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Ecu electrical question


iomlt
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I have a 14 cux 3.9 system from a rrc into a 90. all working perfectly. Then I decide to fit rubber interior and carpet to the truck and now running really poorly and the main wire (orange and something thick wire to ecu) gets hot.

my question is does the ECU need a good earth as in the unit itself? all i did was lift the ecu and two relays up and fit carpet and the riveted them back on (rear bulkhead) over the carpet and then had this problem.

She started and ran on say 4 cylinders and I moved her 50 feet and switch off. I noticed a slight warm plastic smell and noticed that the fuse holder was starting to melt a little (fuse is only 10amp) to the orange cable to ecu (i think its main feed to ecu) I switched off fast. Then rechecked everything i had done and still the same. So the only thing I can think of is the ecu mount itself needs a good earth.

Can anyone suggest anything?

Thanks

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I thought along the same lines also. Just seems VERY odd that since i lifted and re-riveted the ecu back onto the bulk head i have this issue.....I have stipped the out plastic wiring casing to check for any cables that may of rubbed through etc. all in perfect condition..

Any ideas on what i could do to test whats going on?

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Does the negative wire go to the battery direct, and is it attached to the case inside the ecu? Possibly the case is earthed to the wire, and the wire isn't very well connected, or is earthed through the engine block. It's an easy one to rule out, by trying it with the earth onto the battery for a bit.

hth

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OK had a good poke around tonight. all seems ok, wiring is as it should be. i have been meaning to put new plugs, leads rotor arm and cap on for a while (genuine stuff) that got her running again.... (so maybe when i ran her for very short journeys she got alittle flooded) i still notice the fuse getting warm.... not hot like before but warm.... but everything else is ok now..

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Have you got the right relays in the EFI setup? Some of them are not the normal type, and if you put a normal 4 or 5 pin relay in the socket, strange things can happen. I know 14CU setups had a 5-pin relay with two outputs rather than changeover, not sure what 14CUX has.

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Good question... I pretty sure i left them as is... (metal cover type) i may of change the two over between them. It is somthing i will check thou. thank you.

After the leads, plugs, rotar arm and cap its running absolutely beautiful!

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Yeah i agree, but as the relays are the same (not including the fan control relay) i thought no damage would occure. I'm starting to wonder if it is a poor contact on the old type glass barrel fuse. i am thinking of changing it to flat blade type fuse to see if this cures the heat problem. In theory i could connect direct to ignition and perm live as the efi loom has its onwn fuses anyways. i just wanted to play mega safe and unterlise the two spare fuses i had in the fuse box as the efi conntection is next to the fuse box also.

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