Engine cranks but doesn’t start with water damage. Replacing connectors and re-pinning the ecu side of the factory engine harness

bison

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We see more and more of this type of situation on old turbo Regals now that they are 30 plus years old and Edward Scissorhands has had his way with most of them. Here’s the summary. The customer called on a local referral and complained his car cranked but wouldn’t start. I get a lot of these. From internet messages, to phone calls, to can you take a look at Johnny’s car. It cranks but won’t start and has x,y,z ecu. This one had no service engine soon light with key on engine off so we knew an ecu power feed was likely the problem. Pics of what was found and the solution below. The ecu side of the main harness was cut up and had suffered from major water damage. Every pin was removed cut off and re-pinned. Wires that had been hacked were replaced as needed. The correct color wires were used when replacing the wires. This wire is often obtained from a junk harness. These types of cranks but doesn’t start repairs take a lot of time. Plan on 3-5 hours to repair and re-pin as was done here after diagnosis is made depending on how bad the wires were cut. Triple check the pin out before powering and verify the sensors and solenoids are not shorted and fuse block bypassed before sending power to the ecu!
If the harness was cut up under the hood and had this problem at the ecu connectors, harness replacement is usually the best option. When replacing harnesses verify every pin with the service manual before powering up. There’s no need to damage an ecu, or have a situation that’s hard to troubleshoot once the harness is installed.

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That's the first thing I go for on every car. I see a lot of corroded chips as well. It was real shitty place for GM to put the ECM. Even shittier that water can get to it... Thats GM integrity...
 
That's the first thing I go for on every car. I see a lot of corroded chips as well. It was real shitty place for GM to put the ECM. Even shittier that water can get to it... Thats GM integrity...

The circuit board part of the ecu actually takes the water really well with the coating on the board. It’s the leakage from that heater box area that’s the real problem. It would have been better if the ecu was 180* from stock location with a drip loop at the end of the harness. The water would have been less of a problem.


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Ewww! Those pins are plum nasty! But, that rats nest is even worse! I hate electrical and if I saw that under my dash, I’d call uncle faster than you can say spit! (I’d also be one of the pests looking to ship my problems to you too)! Cause that’s no place for an amateur like me! Yuck!!

Question is what’s the fix on the missing prong side? Did you have to cut and replace that side too? This had to be more than five hours to fix huh?

BTW, that last photo looks much mo better! Just saying is all!!


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Ewww! Those pins are plum nasty! But, that rats nest is even worse! I hate electrical and if I saw that under my dash, I’d call uncle faster than you can say spit! (I’d also be one of the pests looking to ship my problems to you too)! Cause that’s no place for an amateur like me! Yuck!!

Question is what’s the fix on the missing prong side? Did you have to cut and replace that side too? This had to be more than five hours to fix huh?

BTW, that last photo looks much mo better! Just saying is all!!


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I’m not sure what you mean by missing prongs but the wires are removed from the connectors one by one and the pins and bad sections of wire are cut off and replaced. New connectors are used. In this case the car was an 86 and had different retention than the replacement. The connectors used are the 87 style



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I’m not sure what you mean by missing prongs
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I think he is referring to the broken/missing male pin on the computer connector.

The ecu was replaced. Once the corrosion sets in even if pins weren’t broken it will be a constant problem. There’s no fixing broken pins on the ecu.


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I’m not sure what you mean by missing prongs
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I think he is referring to the broken/missing male pin on the computer connector.

The ecu was replaced. Once the corrosion sets in even if pins weren’t broken it will be a constant problem. There’s no fixing broken pins on the ecu.


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Sorry, see I said electrical is not my thing! What do you call the Pins on the ECU side, if not Prongs, then is it just Pins?? Anyways, in this photo you circled what appears to be a missing Prong or Pin? So, did you have to remove / replace the connectors and wires on both sides??


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I’m not sure what you mean by missing prongs
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I think he is referring to the broken/missing male pin on the computer connector.

The ecu was replaced. Once the corrosion sets in even if pins weren’t broken it will be a constant problem. There’s no fixing broken pins on the ecu.


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Sorry, see I said electrical is not my thing! What do you call the Pins on the ECU side, if not Prongs, then is it just Pins?? Anyways, in this photo you circled what appears to be a missing Prong or Pin? So, did you have to remove / replace the connectors and wires on both sides??


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The ecu was replaced


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I’m not sure what you mean by missing prongs
Sent from my iPhone using Tapatalk
I think he is referring to the broken/missing male pin on the computer connector.

The ecu was replaced. Once the corrosion sets in even if pins weren’t broken it will be a constant problem. There’s no fixing broken pins on the ecu.


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Responding at the same time I guess! I see now! Thanks. That’s some tedious work there man.


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The ECM side connectors are still available new. But they are not easy to replace.

At this time it is less costly to just get another ECM.

RemoveBeforeFlight
 
I have seen water get into the ECU buy way of the cowl drain.....it it above the ECU grommet and follows the wire down into he ECU . I made a cover for the wiring harness out of rubber so the water runs below the grommet buy staying off the harness.
 
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