Broken ECU.... I think!

[mackempete]

This is my first post to the forum, however I've been a frequent visitor and have found this forum soooo much help with my chimp.
Anyway I picked my car up from the auto electricians on Friday night only to get half way home and for the engine to die. Turns off and on the ignition and the fuel pump is intermittently priming then stopping. Also the relay in the passenger footwell is clicking away at random too. Needless to say it didn't run very well with the pump doing that . I gets straight on the phone and blasts the auto electrician for been incompetent and breaking my baby . He drives out to where I've broken down, has a bit nose around in the foot well, takes the fusebox off, has a bit more of a nose around. Cant find anything! He applies a negative to the fuel pump relay so its on constantly. Car starts then dies again! At this point he pulls out the ECU from beside the battery. Oh dear, turns out the battery has leaked onto the ECU and its all corroded to hell. Sparky says it must of been just hanging on and him working in the area has finished it off.
Anyway I've got lucky and ordered a new ECU off ebay for £100 delivered and i just wanted to check with you guys whether the symptoms I've described would be consistent with a bust ECU as I thought these were well sealed units and not susceptible to a bit of water/battery acid?

[roop]

I'd have thought battery acid getting into the ECU (assuming that's what it has done) would render it knackered in a short space of time. Remember that electrolyte conducts electricity, that's the whole point, so any leaking onto circuit boards etc would just cause a short circuit.

[mackempete]

Its quite well covered in corrosion I've posted a link below (it may take a while to be viewable). I cant get inside the box to check for corrosion internally as the screws are that badly eaten away i cant get a bite on them. I was really just wondering if the fuel pump relay is switched on/off from the ECU?

http://petertread.fotopic.net/c872826

[GreenV8S]

Yes the fuel pump is controlled by the ECU so if the ECU has been damaged it could cause symptoms like that. If you do have acid on the ECU then you have to wonder where else it has got to, is the rest of the wiring, fuse box etc OK.

Battery acid is nasty stuff, if you pick up something that has had acid on it then everything else you touch will get acid on it too, this will rot organic materials so a few days later you may find fingerprint sized holes in all your clothes etc. You want to wash the affected areas with an alkaline solution, sodium bicarb for example.

>> Edited by GreenV8S on Sunday 26th February 13:03

[mackempete]

Thanks thats what i wanted to hear. So with a new ECU on the way it should just be a case of plugging it in and away we go... You know this so isnt going to go to plan!

I'm going to replace the battery and clean the whole area. The rest of the wiring looks ok as far as i can see. Fusebox is fine and so are the fulepump/ecu relays and fuses etc on the loose leads. The connector to the ECU's clean too so looks like i've been very lucky

[GreenV8S]

Remember that just because two ECUs look the same doesn't mean they are interchangeable. If you change the ECU you need to ensure it is set up for the that engine, or transfer the chip across. This might not be trivial, because I think they're usually soldered in and taking the chip out will destroy it. Just plugging the new ECU in and seeing what happens would be a worthwhile way to see if this fixes the reliability problems, just be aware that the fuelling may end up miles out unless/until you get the right map put in. You can solder a socket in easily enough but getting hold of a new EPROM chip with the right map would require help from somebody like Mark Adams.

[mackempete]

I was under the impression that the ECU for chimeras/griffs was the same no matter what size engine it came from? I might be wrong but thats just what i read elsewhere on here?

The ECU I've bought comes from a 4.0 Chimera, the same as min, so hopefully it should be ok? And if it isnt the its a good excuse to get the mark adams treatment

[GreenV8S]

If it comes from another car of the same model then it should work fine. But for example 5 liter is different to 4 liter.