detect if a GP had burnt out with a clever GP relay.


Series plugs have nothing to do with an '85 car and should've stopped production 30 years ago....



1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km

1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD




bricktron
'77 240D

174
04-09-2017, 11:52 AM #5
series is just a bad idea all around. in parallel, like NZScott said, one advantage is in independent treatment of the power lines. i'm not sure if plugs ever ever fail closed but a breaker for each would let one line go out and leave the rest working. if failing open is the only problem then the one failed plug will fall out on its own accord, unlike the series circuit.

what are the more common failure modes of GPs in fact?


english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates




bricktron
04-09-2017, 11:52 AM #5

series is just a bad idea all around. in parallel, like NZScott said, one advantage is in independent treatment of the power lines. i'm not sure if plugs ever ever fail closed but a breaker for each would let one line go out and leave the rest working. if failing open is the only problem then the one failed plug will fall out on its own accord, unlike the series circuit.

what are the more common failure modes of GPs in fact?



english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates




Fishman
GTA2056V

92
04-09-2017, 12:53 PM #6
In the GP relay they are all connected an fed by one relay. So replacing them with 1 wire would be fine.
Fishman
04-09-2017, 12:53 PM #6

In the GP relay they are all connected an fed by one relay. So replacing them with 1 wire would be fine.

bricktron
'77 240D

174
04-09-2017, 10:06 PM #7
series is just a bad idea all around. in parallel, like NZScott said, one advantage is in independent treatment of the power lines. i'm not sure if plugs ever ever fail closed but a breaker for each would let one line go out and leave the rest working. if failing open is the only problem then the one failed plug will fall out on its own accord, unlike the series circuit.

what are the more common failure modes of GPs in fact?


english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates




bricktron
04-09-2017, 10:06 PM #7

series is just a bad idea all around. in parallel, like NZScott said, one advantage is in independent treatment of the power lines. i'm not sure if plugs ever ever fail closed but a breaker for each would let one line go out and leave the rest working. if failing open is the only problem then the one failed plug will fall out on its own accord, unlike the series circuit.

what are the more common failure modes of GPs in fact?



english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates




AlanMcR
mind - blown

400
04-10-2017, 03:49 PM #8
You will need to figure out some way to balance the current to the individual GPs. That will be a challenge if you wire to one, then from there to the next one. Series solves that problem, but then a single burned out GP kills the entire string. Parallel with individual wires gets close to equal distribution, even if the wires are not exactly the same length.
AlanMcR
04-10-2017, 03:49 PM #8

You will need to figure out some way to balance the current to the individual GPs. That will be a challenge if you wire to one, then from there to the next one. Series solves that problem, but then a single burned out GP kills the entire string. Parallel with individual wires gets close to equal distribution, even if the wires are not exactly the same length.

NZScott
HX30W 73/44mm

398
04-11-2017, 01:56 AM #9
Forget series!!! Dead technology. Just put the main wire to the rear cylinder and 'daisy chain' to the rest, /thread


1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km

1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD




NZScott
04-11-2017, 01:56 AM #9

Forget series!!! Dead technology. Just put the main wire to the rear cylinder and 'daisy chain' to the rest, /thread



1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km

1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD




Fishman
GTA2056V

92
04-11-2017, 04:00 AM #10
Series is not even an optiion, since they only get a 6th of the voltage. Like NZScott says, just chain them together.
Fishman
04-11-2017, 04:00 AM #10

Series is not even an optiion, since they only get a 6th of the voltage. Like NZScott says, just chain them together.

barrote
Superturbo

1,627
04-11-2017, 07:16 AM #11
That black box has a lot more to it than it looks at first glance!!! Grab a multmetter and check voltages amps and Hz... u'll be amazed to what u'll find.
Anyway heating the gp works better with a paralel system.

FD,
Powered by tractor fuel
barrote
04-11-2017, 07:16 AM #11

That black box has a lot more to it than it looks at first glance!!! Grab a multmetter and check voltages amps and Hz... u'll be amazed to what u'll find.
Anyway heating the gp works better with a paralel system.


FD,
Powered by tractor fuel

Fishman
GTA2056V

92
04-11-2017, 07:53 AM #12
I opened the black box. All the wires are connected to 1 relay. So they all are parallel. The rest is for glow time etc.
This post was last modified: 04-11-2017, 07:53 AM by Fishman.
Fishman
04-11-2017, 07:53 AM #12

I opened the black box. All the wires are connected to 1 relay. So they all are parallel. The rest is for glow time etc.

baldur
Fast

509
04-11-2017, 09:40 AM #13
The reason they're separate is because the glow relay monitors the current to each plug for diagnostics. A handy side effect of that is you can unplug the glow harness and measure each glow plug at the harness connector without having to remove the inlet manifold.

Baldur Gislason

baldur
04-11-2017, 09:40 AM #13

The reason they're separate is because the glow relay monitors the current to each plug for diagnostics. A handy side effect of that is you can unplug the glow harness and measure each glow plug at the harness connector without having to remove the inlet manifold.


Baldur Gislason

 
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