Chipped p28 - not priming fuel pump

 
Old 02-23-2005, 04:48 PM
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Default Chipped p28 - not priming fuel pump

My fuel pump turned off when I was driving around yesterday. Long story short, I was testing the main relay when I realized that the ECU was powering it when the key wasn't even in the ignition, then it cut off power when the car was turned on. Basically, the exact opposite of what was supposed to happen.


I've been running this chipped P28 for about a month now with no problems. Now it's like something inside got reversed. I would blame my soldering job, but it's worked fine up until now. Any suggestions?
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Old 02-23-2005, 05:01 PM
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Sometimes a capacitor goes out in the board and that causes the fuel pump not to turn on. I forget exactly which one it is, but it is one of the big ones in the middle of the board new the plugs. Check for any leaks, or burns.
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Old 02-28-2005, 11:06 AM
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I'll be damned, you are right. I never would have guessed. Thanks for steering me in the right direction


I was reading on a DSM forum that said something about leaky capacitors smelling like rotten seafood. I thought the article was funny at the time. Then I went out and smelled my ECU yesterday. Sure enough, its like sticking my nose inside my cat's *******.


I can't tell which capacitor is leaking though. Worst case scenario is that I have to replace them all (about five).
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Old 02-28-2005, 11:16 AM
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where is this capacitor at???? where in the ecu?? What number on the board?? i have the exact same problem with my ecu
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Old 02-28-2005, 11:17 AM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93turbo16 &raquo;</TD></TR><TR><TD CLASS="quote">Sometimes a capacitor goes out in the board and that causes the fuel pump not to turn on. I forget exactly which one it is, but it is one of the big ones in the middle of the board new the plugs. Check for any leaks, or burns.</TD></TR></TABLE>

good info!!!
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Old 02-28-2005, 11:19 AM
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C15, C14 are the caps, and Q31, I believe is the transistor. I just had an ecu not want o prime the pump, I am going to take a look at it today, replace it with some parts, and see what happens.
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Old 02-28-2005, 11:27 AM
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thank you, ive been trying to fix that ecu for like 6 months, and noone knew what was wrong. Ill try switching out those parts and let u guys know how it goes.
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Old 02-28-2005, 12:23 PM
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I was going to play with it today, but ran out of desoldering braid.. and snow is keeping me from radio shack.. and a glitch in my main relay.. POS
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Old 02-28-2005, 02:34 PM
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I'm back, and I brought knowledge with me.


So when you open the ECU, you will realize that everything is coded with numbers/letters. Every code that starts with "c" is a capacitor.

You will notice that there are two main types of capacitors - the tan or blue colored disks are ceramic capacitors. They don't go bad. The other capacitors, the ones that look like metal cylinders covered in shrink-wrap, are electrolyte capacitors.

Electrolyte capacitors are like batteries - filled with the same chemicals. Over time, heat and wavering alternator output take their toll and the capacitors begin to leak. THIS IS VERY BAD - your pc board doesn't like battery acid. It will eat through the board and cause shorts.

The symptoms? Well first, if you see any type of chemical that looks like it's oozing from the top of the capacitor, its bad. Also, if the capacitor smells like rotten *****, its bad.

There are 7 electrolyte capacitors on a p28 ECU. Their job is to filter the voltage input going through the ECU. They are all located near the harness side of the ECU. When you open the ECU, you will notice that one capacitor is about 4x bigger than the other six. That's because it's the main capacitor that filters the voltage going into the entire ECU. When this sucker goes bad, it stops turning on your main relay and your fuel pump will stop.

If you have one bad capacitor, it makes sense to replace all 7 at once becuase you know the current conditions will make the old ones leak. Go to digikey.com and buy replacements that match the numbers on the sides of the old ones. Be sure the replacements are rated at 105 degrees and not 85 degrees. The 105 degree capacitors are better quality and will last twice as long as the 85 degree capacitors.
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Old 02-28-2005, 05:58 PM
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right on my friend.
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Old 02-28-2005, 07:00 PM
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I had this exact same problem. Do you have an OBD2-OBD1 harness?? If so it more than likely the harness. I went through two before one was actually (mostly) wired correctly.....and those were harnesses straight from hondata dealer and not like ebay stuff.
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Old 03-01-2005, 09:29 AM
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Wait, the harness caused the capacitors to blow? Cause I'm using a $50 ebay harness.


Anyway, I opened up the ECU yesterday and removed all the capacitors. Sadly, I don't know if I can even salvage the ECU. C14 was leaking a little bit and was likely the cause of my problems, but when I removed C18 I noticed the bigger problem. It leaked out A LOT and fucked up the pc board. When you poke at the board with a soldering iron tip, it's like poking at mashed potatoes.

Anyway, I'm pretty bummed. I'm going to order new capacitors anyway, we'll see if it works.
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Old 03-01-2005, 09:59 AM
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Ive had a few ECU'S with bad fuel pump output or something.
On those we just took the Fuel pump output whichever pin it is, and ground it on the harness side.
the fuel pump should come on with ever you turn the Ignition on now.
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Old 03-01-2005, 10:31 AM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JRciv &raquo;</TD></TR><TR><TD CLASS="quote">Electrolyte capacitors are like batteries - filled with the same chemicals. Over time, heat and wavering alternator output take their toll and the capacitors begin to leak. THIS IS VERY BAD - your pc board doesn't like battery acid. It will eat through the board and cause shorts.
</TD></TR></TABLE>

The rest of your info is good, but I'm just clearing up the fact that electrolitic capacitors do not have battery acid in them. they contain a type of paste, and the most common way these caps go bad is when the paste dries up. or sometimes they explode, but they are designed to explode safely (caps this size it's more of a pop). you don't have to worry about acid eating through your PCB.
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Old 03-01-2005, 10:53 AM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbosi03 &raquo;</TD></TR><TR><TD CLASS="quote">

The rest of your info is good, but I'm just clearing up the fact that electrolitic capacitors do not have battery acid in them. they contain a type of paste, and the most common way these caps go bad is when the paste dries up. or sometimes they explode, but they are designed to explode safely (caps this size it's more of a pop). you don't have to worry about acid eating through your PCB. </TD></TR></TABLE>

You do have to worry about acid eating the board.... it eats through the traces..
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Old 03-01-2005, 01:00 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbosi03 &raquo;</TD></TR><TR><TD CLASS="quote">

The rest of your info is good, but I'm just clearing up the fact that electrolitic capacitors do not have battery acid in them. they contain a type of paste, and the most common way these caps go bad is when the paste dries up. or sometimes they explode, but they are designed to explode safely (caps this size it's more of a pop). you don't have to worry about acid eating through your PCB. </TD></TR></TABLE>

eat your words.. I had a board laying around here that I was meaning to fix, and this made me want to, so I took 10 minutes of my time and took some pictures for everyone to kinda see (the pics are a little blurry) what I mea, about the caps eating the trace, I fixed it, took it out to the car, and it fires right up.

Here is the trace under the big cap at C14 ( this is the one that goes to the fuel pump pin ) You can see the cap has burnt through the board and it has broken connection to a resistor right below it.


SO to fix this, take that capacitor out and junk it, get a spare ecu, that is junk and take out another capacitor that is good.. I recommened changing caps with a new one, but I just wanted to get this done to post it on here. Take a jumper and wire it from the burnt up trace side of the capacitor and run it to the resistor.. DONE!

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Old 03-01-2005, 01:35 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93turbo16 &raquo;</TD></TR><TR><TD CLASS="quote">

You do have to worry about acid eating the board.... it eats through the traces..</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93turbo16 &raquo;</TD></TR><TR><TD CLASS="quote">

eat your words.. </TD></TR></TABLE>

ok, I am still correct about what I said and rather then eating my words I will better explain...

what you are trying to show people a pic of but can't see very well is NOT a PCB trace that has been eaten by capacitor acid. you are looking at a burnt trace caused by too much current being drawn through that perticular trace at the time the capacitor decided to fail in which electrically looks like a short. since that is a filter capacitor with one lead on +Vcc and the other lead connected to gnd, when the capacitor shorts it essentially shorts the ECU power supply to ground. when you force that much current through that tiny trace it will blow like a fuse.

having said that, my previous statement "you don't have to worry about acid eating through your PCB" stands true

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Old 03-01-2005, 01:50 PM
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http://www.tmo.com/howto/ecu1g/caps.htm

read, unless they are wrong.. but I am pretty sure that is accurate. Because I have fixed caps in 1G DSM ecus too, they have the same problem with the electrolyte caps.
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Old 03-01-2005, 02:14 PM
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I read and they are wrong. there's no point to continue this convo since you did point out a problem and how to fix it, but caps don't leak battery acid and they do not eat at traces. traces burn out from caps failing and becomming a short, thats it. I have fixed many boards as well and they will all look the same if there has been a cap that causes a current surge through a small trace.

I was just correcting what is the cause of these issues so people understand what is going on. either way the problem and solution info is good

&lt;--- eletrical engineer in case that holds any merit
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Old 03-01-2005, 02:51 PM
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Heh heh - so say "hypothetically" that I removed all the caps without noting where each one went...


Who would be able to tell me where each one goes?

And which capacitors should I buy from digikey? Digging through their selection is a nightmare. I didn't know there were so many different types


Modified by JRciv at 5:23 PM 3/1/2005
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Old 03-01-2005, 05:11 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbosi03 &raquo;</TD></TR><TR><TD CLASS="quote">I read and they are wrong. there's no point to continue this convo since you did point out a problem and how to fix it, but caps don't leak battery acid and they do not eat at traces. traces burn out from caps failing and becomming a short, thats it. I have fixed many boards as well and they will all look the same if there has been a cap that causes a current surge through a small trace.

I was just correcting what is the cause of these issues so people understand what is going on. either way the problem and solution info is good

&lt;--- eletrical engineer in case that holds any merit</TD></TR></TABLE>

That is all well and good, because that is what my major is.

Also just to add, every single article I have searched comes up with a "leaking" capacitor as being the reason they failed.

Oh, and I never said they have battery acid in them, Caps just store charge they do not create it, they are sepereated equally but opositley charged plates, seperated by a material between them. That is a basic form of a capacitor, no were is there any battery acid or chemicals that creates a potential difference, that I know of.

Then explain the residue that seems to come from all of the caps that I have replaced, it seems they "leak" something.. I can understand why they short, I am just making a point that there is somethng coming from inside the cap, every single one that I have removed has had the same thing on it.
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Old 03-01-2005, 09:43 PM
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Guys guys - I'M the one who brought up "battery acid". Everyone knows that capacitors don't create current. I was just throwing out a relatable phrase instead of "electrolytic paste" or "potassium permanganate" or whatever else the caps may contain. That's not the point here - no need to split hairs.


Now who's going to respond to my last post
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Old 03-02-2005, 06:10 AM
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I can tell you the size caps,

C14; 220uF 35V cap
C15; 33uF 35V cap
C24; 47uF 10V cap
C21; 33uF 35V cap
C19; 33uF 35V cap
C18; 220uF 10V cap
C40; 100uF 10V cap

Too lazy to get the digi key numbers, sorry man, I hate searching their site. But there are the locations and sizes.


Modified by 93turbo16 at 11:48 AM 3/2/2005
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Old 03-02-2005, 07:40 AM
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Thanks, that's exactly what I needed

(isn't that last one supposed to be [email protected] instead of [email protected]?)

Anyway, the link in one of the posts above suggests the Panasonic NHG series. I tried ordering all my caps in that series, but they don't make a 47uf cap for some reason. I wish radiohack didn't suck so much. I don't have anywhere local to go.
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Old 03-02-2005, 07:49 AM
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yea, it is 100...
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