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Discussion Starter #1
I read the " unofficial my car won't start thread" thanks, Guest.

When you bench test a main relay, test one, pos to 6, neg to 8, check continuity from 5 to 7, GOOD, so relay is good

Plug the Main Relay in. WHY does the ECU send power from A7 to #8 MR, and power from B9 to #6 MR. That's 2 power and no ground, so the relay does not close.

So why does the ECU send two power, instead of 1 power, 1 ground.

1993 Del Sol S - D15B7 - Stock - P06-A51 - RZ0159
Any thoughts? Thanks, Inky
 

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I haven't read the thread you're talking about, but this is from an EG workshop manual:

136678


Was the method you were testing from for an EG? EF and EK number their main relays differently, so the instructions can't be cross referenced.
 

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Discussion Starter #3
Thanks for the response.
Yes, same as picture you sent, straight from 92-95 civic service manual.
My question is, why does the ECU send 2 positive voltage to the Main Relay #6 and #8, when a relay requires a pos an neg to close. Thanks, Inky
 

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BATSLOMAN GIVES NO FUCKS.
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one is for the starter solenoid and the other is to ecu.....which probably completes a ground circuit
 

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The reason i asked whether you're using the EG manual is because you mentioned you're finding power on B9 which is mentioned on the EK workshop manual. The EG manual (shown above) does not look for power on B9 during diagnostics.

Regadless though A7 / A8 are ground circuits. You can tell by the direction of the diodes. The diagnostic procedure is confusing, because it says to check battery voltage between A7 (+) and A23 (-), but the power isn't coming from the ECU, it's hot because it's got battery voltage (from the main relay) that's grounding through that pin in the ECU control circuit.
 

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Discussion Starter #6
So, here is where i am now. I have continuity from body ground to A23,24,26,B2, C21.22 on ECU, so I think the grounds are all good. Tested Main Relay again, Good. hooked up timing light and remote start, car cranks and sparks. I can jump #5 & #7 on main relay and fuel pump runs, and i get fuel to the rail. Took jumper off. Went through the troubleshooting flow chart page 11-117,118 in 92-92 civic manual. last test is connect voltmeter to A7 + & A23 - , do you get battery voltage for 2 secons when key is turned on? solution, If YES substitute known ECU and retest. if NO check main relay. i get battery voltag but it stays constant, not just for 2 seconds. so, I have a YES and NO, Honda circle theory must be in place. Inky
 

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So, here is where i am now. I have continuity from body ground to A23,24,26,B2, C21.22 on ECU, so I think the grounds are all good. Tested Main Relay again, Good. hooked up timing light and remote start, car cranks and sparks. I can jump #5 & #7 on main relay and fuel pump runs, and i get fuel to the rail. Took jumper off. Went through the troubleshooting flow chart page 11-117,118 in 92-92 civic manual. last test is connect voltmeter to A7 + & A23 - , do you get battery voltage for 2 secons when key is turned on? solution, If YES substitute known ECU and retest. if NO check main relay. i get battery voltag but it stays constant, not just for 2 seconds. so, I have a YES and NO, Honda circle theory must be in place. Inky
Does the fuel pump continue running then after the 2 seconds?

Hook up a test light to the fuel pump connector power wire (piggy backed, so it's still plugged into the pump and visible while you're cranking), try and start it. Try and see if the car not starting is due to no power at the pump, or whether the pump is getting power but the car is still not starting.
 

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Discussion Starter #16 (Edited)
I will check tomorrow, unfortunately the car is in another town.
Should i leave the ground on MR #8 while testing?
If there is battery voltage at A25 and B1, [Power input] what next?
if there is battery voltage at B9,[start input]. what next?
also, if we were both online at the same time, i could save some trips to the car. I'm on eastern standard time. Inky
 

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remove any jumpers .
test with koeo and cranking.

whats next? make absolutely sure all grounds are good .open ecu case look for possible bad capacitors or find a known working ecu..
 

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Discussion Starter #18 (Edited)
Koeo, A25 12.34v B1 12.39
Crank A25 12.41v B1 12.41 B9 12.39
I plugged in a P06-A01 ECU i have {for a 5 speed} with same results. When i first acquired this ECU it started the car i drove it all around the neighborhood. Next day it reverted to crank no start.
guess I'll buy a new ECU, worst case I'll have a new spare. Inky
 

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Discussion Starter #19 (Edited)
I just plugged in the original ECU, now the cel comes on for 3 seconds and goes off, still no start.
Honda manual says replace with known ECU and retest.
 

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Any way to check the ECU's you've tried in another car to see if you're fking them or if your car has other issues?

Any chance OBD0 injectors have been swapped on without the resistor box and it's burning through ECU's? (Check resistance across the injectors)
 
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