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Looking for some advice; bad ECM?

gerlbaum
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gerlbaum

gerlbaum

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Posted

Hi everyone I hope someone can provide some advice. I have a 1998.5 3500 with a nv4500.  It has an aftermarket lift pump, TST Comp, and ts mvp. The current issue has never happened before and I’ve owned the truck since 2017. Over the weekend my radiator sprang a leak. I noticed it when the check engine light came on and temp read ~240. I pulled over and shut it off. While replacing the rad I had two wires where the insulation wore off short. It was the “Cummins bus power” wires (see wiring diagram). I fixed them and the radiator and went to start the truck and no wait to start light and the truck won’t start. I messed around Saturday looking for bad wires, and checking fuses.  I go to try and start the truck and low and behold wait to start comes on and it runs fine. This morning I had no issues and drove 50 miles. This evening I went to start the truck again and no wait to start and truck is dead. Went back inside and came out and tried again and wait to start came one and it ran fine for 10 seconds then died. I can’t pull codes because it’s like the ECM has no power.

 

I am wonder if the ECM fried when the those two wires shorted. Or, could have the hot truck killed the ECM? It appears there is a short somewhere but I can figure out how to test for it or what to narrow down - bad ECM, wiring short, etc…I am hoping someone can help me diagnose where the short could be. I have a multimeter , I can read wiring diagrams and I have the service manual. I don’t know the truck well enough to understand where to begin testing. Is there a ground for the ECM? Is it possible one of the other sensors fried and could cause this condition?

 

Thank you in advance for any help.

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Great work!

Great work!

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Those larger fuses in the pdc can go bad intermittently look very closely with a light and jiggle the fuse. Beyond that you need constant battery at the red/white wires on the ECM and switched power on the green/black wire, comes from fuse in dash. Don't forget ground. Always clean and reconnect battery terminals always no matter what.

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gerlbaum

gerlbaum

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Thank you. I took your advice and went through the fuses. I replaced the 20amp #3 under the hood. Does the switched green/black white come from the ignition switch (#11 fuse in the dash?). I’ll look at the wiring schematic tonight as well - once my kids are in bed.

 

Also, can anyone confirm where the switched ground wire is located? My searches reveal it’s in the kick panel but I wanted to be sure. 
 

Thank you

 

One other point. I am also going to solder the TST wiring connections in case they could cause a no start condition. I noticed my TST power and boost lights flash instead of remaining solid. So, I am starting to lean toward a bad connection over a bad ECM.

Edited by gerlbaum
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dripley

dripley

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I am having trouble with mine also. I have lost the WTS several times. Most of those times I was able to get it back by running the cluster check and it was right back on. A couple times it came back on its own. I have also  swapped in a spare cluster and unplugged and replugged the cluster with succes to get it back. Maybe I just dont want to admit the ECM needs fixin. Hope I am right. Life is getting in the of testing much else. I have written this up in a thread titled "dead truck".

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gerlbaum

gerlbaum

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Well I think mine is a result of the dash fuse #9 being loose. The PO had a fuse tap in it, but the metal kind you stick in with the fuse. I think it loosened it up. I’ve tightened it down, and put a new fuse in and so far so good. Now, I thought I nailed it with fuse 11 but it didn’t help but it’s right next to fuse 9 so I think it was a false positive. So, we’ll see.

Edited by gerlbaum
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McDaniel24v

McDaniel24v

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Posted

So I’ve been trying to figure out this problem and can’t for the life of me seems my wait to start works however many times I cycle the key until I crank ,if I bump the starter the wait to start light won’t come back on again unless I wait 5 minutes or so , so I’m assuming when I start the truck and it randomly shuts off a minute down the road , that the ecm is turning off which shuts the fuel off then I have to reprise once I get the wait the start light again 

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Mopar1973Man

Mopar1973Man

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If the grid heater cycle is completed it will not run the grid heater to you cycle the key OFF for at least 10 to 15 seconds. Then there is a fresh reboot of the ECM and grid heaters will be checked for IAT temperature and always there is bulb check on the first key on. After that the WAIT TO START will not run again on subsequent tries on the same key cycle. 

 

You might check the PDC fuses for cracks. Bad connection of power. Also there is a fuse in the cab too for powering the ECM and PCM for trigger ON.

Edited by Mopar1973Man
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McDaniel24v

McDaniel24v

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Have checked all fuses and relays to be good , did the WT ground method also the pcm ground splices and rebuilt the ground under the battery on both of the studs and added a ground up to the negative battery post, my issue is the truck will just shut off a few minutes Into driving it and I can’t for the life of me figure out why , when truck shuts off it takes about 5 minutes or so for the wait to start to come on so that I can reprime the injectors , my fass relay harness doesn’t make much sense to me because I didn’t install it , and I ran mine on my 02 differently but it’s been so long I can’t remember not sure if that could be the issue

picture 1 green and red connect to I believe the factory lift pump plug however the red which is spliced into the black wire isn’t connected to the relay , 2nd picture is green from fass connect to the green from the factory lift pump plug which also runs to the negatove battery terminal on the white wire of the relay , 3rd picture red from relay to positive terminal on battery, black from relay to the fass pumps red wire and yellow goes inside the cab to a switch from the switch to the inside fuse panel add a fuse ,

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W-T

W-T

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@McDaniel24vI have to fully agree with Dan @IBMobile in his suggestion to start fresh with this lift-pump relay harness. It's really not hard, the basic aspect is you're using the original control wires (only 2) that previously powered up the factory Carter lift-pump to provide 12 volts in order to trigger the isolation relay and provide a direct battery 12 volt source to your aftermarket lift pump.

I would refrain from butt-splicing and soldier all specific wires followed with quality heat-shrink insulation at each connection. Attempt an effort to match color and wire Gage of the harness to avoid confusion.

 

Dan's link to his protective-lift-pump relay is certainly worth the study time and provides excellent preventative anti-back EMF when the relay is de-energized once 12 volts is removed by turning your ignition to the off position. It just prevents spiking the ECM's driver circuit in shut down.

 

Attempt to mount your slave relay to the firewall for occasional easy access...Velcro tape tabs can help in a pinch as I see by your photo's depiction, the relay is merely plugged directly into a bulk connector. Having a relay flopping around under the hood unsecured should be avoided.   

IMG_0240.JPG.4c8925234ad5c05515ede70ad369c5bb.JPG

 

Additional noise silencing can be easily achieved with a .1 Mfd Mylar cap connected directly to the 12 volt supply line that feeds the lift-pump's remote location. That 12 Gage wire is nearly 9 feet in length to reach the remote lift-pump location and by shunting .1 Mfd to ground will help alleviate the armature noise of the running motor that powers the lift pump. The 12 volt connection point on the relay that provides current to the lift pump is where this capacitor is located and you merely take it to ground with as short leads as possible.

 

This advice is basic and is NOT provided by any of the aftermarket lift pump manufacturers. Dan's instructions regarding the relay coil back-EMF diode across the coil is proper engineering for any DC actuated relay coil.      

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Mopar1973Man

Mopar1973Man

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@W-T is totally correct. 

 

Diodes across the relay coil is so so important. I'll give a good example of the spike of energy from a collapsing coil. I've got a LED rocker switch on my exhaust brake. I did not hook up the switch ground for the LED. Every time I switch it off in the dark you can see the LED on the switch dimly light up. Like I said there is no ground hook up on the switch so it should not light up. If it was hooked up the switch LED work burn up for the collappse of the coil the spike would blow the LED out. Already lost one switch to this problem (burned up LED).

 

In W-T article the long version of the W-T ground wire he explains about the design of the factory lift pump which had good noise suppression, sadly the pump itself is more or less junk. But electrically it was one of the best pumps for noise reduction system build in. None of aftermarket pumps FASS or AirDog have noise suppression. Remember since W-T uses a Ham Radio in his truck all source of spark or arcing has to be suppressed to prevent drowning out the radio with random RF noise.

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wil440

wil440

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With me working for Caterpillar and the UK cat dealer Finning in the past I only use Deutsch connectors with the gold plated terminals, they are more expensive than the plain steel terminals but make a much better connection due to the soft gold when the pins and sockets are pushed together, demountable, reusable (except the pins and sockets) and weather proof

https://www.ebay.co.uk/itm/154466240495 

The crimp tool is expensive here but I bet to you guys it's as cheap as chips

I haven't used bullet or spade connectors in over 20 years

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gerlbaum

gerlbaum

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The update on mine:  I’ve sent the ECM in for a rebuild. I’ve hunted down everything I can and it did it again yesterday. It started, ran for ~10s then shut off. When it does that it sucks all the fuel out of my filter (lift pump isn’t running) and restarting it is like restarting after you change your fuel filter. I changed the PDC fuse and the ones in the truck. It will be perfect for 20 starts then crap out on me like above. This all started after my fan blade let loose on the highway, took out my radiator hose, and I hit 240 before I could safely get over and shut down. I live in Phoenix so I am wondering if the 240 engine heat and the 110 ambient heat finally took a toll on the ECM after 275k miles. I am also dumping the TST and the TS mvp and I bought a Quad from DAP today. Obviously, I told my wife the Quad was required to flash the ECM or it wouldn’t work.

Edited by gerlbaum
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