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?

 

how many volts on the various power circuits when the car is switched on?

1) an alternator shorting to ground would fry itself and the wiring to the short, but shoudn't impact your ECU

2) I don't trust those testers, and prefer using a digital volt meter and verifying everything myself. excessively high voltage when the engine is running would certainly fry stuff.

3) a faulty ignition switch USUALLY results in a no-run condition, erratically or permanently. or, a car that wont shut off, in the case of where the switch jams 'on'.

4) ignition is a completely different circuit, and a different control unit.

5) a problem with the tank pump wiring might blow fuses, and might cause poor running on gas low, but shoudln't take out the ECU

6) possible. IMHO, not real likely unless your harness is in generally bad condition.

 

Thanks for your reply's guys! Well here it is...

Well, I've figured some things out but still have a question or two I could use some help with. So I got out the test light and found that there was only a dim glow when applied to the Oil Pressure Sending Unit (Idiot Light, Not gauge) wire. I found that when I either 1) ran a wire directly from battery to the Oil Pressure Sending Unit or 2) Unplugged the oil sending wire I could start the car. If I reattached it, just turns over and over. So while I do not fully understand why, I figured out the Starting issue. The car still continues to run (and overdrive light turns on for some reason...?) when I turn off the car & remove the key. (I have to pull the Fuel Pump fuse and then turn the key to "Off" position and it will shut off as it should.

Some have suggested Ignition Switch. I have a replacement from the pull-a-part but don't want to go through changing it if you think the Oil Pressure wire (Someone said that the Oil Pressure it is a grounding wire & that's why it tells the idiot light to light up when improperly working?) may be the culprit? Or another possibility (Alternator backfeeding due to bad diodes etc.- even though the O'Reilly tester reads good alt & good diodes?)

Well here are my questions:
1) Is there a way to test if it is the Ignition Switch without the PTA removal?
2) If removal is needed, any tips? (Looks like a hell of a tight spot, upside down with a screwdriver or removing the instrument cluster- fooling with more old wires and potential screwups as a result...
3) Do you think the "Not shutting off" may have to do with the Oil Pressure wire? How to rewire it or reattach it if so?
4) Alternator bad (don't test the O'reilly testing unit basically)

Thanks a lot guys. Again.

 

if the car is running when the ignition key is off, something is fubar with the ignition switch, or there's some bad wiring, or maybe the fuel pump relay (which is also the ECU power relay).

wait. maybe your jumper is backfeeding power through the instrument panel. thats bad news. the oil pressure sensor is a switch to ground. its wired to the oil pressure light on the dashboard, which goes to power on the 15R side of the ignition switch. so you're powering the whole car through that oil pressure light when you flip off the switch, bad news!

ok, remove your jumper, its hiding the actual problem.

yes, the wiring diagrams for a 1991 LH 2.4 do show battery power to fuse 6, and fuse 6 goes to 1) the fuel injection/pump relay

power from the ECU side of the fuel injection/pump relay goes to the ECU also

power from the fuel pump side of the fuel pump relay goes to fuse 4, and to the main pump. fuse 4 powers the OX sensor and the tank pump.

remove the carpet panel under the driver side dash. there should be a ground screw under the dash directly above the fuse panel. hook your test light (or a volt meter) up to that ground and fuse 6, you should see power there even if the car is off. now hook it up to that ground and fuse 4, switch the key on, you may see about 1 second of light/volts, then it goes off, this is the pre-start fuel pump priming. turn the key to start, and if the engine is turning over, fuse 4 should be 'hot' until about 1 second after you stop cranking. yes or no?


hey, if any of your fuses are the silver tin kind, are they grey and dull? are the fuse holder clips shiny brass or are they oxidized? I would replace any grey fuses with copper/brass ones, you can buy these from ebay sold as 'mercedes W123 W124 fuses', for 80s mercedes 300E/300D cars..., those are the real german kind, not the crappy tin american Buss fuses. the kit I bought on ebay was cheap and included more than enough fuses to replace ALL of them, with lots of spares. If the fuse holder contacts are dull/oxidized, clean them with a soft pink pencil eraser NOT sandpaper or something. its the inside of the holder that has to be clean, around the little hole the fuse tips fit in.

 

Two years ago, my 1995 940 Turbo wagon had the radiator replaced...about 15k miles ago. Recently discovered a coolant leak and took back to radiator shop where they pressure tested it and found a tiny leak at the O ring to the water pump. Just had the o ring and gaskets replaced and picked up the car, only to discover a coolant leak at the bottom corner (passenger side) of this fairly new radiator. My mechanic got under the car and crimped the radiator. He then tried to sell me a new radiator. I quickly called the radiator guys who believe the mechanic must have damaged the radiator?? In the meantime, I will keep a very close eye for any leak and when I get back to Nevada the radiator guys want to closely inspect the radiator!! Any thoughts on what might have happened? Trying to keep from putting any money out for no reason!! Thank-you!!

 

pressure testing can stress a weak radiator, and sadly, now days the quality control on new radiators seems to be pretty crappy. PO of my last 740 T wagon had to install two radiators, both Nissen, to find one that didn't spring a leak. it lasted 6-7 years under my leadfooting it, so that second one was a good'un.

 

Good morning, Pierce,

Yes, the last radiator (original) went to 200k on my wagon! I believe my mechanic accidentally whacked it to cause the leak. The radiator guys want to see it and examine where he crimped it to better judge what happened. It was not leaking before they added the new gasket & o ring to the water pump. The original leak from the o-ring was very tiny! I will keep a close eye on it....very disappointed here! Thanks for you reply!