Keeps burning EFI main relays (2 Viewers)

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diego355

diego355

Joined
Oct 11, 2010
Threads
45
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633
Location
Calgary, Canada
Hi everyone.
I have a 1991 3FE FJ80 used for off-road and weekend driver. The problem occurs when the vehicle is run for an hour or more, the EFI main relay overheats and dies. The temporary solution is to switch out the super hot relay with a cool one. Ultimately, I end up switching relays as quick as every 5 minutes:mad:

Does anyone have any information on 1) what causes this problem, 2) how I can fix it, 3) recommended parts to replace that might fix the problem. What could be increasing the voltage to the EFI relay that could cause it to overheat like it does?

Thanks
 
To burn out would take a lot of current. Meaning there is something sucking current on the other side of the relay. Do you have a voltmeter to do troublsehooting? Do you have a wiring diagram?

I would find whats down from the relay and disconnect/inspect etc to find what is sucking the current. Potentiually a loose ground would do that as well so I would make sure you have a good ground
 
Literally 100s of threads on this. The relay socket contacts are most probably corroded by the wire crimps causing a good voltage drop. This combined with the constant heat of the exhaust manifold have most likely baked the wires in the fusebox. If you read through this writeup: EFI Relay Pics 4 U
There is some good info on what to do to permanently fix this.
 
Wires under fuse box too small. Upgrade to 12 gauge. MIke
 
So what i have found so far is to replace 12 gauge wire with 10 gauge from EFI fuse to EFI relay, and install 10 gauge wire from EFI relay to connector EB1 terminal #2.
Does anyone have the diagrams with pictures so its a bit easier to follow? I dont have too much experience working with electrical other than installing a sub, amp or lights.
I do know were the fuse and the relay is but no idea on this EB1 terminal #2

Thanks
 
I've done the 12 gauge rewire to the EB1 connector and changed out the relay with another.
I had 3 or 4 spares i would swap out.

All were temporary fixes until I just made a pig tail, from the box under the hood, and moved the relay inside the cab. This was 4 years ago. Problem solved.
 
diego355 said:
So what i have found so far is to replace 12 gauge wire with 10 gauge from EFI fuse to EFI relay, and install 10 gauge wire from EFI relay to connector EB1 terminal #2.
Does anyone have the diagrams with pictures so its a bit easier to follow? I dont have too much experience working with electrical other than installing a sub, amp or lights.
I do know were the fuse and the relay is but no idea on this EB1 terminal #2

Thanks
Click to expand...

...let me see if i can help.
No pics but this is a step by step of what I did back in 2004 with the rewire.
For some this fix worked, for me this was temporary, not a long term fix..

Access the underside of the relay/fuse box.
I believe you need to unbolt a few things to get this far, 10 to 15 minutes with a 10mm.
There is a 12 gauge wire, yellow with a red tracer that goes from the EFI relay to EB1.
Undo the loom that goes to the EB1 connector.
EB1 is the first connector about 12 inches from the EFI relay, that one needs to be changed to 10 gauge.
There is a 12 gauge wire, red with a yellow tracer that goes from the EFI fuse to the EFI relay, that needs to be changed to 10 gauge.
At first I tried and failed to remove the female connectors that fits in the box for the relay and fuse to plug in.
I just cut the wires leaving about 1/2" and crimped the 10 gauge using heatshrink and rewraped the loom in 3m vinyl electrical tape.
If you wire harness loom is brittle replace it. Mine fell apart like saltine crackers.

Hope this help, good luck.
 
Ive been shoping for an 80 for a while and found one that is priced right. ive been talking to the guy that owns the truck and he seems to be very honest. Its a 94 with the EFI issue. He rerouted the relay to inside the cab and said that it helped but out of the last 40 or so times he has had the truck out it has overheated twice. Should i stay away from this truck? is this a deal breaker? if i end up with the truck my plan was to upgrade the wiring in hopes that it would take care of the problem. Really like this truck but this issue really scares me as this will be my DD. Should i RUN??
 
KyHL said:
...Its a 94 with the EFI issue. He rerouted the relay to inside the cab and said that it helped but out of the last 40 or so times he has had the truck out it has overheated twice. Should i stay away from this truck?...
Click to expand...

What overheated? The relay? Or are you talking about the engine?
 
Electrical issues can be a pain to track down and repair (or they can be kind of fun depending on your paradigm). Certainly the problem could be traced and fixed, but there are a lot of factors to consider; what kind of shape is the rest of the truck in? How many miles? What kind of technical ability do you have? If the electrical problem and whatever else the truck needs is not something you can tackle yourself, does "priced right" account for repair costs?
 
anyone have a pic of EB1? and guess what, my 92 FJ80 doesn't have an EFI Relay at all. I have a '91 next to it though. or what page on the Manual to search it out?
 
Two 3FEs said:
my 92 FJ80 doesn't have an EFI Relay at all.
Click to expand...
If there was no relay for the EFI circuit, then your battery would be flat within 2 days of sitting. There is most certainly an EFI relay in the same location for every EFI equipped 80 Series. If it is not in the stock location, then most likely it has been relocated.
 
OK. But how can I find it? I am not seeing any replacement wiring going back through the firewall. and no sign of it under dash.
 
Two 3FEs said:
OK. But how can I find it? I am not seeing any replacement wiring going back through the firewall. and no sign of it under dash.
Click to expand...

Go to the one that has the relay in the stock location. Find the wires that go to the relay on it and trace them back to the loom. Locate the loom on the missing relay vehicle and trace to the new relay mounting location.
 
I found it. what they did was use the CDS fan connector for the EFI relay. now I don't have the fan anymore.
 
Two 3FEs said:
I don't have a fan running after shutdown like the 91 used to have. which fuse or relay might that be?
Click to expand...
That is the "engine compartment cooling fan". It is controlled by a thermistor on the exhaust manifold heatshield, a timing circuit in the passenger kick panel, and a relay in the driver kick panel.
Power comes from the DOME fuse under the hood and the ECU-IG fuse by the driver's left knee.
 
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