View Full Version : blowing the EFI fuse
09-03-2009, 09:33 PM
Well there you go:
Car was running fine all summer and yet when I fired it up on tuesday morning this skreeching sound irritates my ears at the very moment its started, so mistified, I roll it around the house and it does not stop. I opened the hood and it seemed to come from the water pump wich was put on the engine 2 years ago...strange, but wathever.
Left the car there for the day, come back from work and set out to find the confirmed origin of nois but instead the car wont even start!!!
As soon as I put the switch to ON, the EFI fuse burns out!
Call it what you want, I say it`s a PITA!!!
I tried a bunch of things and for something to help the search:
- When I put a 25 amp fuse it does not blow but a 20 will.
- the fuel pump does not respond even with the 25 fuse... it`s been silent since the car went dead.
I need some more input to what the EFI fuse is providing power to.
I know my megasquirt computer is hooked on it and I think the fuel pump too, but what else???
I`ll be pulling down the gas tank this w-e to see what the pump has to say, but would love to have other thing to look at if it`s not that.
Really in all the years I`ve been here, I think this is one of the rare times I ever asked for help, so please, if you have any insight at all, just post!!!
Thank you all!
09-03-2009, 09:56 PM
I would pull the alt out and get it checked. It will blow the EFI fuse if it pumps out too much voltage/amps, and it could very possibly be what was screaming at you.
09-03-2009, 09:58 PM
WHat he said ^^ sounds like a good possibility. Hope he's right Nic !!
09-03-2009, 10:00 PM
Take a copy of the Electronic wiring diagram.
and the TSRM at the same time if you don't already have it:
EFI fuse at page 19 of the pdf.
Don't forget you have had some wiring changes.... !
09-03-2009, 10:07 PM
...alt has nothing to do with, according to page 25 ? !
09-03-2009, 10:24 PM
Yeah, I looked too at the EWD and the TSRM and did not see how it happens, but I know that a few years ago I knew someone with the same problem, I put a 25A fuse in there and watched the batt gauge in the cluster peg out right away.
09-04-2009, 06:27 PM
I had this problem b4...its usually different for everyone...but i broke a wire that went to my ISCV under the intake mani and it was grounding out on the mani...everytime i turned the key "pop" it went...took me a week to find it under all that stuff...could be a broken wire anywhere grounding on something. G/L.
09-04-2009, 10:50 PM
I'll work on it again tomorrow and see what limit my patience has for the day...hopefully things will work out!
Keep ya posted!
09-08-2009, 10:19 AM
I dont want to be a stick in the mud but the efi fuse on my ma61 (5m-eu) kept blowing - never did find out why !!!! - various "experts" were worse than useless and I tried just about everything to sort it out - any rate after THREE YEARS off the road I pulled that stinking efi off the engine and threw it in the bin - I put a carb + manifold and distributor from a 4m on and hey presto I am back on the road !!!! - not as much top end power but hey even the jetting seems ok - this may seem extreem but take my advice - get somebody who KNOWS what they are doing to sort out your efi problem
09-08-2009, 01:59 PM
Yep, I'm still at it... not found the cause yet.... ugh.
It's very obvious I have a short circuit but have not found it's roots.
Ruled out a bunch of things so far but I guess I still have ways to go, I'm actually taking a break today as I cant manage another evening of frustration and be going for a massage instead.
Tomorrow I'll be better off to continue on!
Thanks for the inputs it helps with some of the plausible routes to cover
09-09-2009, 01:21 AM
MR Tech...Your signature has more modifications listed in it than I think I have ever imagined to do to my Supra so I am probably not the one to speak up but since you are at a loss perhaps a novice approach will help. Since the 20 amp fuse blows and the 25 amp one does not, you have to determine what pulls a load over 20 amps and under 25 amps. So far that is the best clue we (you) have. Since it ran well until the screeching started, which is probably a "rotating thing", you said water pump but I am leaning toward the alternator since your problem has little to do with water and more to do with electrical power. What if you disconnected the alternator, and tried it ?? I don't know anything about the 1JZ-GTE but it would work on a 5M. My alternator grounded out so bad that it would not allow power to go to the starter, disconnected the alt and it started right up. I replaced the alt and everything is OK now. Just a thought, hope you get it fixed.
09-09-2009, 01:27 AM
My 91 Celica did the exact same thing, fuel pump was blown. Make sure that's not your problem.
09-09-2009, 07:07 AM
thanks guys, I'll make sure to check both these tonight as they are the top 2 probabilities on the list. Either one could be, it only makes sense at this point.
I'll let you know what I find tomorrow!
09-10-2009, 06:36 AM
Alright, found the darn bugger!
Turns out it was not the alt and not the fuel pump, but the wires to the fuel pump.
Saw it after droping the tank, the shielding around the wire was badly squashed. Removed the shield cut the wires, spliced them back together and Voila!!! Car is running again!
But... the skreeching is back as well.... I'll take the belt cover off tomorrow to find out wich pulley/part is causing the noise.
That and I have to put the car back together... I went pretty deep to find that wire... To be continued!
09-10-2009, 07:06 AM
I hope you remembered to clean up in there while you had the gas tank dropped!
I'm happy to hear that she's running again.
09-10-2009, 06:44 PM
...could be a broken wire anywhere grounding on something. G/L.
hmmm....sounds like something mentioned earlier...good job finding it...these types of issues can drive you completely nuts for a looooong time...i know....
now onto the screaching...when moving? idleing?
09-10-2009, 09:55 PM
Nic, I see walbro pump... must have been squeezed there on reassembly...
tought location to find! Bravo !
09-11-2009, 06:47 AM
Yeah, I'm glad I found the wiring problem.... could have gone trhough it without noticing, but I had a feeling the wires were involved in that location.
funny thing is that its the oem wires from the pump assembly that got broken, I guess they got squeezed between the tank and the chassis.
As for the screaching, its on as soon as I fire up and does not stop even when I push the gas or drive it some. Doesnt sound like a slipping strap as far as I can tell... I'll see tonight after I removed the timing cover.
Cheers for the encouragements and guidance!
09-11-2009, 08:12 AM
A similar situation has arose for me as well, but my EFI fuse will only blow while under mid to WOT acceleration. You can blerp the throttle in bursts, but the second you maintain that high throttle position it will blow the fuse. Currently a 10 amp fuse is in the EFI bank, works fine under normal driving circumstances. All equipment is stock, other than a walbro in the tank, which has been working fine for about 6 months.
Anyone have any ideas what could cause this?
09-11-2009, 08:42 AM
when you had the trans out, how was the throwout bearing or the pilot bearing? can you hear the screaching from that area when the car is running and youre listening underneath?..
09-15-2009, 12:14 PM
any progress? I assumed you had the trans out for some dumb reason, idk what i was thinking. Ive been fighting an oil leak for 2 weeks now, so i understand your pain...its coming from the passengerside front..ugh!...think im gonna have to remove the rear timing cover and change seals....wanna trade problems?..haha!
09-15-2009, 01:25 PM
nah, mine are just about solved!
Since I found the faulty wire, the car runs fine, but the screaching is much related to the timing belt. It looks like it's off the center of the cam gears and the belt is eating itself on the edges of the casing. I'll replace it and see how the pulleys fare.
Oil leaks suck...they always persist to a point of major anoyance.
Well good luck with it, hope it's going to work out without to much pain.
09-15-2009, 03:30 PM
I know you know this but I'll say it anyway - make sure you replace the belt tensioner when you replace the belt!
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