Is it my ECU?

[paradoxbomb]

First post here, hi everyone!

Got myself a 1983 Dodge Power Ram 50 that, mostly, runs great (1989 crated 4D55T w/25k miles). It's got a few problems, and I think they all point to the ECU, but I wanted to get a second opinion before sending mine off for a $200 rebuild. Here are the symptoms:


Gauges: My fuel, tach, and temperature gauges work intermittently. They most often work after the truck warms up, is shut off, and then restarted a short while later.
Diesel indicator panel: the glow plug indicator shows they're ready after 1 second, and the fuel filter indicator is always on, even though I just had the fuel filter replaced.
Clicking: Very occasionally, I'll hear some solenoid somewhere click on and off rapidly, like it should do only once when you turn the ignition on


There was some good advice on one of the archived threads that the ECUs in these trucks all go bad at some point (http://www.mightyram50.net/phpbb3/viewtopic.php?f=81&t=1780).

So, is it my ECU? And is this still the best place to send for a rebuild? http://www.foreignecurepair.com/ECMs_ECUs_mightymax.htm

Thanks for the help in advance.

[4doorciv]

Welcome to the board. First things first, I don't know about the tach because I'm not much informed on the diesel engines, but I know the fuel level sensor isn't controlled my the ecu. I would more look into wiring faults like burnt wires or damaged and corroded ones. Have you removed the gauge cluster and seen the condition of the wires? Usually multiple problems could usually mean that there is a common problem and since your problems as I understand is related to the whole cluster.

[paradoxbomb]

Hmm. Sounds like I may need to have a look at a wiring diagram. I haven't removed the gauge cluster (that I know of--not entirely sure where that is), but I have inspected and cleaned as many connectors as I could get my hands on without disassembling my dashboard. It had no effect, and most of the connectors were actually in decent shape.

There definitely is a common problem, since malfunctions don't happen to just one gauge at a time.

[4D55 Performance]

The diesel engines have nothing in common with the gas engines other than they are both built by Mitsubishi. The problems with the guages working intermittently sounds like you have a loose connection. I recommend you pull the cluster and go from there. Because you have a 1983 wiring harness glow controller etc. and a newer model engine it is very difficult to know what you have going on. The 1983 pickups had a different glow controller and glow control indicator light than the later model trucks. The 1984-85 model year trucks did not have a glow plug light because the plugs only needed about 1 second to preheat. The 1983 truck had a glow light and would take around 3-5 seconds to preheat. While all model years use super quick glow plugs the 1983 glow controller is a 10 volt system while the 1984-85 pickups use a 12 volt system with a dropping resistor. Without looking at the hack job personally, it is hard to say what is causing your issues. My guess is the engine is starting properly but the glow indicator display is not functioning properly due to the fact you've combined a 1983 10 volt electronics with a later model 12 volt glow setup.

[CRIChouse]

What's from the 89 engine? If you used the glowplugs and electronics off the '83, then it doesn't matter; we're dealing with an 83 for all electrical purposes.

The ECU is just a glowplug controller. It does not affect the gauges. The tach gets a signal from some pickup, at the injection pump IIRC. The fuel and temp gauges get a 12V signal from the ignition, that goes through a 7V voltage limiter, and the respective sending units are resistors that vary the amount of current passing through the gauges.

The glowplug controller has nothing to do with the fuel filter sensors (water and heater). Look into a bad sensor or bad contact at the filter.

The fuse that says "Tail/backup lights" also powers the glow plug controller and the entire gauge cluster. If it works intermittently, you have a bad contact somewhere. The gauge cluster has one big round black connector powering everything except the gauge lights and the highbeam indicator.

[mikewarme]

OK STOP! the 83 truck has it's own glowplugs. If the 89 engine still has its original plugs than they r wrong. They look similar but the resistance is diffrent making the controller not want to respond correctly. Tach problems have zero to do with computer as temp guage also. As far as fuel indicator...... there is a float switch attached to bottom of the filter which is most likley bad. THE FUEL SENSOR DOES go through the controller as the controller operates the diesel indicator.

CRIC is right you need to have 83 plugs for it to work correctly. The books are all wrong BTW at all of the parts stores. I have an 83 truck and I sourced a new controller from Japan for a 84 truck which is plug and play compatible with the exception of the plugs which I changed as well. This made my truck a Ultra quick glow system. The 83 controller is no longer available. If yours got water in it which many do "The windshields leak in the corner!" ,than forget it they won't fix it.

Mike Warme 818 268 3012

[paradoxbomb]

Wow, thanks for all the insight!

The truck isn't my own build so I don't know the details of how exactly the engine is set up. I do know that it takes about 7 seconds for the glow plugs to warm up, so it probably has '83 electronics.

I'll check the part numbers on the glow plugs to make sure they're the right ones for the ECU, then pull the cluster and spend some quality time with a wiring diagram and a volt meter :)

[mikewarme]

even the 83 year only needs 3 seconds. My guess is they r on there way out

[paradoxbomb]

Damn :(

Slight aside here, but what do you think the best manual and wiring diagram for the truck are?

[DroppedMitsu]

OEM factory service manual. Look for some on ebay is your best bet

[paradoxbomb]

Follow up: It turned out to be a short. The truck dumped me at a 7-11. Turn the key and absolutely nothing would happen. My mechanic was happy to get it "nice and broken" (his words), and fixed the short in about 20 minutes. All the gauges are now working properly and consistently, and the truck starts faster when cold too.

Thanks for all the advice!

[4D55 Performance]

Follow up: It turned out to be a short. The truck dumped me at a 7-11. Turn the key and absolutely nothing would happen. My mechanic was happy to get it "nice and broken" (his words), and fixed the short in about 20 minutes. All the gauges are now working properly and consistently, and the truck starts faster when cold too.

Thanks for all the advice!


I know Mike knows more than me, but every once in a while I get lucky. I don't want to say I told you so, but I can't resist. "I told you it was a loose connection":))