HiYa REBEL59 - Agreed. The O/P did however say :

- does not want to start when its cold
- I have checked the Glow Plugs and they are all ok,
- I have also checked the Voltage to the Glow plugs on start of the car and there is no voltage at all.

IOD issues are a huge and eternal problem for Voyager [[color=#282828]functions that are 'live' when you think your car and battery are asleep] CRD lumps in the UK. As Scotsman4th says putting a 33K Ω @ 1/2 watt to 22K Ω @ 1/2 watt resistor in-line will help move the charging rate back to 'old school' numbers. 20pUK currency + 10 minutes only ..... This is particularly the case for 'lifestyle' [short infrequent journeys] drivers.

So fuel / battery / leak-back injectors. All are easy DIY eliminators, in the absence of O/P info I always go :

- LP fuel
- battery
- HP fuel

 

Also stated by the OP that NO POWER at glow plugs at start of car. Thus my responses. There are MANY conditions the OP has not stated Like type of use(important for a Diesel), and with what they are using to test and what readings are(again important),just they "click" on bench test(relays) and Glow plugs are good(how determined/ what ohms resistance?)
As I said the modern Diesels are a bit out of my league,and we don't have the Diesels in our Voyager/T&C/Caravans here. BUT I spent many years with the EARLY VW diesels here...Maintaining / repairing them as a PROFESSION.

 

The diesels are a law onto themselves mate, mines didn't always appear to be turning over any slower
Reading the OP again, not 100% on this, but mines had 4 relays under the hood I think the 4th one is the glowplug relay, grey not one of the 3 black ones.

Quick google suggests the 3 relays tested are for the cooling fan, the 4th one is for the glowplugs. Diagram I looked at said there were 2 glow plug relays, but it didn't show the second one. The diagram was for a 2.5 though. Can't recall the 2.8 being different, but after doing the battery mod virtually right away when I bought it, I had no reason to look at the glow plug side of things.

 

Agreed there with you about Diesels...They are only recently regaining "favor" here in the "Colonies"! I believe you are onto the needed path for the OP about just what relay does what...and that there HAS to be power going thru all those electrics AND reaching the glow plugs for a "cold" diesel to want to fire up!
By no means was I trying to "pick a another revolutionary war" here with you (member here) LOYAL SUBJECTS!

 

Well, I realize that nobody is required to respond to a forum, BUT on the other sites I spend more of my time on than here, people who post asking for help with a problem usually as a matter of good manners respond when assistance is offered!
I've noted that the OP of this thread has "checked in" at least 2x(reading this thread) after all has been posted, and has yet to respond! You other Diesel owning members can do what you feel,but I am leaving this situation and looking to be of help to others elsewhere!

 

Yep, has been happening a lot recently. Long time members suggest stuff, and the OP's never reply.
To be fair, between our back and forths, and original suggestions, they've probably found a solution and don't care to give feedback on the issue. The feedback would help other forum users in the future.