Fried ECM from lift pump wiring? Also ECM pin 44?

[the7t7]

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, 2019 by the7t7

[Dieselfuture]

13 hours ago, the7t7 said:

Fass recommends using an ignition switched trigger instead.

Weird, many have used ECM as a trigger for a relay for a long time even before protective relay. Many have gotten away with running directly of the ECM itself. 

Who are you getting your ecms from. 

[dripley]

Almost 9 years on my AD with a standard relay with ecm trigger. Might be time to look elsewhere. What is your ac voltage off the alternator? WT's mod will lower the stray voltage but if it is excessive it cant get rid  of it all.

[the7t7]

1 hour ago, Dieselfuture said:

Who are you getting your ecms from. 

ACS as most here suggest

 

1 hour ago, dripley said:

What is your ac voltage off the alternator?

Can’t check at the moment but when I checked before I did the mod, it wasn’t too bad, I think around 20 mV. Testing my alternator is on the list.

 

Does anyone know the answers to the last part of my post? Why my 98 doesn’t have a vp44 connector going to ecm pin 44 and what that pin does? It’s labeled as “datalink shield injector pump” Could this be an issue?

Edited December 20, 2019 by the7t7
Spelling

[Dieselfuture]

2 minutes ago, the7t7 said:

ACS as most here suggest

What do they have to say on your issue?

 

3 minutes ago, the7t7 said:

Why my 98 doesn’t have a vp44 connector going to ecm pin 44 and what that pin does?

I'm not a wiring guru, but if that's the pin to do a hot wire test on it would think it should be used to make vp run when ecm commands it. Can that pin be pushed in too far in the plug? Has anyone else worked on the truck or it just quit running one day. 98 meaning 98.5?

[the7t7]

1 hour ago, Dieselfuture said:

What do they have to say on your issue?

2nd ecm was just exchanged for a remanufactured one, so no diagnosis. But first one can back with this explanation....
Our findings:

 ECM(engine control module).. unit was DOA (dead on arrival), based on recovery file from cummin they units communication was taken out by altering of our factory programming & low voltage from trying to program.. upon recovery data info was corrupt unit unable to save.

Prior to installing repaired unit:

a problem still lies in vehicle (it keeps taking out the injectors ). Battery & terminal must be changed.......
 

When the first one happened I was running a Smarty with command module and custom tunes. Now I’m running a Quadzilla. However they both failed within about 500 miles of each other. I was having trouble communicating  completely with the smarty and couldn’t figure that out (after a bunch of posts here too). So I switched to the Quad and did the W-T mod, check all the wires between ecm, pcm, and obdII and thought that would solve the problem. I didn’t check vp44 and lift pump wires then but have now and everything seem good. 

1 hour ago, Dieselfuture said:

Can that pin be pushed in too far in the plug? Has anyone else worked on the truck or it just quit running one day. 98 meaning 98.5?

 Actually just looking at 99 wiring diagram shows pin 44 going to vp44 connector as a non numbered 9th connection. I have the normal 7 pins in the 8 pin plug.  98.5 and it seemed to struggle and stumble (probably lift pump first) driving around in town and then died completely (then no vp44). My testing after both ecm failures revealed working pumps but no communication with ecm.

Further looking at diagrams shows that the "datalink shield" is something that goes around the yellow/pnk datalink ecm wire going to the vp44 and comes from the ecm at pin 44 and attaches at S170. My 1998 factory manual doesn't show a splice 170. I'm going to check the ecm plug to see if I have a line coming out of pin 44 (should have done this before) and if there check further down the vp44 harness to see if I can find the splice.

.....Well I have the datalink shield and its a thick casing around the datalink wire shortly after exiting the vp 44 plug. It disappears down into the large wiring harness. I don't think that's my problem then unless its not functioning but I wouldn't know how to test that.

Edited December 20, 2019 by the7t7
Clarification, wire color,

[IBMobile]

Data link shielding is usually a braded cable around a wire or wire bundle.  It is uses to keep stray electromagnetic from interfering with a low voltage signal.  it acts like a Faraday cage.  Sometimes the specs call for the ends to be grounded.  

[the7t7]

This is where on the ECM it failed on the first failure. Don't have the report back on this last one yet. Anyone know what the circled parts relate to on the ecm?

[the7t7]

I’ve checked all the wires to and from the ecm, vp44 connector, pdc, and lift pump. Everything checks out with less than 0.4 ohms. I’ve also checked the fuel pump relay in the pdc and it shows 73 ohms across the trigger connections (85 and 86) which is the same as all of the other relays in the pdc. The only thing I can think of is that the vp44 shorts intermittently somehow over the data, bus or power leads and eventually kills the ecm all while not throwing a code.  BTW after first ecm failed, I thought problem was fixed and put it on the Dyno. DPS compound kit and my Quadzilla tune put up 620hp and 1250 ftlbs. So vp44 could supply the fuel, however ecm failed again after about 100 miles.

 

So I’m not really confident that replacing vp44 will solve problem and not really willing to chance $999 ecm on a guess. Would Blue Chip Diesel or Oregon Fuel Injection (current pump) be able to tell me if I sent in my vp44?.

 

 

[gipperkid]

So I'm guessing ACS blamed the failed repaired ECM on a still existing problem on your truck?

[the7t7]

1 hour ago, gipperkid said:

So I'm guessing ACS blamed the failed repaired ECM on a still existing problem on your truck?

Yes, but it probably is something with the truck since I’ve had 2 fail in a similar way with different tuners and before and after w-t mod.

 

I have tested every wire I can get at reasonably easy short of pulling the harness and taking apart the pdc. Only thing I can think of is that I am getting a short that happens under driving conditions that doesn’t show up in static testing or that something is failing intermittently in the psg on the vp44 itself.

[the7t7]

I may have found something while checking b+ line through 20 amp fuse in pdc. While figuring out which blade of the fuse was the b+ side I noticed I had some very high (fluctuating million ohms) resistance between b+ and the open side blade. I let the tester sit there and it gradually decreased and eventually settled on 30k ohms. there shouldn’t be connection between power b+ side of pdc  and the fused side right? This suggests to me that I have a short somewhere in the pdc wiring. I pulled every fuse and relay from the pdc and watched the meter thinking this might help me narrow down where the short was but it held pretty steady at 30k ohms. So unless someone tells me this is normal then looks like I have to pull the pdc and check it.

[JAG1]

Fuses that service each circuit should be fully connected thru the fuse as long as the fuse (fuse designed to disconnect only in the event of a short) is not burnt. Sounds also like a bad connection/ corrosion possible. However, I may not be understanding your findings/ explanation correctly either.

 

What I'm trying to say is the fuse should read the same voltage either side of the fuse that is designated for that circuit. Provided it is good clean connection surfaces, it should also be close to the same ohms on both sides with the circuit shut off for OHM testing.

 

Also check the important ground down low on the fender in front of the drivers battery. It is for the PDC. That ground was done poorly with a poor location subject to rust and corrosion. If you cannot see it, as in my case on my 01 and 02 trucks, move that wire harness just enough and you will find it there.

[the7t7]

1 hour ago, JAG1 said:

I may not be understanding your findings/ explanation correctly either.

Batteries were disconnected. I put one lead of the tester (set on resistance) on the plate after the 140amp fuse (where power enters the pdc) and the other on the fused side of the fuse no 3 (fuel pump) without the fuse in it. So it should have been an open circuit. Somehow some small amount of current was getting through the wiring downstream of that fuse back to the b+ side of the pdc. Downstream of that fuse is everything connected in joint number 2 (white bar) in the pdc including fuel relay and a bunch of other relays I think.

 

I did manage to pull apart the pdc and didn’t see any corrosion or melted plastic. I did notice that not all the connections in joint no2 had continuity. There are 3 solid green wires (one of which goes to the wiper motor relay pin 87a) that had continuity for a second and then went to fluctuating resistance in the kohms range. That’s as far as I’ve gotten today. I have a feeling I’m not getting something simple related to resistor relay wiring. But I’ll keep looking, specifically at everything that goes through joint unless someone tells me different.

[the7t7]

 

On 12/21/2019 at 3:44 PM, JAG1 said:

Also check the important ground down low on the fender in front of the drivers battery. It is for the PDC.

A bit of an update. I was saving the pdc grounds for later since I have to pull the battery box to really get to them easily and whenever I checked other grounds they were always good. All the ground wires from Joint connector 1 to the PDC ground under battery came in at around 4 ohms so those aren’t very good. Not sure if that’s enough to fry an ECM. There was also a ground from Joint 1 to just beside the Antilock brakes controller that wasn’t hooked up. Since a bunch of circuits share the pdc ground, I’ll have to delve deeper into those

 

Also spoke to Doug at Bluechip Diesel. He  hasn’t heard of a VP44 frying an ecm because of bad PSG connections without throwing a code. This was the same as what Oregon Injection said as well.

[JAG1]

just speculation here, but what if the FASS has a jammed up gear or motor creating an overload that back fed thru the ECM by way of the non protection relay. This my suspicion so is there a way to tell if the FASS is bound up and running hot? Amp meter?

 

This brings me to my next question... is the grid heater relays a diode protected relay? I'm wondering about these two important possibilities.

Edited December 24, 2019 by JAG1

[IBMobile]

17 minutes ago, JAG1 said:

what if the FASS has a jammed up gear or motor creating an overload that back fed thru the ECM by way of the non protection relay.

That wouldn't do it.  The power to the fuel pump would be battery/PDC fuse, to relay terminal 30, to relay terminal 87, to fuel pump. In a proper installation the fuse would blow.   The ECM powers relay terminal 86 to the relay solenoid.  The power draw on the ECM would be .175 amps at 14V.

 

34 minutes ago, JAG1 said:

is the grid heater relays a diode protected relay?

They are resistor protected.

[the7t7]

1 hour ago, IBMobile said:

That wouldn't do it.  The power to the fuel pump would be battery/PDC fuse, to relay terminal 30, to relay terminal 87, to fuel pump. In a proper installation the fuse would blow.   The ECM powers relay terminal 86 to the relay solenoid.  The power draw on the ECM would be .175 amps at 14V.

I will check that the Fass is moving fuel properly but I suspect it is. I jumped the relay as well as the vp44 and got the truck to idle.

 

I have a feeling it’s the fuel pump relay ground (85). My 98 factory manual supplement says it grounds to G102, whose location is “L fender shroud RWAL”. This ground is not shown in any location figures. I’m assuming RWAL means rear wheel antilock. I do have an unattached ground in that area that connects directly to Joint Connector 1, which shares grounds with those that go to G100, the PDC ground at the forward fender below the battery. Interestingly the 99 moparman diagram says it grounds to G100. Either way the ground there is corroded and showing 4 ohms from JC1. I would guess this would make the fuel pump relay trigger signal (86) from the ecm be unstable and cause the vp44 power to be intermittent. Would this be enough to damage the ecm? I will for sure clean those grounds up. I think I’ll also run a wire from G100 to the B- in a similar way that the vp44/ecm grounds got a B- connector in the W-T mod. Let me know what you guys think. Thanks.

[the7t7]

I rechecked the pdc grounds and they weren’t as bad as I thought. They are a little corroded but when I put the meter clip on bare metal right beside the grounds and the other clip on joint connector 1, resistance was fine. So I don’t think it’s those grounds. 
 

I did thoroughly check the fuel pump relay for resistance and voltage drop when triggered and compared those numbers to the horn relay. The fuel pump relay works properly but it did heat up more than the horn relay and had slightly more resistance when hot across pins 30 and 87 when triggered(@1.5 ohms). That should make the voltage less at the injection pump but I don’t think it’s enough to cause problems, unless the heating up gets worse with time. 
 

For anyone that’s interested, I did trace the the small current leak to ground from the pdc + supply. I pulled every fuse and relay (power too) and disconnected the big harness block connector at the front. I then measured resistance from the b+ bar by the 140 amp fuse to the pdc ground. Of course at this point it was an open circuit. I then inserted a fuse or relay one at a time in every position and watched the meter. All circuits were open except for Fuse 1 (cab fuse panel), fuse 11(Abs), and fuse B (hazard). I forget the numbers, but hey were between 22k and 500k ohms. I then traced the cabin fuse panel leak to fuse 12 and 13 which are a lot of things like a bunch of lamps, data link, and the integrated electric module. My guess would be bulbs for the resistance to ground here. Abs, I didn’t explore. The hazard circuit has the flasher module which has relays built in and possibly resistors so possibly resistance there. None of these circuits have anything to do with the ecm so a dead end for possible ecm failure sources.

 

 I can’t really do much more. I’ve found some possibilities but nothing definitive. Not sure if I want to risk the new ecm on a new fuel pump relay and some better grounds.

 

I’m not sure if anyone is still following this. I don’t think my long winded posts are helping but it has helped me to write it all out. Maybe it will help someone else who flails as badly as I do with wiring. 

[dripley]

I garauntee you folks are still reading. Simple eledtrical problems drive me crazy. I woild be lost having to dig this deep into it. I lost an ECM back in 2009. The worst time I ever had trying to fix something, but fortunately a new ECM fixed the problem. Never knew why the OE failed.