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Discussion Starter #1
So i literally just assembled a fresh rebuild bottom end and cleaned and tested head both have minimal work done per fsp rule set. All new gaskets , water pump tb, the whole deal. finally have it back in the car for the 1st start up and it runs good at idle for a bit until it gets to around 175-180 degrees then it startes bubbling like crazy in the burp funnel attached to the top of the radiator. it happened last night and the thermostat hadnt opened yet, so instead of trying to trouble shoot last night i left it sit and topped off the burp funnel and let it sit overnight. fast forward to today fired the car up and messed with idle a bit and closed loop running due to the obd2 sensor not working. all the while keeping and eye on the cooling system no issues so far. about 20 minutes in the thermostat opens " good deal" return to passenger side of car to laptop to monitor coolant temp and next thing i know smell coolant look up ect is 206 and coolant is violently being spewed fromt eh burp funnel... turn off the engine and within a minute the burp funnel is empty. so do i have a air pocket somewhere or what could it be. all coolant lines are correct, there is heat in the heater core.im at a loss ive been rounds like this before but it was on 150k motors that had questionable previous maintanence. any help would be great im going to get another thermostat tomorrow and try that maybe thermo stat is no opening completely.
 

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BATSLOMAN GIVES NO FUCKS.
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lower radiator hose warm when fans kick on? fans kicking on? front end jacked up with heat on full blast? pressure check the system?
 

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Discussion Starter #3
once thermostat opens yes lower hose is hat, no fans yet since the fans usually dont come on for another few degress . and the bubbling start right or or around the thermo opens. heat on and is hot ,not pressure tested yet.
 

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BATSLOMAN GIVES NO FUCKS.
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youre supposed to burp it until the fans kick on atleast twice. with the front jacked up of course so the rad cap is the highest point
 

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Brokedick Millionaire
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youre supposed to burp it until the fans kick on atleast twice. with the front jacked up of course so the rad cap is the highest point
Burp funnel raises the "highest point" so the jacking up isn't needed.
 

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Discussion Starter #8
both fuses are good interior and under hood. jumped the ect and the fan did not come on. wired fan direct and no issues with fan. wondering if there is another issue with the chassis harness being obd2a and the engine harness is obd2b. i had to run a separate rpm signal wire since the obd2b gets its rpm signal from crank sensor.

also of note the brand new obd2b oxygen sensor has no reading on s300.

wondering if my p28 that has obd2b plugs needs to have some of the pinouts changed to work correctly.

think i figured out the issue , dont have a plug "A" to plug into my ecu... wondering what the simplest most economic solution is at this point. 98 dx hatch previously running y8 manifold d16y7. so grand plan was build d16y8 per fsp rules. obtained the engine and had it rebuilt. at teh same time purhased a hondata build p28 pinned obd2b. so figured no big deal get an engine harnes call it a day. pulled the old motor harness and all accessories intact. assembled rebuild y8 motor installed harness and dropped in the car. easy enough right well im finding out, no not that easy. So wondering do i swap engine harness's back and try to find a p28 ecu to accept my s300 or is there an easier solution? right now the car has no coolant fan and no oxygen sensor being read at the ecu.
 

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93 Civic HB SI
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486 Posts
It sounds like someone tried to splice in OBD1 connectors to the dash harnesses in order to utilize the P28? If that's the case, you need to finish adding all connectors to the vehicle harnesses that will allow you to completely plug into the P28.

Not sure why people go this route when they make nice OBD2a/b to OBD1 plug and play conversion harnesses?

Why don't you just use stock OBD2a/b engine and dash harnesses with the Y8, then just get an OBD2a/b to OBD1 jumper harness? For the engine harness to bring it round to OBD2a, just go to a junkyard and grab one. The conversion harnesses allow you to plug your OBD1 P28 ECU directly into your OBD2a/b harnesses, no messing around with wiring. Your cooling fan and O2 sensor would end up at the OBD1 ECU exactly where they need to be:


OBD2b to OBD1 conversion harness:

20200324_144434.jpg


Plugged in to a P28:

20200324_144514.jpg


Plugged into an OBD2b harness:

20200324_144827.jpg

20200324_144832.jpg


No messing with wiring.

wondering if my p28 that has obd2b plugs needs to have some of the pinouts changed to work correctly.
I need a picture to see this. How does your P28 have enough room to house the OBD2b type ECU end terminals? Why would someone go through this trouble to mod the board directly?? Lol.

OBD2b ECU end terminal cavity size (1 inch):

20200324_150105.jpg


OBD1 ECU end terminal cavity size (approx. 11/16"):

20200324_150153.jpg


Side by side:

20200324_150159.jpg


There would have been a lot of headache to make this work. I'm not saying it couldn't be done, but damn that would be an assbackwards way of making OBD1 to OBD2b! You would have to transplant the entire front face of the OBD2b ECU terminal set into the OBD1 ECU, then solder tiny individual wires between the OBD2b interface and the OBD1 board.

I would NEVER directly mod an ECU like that when 1) conversion harnesses exist to prevent doing something like that and 2) splicing entire OBD1 connectors to the OBD2b harness is a second best option.
 

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Discussion Starter #10
this may of been hondatas answer to not having jumpers...? it is a p28 board that hondata then took obd2b terminal set and mated to. I have no y8 dash harness my chassis harness is obd2a. i was unaware at the time this would be an issue. i think the easiest thing for me to do is get another p28 pinned for my s300 and try to sell the bastard obd2b p28... then just re harness my engine and add vtec and be done.

i have obd1 to obd2a jumper already, heck i sold a pinned p28 to purchase the obd2b p28, not knowing it was not going to work. but this explains why the fuel pump doesnt prime and just continually runs, why the coolant circuit is not working properly, and why the o2 sensor is reading 0.0v with a brand new sensor. so in trying to make a super clean y8 swap i instead wasted about 300.00 in the process and now have to spend more money to get the correct ecu. o well , im to old for all this mess.
 

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93 Civic HB SI
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That sounds like a plan.

I still want a picture! I've never seen one of those ECUs!

I just googled and found a picture of it. Sure enough, they proprietarily designed and built a hard soldered OBD2a or b front end that replaces the entire OBD1 front end. It sticks out, but it does work.

Could you not just go to the junkyard and cut some OBD2b dash harness connectors off, grab some schematics for both car variants between OBD2a and b then go to town soldering in the OBD2b connectors to your dash harness to replace the OBD2a connectors?

Then everything will plug right into your P28 as it is.
 

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Discussion Starter #13
seems like there is alot more then just dash or interior stuff in teh dash harness. not trying to be difficult but im not sure id know where to obtain all of these from.
136022
 

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Discussion Starter #15
yes key on and jumping the ect terminal should of kicked the fan on basically simulating the the switch closing the loop and this did no happen. later found out it was because i was not completing the circuit via the plug "A" or dash harness. I have since swapped the obd2a harness back into the car and wired vtec accordingly just need to sell my ecu and procure an obd1 p28 pinned for my s300.
 
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