The elusive 1987 D21 North American Manual

[subwar2001]

Here is my question, does anyone have the manual for the D21, with the SD25. I have the engine manual but not the rest of the truck, especially the glow plug circuit.

[asavage]

I recently acquired (paid a small fortune for!) the 1987 D21 Truck/Pathfinder manual, and it does cover the SD25. There are nine pages of glow control information (EL-47 thru EL-55).

The glow plug control circuit is very, very simple. It does main glow and afterglow, so two relays. If you use the diagram Philip posted of the Type II system in this post, it's identical except for two add'l wires to the Glow Plug Controller ("GPC"):

• A wire runs from the alternator's L terminal to the GPC (presumably, to let it know when the engine is up to speed, when the alternator goes online);
• A wire (with an inline fuse) from the GP bus bar or wire on the head, back to the GPC (presumably so it can know how much voltage is present and for how long, at the bus).

These add'l wires make the later 1986/7 (?) SD25 GPC system very much like the GPC system on all the '81-3 Maximas/LD28s.

If you must have exact wiring info and wire colors and plug pinouts, let me know and I'll try to make time this week to scan those pages and put them online. Meanwhile, start with the basics: put a 12v test lamp on the GP bus and put the lamp where you can see it before and while you are cranking, and see if you are actually getting pre-glow of sufficient voltage.

Experience has shown (on the Maxima and 720 diesels) that the fusible link to the GP Relay 1 is the first suspect, followed by any spade terminal connector on the heavy wiring.

HTH

[subwar2001]

The funny part is that a previous owner bypassed the controller with a switch running from the battery to the cab and then to the relays, so the switch takes place of the controller. I'm just looking for obvious faults or not so obvious faults so that I can use the proper circuitry again. By the way, where did you find the manual?

[asavage]

By the way, where did you find the manual?

Where else? eBay. First one I ran across in three years of looking. I believe I paid north of $80 for it.

[plenzen]

Just FYI for another D21 SD25 owner I did a voltage test this morning.
Ambient Temp was 12 C
Battery voltage (X's2) was 12.8
I turned on the key and voltage to the GP's was 10.3. The dash light went out after 5 Seconds and the voltage dropped to 4.7 after an additional 5 seconds (10 Sec. total @10.3 V)
I then started the truck and the voltage stayed at 4.7 (after glow) for 40 seconds. It moved between 3.7 and 4.7 but I suspect that was the regulator in the alternator doing its thing because when I shut it off and cycled it again it stayed at 4.7 for 40 seconds. The entire glow sequence lasted 50 seconds.
This changes with ambient temps as well as when there is heat in the engine. The "Quick Glow" will always come on for 10 Sec. but the "After Glow" will not. I believe that it is controlled by one sensor in the thermostat housing and another temp sensor in the intake manifold. The quick glow I think is always 10 seconds even when it is really cold. I have Delphi glow plugs in the engine as well and they are of a little different design than the NGK's. The tips are shaped like a sharpened crayon for lack of a better description. They seemed to have helped considerably with the starting as well as the air heater that I installed.

Hope this is of some assistance.

P