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Fuel injection double relays

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ancientbugger Custom Title Time!

1,986 posts · joined Mar 2004 ·

#999150
Does anyone here have a clue why the double relays on my 79 cabriolet only seem to last for about 2 years? when they do stop working it seems to happen when the car hasn't been used for a while, I'm talking maybe for a week or two. It's very frustrating as when it's running it goes like a dream then a week or so later it's not starting at all. All fuses are intact just no power comes from the relay (redblue wire) to the pump whereas I get power from the starter (redblack) to the relay. This is probably the 5th relay in about 12 years and each one so far has to come from the US, very frustrating. Btw the power from the relay to the pump was checked at the relay so wire breakage is not the problem.

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 ·

#999166
Depends how the relay is made. I'd think it'd be a single solenoid with dual contacts.

Crack it open and have a look see inside. It could be that the starter and fuel pump are on a common rail and the starter contact is stopping the pump contact making contactcos it's bent.

Just an idea but looking inside will give a better idea as to why they fail.
madness is in the eye of the beholder 👍

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999224
psimitar wrote:Depends how the relay is made. I'd think it'd be a single solenoid with dual contacts.
No it's a double relay. 2 coils
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

vduboy Insano Dub Head

702 posts · joined Oct 2012 ·

#999227
Are they just a pair of normal relays in the one box? Narva does something similar if so, are you getting new relays each time or second handies?
It will all be OK in the end, if it's not OK it's not the end!

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 ·

#999272
AA003 wrote:
psimitar wrote:Depends how the relay is made. I'd think it'd be a single solenoid with dual contacts.
No it's a double relay. 2 coils
So not an SPDT then but a DPDT? If it has seperate actuating inputs then defo a DPDT relay and hence a coil has failed or the contact has burnt out.
madness is in the eye of the beholder 👍

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999280
psimitar wrote:
AA003 wrote:
psimitar wrote:Depends how the relay is made. I'd think it'd be a single solenoid with dual contacts.
No it's a double relay. 2 coils
So not an SPDT then but a DPDT? If it has seperate actuating inputs then defo a DPDT relay and hence a coil has failed or the contact has burnt out.
Neither, it's a double relay. 2 coils
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

ancientbugger Custom Title Time!

1,986 posts · joined Mar 2004 ·

#999291
Each time I buy a new one as to what the rest of you are talking about 😵‍💫

vduboy Insano Dub Head

702 posts · joined Oct 2012 ·

#999305
What is the relay running? Just a pump? Some of the old beemer fuel pumps can draw quite a few amps, might be worthwhile seeing if your not coming close to the rating of the relay, although I doubt it, have you got a wiring diagram to see if you can wire up a couple of conventional relays? At least they will be cheap and easy to get..
It will all be OK in the end, if it's not OK it's not the end!

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999308
Do you have any old ones that can be rebuilt? We have the technology, we can rebuild them.
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 ·

#999324
AA003 wrote:
psimitar wrote:
AA003 wrote:
psimitar wrote:Depends how the relay is made. I'd think it'd be a single solenoid with dual contacts.
No it's a double relay. 2 coils
So not an SPDT then but a DPDT? If it has seperate actuating inputs then defo a DPDT relay and hence a coil has failed or the contact has burnt out.
Neither, it's a double relay. 2 coils
That'll be a DPDT then.
madness is in the eye of the beholder 👍

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 ·

#999326
Following the diagram for J40 within the diagram then you possibly could use 2 normal relays in place of the dual relay.

Just looks like there's a resistor on the fuel pump solenoid and possibly a diode but opening a dead dual relay would confirm this.
madness is in the eye of the beholder 👍

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999328
psimitar wrote:That'll be a DPDT then.
No, DPDT has 1 coil and 6 contacts. (2NO 2NC 2Common)
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 ·

#999335
AA003 wrote:
psimitar wrote:That'll be a DPDT then.
No, DPDT has 1 coil and 6 contacts. (2NO 2NC 2Common)
DP means dual pole so 2 solenoids and DT is dual throw so 2 contacts either NC or NO. Being an electrical engineer means I've been making switchboards wrong for a fairly long time now 😂
madness is in the eye of the beholder 👍

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999353
psimitar wrote:
AA003 wrote:
psimitar wrote:That'll be a DPDT then.
No, DPDT has 1 coil and 6 contacts. (2NO 2NC 2Common)
DP means dual pole so 2 solenoids and DT is dual throw so 2 contacts either NC or NO. Being an electrical engineer means I've been making switchboards wrong for a fairly long time now 😂

What a load of shit!

DP = switches + & - at the same time.
DT = switches between NO & NC.



http://www.learningaboutelectronics.com/Articles/DPDT-relay-wiring-diagram


I was a rocket scientist for NASA. They even named a spacecraft after me.

Spacecraft: Lander
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

ancientbugger Custom Title Time!

1,986 posts · joined Mar 2004 ·

#999372
And there's me thinking DP stood for double penetration!

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matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#999375
I'm with spaceman on this one, and I'm only an electrical fitter mechanic/electrical technician/automotive technician.......
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999379
matberry wrote:and I'm only an electrical fitter mechanic/electrical technician/automotive technician.......
I did that once. But that was before I was a pilot on Air Force One.
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

Phil74Camper Head in the Clouds

2,703 posts · joined Aug 2002 ·

#999395
If you can fix the M-set Millennium trains then you can fly Air Force One!

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 ·

#999396
No it wasn't the real Air Force One. Now that would be BS. It was just the one in the movie. However I did get an Oscar nomination for it.
I read it on samba, so it must be correct.

Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!😂

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 ·

#999423
AA003 wrote:
psimitar wrote:
AA003 wrote:
psimitar wrote:That'll be a DPDT then.
No, DPDT has 1 coil and 6 contacts. (2NO 2NC 2Common)
DP means dual pole so 2 solenoids and DT is dual throw so 2 contacts either NC or NO. Being an electrical engineer means I've been making switchboards wrong for a fairly long time now 😂

What a load of shit!

DP = switches + & - at the same time.
DT = switches between NO & NC.



http://www.learningaboutelectronics.com/Articles/DPDT-relay-wiring-diagram


I was a rocket scientist for NASA. They even named a spacecraft after me.

Spacecraft: Lander
Well bugger me. Things musta changed since I was in the trade then as DP always meant a dual magnetic source. ie 2 poles just the same as motors are designated. Single pole, dual pole etc.
DPDT makes no sense as it's just a SPDT with a pair of DTs but if that's how the industry wishes to label things then who am I to say otherwise. 🤪

Really it should be DTDC for dual throw dual contact. That makes more sense. 🙂
madness is in the eye of the beholder 👍