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Author Topic: shorting out 5 prong ECU's? (solved)  (Read 1138 times)

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Offline Unfortunate_Sam

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shorting out 5 prong ECU's? (solved)
« on: March 11, 2012, 04:15:46 PM »
hmm well after having delve into my 75 ramchargers whole no spark issue It seems to be that the truck is eating ECU's. At first I though that my ECU was not the problem after having tested a known to be good 5 prong ECU. However The truck shorted out the known to be good ECU. I also tried a known to be good 4 prong ECU but it made no spark and it definatley didn't short out.

I took apart my engine wiring harness to see if there were any shorts or anything, but its all factory clean so all that did was waste some electrical tape and allow me to route a couple things more efficiently.

After the ECU's short out they back-feed power down the blk/ylw wire that runs to the negative side on the coil.

Does anyone have an idea of what is going on with this and any possible fixes.

After going through several ECU's and having them all short out I am not sure what to think or how to fix it since it only seems to happen with the 5 prong ECU's and I get no response one way or the other from the newer 4 prong ECU's.

(bad coil, was shorting out my ECU's with five prongs and it was giving no spark replaced coil threw in new ECU, got spark gained and gained a pretty bad short somewhere so I'm onto the next issue)
« Last Edit: March 19, 2012, 07:17:38 PM by Unfortunate_Sam »
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline 88raminator

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Re: shorting out 5 prong ECU's?
« Reply #1 on: March 11, 2012, 06:26:03 PM »
Had the same problem on the 57 after installing the electronic ignition conversion. I thought it had to do with Accel super coil I installed but , my brother found I hadn't wired it properly to the ballist resistor. Have no clue what he changed, but my ECU's would melt the silicone off the back. I would start by looking at the harness from the ballist resistor to the ECU
2-88 ramchargers, 57 dodge 1/2 ton 340 auto ,really miss 80 ramcharger and 98 v-10 3/4

Offline SuperBurban

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Re: shorting out 5 prong ECU's?
« Reply #2 on: March 11, 2012, 06:45:39 PM »
I would start by looking at the harness from the ballist resistor to the ECU
Agreed.

The second side of the 4 pin ballast, provides a lower voltage for the ECU's internal workings. The 4 pin ECU's eliminated the need by having an internal voltage regulator. A 4 pin ECU should work in your system. Many aftermarket 5 pin ECU's are really a 4 pin internally, and have the 5th pin as a dummy, and charge a higher price.

Since you say they keep shorting out, I suspect your ballast might be feeding to high of a voltage, Possibly a reversed wire at the ballast.
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Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #3 on: March 11, 2012, 07:21:45 PM »
hmm, then why didn't it short out my 4 pin ECU, I'll just have to do some experimenting i guess..... good thing my new fried ECU has a lifetime warranty.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline offroader_dodge

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Re: shorting out 5 prong ECU's?
« Reply #4 on: March 11, 2012, 08:34:24 PM »
warranty is good for shit,especially if something external fried it.you can try,dont expect them to keep replacing the part til you find the problem.
coil could be incorrect for the application.
short circuits can be a real pain to trace.
maybe dodgeboys will chime in with a wiring diagram.
he's usually good with this stuff.
i'm more of a hands on type of diagnostician.
the 5 pin ecu's should be replaced with the 4 pins,in my opinion they are less trouble.
« Last Edit: March 11, 2012, 08:41:06 PM by offroader_dodge »
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Offline SuperBurban

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Re: shorting out 5 prong ECU's?
« Reply #5 on: March 11, 2012, 08:49:01 PM »
hmm, then why didn't it short out my 4 pin ECU, I'll just have to do some experimenting i guess..... good thing my new fried ECU has a lifetime warranty.
I'm suspecting the 5th pin is getting too much voltage, possibly from a bad or mis wired ballast. The 4 pin ECU would not care about the voltage on the 5th pin.

Why won't the 4 pin work? that leads me to think more of a wiring problem with the ballast.
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Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #6 on: March 11, 2012, 11:08:29 PM »
Ok well my ballast hook ups are the cleanest they have ever been the whole engine harness is unused OE mil surplus, so everything is where it is supposed to be could they just be on the wrong prongs maybe? I'll try them reversed when i pick up my replacement ECU tomorrow afternoon.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #7 on: March 12, 2012, 06:54:01 PM »
Ok well I burnt up another ECU this afternoon, and the only progress made is that the distributor is not the issue, which sucks because I was hoping it was :'(. However That only leaves so many options, most of which revolve around the green wire that hooks up to prong #3 or the 5th prong that isn't there in the 4 prong ECU's.

Since I have no idea why, and I've been pretty thorough when troubleshooting, any idea's of what might be happening here? I and everyone I've talked to including a lot of experienced mechanics are well stumped... which blows because this is as far as I can tell the last real issue with this stubborn RamCharger.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline SuperBurban

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Re: shorting out 5 prong ECU's?
« Reply #8 on: March 12, 2012, 07:05:31 PM »
Check the voltage on that extra pin (With the ignition on), if it is 12 volts then you found the problem.
« Last Edit: March 12, 2012, 07:07:08 PM by SuperBurban »
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Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #9 on: March 12, 2012, 07:53:29 PM »
it puts out about 11.75 volts, damn this is messed up.... I think I'm going to go through all my connections again tomorrow and triple check that every thing is right where it should be.

Anybody ever feel like beating your head against a wall, I bet that its something stupid that I have overlooked time and again....
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline DODGEBOYS

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Re: shorting out 5 prong ECU's?
« Reply #10 on: March 12, 2012, 08:12:03 PM »
clik pik to enlarge


(Sorry, but you are not allowed to access the gallery)

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put your truck info HERE
MOPAR TO YA! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
ramchargercentral@hotmail.com
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Offline offroader_dodge

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Re: shorting out 5 prong ECU's?
« Reply #11 on: March 12, 2012, 09:11:47 PM »
there ya go.
follow the diagrams,test voltages compared to battery voltage.
80 power wagon 318 short box /macho package 35x12.50 DUNLOP RVXT\\\'s 4\\\" RCC LIFT,<br />.Many thanks to all the helpful members of this site.Dream job:fixing atvs and other toys,small engines building stuff with all the tools.copter and float plane rides mandatory

Offline SuperBurban

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Re: shorting out 5 prong ECU's?
« Reply #12 on: March 12, 2012, 09:17:01 PM »
Be aware, the 4 pin diagram posted above has the handwritten run, and start labels reversed.
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Offline DODGEBOYS

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Re: shorting out 5 prong ECU's?
« Reply #13 on: March 13, 2012, 06:07:11 AM »
Be aware, the 4 pin diagram posted above has the handwritten run, and start labels reversed.

yes thats right about the writing being wrong / brain fart when l wrote it
put your truck info HERE
MOPAR TO YA! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
ramchargercentral@hotmail.com
DO NOT use the site IM,s to contact me  l have them turned OFF

Offline Captain Obvious

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Re: shorting out 5 prong ECU's?
« Reply #14 on: March 13, 2012, 06:18:24 AM »
Is the back of these modules and the firewall clean of paint and rust? Module grounds through case.

How is coil primary resistance? Low resistance (internal short) can pull excess current through module.

Remove both small coil wires and measure resistance between the 2. There is a spec.


***One more note. If this engine runs for a short period of time before burning modules, have the alternator tested for diode ripple. If it burns w/o starting, suspect coil or case ground problems.

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #15 on: March 13, 2012, 10:19:40 AM »
ya ECU is grounding fine I'm sure of that its right where they have always been.
 
My battery is dead now so I need to charge it. Before I do anything else, and the truck is outside and its raining.

I've been thinking the last couple days if I switched over to a HEI could this problem possibly be bypassed? or would it persist still, also i can't think of any reason my coil would be bad but it never hurts to test something.

« Last Edit: March 13, 2012, 10:34:27 AM by Unfortunate_Sam »
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #16 on: March 13, 2012, 10:42:18 AM »
and ya its burning the ECU as soon almost as soon as I plug it in it live jsut long enough for me to test to see if the coil - is getting power and after it doesn't for a second the positive loses power and then they both have power a seconds later, I completely disconnected my distributor to see if that might be the problem after talking with a few people, but it was not. But the coil has always been hooked up so I mean maybe?

I hate having to check the voltage and resistance etc of stuff, but I guess I'm pretty much out options. Although when I go get another replacement ECU I guess I can just plug it in with the coil disconnected and then see if it'll start my little brothers crazy mopar powered jeep.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline SuperBurban

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Re: shorting out 5 prong ECU's?
« Reply #17 on: March 13, 2012, 10:59:08 AM »
You need to find out why that green wire is getting 11+ volts. unplug the ballast, then check the voltage at the extra pin, there should be nothing there, with the ballast unplugged.


I suspect something is messed up with the ballast, and or the wiring.  do you have the stock connecters?

With a 4 pin ECU, you should be able to unplug the ballast, and it should start, and then die as soon as you let go of the key. This test will not work with the  5 pin, as the 5th pin is what gives the ECU power.

Have you tried a known good coil? I wonder if a coil with a dead short could be your problem.
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Offline Captain Obvious

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Re: shorting out 5 prong ECU's?
« Reply #18 on: March 13, 2012, 11:02:10 AM »
Who ever was claiming the distributor, doesn't understand how mopars work. The distributor doesn't get any power, not on pickup side anyways. The pickup makes it's own power with a small generator that depends on distributor moving. No movement, no electricity from pickup.

Any voltage testing needs to have negative test wire on the engine block or battery, not the coil. Any resistance testing needs to be done unplugged.



Ballast was likely reading nearly full voltage because the ground side was open circuit. No load=nearly full source voltage all the way to the point of high resistance or open circuit.


Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #19 on: March 13, 2012, 11:41:21 AM »
Ya I think I'm gonna try a known good coil today, since it seems to have cleared up a bit. I'm also gonna "borrow" a charged battery so I can do some more testing. Hopefully it will end up being a bad ballast or coil since I'm running out of options....
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

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Re: shorting out 5 prong ECU's?
« Reply #20 on: March 13, 2012, 11:50:45 AM »
l,d say coil or wiring
put your truck info HERE
MOPAR TO YA! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
ramchargercentral@hotmail.com
DO NOT use the site IM,s to contact me  l have them turned OFF

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #21 on: March 13, 2012, 11:54:11 AM »
well how hot is ballast supposed to get, cause while doing some tests i started to smell some burning and I looked all over for it and couldn't find it so i just kept testing and then i touched the ballast and burnt three fingers I remember my ballast getting warm before but not that warm...
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Captain Obvious

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Re: shorting out 5 prong ECU's?
« Reply #22 on: March 13, 2012, 12:05:52 PM »
Why work so hard trying to avoid the simplest of measurements? Put a lead on each screw and you know for sure whether it's bad or not, w/o even having to remove it or risking damage from some other short.

How hot the ballast gets depends on how much of a short there is.

Are you actually bolting up these "new" modules you are testing with? Or just setting them on the fender or something?

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #23 on: March 13, 2012, 12:07:45 PM »
Yes I am bolting them up, i bolt them up them up three times, once to the jeep to make sure they work, once to the truck where they die, and once more to the jeep to see if they still work, every time unbloting and bolting them exactly where and how the previous one was, and ya I'm gonna go test to coil right now
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #24 on: March 13, 2012, 12:14:36 PM »
ok, my coil is reading, below .05 "ohms"
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Captain Obvious

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Re: shorting out 5 prong ECU's?
« Reply #25 on: March 13, 2012, 12:16:30 PM »
Unplugged right? If so, replace and drive.

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #26 on: March 13, 2012, 12:18:58 PM »
ya, unplugged. I took another reading and it was 1.5 ohms. So then I've got a seriously jacked up coil I'm guessing? Looks Like I get to make a trip to kragens and then watch it rain.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #27 on: March 13, 2012, 12:21:04 PM »
ok, i just double checked and the coil is putting out pretty much nothing as far as my ohms are concerned so hopefully, I jsut need to replace it tune the new carb install/balance the rear driveshaft and start wasting some gas.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)

Offline Unfortunate_Sam

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Re: shorting out 5 prong ECU's?
« Reply #28 on: March 19, 2012, 07:15:06 PM »
Ok, I have spark now, it was a faulty coil shorting out good ECU's, I got my battery charged today and went out after it had stopped snowing and tried to fire it. However I must have a bad short or something cause all I get is a click with a tiny spark and then all the power is drained for several seconds, I think I have a bad short so I'm gonna have to do more wire patching when it dries up.

I don't know why it wasn't shorting out 4 prong ones but whatever root cause was a bad coil. So now I'm onto the next problem.
1999 RAM2500 V10/NV4500HD/NP241HD(TX)
1988 Jeep Cherokee I6 5speed 4x4(TX)
1975 Dodge Ramcharger 318/727/NP203 pt(CA)
1952 M38A2(CJ5) 273V8/3speed w OD/4x4(CA)