The glow plugs will cycle on and off until the engine warms up a bit. If you watch the ammeter/voltmeter you'll see the charging indicating needle drop when the glow plugs energize and the engine will load up a bit. The process is often accompanied by screeching belts, if the belts are at all loose or glazed.
You haven't stated what the ambient temps are but 20-30 seconds seems a little long.
If a couple of plugs are bad the rest still get all the amperage intended for 8 plugs and the failures accelerate so, check them soon.
We throw a full set of Wellman 070s in every CUCV as a preventive measure, at the first opportunity after buying the truck. It also lets you better troubleshoot any other starting problems. Wellmans can be had from "INDUSA" on Ebay for about $65 or $70 a set. They're the best plug out there.
If the truck doesn't start the first time, do you turn the ignition all the way off and let the plugs warm up again?
Also, on the back of the sun visor are the starting directions. Above 32 degrees, depress the pedal halfway. Below 32 degrees, depress it all the way.
Long cranking times may also indicate a compression, an air filter or fuel issue. How old is the fuel filter? Have you checked the lines? Is the air filter dirty?
We normally replace all the vacuum and fuel lines, right off the bat. For about $10 and an hour it really cuts down on problems. You should be able to buy 4 filters for under $40 on Ebay. Just search "CUCV" for them and the plugs.
Remember, these are, typically, 23-26 years old. I hate being "nickled and dimed" with maintenance issues. When we buy one, we go through the whole truck in the first month or so. U joints, fluids, filters, hubs, brakes, hoses, plugs etc. Usually costs $150-200 and the peace of mind is priceless.
Lance
