* DPC MODULE & INJECTION PUMP CONTROLLER *

[asavage]

Just some pictures to start with.





Water DOES get inside these things which in turn washes out the wee bit of grease on the motor bushings.

Before and as ... you disassemble one of these things, pay particularly close attention to

1) the timing / alignment arrows on the gears
2) the index mark on the Geneva Gear shaft and the mark on the little crank lever
3) the little friction clip that presses against the worm gear end of the motor armature.
4) hardened grease on the contacts and plates.
5) the little friction clip that presses against the worm gear end of the motor armature.

Quick test: If you turn the key ON and then unplug the transmission connector, the DPC module will energize the IPC to rotate. The IPC will move the Fuel Control Lever from OFF to START to RUN. Plug this connector together again, the IPC will rotate from RUN to OFF position. This is the quick and dirty field test of the DPC/IPC system.

[philip]

The DPC module.

If you know this critter by name, you likely know the Digital Pump Control (DPC module) is the "brains" that signals the Injection Pump Controller (IPC) when to move to its next position. The DPC is the black box (3x4") located on the right side fender well next to the glow plug relay.



The DPC module fails due to fractured solder joints inside the box (fixable) or the contacts in the tiny relay inside are rusted or burned. It can also fail due to a severe voltage spike just like any other electronic logic circuitry.

[asavage]

The test procedure for the DPC is on this page.

[Zoltan]

Just got my truck a few weeks ago and the previous owner bypassed the start key with a glow-plug/ignition-on switch and a push-start button . Ergo the IP lever NEVER goes to the START position 1.

Is this detrimental to the IP or the engine in any ways?

Since the temp here in HI is always over 60, the truck always starts up w/o any problems.

[asavage]

The second '82 720 diesel I sold last fall has been starting fine for the last seven months without the IPC installed at all (it's on my workbench).

He just floors the accelerator when cranking -- not that I think that that does anything. He broke the fusible link that feeds the GP relay though last week. I had to go repair that yesterday.

There seem to be a few folks who have replaced the Iinjection Pump Controller mechanism with some kind of cable-and-knob arrangement that seems to get them by.

[philip]

Philip owns an '82 720 diesel, and I've owned two (the first one for a couple of months, the second one for a couple of days -- I bought it for a friend). I have FSMs for the 720 from 1980-85 I think.

Should I pat myself on the back or cry?

I've logged 41k miles in 26 months on this old "project" truck.

[asavage]

Should I pat myself on the back or cry?

Whatever comes naturally.

[ecomike]

He just floors the accelerator when cranking -- not that I think that that does
anything.

Al,

In my case flooring the accelerator does keep the engine from dying once it starts. Other wise it keeps dying, unless I stand under the hood and hold the lever in the start position.

I need to hold down the accelerator peddle partially for about 60 seconds while the engine warms up a bit. After that it runs fine with the IP lever in the run position.

The way my cable is rigged up I can put in the run and stop position only. (so far).

[asavage]

As mentioned above, there's an SD22 here that starts fine on a reasonably cool day (cold start) without placing the IP in the "Start" (excess fueling) position.

If you have trouble cold-starting an SD22, and if it comes up rough and shuddering and smoking, look hard at the glow plugs first and GP wiring second -- and air in the injection system after that. The "Start" position is to provide a little more fuel while cranking, it has no effect three seconds after you've left the "Start" position on the ignition switch. Where's that video of Philip's . . . Ah, here it is:

SD22 Controller Action.wmv

If you have to hold down the accel pedal beyond three seconds after releasing the key, it's not a DPC issue, it's something else.

That's why I typed, "Something ain't right then. I assume it comes up rough?"

If it comes up on all four and runs smoothly but dies when you let off the accel, that may be an internal IP problem, maybe the diaphragm, or just the effects of plain old COLD weather. But the "Start" IP controller lever position is not a mandatory thing to use. Desireable maybe, but not necessary in reasonable climes.

[ecomike]

Al,

Today I tried a 30 second glow plug warm up time and with out using the accelerator peddle for the first start today, with the ambient temp at about 70 F. It started and ran fine after about 2 seconds of cranking on the second try. It almost started in 2 seconds on the first crank. I probably was not allowing the glow plugs enough time to heat up all the way.

I also made one more final adjustment of the smoke set screw and it runs and starts better now. The adjustment I made was about one full turn. I have a lot more power at full throttle now (a lot closer to what it should be) and it just barely starts to smoke now (black) at full throttle, but only in first gear and only at full throttle for the first few seconds from a dead stop.

Philip was right about me needing to adjust the smoke set screw in an earlier email. This is the second, and probably final adjustment I will make to the smoke set screw setting.

The way it runs now, all I can say is "I NEVER HAD IT THIS GOOD". Runs like a champ. Finally took it out on the highway for a 40 mile round trip run last night.

Now I just need to replace the A/C compressor once the new one finally arrives. The old one is slowly leaking oil out the front seal. Then I just need to finish cleaning up the electrical wiring modifcations I started last year.

Mike

[philip]

I'm in the minority here about maintaining the OEM DPC/IPC controller setup. Granted the system seems a bit over complicated. BUT there are two very useful SAFETY measure incorporated.

1) After the engine oil pressure light goes out, IF THE ENGINE loses oil pressure sufficient to turn ON the oil pressure light for one second, the DPC/IPC system moves the fuel control lever to the STOP position.

Considering the oil pressure idiot light's low visibility and absence of an audible signal, this is a real plus.

2) Should the engine die for any reason, the DPC automatically moves the Fuel Control Lever to the OFF position. This prevents the engine from actually firing off and running in reverse rotation (ie, rolling backward in gear/clutch engaged).

[philip]

I wasn't quite sure if I should put this "story" here or User Rigs so ... here it is.

After letting the truck sit for several hours at the LA Convention Center, I started it up and headed for home. On every hard acceleration I noted a lot of black exhaust smoke. The smoke would cease as I backed out of the throttle ... and none at cruise.

When I got home the little bugger would not shut OFF. Got under the hood and noticed the Fuel Control Lever was positioned at the START position. The engine was still running so I pulled the transmission connector. No change. Reconnected and then pulled the IPC motor plug apart. No change. But when I plugged it back together, the IPC repositioned to the RUN position. Back inside, I turned the ignition key OFF. Engine shut down.

There wasn't any obvious corrosion on any pins but I cleaned all the pins anyway. We'll see if that was really the issue.

[ffdjm]

The IPC is not reliable. The IPC in my truck failed at an early date and was removed. The truck starts fine with the fuel control lever in the run position (remember, I live in the arctic). Engine stop is accomplished with a cord through the firewall to the fuel control lever.
One pull and the engine stops. Keep It Simple, Stupid.

Douglas

[philip]

The IPC is not reliable. SNIP Keep It Simple, Stupid.

Douglas

Welcome back, Doug.

This is the first glitch I've had with the IPC which hardly earns the label of "unreliable." I also prefer to retain the automatic engine shut-down in case of oil pressure loss that the DPC/IPC system affords. That little oil pressure light is dim and there is no audible alarm.

Also, having the DPC automatically moving the Fuel Control Lever to the OFF position in the event the engine dies prevents the engine from rotating in reverse of normal rotation.

[philip]

Well ... the DPC system failed completely this morning. Suspecting the mini relay inside the DPC, I disassembled the module and examined the relay points with a magnifying glass. This is the original module that I had resoldered all the board joints on 2-1/2 yrs ago ... the last time it acted up. But this time ... the points were toast. This relay handles the amperage load of the IPC motor.




Considering this unit is the original with 170k miles and 24 yrs in service, I am not complaining.

So I installed one of the "rebuilts" I have on hand. Problem solved.