Hey all,

I have an ongoing problem that began over a month ago and I am at a loss of what to do/try next. I have blown 2 ECU's and have 1 remaining in reserve so no more trial and fail when I blow yet another one...Figured I would ask before giving up completely and getting raped at the local auto-electric shop for something that may be simple, I am just not searching right? Ok here goes...

1991 Volvo 240 Base Model B230F Engine, Automatic Transmission. Gold/Black in Color.
Please note: This is a 1991 and there IS NO 25AMP Fuse located in Engine Compartment- I have read it was replaced with Fuse #6 in the fuse panel (if my source was correct, if not then I can't locate it).

My History purchase & aftermath:

• Bought 1991 Volvo 240, car running but sat for 6mo-1yr and had old gas in it. Drain old gas, fill with premium & bottle of Heet to remove any water. Runs better.

• Main Fuel Pump has louder than “Normal” noise & starting hesitates, takes a second or two. Check In tank pump and it is not working.

• Car starts “okay” but once running, still runs on main pump well.

• New Car Maintenance Performed:
1. New Spark Plugs (4) gapped & Installed
2. Air Filter
3. Replaced Main Fuel Filter
4. Oil & Filter Change
5. Fluids Checked & Topped off
6. Replaced all belts except timing

• Drive for 3 weeks without issues (aside from only 1 pump).

Problem Begins:

• Week four, alternator belt squealing. Tighten Belt, still squealing.

• Remove alternator check in testing machine and tests good, replace bushings, replace belt. Replace alternator. Corrects squealing but now no start or even an attempt to start. Just turns over & over.

• Check all fuses. Appear Ok but clean terminals and replace all fuses. Nothing.

• Replace in-tank fuel pump, test & it now pumps fuel as should. Nothing. Figure should be replaced anyway.

• Check Diagnostic codes and get code from port #6 (Coolant Temp Sensor) but when check port #2, No reading at all. Forums suggest blown ECU.

• Replace ECU with unit XXX-XX-X951 (as suggested compatible with XXX-XX-X561 and supposed to not blow as easily). Car now starts up but with a little difficulty. Drives but doesn’t seem performing as well? Pull in after test drive and when try to turn off car- does not turn off (even with key removed) and when turn key to “off” position, Overdrive light turns on? Pull ignition coil wire (and see spark between ignition coil post and forward terminal but car stops.

• After a bit of trial, find that can start car easier each successive time but to turn car off must remove fuse #6 then turn key to off position and turns off as should. (If turn “off”, then pull fuse car remains running?)

• Go back to start. Check alternator wiring. Find I have improperly grounded alternator –end #1: alternator case bolt to end #2: block/alternator bracket/ground wire/bolt. As alternator bracket =Aluminum, wrong & not grounded properly. Change end #2 to Block/Ground Wire/Alt. Bracket/Bolt configuration (and even run a secondary ground end #1: alternator case bolt to end #2: bolt on lower part of engine block)

• Start car. Still hard to start (first start, easier each time) runs “okay” but 90%? Still doesn’t shut off as should. Drive to auto store. Check with handheld machine and Battery tests good. Alternator Output (13.94v, 46a) & diodes test good. Test fuel pump relay with new one- no change so figure not fuel pump relay. Try replacement ICM and no change so figure ICU good. Drive home. Still doesn’t turn off as should.

• Try to start next day, no start only turning over with no attempt to start at all. Test diagnostic codes as had same no start with last blown ecu and nothing on terminal #2 or #6 at all, suspicions confirmed. Blown ECU AGAIN suspected.

• As only have 1 ECU left (another XXX-XX-X561), stop here as do not want to put it in before more certainty- cannot keep buying ECU’s (this is the third working one, 2 blown already) if keep blowing by trial & error.

Side note: When I bought the car the previous owner did mention he replaced the master cylinder, brakes etc. Etc. and there was an old ECU XXX-XX-X561 he replaced included in the parts bin he gave me with the car so it may have been changed within the last year or so before purchasing it. Figured I would mention this just in case…

Thoughts on possible problem:
]• 1st thought: Alternator wires/ground shorting or back-feeding? (Checked them and look correctly installed?)Maybe incorrect and just not seeing it?
• 2nd: Alternator/ Diodes fried (Tester said okay but maybe not accurate when alt is on car w/power to it?)
• 3rd: Ignition Switch faulty? (Explain no shut off but would this fry ECU? Don’t believe so & car shuts off as should when remove fuse #6 before attempt?)
• 4th: Ignition coil shorting? (As a result of arc when removing to shut car down wire?)
• 5th: Fixing inoperable in tank fuel pump causing short or something as was not running when driving car (don’t think so but thinking through all things I touched)
• 6th: Wires in Harness near alternator cracked where cannot see and causing short after moving while re-installing alternator?
• 7th: Other?