Mk 1 diesel glow plug voltage.

[dalderton]

I have had a bit of trouble starting the Mighty diesel (we have regular below 0C. temperatures here and I run Veg Oil) and I found that I had a dead glow plug.I replaced that and then checked the voltage at the glow plug bus bar and found that it was getting around 9V. I then connected the battery direct to the bus bar and the same voltage was showing. This seems a bit odd but resistors in series or parrallel and all that ohms law stuff may be the answer. In my declining years my limited knowledge stops me from going further with this.
Is there anyone out there who can tell me if what I have is normal or not? Any input would be appreciated. Also I have to heat mine on a cold morning for over a minute to get it to start.is this normal
Regards Dennis Alderton

[gldgti]

the voltage you measure at the bus bar is with the glow plugs drawing current, and so shows lower.

in order to test the voltage getting to the glow plus, you need to disconnect the supply wire from the bus bar and check it with no load connected. the glow plugs draw LOTS of current and the subsequent voltage drop is usually very apparrent - that is what your measuring now

[dalderton]

It seems a lot of voltage drop but I guess that they factor that into the design of the Glowplugs,they must be designed to operate at the reduced voltage.It was notable when testing them that they got hot quickly when tested one at a time..On the other thing how long would you have to operate the glow plugs on your GLD to start on a 1-5 C morning?
Thanks for the info. Regards Dennis

[gldgti]

with original wiring, and all plugs working, it'll glow for about 20seconds.

to really check the plugs, pull them out and use a jumper lead to earth one out straight onto your battery. if it doesnt glow red hot in a couple of seconds, it probably shagged.

the proper way to check them is to measure their resistnace. should be in the ballpark of 4-6 ohms. no more.

also, i agree that your 9V reading is low. maybe your battery has dropped a cell? could happen after many hard starts (much cranking).


*** also, make sure your timing is OK. better to be a timy bit advanced for cold starts thn too retarded. and, good battery straps to the starter and engine/box will help with cranking speed a lot. the old standard earth strap from body to gearbox is often very bad.

[dalderton]

Yes I did the direct test and discarded one that was a very slow.I have new ones in my spare engine and robbed one of them. The battery is good and I have an extra earth wire as well as that little woven thing so it should be OK.After I put the new plug in it started pretty well but I did not use it today so I have not started it in the marginal condition.
Thanks again for the info. Regards Dennis