Need help with fuel pump or ECU problem

okay some decent progress:

genesis, i checked the relay, it runs a 12VDC coil. as you mentioned and in keeping with the way the relay works, the open circuit showed complete continuity, while the other showed resistance. thx for the diagnostic pointers.

grifty, i ran thru all the pins again to check against the layout. i disconnected the wires from the relay and tested them off and on ignition. checked em all again just like u mentioned, i must have missed the fact that some of my wires weren't powering up.

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just got up from downstairs and this is what i did:

86: i noticed that blue/red wire from the ecu was reading 12v when the key was turned. i used this as ignition and plugged it to 86.

85: i ran a brand new ground instead of using the ground wire in the harness, this would eliminate any problems with the wire.

30: i traced the thick blue/white wire that i was using as constant power, noticed it to go thru the firewall and into the engine bay battery side. i assumed this was the wire providing constant power. however, it was reading no voltage either on or off ignition. this may be where the problem lied. for the time being (and seeing as i dont have a head unit) i tapped into the constant 12v line off the headunit harness (with fuse) and into the 30 pin on the harness as main power.

87: i connected this line to the fuel pump positive.

result: car fired up and maintained idle for the first time off the harness!

im gonna go back down and neaten up my wiring. there are now 2 wires that are being unused from the harness (i assume these to be the dud power, and possibly dud ground).

with regards to the pin 30 12v power wire, can i run a new wire from the battery +ve terminal thru the firewall and directly to the relay pin 30? or does it need to be a wire with fuse for safety, or come off the ecu? otherwise im pretty happy with my 87/86 and 85.

i would use a fuse from the battery+ to terminal 30 to give me peace of mind that a short circuit will not burn up all the wiring, there cheap aswell anyways.

cheers, will do that tmrw. currently running from a 10A, reckon that would do the job?

is it normal for the relay to get very hot also?

also, on testing, ignition, idle and acceleration, signal to the fuel pump was always above 12v. i guess its always running full duty, this normal?

Regarding the wiring, I'd re-run the existing wiring to bring it back to stock as much as possible. This problem began because of mish-mash wiring, and whether you keep the car or sell it, the world will be a better place if the wiring is tidy and predictable. If you can re-run the wire in the loom back to the fuse panel, all the better.

Regarding the relay getting hot, yeah, the coil is a giant resistor and generates heat as current passes through it. Since the car needs fuel all the time, it makes sense that it'd be working full time to supply that fuel to the car. Since the coil is only a switch and not dependent on how much fuel you're using, it's running the coil at full capacity even at idle. That's why it's hot.

Congrats on getting the car up and running, good job. Once it's all tidied up, you'll be able to enjoy it with peace of mind.

I'm going to join the discussion here because basically I have exactly the same problem (or at least the consequences of a similar problem). Even though the car has had an engine transplant and an aftermarket ECU I don't understand why you need another relay when you should have an EFI Main Relay (like in the photo). The only answer seems to be that the conversion shop went with the standard non-EFI relay and then just added a bunch of extra wires to complete the conversion to EFI. Always a recipe for disaster, especially as the wiring looks like its been done with crimp connections, notorious for working their way loose over time.

The first thing is always to test the fuel pump is actually working. As you have found out, and others have suggested, a simple 12V feed to the correctly grounded pump will tell you if it is working. So far so good.

Your main issue is with power and you seem to have solved that, at least temporarily, with some new wiring. But I wonder if you are getting VTEC engagement as that is a function, in some ways, of revs. My understanding is that the fuel pump needs to be switched via the EFI Main Relay, and communicating that to the ECU. I'd be interested to know your final solution.

Peter

Quote:

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Originally Posted by GenesisEG

Regarding the wiring, I'd re-run the existing wiring to bring it back to stock as much as possible. This problem began because of mish-mash wiring, and whether you keep the car or sell it, the world will be a better place if the wiring is tidy and predictable. If you can re-run the wire in the loom back to the fuse panel, all the better.

Regarding the relay getting hot, yeah, ..... That's why it's hot.

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totally agree. yeah, i'd love to bring it back to stock as much as possible, the only problem is that i'm having to work with a car thats was in a state very far from stock, with poor quality and incorrect wiring.

was getting a little worried about the heat, thanks for clearing that up :)

Quote:

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Originally Posted by jdm_b16a

...I don't understand why you need another relay when you should have an EFI Main Relay (like in the photo). The only answer seems to be that the conversion shop went with the standard non-EFI relay and then just added a bunch of extra wires to complete the conversion to EFI. Always a recipe for disaster, especially as the wiring looks like its been done with crimp connections, notorious for working their way loose over time.

But I wonder if you are getting VTEC engagement as that is a function, in some ways, of revs. My understanding is that the fuel pump needs to be switched via the EFI Main Relay...

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thanks for joining in mate. the more the merrier, as every single person joining in so far has been incredibly helpful. :)

agreed. i seem to not have a real EFI main relay at all. they may have kept the standard non-EFI relay (eg4 breeze w/ carby originally) and just added this separate floating 5-pin relay to act in its place. the wires have also been done in a very average manner. the thing is im not sure what to do about it but run the relay i've been given, except with secure and quality wiring.

that's an interesting point. i will try to see if VTEC engages or not soon when i've got the car to safe operation.

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its good that the car is up and running, but i'd like to get the wires running the way that they should in a safe and reliable fashion. i still want to try and figure out the original problem as i still have a few question marks. have learnt so much about the car already in the 2 weeks that i've owned it (my first honda), thanks to the help of many of you.

so i've plugged the following:
30 - fresh wire to battery w/ 10A fuse holder (not sure if this is right)
85 - fresh earth wire
86 - wire from the ecu that has voltage when key is set to 'on' (i.e. ignition switch)
87 - line to the fuel pump

there are two wires left over that are not being used from the original harness. i have closed their ends for now so there is no chance of contact. these would be 30 and 85, where i have run fresh wire from their sources. this would assume that they would have been ground and constant power. i can't seem to trace them back that far as they get lost amongst the harness. both of them test zero voltage both off and on ignition.

in the stock format, does anyone know the layout of the constant power? e.g. does it go from battery to fusebox to relay? or battery to fusebox to ecu to relay? the origin of the original power wire seems to be the biggest question mark for me.

visual summary:

http://img.photobucket.com/albums/v3..._original1.jpg

voltages tested at the relay pin/wire junction to be more accurate
http://img.photobucket.com/albums/v3...y_problem1.jpg

also with new battery
http://img.photobucket.com/albums/v3...lay_fixed1.jpg
car is up and running with this layout

some thoughts:
?safety concerns
?which fuse to use on power wire (currently 10A)
?pin30 power source from battery instead of oem fusebox or ecu
?when the engine is running, there is constant 12v+ out at pin87, how is the circuit i've set up different from running the direct wire from ignition to fuel pump in regards to fuel pump duty/operation

i would double check that the wire to 86 is coming from the ecu. To find the correct fuse rating for the fuel pump i would check the interior or exterior fuse box lid. other than that it looks all good.

As far as the current rating of the fuse, what is the rating of the pump?

Just divide the watt rating by 12 and you'll get the current rating of the pump. The fuse should be slightly higher than that.

I would hazard a guess that the original power to pin 30 would have come from the OEM fuse box. I'm not familiar with the wiring but some cars have a fuse box in the engine bay and one in the dash, check both.

It doesn't really matter, as long as the pump feed is protected, it'll be fine.

As for pin 86... I dunno. I would say it comes from the ECU, it needs to be powered BEFORE the car turns on to pre-pressurise the fuel.

Quote:

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?when the engine is running, there is constant 12v+ out at pin87, how is the circuit i've set up different from running the direct wire from ignition to fuel pump in regards to fuel pump duty/operation

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There probably isn't much difference, but since fuel management is run by the ECU, if, per-chance, the ECU wishes to cut off fuel from the engine, and you've run the coil feed from the ignition, it won't be able to.

There should be 12V constant at pin 30, probably straight from the battery, although running it from accessory should be fine too, since accessory is going to be running when the ECU starts.

From pin 87, there should also be 12V constant, as long as the ECU is holding the contacts closed. It probably won't need to open the contacts unless you have a serious problem with air/fuel ratios or something.

Regarding the VTEC issue... I highly doubt the fuel pump relay is going to have any effect whatsoever on it. The relay turns the fuel pump on and off, it can't control how much fuel comes out of it. The only problem you could possibly have is if the pump can't keep the pressure up, and that would be because the pump is too small.

Anyway, let me know how you go. Sounds like it's all under control. Just double check the rating of the pump and make sure the fuse is rated accordingly. Remember, watt rating of the pump divided by 12, that's your current rating. Make the fuse slightly bigger than that.