Dear Guys:
At first I had a problem with the glow plugs on my B2500 too. Part of the problem is the design of the WL-31's cylinder head and its low compression ratio. The aluminum cylinder head cools better but also loses heat more quickly than a cast iron head, making for more difficult start ups.
The other problem is the relatively low compression ratio of the WL-31 engine which is only 21.6 to 1. Divided chamber diesel engines (like the turbulence chamber design of the WL-31) usually require higher compression ratios for good starting characteristics.
As a comparison on our 96 Toyota HiLux, the compression ratio is 23 to 1. No problems starting up here.
On my old Mercedes-Benz 190D the compression ratio was a low 21.5 to 1, making for very difficult starts, even with a 6MF (read - truck sized) battery.
But then I found that you can use Kitahara glow plugs as a replacement. Take out the original glow plugs (they are NGK's) and use them as a sample for size and thread.
Fordmaster along Banawe carries KHT - Kitahara glow plugs. The secret to long glow plug life is to go from the original 11.5 volt NGK's to 12 - 12.5 volt plugs with the same pattern, length and threads.
The lower voltage means that they will take a little longer to heat up (maybe 3 to 5 seconds more) but it also means they wont overheat and burn up as frequently.
If you want you can even use the one's for WLT-31 turbo diesels which are longer and so will go deeper into the turbulence chamber, but they are a little more expensive.
That shouldn't really matter as the whole set of four (4) is less than Php 1000.00 for the Kitahara's - which is about the cost of just 1 NGK glow plug.
Word of warning to the inexperienced - some unscrupulous people will try to sell you reconditioned glow plugs - they are crudely repainted and have damaged threads; so buyer beware!
To be safe stick with the better known auto supply's like FordMaster.
Hope this helps.
Best Regards,
Dusky Lim
PS : Thought I might include this for newbies.
To test a glow plug initially, use a VOM (volt-ohm meter, i.e. tester). Place the meter on the 1x to 10x OHMs scale.
Place one electrode on the plug body and the other on the supply terminal. The meter should read no higher than 5 ohms (if it reads higher the plug has too much internal resistance).
If it read infinite then the plug is open.
After performing these tests, get a battery charger and clamp the black lead (ground) to the glow plug body, and then lightly press the red lead to the plug terminal, the plug should lightly heat up. If it doesn't then its a bad glow plug.
If the seller won't allow you to perform this test, don't buy from him. A bad glow plug will burn out from the test alone.


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