PCB questions, bad solder joints

Thread Starter

cjcocn

Joined Jan 1, 2021
11
Hi.

New to electronics and am working on my 2000 F250 diesel. My PCM has a bad solder joint on at least one pin and is causing a no-start condition.

I can send the component to the US (I am in Canada) to someone who specializes in this component, but if this is something I can repair myself I would rather save the time and get my truck back on the road.

I can see the bad joint, but cannot easily access it as the PCB is screwed onto an aluminum housing. The bad joint is directly under the housing

There are six machine screws holding it on and two of the machine screw heads are soldered.

Also, there appears to be a glue or form of gasket material between the PCB and the housing. I am not sure what the material is and if I can easily remove the PCB from the housing or if I will risk breaking it during removal.

Lastly, the silicone (?) covering would have to be removed at the bad joint area and I am unsure as to what type of silicone replacement would be best.

I am attaching pictures that show the bad pin joint, the soldered machine screw head and the grey gasket-like material.

Thanks for any suggestions.
 

Attachments

jivenene

Joined Jan 2, 2021
5
CJ,

Yes it has conformal coating, but sometimes they use a coating that doesn't dry hard and can be scraped away pretty easily.

I have opened a few ECUs up, and they are built fairly ruggedly. The main thing I would say is you need the right tools. You would need a good iron, and probably a high wattage solder gun like the Weller D650 to get enough heat into the solder to be able to suck it out.

Having said that, the problem may not be with the PCB and solder joint that you show. The joint that is circled is a through hole, and there may be solder on the other side of that board. Those PCBs are so overbuilt, I doubt it is cracked solder that is your problem.

Your 2000 F250 is OBDII, have you used a scanner to read the codes?
Have you done an exhaustive search at the F250 forums? There would probably be some useful info.
There are so many damn things to go wrong with cars, could be fuel pump, relays, etc.
Actually, it might be more likely that a wire in some harness or connector broke or corroded and the ECU is not getting the proper signal to start.


I only say all this because it's a PITA to take everything apart and find out that it was fine after all (ask me how I know).
So unless you can see burned parts or traces, I would venture to guess that the ECU is not the problem.
Also, if you could get your hands on a spare ECU and swap it in, that would be a great way to narrow it down.
 

Thread Starter

cjcocn

Joined Jan 1, 2021
11
Jivenene

Thanks for the response.

All relays and fuses test as good. I’ve pulled the wiring harness from the engine valley and visually inspected it as well as tested for continuity.

The only way I can start the truck is to push one the connector in a sideways motion until I get my 5 VREF. I can accomplish this as well by pulling the harness itself sideways in the same direction until I get proper contact.

I’ve wiggled the wire itself and there is no change at all. It is only when I push on the connector housing or pull the harness sideways that I can get a connection (and my 5 VREF).

I’ve removed the wire from the connector and it and the (female) pin look good with no melting, pitting, oxidation, etc.

I’ve also removed the main power wire from the connector and it too looks good.

The engine runs well when it gets the 5 VREF.

It is a 104 pin connector with about 90 pins in use. Since everything is closed until Monday and I cannot mail out the component if that’s the route I go, I have bit of time to pull all wires from the connector and label them to make reinstalling them easier. This would allow me to get a look at each individual wire to see if another connection is causing my issue.

cheers
 

Thread Starter

cjcocn

Joined Jan 1, 2021
11
PS

My soldering gun is a Weller (I am not at the garage right now so cannot check the model number) and my soldering iron is a Weller WEP 80. I have a solder sucker in the mail that should be here in a week or two.

The coating should be silicone according to the videos I’ve watched where specific companies have done work on this model unit (mainly the addition of a performance chip). I also have some 99% isopropyl alcohol coming in the mail, which according to what I’ve read is suitable for cleaning the PCB and removing the silicone.

Thanks
 

drc_567

Joined Dec 29, 2008
1,110
... I suggest that you try disassembling the connector headers and cleaning each connector side ... both socket and pins. Use alcohol and a swab of some sort. ... Then allow to dry. Frequently, an accumulation of oil, dust or other foreign material can cause a bad connection such as you have described. Try this before any soldering.
 

Thread Starter

cjcocn

Joined Jan 1, 2021
11
... I suggest that you try disassembling the connector headers and cleaning each connector side ... both socket and pins. Use alcohol and a swab of some sort. ... Then allow to dry. Frequently, an accumulation of oil, dust or other foreign material can cause a bad connection such as you have described. Try this before any soldering.
Hi.

I have cleaned the connectors with non-electrical contact point cleaner and a cotton swab. This did not affect what appears to be a bad contact on pin 90.

If there is a short in another wire that is affecting pin 90, then perhaps I may be able to trace it. I received one of my testers in the mail and will use it later today.

I will also pull each individual wire from the connector (after labelling them) and will look for a bad connection etc.

cheers
 

jpanhalt

Joined Jan 18, 2008
11,088
Nothing dissolves silicone, as I suspect you know. Isopropyl alcohol (IPA) may help a little, as it will keep the small chunks scraped off in suspension. I have used a mixture of IPA and mineral spirits/VM&P naphtha. The naphtha helps break the hydrophobic adhesion. It seems a little better than IPA alone. IPA is great for removing "hot melt" adhesives, but I don't see them in your pictures.

If the "silicone" is actually a silicone modified acrylic, it may be easier to remove. MG Chemicals sells two conformal coating removers (#8309 and #8310A). The latter is a gel version of the former. They do not contain chlorohydrocarbons (e.g., methylene chloride). They contain acetone, dimethoxymethane, and 1,3-dioxolane (like dioxane but with a 5-member instead of 6-member ring). The latter two compounds are like ether but higher boiling. I have not tried that solvent. If it works, a good lacquer solvent might also work.
 

jpanhalt

Joined Jan 18, 2008
11,088
I would just solder from the other side. If the hole is clean, solder should wick in. If the hole is not clean (e.g., has conformal silicone in it) , then it won't solder well from the top either. Some conformals can be soldered through, but that doesn't change the situation.
 

jivenene

Joined Jan 2, 2021
5
Jivenene

Thanks for the response.

All relays and fuses test as good. I’ve pulled the wiring harness from the engine valley and visually inspected it as well as tested for continuity.

The only way I can start the truck is to push one the connector in a sideways motion until I get my 5 VREF. I can accomplish this as well by pulling the harness itself sideways in the same direction until I get proper contact.

I’ve wiggled the wire itself and there is no change at all. It is only when I push on the connector housing or pull the harness sideways that I can get a connection (and my 5 VREF).

I’ve removed the wire from the connector and it and the (female) pin look good with no melting, pitting, oxidation, etc.

I’ve also removed the main power wire from the connector and it too looks good.

The engine runs well when it gets the 5 VREF.

It is a 104 pin connector with about 90 pins in use. Since everything is closed until Monday and I cannot mail out the component if that’s the route I go, I have bit of time to pull all wires from the connector and label them to make reinstalling them easier. This would allow me to get a look at each individual wire to see if another connection is causing my issue.

cheers
Great, sounds like you are doing everything right! If you can push the connector to get your 5Vref, then yeah that's your problem. Sounds like you eliminated the possibility of cracked wires or corroded pins, good job. When soldering these big thick boards, you need a big gun, the Weller D650 is 300W at the highest setting, that is enough for 99% of jobs, and you might not even need that. Also , don't know how much experience you have, but one of the easiest ways to get solder to melt at the pin, is to add some fresh solder. It wets the whole connection and allows heat to flow to all the solder. You can then use a sucker or wick if you need to. But I guess all you need to do is add solder so that's good. I don't think you have to worry about getting the old solder out. Good luck and good troubleshooting!
 

bwilliams60

Joined Nov 18, 2012
1,398
Thank you @MrChips for the vote of confidence.
If I may add a few things, my first thought would be to go back to the beginning and look at the connector itself. It is great that you have nailed it down to this point. I would now drag test all those terminals in that connector before I condemn that ECM. As mentioned, they are pretty hardy beasts and don't often fail. Especially back in that time frame. Usually electrolytic cap failure but rarely anything else. Were there any codes? I have a list I go through before condemning ECMs but it sounds like you have covered a few. Repairing an ECM is not for the faint of heart so strap on your big boy panties if you are going in. You can cause more damage than you started with if you ate unsure of what you are doing. I am in Ontario if you need some help. Cheers

In terms of photos, can you explain what the three pictures are showing us? The third pic is self explanatory but the first two I am not sure what it is you want us to see. Keep in mind that if you are wiggling the outer connector and it is a bad solder joint, it is probably located in a group of joints right at the front of the board. I have not seen failure in this area yet on a Ford, not to say it can't happen. Can you take a picture of the whole ECM along with the tag number on the side as well as the complete board?
 
Last edited:

Thread Starter

cjcocn

Joined Jan 1, 2021
11
@bwilliams60 the first pic shows what I perceive as the bad solder joint and it’s positioning under the aluminum frame that the PCB is attached to.

The second pic shows the grey substance that I think is either an adhesive or more likely a “shock absorber” to reduce impacts to the PCB.

The third pic shows one of the machine screws that has the head soldered. If I remove the PCB to access that area that is circled in the first pic, I would have to heat up those two screw heads and wick away that solder to access the screw head and facilitate its removal.

When you say drag test, are you referring to back probing the connector? I am in the process of removing each individual wire from the connector and looking for issues at the connector. I can reinstall the wires I’ve pulled so far and drag test (back probe).

My tester should be in this week. I’ve ordered other tools since I ordered the tester and they’re starting to show up so hopefully it won’t be too long now. It is the ECT3000 and will help me locate any shorts in the wiring, but I don’t know that it will be of any help in determining if it is a wire at the connector or a pin at the connector.

I’ll attach some pics.
 

Attachments

jpanhalt

Joined Jan 18, 2008
11,088
Background: My F150 is at a small hobby farm. One year, several faults occurred, including failure of the ABS and 4WD. The main control was OK, but as I searched from sensor to connector, I found some open circuits. Rodents had chewed through a few wires. A couple were really close to the firewall but were repairable, another was at the shift on fly (4WD) and was so close to that device that it had to be replaced. ABS vacuum lines were cut too and replaced.

Current Problem: Your diagnostics are impressive, but I would try continuity checks between the affected pins and the sensor/devices. Once I knew where to look, I could see the defects, but they were not obvious until I got to that point.
 

bwilliams60

Joined Nov 18, 2012
1,398
Drag testing is a method of testing a terminals structure for proper shape and size. A female terminal can often be damaged or expanded by vibration or negligence. A terminal tester kit is available and you would take a male terminal of the same size as the ECM terminal, insert it into the female terminal and pull it back out again. You want there to be some drag on the terminal as you remove it. If it comes out easily with no resistance, the female terminal has been compromised and needs to be replaced. Those terminals are available and I highly suspect this to be your issue. You can also do the same with the male ECM terminal.
The grey substance is a silicone sealer and you will need to use the same type of sealer if you remove that board. The screw heads will be attached to a ground plane on the board and shouldnt pose a problem. The connection you suspect is probably soldered on the backside of the board and not an issue.
If you are wiggling the connector and you can make it wor, you do not have a short. You have an open circuit. I think your issue is in the connector and yes the 5v reference line will take down those components. So will an internal short on one of them.

This is an advanced version of the drag test kit I refer to. This one will cover most terminals.
https://www.aeswave.com/uTest-Advanced-Terminal-Test-Kit-p9748.html
 
Last edited:

Thread Starter

cjcocn

Joined Jan 1, 2021
11
Drag testing is a method of testing a terminals structure for proper shape and size. A female terminal can often be damaged or expanded by vibration or negligence. A terminal tester kit is available and you would take a male terminal of the same size as the ECM terminal, insert it into the female terminal and pull it back out again. You want there to be some drag on the terminal as you remove it. If it comes out easily with no resistance, the female terminal has been compromised and needs to be replaced. Those terminals are available and I highly suspect this to be your issue. You can also do the same with the male ECM terminal.
The grey substance is a silicone sealer and you will need to use the same type of sealer if you remove that board. The screw heads will be attached to a ground plane on the board and shouldnt pose a problem. The connection you suspect is probably soldered on the backside of the board and not an issue.
If you are wiggling the connector and you can make it wor, you do not have a short. You have an open circuit. I think your issue is in the connector and yes the 5v reference line will take down those components. So will an internal short on one of them.

This is an advanced version of the drag test kit I refer to. This one will cover most terminals.
https://www.aeswave.com/uTest-Advanced-Terminal-Test-Kit-p9748.html
Thanks .... I am learning a lot by working on this myself, which is a good thing because I have to safety a 2001 F150 after this and then do a frame swap on my 1979 ext cab Ford. I will need all of the info I can get!

I am back at work after the Christmas break and will hopefully get some time this evening to start doing more tests.

It would be nice if the issue is not a bad pin as I should be able to resolve it more quickly and be able to drive this truck again.

More updates will follow and I certainly appreciate everyone's input!

cheers
 
Top