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Discussion Starter #1
Hello guys
i have p28 chipped Chrome
its started about year ago
the Fuel pump was delayd,i turn the swith on and it take about 2-3 min before it started to pump,in cold weather it took about 5-10 mins.
and today i surpriesd
it even dont want to work after 30 mins..
i got the check engine light on(its was before too when i waiting to the fuel pump ) and nothing happend...
i have replace main relays and fuel pump relay,
the problem is in the ecu cuse i have tried with another p28 with my chip
and it works with no problem
i replaced the resistors and the Capacitors and no changes...
the ecu look OK
Nothing burnt ,Nothing smells burnt

Any Body Got Idea?
Thanks.
 

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Well, you can find the signal pin for the main relay, open the case and trace back it testing all the circuit board items along the way. Without a pretty good understand about how the circuit components work though, it's not going to be easy to trace the circuit.

If you have a spare good working ECU, I'd have them both open and that way you have a point of reference for testing (ie: are parts of the circuit hot when they're supposed to be? are you getting continuity through mosfets at the right time?)

Electronics are only a hobby thing for me though, so i'm sure there's someone with actual real knowledge who could offer better advice.
 

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A break down in the ECU huh? I'd want to also find out how it got a burnt pathway without affecting anything else. Setting the map but not allowing the circuit to break the fuel/main relay?
 

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You don't have a solid CEL on or anything do you?

When you say "fuel pump activation was delayed", can you better describe this? Like, are you going key on engine off and letting it sit for 5 minutes then all of a sudden the quick 2 second prime signal activates? Or are you going key on engine off, the 2 second prime either works or doesn't work, waiting 5 minutes, trying to crank and it starts because of it waiting 5+ minutes? The differences can mean different things from a diagnostic point of view.

Have you tested main relay / fuel pump control out of the ECU connector and not at the main relay? You could have wiring issues between the ECU and the main relay.

Also, have you tried jumping the fuel pump relay terminals to run the pump all the time, then crank and see if the ECU allows the engine to start and run normally? This could rule out and narrow down the problems to only fuel pump control. If you manually get the fuel pump to run the whole time, but the ECU will not let the car start during your 5-10 minute waiting period, you have issues that extend beyond just fuel pump control. If it doesn't start with the pump wired ON, check all ECU inputs to make sure it is getting everything is needs to completely power up BEFORE replacing the ECU.
 

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Discussion Starter #10
You don't have a solid CEL on or anything do you?

When you say "fuel pump activation was delayed", can you better describe this? Like, are you going key on engine off and letting it sit for 5 minutes then all of a sudden the quick 2 second prime signal activates? Or are you going key on engine off, the 2 second prime either works or doesn't work, waiting 5 minutes, trying to crank and it starts because of it waiting 5+ minutes? The differences can mean different things from a diagnostic point of view.

Have you tested main relay / fuel pump control out of the ECU connector and not at the main relay? You could have wiring issues between the ECU and the main relay.

Also, have you tried jumping the fuel pump relay terminals to run the pump all the time, then crank and see if the ECU allows the engine to start and run normally? This could rule out and narrow down the problems to only fuel pump control. If you manually get the fuel pump to run the whole time, but the ECU will not let the car start during your 5-10 minute waiting period, you have issues that extend beyond just fuel pump control. If it doesn't start with the pump wired ON, check all ECU inputs to make sure it is getting everything is needs to completely power up BEFORE replacing the ECU.
Thank u for ur good answer.

Before,i put the key on,check engine light on
And need to wait about 3-15 min depending on weather,when hot outside ita take about 3-5 min,when cold outside(+20c) its can take about 10-20 min,then the fuel pump started prime and check engine light off.

Then i start the engine and no problems with fuel map/fuel pump.
The problem is only START the fuel pump prime,and then all good.

Its ecu problem cuse a have tried anothet p28 and its work perfect,even with my chip.
 

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Thank u for ur good answer.

Before,i put the key on,check engine light on
And need to wait about 3-15 min depending on weather,when hot outside ita take about 3-5 min,when cold outside(+20c) its can take about 10-20 min,then the fuel pump started prime and check engine light off.

Then i start the engine and no problems with fuel map/fuel pump.
The problem is only START the fuel pump prime,and then all good.

Its ecu problem cuse a have tried anothet p28 and its work perfect,even with my chip.
Interesting,

So Check Engine Light stays on solid until your posted times pass, the fuel pump primes, then the Check Engine Light turns off and it allows you to start.

It's good that you have tried another ECU and confirmed that the problem disappears with a new ECU. You've definitely narrowed it down, unfortunately until I finish my OBD1 ECU simulator I have no visual into which ECU components are responsible for certain tasks such as main relay control/pump prime control. All I can do is my own research through other people's experiences, same as you! I have not run into this situation before, so I don't know and I can't offer any personal experience.

Hopefully you find the answer you are looking for somewhere out there! As another member said, PGMFI.org is a wealth of DIY reverse-engineering for the OBD1 Honda world. I'm sure the answers you seek are in there!

Good luck, let us know what you find!
 

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Discussion Starter #13
Just update u guys
i have tried all you reccomended for me ,
and replaced again all caps
and still nothing :S
 

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Check continuity from logic ground pins at ecu all the way to the thermostat housing ground. Recently had similar issues. I crimped a new ring terminal at the thermostat grounds and it fixed my issue.
 

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See? Circuit continuity ...
 

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Discussion Starter #16
Check continuity from logic ground pins at ecu all the way to the thermostat housing ground. Recently had similar issues. I crimped a new ring terminal at the thermostat grounds and it fixed my issue.
Its not the problem...i take anothrr ecu and all works perfect
 

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Exactly the point. The other ECU doesn't have shutdown pathways limping to success. You got your alarm hooked into it or have it programmed in some way?
I had to disconnect that whole fucker once before i stopped limping.
In the end it's a pit stop for throw off codes. I'd say it's shot if you dont get any repeat codes just off hand.
Study extra p28
Learn from it. Sounds captain obvious but it's not in front of me.
Get a circuit checker with a running light. That will help narrow your search.
 

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Just wanted to say i have the same issue. I have not tried to diagnose it but should in about a week or so. Let you guys know what i find.
 

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When you say, "the problem is in the ecu cuse i have tried with another p28 with my chip and it works with no problem"

What do you mean by this? You put your chip in someone else's car and it worked?

Are you burning the chips? What are you using? Moates? Or old school EEPROM burner?

I have extensive experience in Crome and burning chips...and all the weird
stuff that happens when doing this stuff..

I've had the same map do the exact same thing multiple times. Somehow, it was corrupted or the ECU just didn't like it. Eventually, I copied the tables over and created a new map..and it was fine.

Also, does your ECU have the little clip lever that locks the chip in? Or is it the cheaper ones that make you force the chip in and out of the socket?

When you cut the resistor / wire that enables that socket to control the ECU, does the ECU work fine? Meaning, when you disable the socketed area of the ECU, does it work as it should?
 
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