Timing Terminal Connector(s)

[SA22C]

Hi fellas... Got a question that I hope will result in a quick and straightforward answer.

I have a Haynes manual for my 95 Max. In an effort to sort out the pinging issue in this brutal heat, I set out to check and set my timing.

I drove the truck into the workshop (hot after a drive home from work) and got the manual out to read while it cooled down a bit. As per the Haynes instructions I removed the cap from the timing terminal and grounded it with a jumper. I go to start the truck and it refuses to even attempt to start.... I disconnect the timing jumper and try to start... Nothing.

I jump on here to look for a possible hint at what the heck is going on and discover that the Haynes manual shows the wrong terminal to use for base timing. Instead of jumping the brown (round) connector I jumped the white connector it's bundled with.

Now I'm in panic mode... I checked all fuses and fusible links and they are all fine. What the hell did I mess up by grounding that mystery wire?

[geezer101]

I have a feeling you may have baked the ECM. The only way to start deciphering this by trying to get error codes out of it. A cooked ECM is bad but at least it's a straight forward unplug-and-replace deal.

[SA22C]

I was hoping that it would fry the relay before the ecm. There's a thread where a guy experienced the exact same issue but never updated his thread... I hate when people do that.

[SA22C]

So... After a day of messing with this thing I'm even more confused. I took the ecm out and apart and looked for any blown capacitors or resistors. Looks fine. Take out the mpi relay, trace the schematics to determine how the relay actuates. I apply ground and power to the relay and it actuates fine. I put everything back together and try to start... Nothing. I run a 12v supply to the fuel pump test connector and try to start... Starts and runs fine. It dies the instant I pull the jumper wire out of the test terminal. Any ideas?

[geezer101]

Ground and power doesn't necessarily mean the bridging contact inside of it isn't roasted. You need to run the power + ground, then do a resistance check on the other terminals to see if it's making a closed circuit. From your diagnostic test so far, it's looking more like the relay took the hit (not so bad). Fingers crossed this is issue. Wasn't your fault, Haynes manual got you in trouble...

[SA22C]

I did a resistance test with the relay actuates and not. With power and ground applied there is zero resistance between the fuel pump contacts (by and bl). I'm hoping, as you said, the relay took the hit. I'm gonna run to u pull it and get a relay and an ECM. The parts truck is a 92 and the relays are the same... I hope it's the relay, and if not, I hope I can get the ecm working.

[85Ram50]

Haynes and Chilton have their uses, but Factory Service Manual is best and MightyRam50 beats them all

[claych]

sa22c
Update???

[SA22C]

I swapped ECM's with one from a 92. I re-pinned the connector and I am experiencing the exact same symptoms. This along with the resistance test performed on the relay leads me to believe the relay is bad. A new one arrives via the mail on Thursday. Ill update as soon as I get done.

[SA22C]

Also scored a set of service manuals for the Ram50. $15.... Couldn't resist. Has both the engine/body and seperate electrical book. More information and more accurate than any one person could need.

[claych]

Thx for the update sa22c !

[SA22C]

So... After I got the new Mitsubishi produced service manual and some time I did more digging because the relay I ordered got lost in the mail...

There is a procedure outlined in the service manual that step-by-step tells you how to test the mpi relay and what resistance values to look for. After performing the test(s) I discovered that the relay was fine. I then tested the ecm and it was also fine. I began tracing wires from the relay back... One by one... It led me to the fuse block by the battery. I had already checked all those fuses and they were fine, but just to be double certain, I pulled them out individually. Much to my surprise, the 20a fuse was broken at the insulator... I couldn't believe it.

So, after an ECM swap and a few (ok more like 20) hours chasing my tail and reading wiring schematics it turned out to be a damn fuse.

Anyone want to buy a perfectly good ECM for a 92?!

[geezer101]

^a word of advice - keep it. If you ECM ever kicks off, you will have a plan B that will take all of 10 minutes to swap into your truck. On the bright side, your truck is up and fighting again so that is a good thing

[SA22C]

My truck seemed to idle a little strange with the 92 ECM. It idles fine until you would drive any distance. After moving and then returning to idle, the rpm's would dip really low and then return to normal.

[geezer101]

^Hmm. Was the ECM for a manual or auto truck? It might be searching for an A/T input signal

[SA22C]

It was out of a 5 speed...