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Hello gang. I’m getting no spark from the distributor on my 745T. I’ve got spark at the coil, all the wires are new, and I checked the timing belt. Can I safely assume that the new cheap-o distributor I put in last year has taken a crap, or is there something else I’m missing?
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Well, new cap and rotor did the trick. Thanks everyone for the input. It’s funny, I’ve been burned so many times replacing parts that seemed like the obvious culprit, only to discover that the problem was something else entirely. This time, when I’m completely broke and really need to make sure I’m making the right move before I spend any money, it was the obvious thing that any shade tree mechanic with half a brain would have replaced right away. Now I want to dissect the old and figure out what the heck is going on in there...
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My guess would be poor casting in the manufacturing process. Cheap quality.
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Post Back. That's whats makes this forum work.
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Most likely the difference between coper and aluminum contacts.
Dan
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Thanks for all the input everyone, but I’m still going in circles on this one, completely vexed.I’ve got the cap removed, facing up with the rotor manually held in place, and when I crank the engine,I can see that I’ve got spark leaping from rotor to post, then onto my test plug, but when cap and rotor are installed, I’ve still got spark at the input to the cap, but nothing at the cap output. It stands to reason that the problem is somewhere between the cap and rotor, but I tested continuity and resistance in the 6 month old cap/rotor and everything checks out. The rotor spins when the engine’s cranked, so the timing belt is intact. WTF?!?!?!
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Sounds like the cap might be bad or perhaps it is the wrong cap?? As I recall, you said the cap and rotor are cheapies. Replace them with Bosch parts (OEM). Cap and rotor are pretty cheap. Then you will have all OEM cap, rotor and wires.
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Will I buy another Volvo??? We'll see....
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That seems like the obvious choice, although it’s run fine with that cap for the last six months and there doesn’t seem to be any problem with it based on the various tests I’ve made. I’ve gone down the needless-replacement-of-parts road enough times to shake a stick at, but I’m at my wit’s end,
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Replace both dizzy cap and rotor. Bosch only. Even if cap continuity test is ok there's energy lost somewhere. Sort of internal short. All is not lost however if it turns out to be something else. You still end up having good cap and rotor for future use.
Amarin.
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i warned you in my first post on the 24th. people wonder why i don't post much. because nobody pays attention. could've been on the road that much sooner. pity.
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Sounds like a defective cap to me. If you are not getting spark from the cap to the wires it seems to me that the changing the cap makes sense. At last it is a cheap part to throw at it!
Years ago I put cheap wires on my 90 244DL. The car never ran right right with those wires. Well, maybe at first. Changed to Bougicord wires - end of story.
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OK, so I’ve got spark coming into to distributer cap, and when I turn it over with the cap off and the rotor sitting inside, there’s spark going through the rotor to the poles that feed the plug wires, but when I install the cap and rotor, there’s no spark. This May be a stupid question, but is the distributer supposed to be insulated from chassis ground? The reason I ask is cuz I hooked my ohmmeter up and there’s continuity there. Wires are new Bougicords btw.
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Maybe it's just your phrasing but you wrote--"OK, so I’ve got spark coming into to distributer cap, and when I turn it over with the cap off and the rotor sitting inside, there’s spark going through the rotor to the poles that feed the plug wires, but when I install the cap and rotor, there’s no spark." -- doesn't make any sense. Rotors can be bad. Also - is the little spring loaded carbon post in the middle of the cap still there? The distributor is NOT insulated from the motor/ground. -- Dave
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Sorry for the confusion. With the cap removed, but with the wire connected to the coil, I touched my spark plug wire with test plug to the spring loaded post and got spark. Having determined that the spring loaded post wasn’t the culprit, I sat the rotor in place in the still uninstalled cap as it would be if the cap was installed rand got spark going through the rotor to the post, but when the cap and rotor are installed, there’s still spark at the coil wire/cap connection, but not at the plug wire terminals. It seems like there’s got to be a short somewhere.
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https://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#Testing_Hall_Sensor
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Post Back. That's whats makes this forum work.
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the hall sensor's job is to tell the coil when to fire.
if the coil has spark, the hall sensor works. the cap's job is to distribute the coil output to the wires, using the rotor.
if there's spark at the coil tower on the cap, the coil and hall sensor are working.
if there's spark at the coil tower but nothing to the plug wires, the it's the cap and/or rotor.
if there's spark at the all the wire towers on the cap and nothing at the plugs, it's the wires.
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That was my first thought, having been down that road last September. I tried John Sargent’s hall sensor test (pull distributor, ground the coil and listen for the sound of injectors as you rotate it) and it checked out. I’ll take another look at the link, though. Thanks!
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So you get spark on the center coil to distributor wire and when you make a direct untimed connection with the rotor to the inside of one of the posts on the distributor you get spark on the outside of that post. I'll assume you checked more than one of the posts with the same result.
Sounds like a timing issue. You mentioned that the timing belt was okay. Was that a visual on the belt, or did you insure that the cam was turning while you cranked?
Maybe jumped timing? Used to see this a lot on older cars with stretched out chains, not so much with rubber belts which are more likely to break than stretch. Try checking if the rotor is pointing to the #1 post when #1 cylinder is at TDC.
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I agree. Check the little spring’s condition on the cap and look for subtle cracks in the plastic. Also look for extreme scoring on the rotor tip and cracks.
That’s got to be a frustrating problem - good luck!
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Will I buy another Volvo??? We'll see....
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if you have spark at the coil, the dist is ok.
1 spark with key on? probably the igniton module-not the ecu.
lotsa spark at the coil? check for spark at the dist cap and again at the plugs. no spark there, then cap rotor and wires. cap and rotor-bosch only. don't cheap out. wires-no bosch, they're lousy. bougicord or oe only. good luck, chuck.
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Lotsa spark at the coil. Dist. cap is new as of last Sept, but it is a cheapy. Hard to believe that a cap could crap out after 6 months, but t does seem like the logical choice.
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I totally agree with Chuck. Go with Bosch cap and rotor. And Bougicord wires (OEM). I’ve seen personally and read here about issues with non-OEM ignition parts.
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Will I buy another Volvo??? We'll see....
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Me again, if you do need a computer, see if you can find someone who has a parts car, or try eBay.
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How are you getting a spark from the coil? Are you getting multiple sparks from the coil when you turn the engine over? (probably a stupid question!)
I had the same issue with our '90 744 Turbo.
I got a spark when I turned the ignition on, but no others.
I do not remember getting any codes from the test plugs - I think that my car was the first model that had a box that you could pull codes from. Your car may not have this box.
I checked all codes and plugs that I could find instructions for in a Haynes or a Chilton manual. I spent a lot of time on this as it was one of 4 cars that we had at the time.
Eventually my dealer told me that the main computer was faulty.
I tried a few local junk yards, including a great one that had over 600 Volvos, most of them 740s.
They had about 150 computers for NA 740, but NONE for turbos - This was because of the failure rate for each.
If it is your main computer, good luck - the computer cost over $900! Replacing it did fix the problem without any other work needed.
The only thing that I would add is that I did charge the battery a couple of times and I may have left the battery connected once during charging. This may have caused a high voltage, but because the car was never turned on during charging, I doubt it.
One thing that you might look at is the wire from the coil to the distributor - on one of my 740s, the wire had burnt away inside the clip that holds it to the firewall, and it shorted out.
Also, are you sure that the spark you see is strong enough to fire a spark plug - It could be your coil - try to connect the coil to a spark plug to see how it fires.
In an old motorcycle book, it advised one to check your ignition for a nice fat spark when it is running good, so you can actually see if the spark is good when your bike won't start on the road!
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Check your dizzy cap n rotor. Continuity test with voltmeter across those cap n rotor terminals.
Amarin.
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Check the plastic connector on the base of distributor. It may have cracked etc. Hall sensor.
https://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#DoesMyCarHaveaHallorRPMSensor
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Post Back. That's whats makes this forum work.
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