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Changed battery, car cranks won't fire

OldGrandpaTune

The Road Warrior
Joined
May 7, 2013
Location
Rural Ohio
I have an 88 765 with a B230FT.

The car was more and more sluggish starting and eventually wouldn't. I measured voltage which was low 12's, then measured running at 13.6 showing the alternator is doing it's job.

When pulling the old battery out (which was too big) I touched the wrench from the positive terminal for just a second to a fitting on my catch can which caused a spark. All of the connections and terminals were in good shape, but there were some old wires all disconnected to an ancient alarm system here and there around the battery.

The new battery is in and the car cranks just fine but will not fire. My car always starts with just a turn of the key instantly.

Pulled a fuel line and there is plenty of fuel when the car is cranked. Pulled a spark plug and with it attached to the wire and the body grounded there is no visible spark. The plug was bone dry and did not smell like gas.

There is 12V present at both sides of the coil when the car is cranked. The distributor is a new Bosch installed for a couple of weeks, and the plugs and wires are within the last six months.

I double checked all around the battery to see if anything was disturbed, but the wires and the terminals are in good shape. Electrical seems to go to everything in the car.
 
Something arched?

Check fuses?

It was a quick arc, but none of the fuses appeared to be blown in a quick check. I'll have to research and find a complete ignition circuit and run it down. Hopefully that didn't fry my computer or something.

I pulled the coil wire, and nothing comes out of the coil high voltage connection. This is really perplexing. Found a great schematic for the B230FT down the page here:

http://www.autoelectric.ru/auto/volvo/740/1989/740-89.htm

To add to the day, someone backed into the Subaru at auto parts. He was a nice guy, and offered cash instead of my making a claim. Little rear corner panel body work, and gotta get into that anyway.
 
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It was a quick arc, but none of the fuses appeared to be blown in a quick check. I'll have to research and find a complete ignition circuit and run it down. Hopefully that didn't fry my computer or something.

I pulled the coil wire, and nothing comes out of the coil high voltage connection. This is really perplexing.

To add to the day, someone backed into the Subaru at auto parts. He was a nice guy, and offered cash instead of my making a claim. Little rear corner panel body work, and gotta get into that anyway.

1) 'lektrons are STUPID they do ONE thing (and that is to follow the path of
least resistance).....but they do that ONE THING at the SPEED OF LIGHT....

2)here are your "FILE ME" resources:
http://www.k-jet.org/documents/greenbooks/200-series/
http://www.k-jet.org/documents/greenbooks/700-series/
http://www.volvowiringdiagrams.com/
http://www.volvowiringdiagrams.com/?dir=volvo/Ignition Systems (get BOTH of them!)
 
Thanks for the much better links. I'll put them in the ever expanding file box.

The power stage is looking like the hopeful culprit (as opposed to the computer). Got a mighty fun Saturday with 28 degree and snowing conditions making it perfect Fluke meter weather.
 
There should not be a constant 12V at the low side of the coil when cranking (or running). The ignition module (power stage) is just a switch to ground. It pulls current through the coil in sync with the distributor signal. So the voltage on the low side of the coil should be pulsing from about 0-12V.

Re: the spark. It don't matter much how quick it was, electrons move at the speed of light. It's just a matter of weather heat from the short built up enough to fry something. Always disconnect the ground cable first and reconnect last. Then you can short the plus side of the battery to the body all you want cause there is no path back to the battery.
 
Most likely fried the volt reg/and/or the diodes in the alt. Just have it rebuilt by a alt shop/do it yourself.
 
Most likely fried the volt reg/and/or the diodes in the alt. Just have it rebuilt by a alt shop/do it yourself.
I know rules for electrical but biffed changing the battery in a snowstorm and got in a hurry. I'll test out the power stage Saturday and go from there. Got the prints so just reading it out now. I will see about borrowing a scope from work to look at the pulsed signal to the coil. Thanks everyone!
 
Woohoo fixed it! Thanks again Mick for the schematics which I will treasure and keep in the big binder.

The battery that was in there was at least three inches too long, and when I went to take out the power stage today noticed the plug was partially pulled out. Plugged it back in, and it took the usual two seconds to fire. The alternator is fine.

This one is a freebie, and I got off lucky. All that is hurt was my brand new 10 mm wrench with an arc spot in the plating and my pride. Next time I don't care how cold it is, I won't get in a hurry. The bolt on the negative side is replaced so it is easy to take off now.

Anyway the troubleshooting did go well and I never would have known the power stage thingy is inside the fender without the prints.
 
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