Glow plug system question

[cdalejef]

So I'm going to swap a 4d56 into my truck but I don't have a glow plug system. Do any of you know if one from an Isuzu Pup 2.2l is similar to the Mitsubishi's? They do have a voltage drop down unit so this makes me think that they are similar.
I have access to one of these that works and hopeing that I can use it in my swap.

[cdalejef]

Here is some info that I found on the Isuzu system. I haven't found numbers for the Mitsubishi system to see if they are similar yet.


Based on the technical report http://www.sae.org/technical/papers/811271 and measurements on an 82 Luv, here’s how the glow system works. If you don’t want the details, skip to the conclusions at the bottom.

There are two separate circuits: the electronic Quick On System (QOS), and a manual circuit. The QOS controls Relay 1; the START position on the ignition switch controls the manual circuit through Relay 2. Both circuits connect the battery to the sense resistor; Relay 1 directly, and Relay 2 through the dropping resistor. The sense resistor is in series with the glow plugs. The sense resistor is 0.027 ohms, and the dropping resistor is 0.12 ohms.

The glow plug resistance is proportional to absolute temperature. At 300K (about 80 F) the four glow plugs in parallel measure .033 ohms. When the ignition switch is turned ON, QOS closes relay 1. The voltage at the glow plugs is shown in the chart below. QOS senses the temperature of the glow plugs by comparing the voltage at the glow plugs to the voltage at the sense resistor. QOS uses the ratio of voltages, rather than absolute voltage, to compensate for battery variation. When the ratio of these voltages is 5:6, indicating 1173K, (about 1650F) Relay 1 drops. Because the ignition switch is in the START position, the voltage drops from 7.5 to 5V since Relay 2 is engaged. If the switch is ON, the voltage drops to zero.

If Relay 1 is unplugged, only the manual circuit operates. This is shown as Without QOS in the graphs. With the ignition switch in the START position, Relay 2 engages, and connects the battery through the dropping resistor to the sense resistor. Because the dropping resistor is in circuit, the voltage at the glow plugs does not go above 5 V, and the glow plugs heat much slower

The temperature of the glow plugs is shown in the second graph. This graph is developed by using the voltage and current at the glow plug to determine resistance, and therefore temperature. The current is determined by measuring the voltage across the sense resistor just before and just after Relay 1 drops. Just before drop it’s 59A, just after its 38A.

Conclusions:
1. The QOS gets the glow plugs to operating temperature in 5 seconds, the manual circuit takes 15 seconds.
2. The glow plugs are rated for 5V continuous. QOS takes them briefly to 7.5V to heat faster, while monitoring temperature. Unless the temperature is monitored, use the dropping resistor to avoid burning out the glow plugs.
3. All Pup/Luv diesels include the manual circuit. If QOS fails, just hold the ignition switch in START, clutch out. After 15 seconds, push in the clutch. This manual circuit is the same one shown by Jerry and others on the forum, except it uses the ignition switch to engage.
4. The sense resistor dissipates 38 Watts, and the dropping resistor dissipates 169 Watts steady state. That means both get hot quick. It also means there is no practical substitute available from Radio Shack. You need both of these original parts to get the complete glow system working. You don’t need the sense resistor if you only use the manual circuit; however the glow voltage will be go up to 5.5V. This will shorten the glow plug life a little, probably not enough to notice.

[sassafrass]

there is a lot of support for the 4d56t in canada, at least out in BC. you should be able to find the glow circuitry from a Delica or such. i know there is at least one company that makes it own modification to the glow start-up for extreme cold. i don't believe they sell it as a kit though, only an install.

my take is the sensors on the engine would not be compatible, though the function of both systems is the same from the operators point of view.

the glow plugs on the 4d55t are .23 ohms.

best,
tom