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DIY low cost main relay replacemet/upgrade

64K views 24 replies 13 participants last post by  torreslife88  
#1 · (Edited)
if your main relay is acting up or has gone bad this is a way to get it fixed with a standard 4 pin automotive relay you can find for around $5.

it is also an upgrade from the stock main relay. as you will see in the pick below the main relay send power directly to the fuel pump and works on a circuit board with paper thin copper foil.

im assuming that fuel pumps dont take too much current to run since i was running a walbro 255 on the stock main relay and wiring.

material needed
1 automotive relay with harness ( i used a basic 30 amp 4 pin)
**** if you cant find one with a harness you can use female quck**** **** disconnects onto the relay directly ****

5 male quick disconnects
**** one of them must be larger to hold 2 wires to bridge required **** **** terminals ****

heat shrink wrap for each quick disonnect


i wasnt able to find a harness for my relay so i only have a pic of the prototype that i slapped together.

the wiring instruction are simple just check the correct diagram below. ive got it figuered out for the larger acura main relay but i need to fidn a pinout for the harness, the integra main relay is the same as the one one as the honda"s.
 

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#2 ·
every single time I've ever had a main relay problem I've taken it out, held it about waist high from the ground, Drop it on the pavement, and reinstall. lol thats it. its worked every time for me. Ive done this with two different relays and its worked. just an old trick i guess ha. good DIY!
 
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#5 · (Edited)
its not just a fix but an upgrade. a fuel pump shouldnt be getting power from a flimsy copper foil lined circuit board.

maybe its all in my head but my idle seems smoother.

another thing that is cool is you can use it as a security feature. i know a guy that puls his main relay when he parks his civic at work cause it was stolen. with a regular relay its liek 3 times small and can fit in your pocket a lot easier. plus it would make it easier to wire in a turbo timer or remote start.
 
#10 ·
around my way all the main relays are gone. finding a main relay in a salvage yard around here is like finding a honda distributer or manual tranny ECU!! all the honda guys out here know what to grab when a car comes in fresh. i know guys that go to the yard everymorning to check on fresh hondas and integras. on top of that you got honda enthusiast workign at teh salvage yards and selling stuff locally on ebay. my boy miguels garage is ful of stuff. once oen of those gusy tried selling me a vtec spool valve for $100 it took me a while befor ei found one on here. it held up my head swap for months.

now you dont have to haggle with salvage yard buzzards for a main realy!!!
 
#18 ·
Off topic, but I can only extend my sympathies to you. I'd say Hondas around where I am go to the crusher about 60-80% untouched. In fact, I don't know if I've seen a Civic that's EVER had its main relay removed ... well, ok a couple of times. But that is the exception, not the rule. I frequent a couple in my area and there are still 5th Gen Coupes with the front spoilers on them, ECUs intact, clocks and black armrests still in them ... hell I even saw a cluster w/ tach sit around for 8 months before I finally pulled it myself for a project.
 
#21 ·
the guy told me it needed oen when i bought my car actually, he even told me about resoldering ti btu i figuered i would just replace it. its made me late to a few dates thats about it so i never bothered to replac eit once i found it it was $60. than this past 2 weeks when my car was realy acting up i figuered it was time to change it.

i think my main relay only acts up in the summer heat, turns out the problem i have now is something else liek a bad ecu connection somewhere.
 
#22 ·
Oh right ... I remember now that I had something quasi-useful to contribute to this thread: If your relay is acting up (usually in hot weather) ... give your dash near where it's mounted a smack ... often it's enough to get the contacts to connect and get you going.
 
#23 ·
Thumping your relay to get it running is a VERY temporary fix. I tried that for a day or two, and finally the joints were so loose that I had to keep my car running on compression. It kept bucking and trying to shut off, then kick back in, then buck some more. I got it home, pulled that bitch out, soldered it up in 5 minutes, and never had an issue again. Ever since, I automatically resolder the joints before the issue begins.

The joints are always the same ones, but might as well go over them all to be safe. But you can normally see the little circular breaks if you look closely enough.

And the reason it happens in hot weather, is because of the heat that traps in your car while its sitting in the parking lot. It causes the circuit board to contract and expand to the point where it separates the dry joints.

Just solder them up. A 30 watt iron with tools and a tube of solder is 8 bucks at Radio Shack. Or an iron is 5 bucks at Walmart, and a tube of solder is 1.69.
 
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#24 ·
I rather run it my way with a regular relay, a realy soldered to a circuit board makes no sense. It should have been just been put into the fuse panel or a relay panel, every other car I've own had all the relays in the fuse panel not on a circuit board,
 
#25 ·
if your main relay is acting up or has gone bad this is a way to get it fixed with a standard 4 pin automotive relay you can find for around $5. it is also an upgrade from the stock main relay. as you will see in the pick below the main relay send power directly to the fuel pump and works on a circuit board with paper thin copper foil. im assuming that fuel pumps dont take too much current to run since i was running a walbro 255 on the stock main relay and wiring. material needed 1 automotive relay with harness ( i used a basic 30 amp 4 pin) ** if you cant find one with a harness you can use female quck** ** disconnects onto the relay directly ** 5 male quick disconnects ** one of them must be larger to hold 2 wires to bridge required ** ** terminals ** heat shrink wrap for each quick disonnect i wasnt able to find a harness for my relay so i only have a pic of the prototype that i slapped together. the wiring instruction are simple just check the correct diagram below. ive got it figuered out for the larger acura main relay but i need to fidn a pinout for the harness, the integra main relay is the same as the one one as the honda"s.
which wires go where there's 7 wires and I have a 5 pin relay which wires do I bridge?
 
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