84 Volvo glow plug light stays on ??? and is old diesel algae prone

[SRHeer]

I brought this 84 D24 out of hibernation day before yesterday and finally got it started after it had sat for like 5 years - the glow plugs apparently are not working in that when I would turn the key on the glow plug light comes on but stays on - I cycled the eng over trying to start several times - no go - I turn it on again several times and felt the glow plugs - they were not getting warm - did not have time to get meter and check for voltage as I was on the fly and now am not where Volvo is but next time I will take my infrared thermometer gun that I bought from Harbor Freight and that way with ign on I can pin point which if any plugs may not be working by pointing gun at plug - I would think that the glow plug base itself would heat up a bit if bulb was working - is this correct?

Now as far as the glow plug light staying on - if the plugs are not getting voltage could it be the glow plug relay? and if so where it is? and does anyone have the part number? - it also may be the fuse which I think I noticed was on the left fender well - but could not check without meter - so anyway next time around I just want to be prepared to get the plug system working.

I did squirt a bit of starter spray onto the air filter and it fired right over for a bit and really clattered - but once I got it running it quieted down and oil light went out - at first though while trying to start oil light would not go out - i had checked and it did have crankcase oil so - but maybe this is normal for an engine that has sat for 5 years.

It turned over no problem and started right up with oil light going out after the initial clatter and bang of first go around.

It does have some diesel fuel in tank - would it be ok to add some diesel fuel octane booster and cleaner and water absorbing additive and just run or would it really be necessary to syphon old diesel fuel out before using? I have heard of algae growing in tanks - how can one tell if it has and would it be common here in Texas for that to happen with a diesel car that has been sitting like this one?

Thanks for any info and advice!