I recently fried my second ECM. It died in the same way as the last one. Stumbled will cruising around town and then died completely. It felt like the lift pump failed but the VP44 kept trying for a bit and then it stopped too. After getting it towed home I could get both the Fass lift pump and the injection pump to run (and the truck to idle) by bypassing the ecm but got no voltage signals from ecm to either lift pump or injection pump when trying to start the truck with e dry thing wired normally.

 

After reading the article here by IBM mobile about proper lift pump wiring, I believe the ecm failed because the relay that was used in the lift pump wiring didn’t have a diode which allowed the relay coil to back feed to the ecm and fry the lift pump circuit in the ecm. I believe I’m in the same boat as another thread’s poster as my instructions from Fass had me using the ecm lift pump feed as the trigger for the relay, but now Fass recommends using an ignition switched trigger instead. I will probably not use the ecm to trigger the lift pump with the next ecm (even with a diode relay) as I just don’t want to take the chance.
 

I want to really be as sure as can that this is really the cause because if I fry another ecm, I’ll probably drive the truck off a cliff. I have done the W-T mod and am in the process of upgrading all my battery cables and grounds, though they weren’t in that bad of shape. I have ohm tested the ecm’s power leads and grounds as well as the injectin pump’s ecm power and ground wires. All wire runs read less than 0.5 ohms. Anyone have any more suggestions to check?

 

Also, while testing the vp44 connector’s wires back to the ecm and pdc, I noticed that my truck is missing one vp44 connector pin that goes to ecm pin 44. I am using the wiring diagram from here that is I believe either for a 1999 or 2000. My truck is a 1998. A pin out that I have describes the pin as “datalink shield injector pump”. Anyone know what this wire/pin is for? It doesn’t look like my truck ever had this pin as there are no extra wires in the harness. Thanks for any help anyone can give me.

Edited December 20, 20195 yr by the7t7

ACS said they are working on my old ecm now and they should have some info for me in the next day or so. I sent my vp44 to Oregon fuel injection since they are fairly close and they are testing it.
 

The 99 wiring harness arrived and I only had time to give it a quick look. An obvious difference is that my PDC connection is different or the 99 has 2 connectors before the PDC connector. My connector is the first pic.  The 99 has the 2 connectors in 2nd and 3rd pics. Does anyone know if this is normal i.e. is the harness I was sent actually a 99. The rest looks normal. Another difference is that I have 25 wires going into my pdc and the 99 has only 20. my extra wires mostly seem to be grounds. I’ll give it a more detailed look tomorrow. I haven’t forgotten about posting pics of my harness mods. I’ve just been waiting on the 99 harness to compare it to and doing other work on the truck.

So I’ve never been so happy to find out something’s broke and going to cost $1500-2000. Got news back from Oregon Injection that the psg in my pump has a bad chip. It passes the flow tests and code tests but didn’t pass the psg test. So it worked but could easily be the issue that’s making my ecm’s fail. So I need a new injection pump. 
 

Since I have compounds and 200hp injectors they suggested their hot rod pump. It flows much better and has a new psg. My concern is they do have a warning on their site that says “Note: may cause minor surging or rough run at light load up to 1500 RPM if using performance injectors (above +40).” Any one have any thoughts on this or experience with a hot rod pump, injectors and quad running issues? I still want it to be daily drivable. I need to decide tomorrow. Price is reasonable compared to Bluechips performance pumps. Or should I just get a standard rebuild.

Go with a standard pump. You have a Quad. No need for a hot rod pump. I believe most here would agree.

I see OFI is on the certified rebuilders list. If all that's bad is the PSG why not have them put a new one on, recalibrate, and send it back? Did they even offer that? Should be a cheaper alternative.

2 hours ago, dave110 said:

If all that's bad is the PSG why not have them put a new one on, recalibrate, and send it back? Did they even offer that?

Yes they did. However, it’s around half the price without any warranty, which would be nice to have.  I think I agree about the standard pump. I’ve already got a decent tune for my injectors, I don’t really need more fuel.

Auto Computer Specialists finally got back to me about their diagnosis of my old ecm; which was that they couldn’t diagnose it. They said they couldn’t establish communication with the unit and therefore couldn’t help. And for that, I had to pay $150. I’m definitely annoyed at that answer. Last time they gave me a photo of the damaged area on the board. They could have done that this time, compared it to my old one, and let me know what that could mean. They could also have told me  what operations any damaged area of the board dealt with. How do I know they even really did anything? 
 

Anyway, since I have a good candidate for the failed ecm in the bad chip in my vp44’s psg, I’m going to wind this thread down. I know I was going to post pics of my harness mods but I thought I would make a new post about that related to electrical and harness restoration and maybe show some differences between the 99 harness and my 98.5. I also came across an interesting alternator alternative when I took mine in to gets tested. I can post more details in the new thread but basically a local company in Redmond Oregon (Hagemeister Enterprise’s, INC) builds a 1 wire upgraded Bosch unit for these trucks that takes the PCM out of the equation. This keeps the pcm from possibly getting damaged by the alternator or one on the batteries getting overcharged. I know about Mopar1973man’s article dealing with protecting the pcm with a fuse on the blue wire. This alternator is an different approach. You put a resistor between the blue and green wires and don’t connect them to the alternator to fool the pcm into thinking it’s there. The Bosch unit is then regulated on board. You get a bump in amps to 135 and a better base unit than a rebuild (which is what I had). The pcm does a good job regulating voltage in general. I talked to another electronics guy here in bend and he said that he’s seen a guy come in with 18 year old dodge factory batteries that finally needed replacing. I’m just wary of the increasing cost of pcms a and ecms and that if they go down, your truck is down.