This isn't "new" news - it's been discussed here several times how our PCM's are increasingly failing due to capacitor leakage. Here's some further info w/ pics if you're not familiar with this problem....A9x ECM's (and same years ECM's) Failures Due to Age

So tonight I thought I'd dig a little deeper and cracked open several EEC-IV PCM's that I happen to have. First, I opened up my spare for the truck, and sure enough, two of the three capacitors show signs of leakage. Then I checked several others - at least six, ranging in age from the late 80's to early 90's. None of them showed any problems at all.

I should add, there are several different types of EEC-IV PCM's - I went through 4 different cover configurations across the 6 different units. They all use blue-cased capacitors, but only the F-150 one showed capacitor leakage problems, and the F-150 case configuration is unlike any of the others I have.

My best guess is that the F-150 PCM's of this era were produced by one particular vendor who used inferior capacitors. Check yours today.

 

Now that scenario wouldn't be too hard to believe.

Yes, it'd be well worth the time spent pulling the PCM, EEC, ECU, computer (all those terms may help in a google land search) and visually checking it to avoid an unexpected "side-of-the-road breakdown".

Good post Brad.

Bob

 

I had never heard of this problem until owning a F150, even though I've owned a couple EEC-IV vehicles. Initially I was skeptical - lots of times PCM's get replaced by parts-swapper "mechanics" looking for an easy fix, and more often than not, there's nothing wrong with them at all.

In the case of the F150 PCM's, indeed it's been confirmed that it's a real, almost inevitable, problem. My small sample-size research conducted last night seems to point to the problem NOT being universal across ALL EEC-IV PCM's, just some.

I'm reluctantly planning to check the one currently installed in my truck this weekend. Ignorance was bliss.

 

Electrolytic cap breakdown is tied directly to hours in service and I'd be willing to be that of all the EEC4 vehicles left out there these trucks rack up more hours than anything else. You will find some old Crown Vics and Mustangs still on the road but they don't often have 200,000, 300,000 or more miles on the clock like many of these old trucks do.

 

That may very well be a factor, but the theory doesn't hold up to my sample. The one from my 122K-mile truck has two that are leaking, and I know for certain that a couple of the other ones I looked at (which were problem free), have greater mileage on them.

Perhaps the caps are somehow getting worked harder (electrically) in this application? Just throwing ideas out there.

 

Physical age, heat (especially), power "cleanliness", and hours of use all affect electrolytic capacitor life.

Also keep in mind there are several generations of EEC-IV, and different types within those generations.

You have the TBI and Feed-Back carb very early EEC-IV. Then you have the early multi-port generation which came in both SD batch fire, SD SEFI and MAF SEFI. After that you have the "Gen 2 EEC-IV", which came around 92 or 93 I believe. This generation added support for live serial datastream through the diagnostics port. You could find these in SD batch fire and MAF SEFI.

..and even within those sub-types you'll find different hardware inside depending of it it's automatic, manual, has a knock sensor, which automatic it has, etc..

 

I neither agree nor disagree, but I would like to make a few comments.

1. A failing electrolytic, in an automotive environment, after 10-20+ years is not really too amazing.
2. It's just possible that there are sometimes other culprits. (This is all guesswork). I suspect that most of these caps are used to filter the voltage. There are probably also diodes designed to limit reverse voltage spikes. Should a diode fail open, the cap will probably still mute the spike -- but it will eventually fail as a result. ( As will a new one, but not right away)
3. The 'lifestyle ' of many 150s may contribute. Off roading, heavy loads, etc, probably mean more shock and vibration. These stresses can play heck with electronic parts. There may be other such usage issues. ( If there's anything that I've learned around here is that you guys USE your trucks )

Just my .02

hj

 

As several others mentioned, a Capacitor failing after 10+ years, simply means it has served it's lifespan. I've replaced dozens of caps in desktop computers, and there was a period of time between 2001 and 2003 when there was faulted number of caps due to a cheap blend being manufactured in China. The stresses the PCM must handle is far more harder than a desktop computer, hence the different outcome. But just like an engine, a fuel pump, the PCM is a servicable part, that may need to be replaced. It's failure can be addressed and if needed, be repaired or replaced. I'm surprised that many of the trucks with 100k + miles are still running with OEM PCM's considering all of the factors mentioned.

 

Unquestionably true. Although the basic form factor was set across all EEC-IV PCM's, the stuff going on inside is way more different than one might suspect. Heck, they didn't even standardize on one case design - I've got 5 different types here - all EEC-IV - they each open up differently, using either 5.5mm or T-10 headed screws.

I don't really buy into the harsh environmental usage being at cause here. One of the units I looked at came out of a 200K+ mile "beater" Ranger, and the circuit board looked like it had just rolled down the assembly line.

I'm fairly convinced it's a problem with inferior capacitors having been used (relative to other EEC-IV PCM's) and/or the electrical design of this era of truck PCM's putting more stress on the capacitors, leading to their shorter lifespan.

While it's mildly interesting to discuss, the "why" part doesn't really matter too much, especially if it's something we can't do anything about. What is important is knowing that this is a real issue and thus you should be proactively checking for the problem before it leaves you F.O.R.D.

 

The circuit boards are coated in conformal coating, and the ECU is located inside the truck. Both of those will keep the circuit board looking new.

I see nothing special about Ford's electrical design that would cause more or less stress on the capacitors.

As far as inferior brand, what color and name do the capacitors say on them? If the have a logo, can you take a picture of it?

 

I thought about this after I bolted them all back up - i.e. looking closer to compare brands of the failed vs. operational ones. If I get motivated enough I'll open them back up and take some pics. FWIW, they all were blue - not sure if multiple suppliers made the components in the same color, or they actually are from one supplier (which would kinda kill my theory).

 

Having pulled apart at least ten PCMs to examine more closely the capacitors, I've got some additional data that I believe supports my previously proposed theories.

For starters though, all of the circuit boards use Nichicon capacitors rated at 105' C. From there, things get different in two ways. First, and perhaps most significantly, the F150 caps are physically smaller than all the others. The ones used in the F150 PCM are 6.5mm in outside diameter while all the others use caps that are 8.3mm in O.D.

Second, the specs for the F150 caps are unique, as follows:
Qty 1 10uF 63V
Qty 2 47uF 16V

Compare that to what is used on the others I examined ('88 - '94 Mustang & Ranger):
Qty 1 3.3uF 63V
Qty 1 47uF 10V

Or, for those that also use three capacitors ('87 - '89 Merkur XR4Ti):
Qty 1 3.3uF 63V
Qty 2 47uF 10V

Lastly, I had one EEC5 PCM that used the following (1997 Explorer):
Qty 1 47uF 63v
Qty 1 47uF 10v

My best guess is that the smaller physical size may be the biggest thing that's causing the earlier death of the caps in the F150 PCM. Smaller size would likely mean greater heat build-up.

I don't understand the ratings well enough to have an opinion on the changes there. Anyone have any thoughts there?

 

Capacitors are like a dry-cell battery. They will leak or dry up over time. I have replaced many capacitors in various electronics over the last 20 years I been doing electronics repair.

I have changed afew in my vehicles(ford and chrysler) and I don't think off-roading or heavy driving causes them to fail. Its just CHEAP parts they make now days. I think most manufactures are using the "less-than optimal part" to cause problems.

Think of "planned obslesents" after xx years of use, have a cheap part that can fail. You either fix it(not now days with disposable technology) or replace it(what the manufacture wants). I am now jobless due to this......


I have capacitors leak just sitting on the shelf. I went to fix my Dad's meter(full of bad caps) yesterday and found most of my stock leaking acid out! Only two out of 20 checked good with the cap tester. But do I trust the "good" 2 caps after 18 failed? NOPE! Hope Rat Shack still stocks them.

 

The physical size of a capacitor usually doesnot cause premature failure. Its mostly voltage/polarity related. Capacitors should never get hot by use. If it does, then who ever designed the circut over looked the voltage rating or voltage spikes.

The 10V rated caps should never see any voltage over 8VDC. The closer to the voltage limit of the cap means the electrolite will brake down(cap gets hot) and usually leaks acid or sometimes blow its top off! The 63V cap should be well with in spects for a automotive 12V to 14.8V system. But they still can fail(read above post)

If you do replace caps, get the same Uf(microFarads) rating but get the higher voltage rating. I would get at least 25V to replace the 10V rated caps. I mostly use 50V rated caps for anything under 24Vdc powered.

 

That's precisely what Guy recommended - see the 10-page long thread on this topic. It just struck me as odd that the F150 caps were rated at 16V and commonly failed while the other PCMs I checked (mostly later ones) were rated at 10V and were NOT failing.

I realize I don't have nearly enough data (or knowledge), to come to any conclusion from that; it just caused me to hesitate in seemingly going the opposite direction from what the factory did. i.e. They went from 16 to 10V while I'd be going from 16 to 25V.

This could very well be the case of me coming to an erroneous conclusion from mis-interpreted data. I'm totally fine with being told that.