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91 Regina 740 No Start

First start by pulling the flexplate shield and do a visual inspection.

You could also do basic stuff like use a test light to the coil negative wire and see if it blinks steadily while cranking. You may see something.

I find it tough to believe two wires aren't sparking. Maybe....

I would first do the test light method mentioned above. I would also look to see if the king lead is consistently sparking. A scope could also be used here since it may be so fast it would be tough to see the pattern.
 
ZVOLV said:
First start by pulling the flexplate shield and do a visual inspection.

You could also do basic stuff like use a test light to the coil negative wire and see if it blinks steadily while cranking. You may see something.

I find it tough to believe two wires aren't sparking. Maybe....

I would first do the test light method mentioned above. I would also look to see if the king lead is consistently sparking. A scope could also be used here since it may be so fast it would be tough to see the pattern.
Click to expand...

No luck finding a lab scope, and not really in the budget for me.

Having no spark on only 2 and 3 is weird, i agree. But I can pull the wire off and ground a plug against the head and see NO spark. Swapped king leads with a known good but I’ll check for a constant spark while cranking, not a ‘on off on off’ while cranking, right? It’s like the computer is telling the coil to NOT fire when 2 and 3 approach TDC. One thing I did notice was that it’s not getting spark while running, but when I turn the key off, I see one spark from the dead cylinders plug, like every time. So i know it has spark going to the cap, but the computer is telling it to pull all spark. It makes no sense it me.

It’s about 90F and sunny but I’m going to try to remove the inspection plate and inspect the tone ring throughly for any obstructions.

I know a DVM is essentially useless, but I just went and bought the cheap harbor freight one to replace mine that had broken. Idk if there’s anything at all I can do with it, like measure CPS voltage and resistance maybe.
 
You can check resistance of a crank sensor, but it prob won't tell you much. You know it's not totally open.

I would really analyze and inspect for a steady primary and secondary ignition pulse with whatever tools you have.

Do you own a test lamp yet? You can always make one.
 
ZVOLV said:
You can check resistance of a crank sensor, but it prob won't tell you much. You know it's not totally open.

I would really analyze and inspect for a steady primary and secondary ignition pulse with whatever tools you have.

Do you own a test lamp yet? You can always make one.
Click to expand...

I do not. Should I be checking for a constant spark from the king lead wire from the coil while cranking?
 
A test lamp to the coil control circuit (ground) should illuminate the bulb with key on, and blink while you crank. Build one with a spare bulb and solder some wire onto it. You should see a steady blink. One end of test light to coil ground, the other end to a known good ground.

The test lamp is a very strong diag tool. I use mine all the time. It's better than a meter because it loads the circuit. One strand of wire can pass 12v and show as such on a meter, but it wouldn't illuminate a bulb.

Do you own a timing light yet? This is a safe way to check secondary ignition. It also provides a good visual.
 
I fail to see how twisting a crank sensor in the bore would do anything. Sounds like the wiring may be bad.

Nice find.
 
ZVOLV said:
I fail to see how twisting a crank sensor in the bore would do anything. Sounds like the wiring may be bad.

Nice find.
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I would think that too. Maybe twisting allowed it to go further in where it needed to go. I don’t think it’s a CPS wiring issue as I’ve tried 2 or 3 different crank sensors, and the jiggle test changed nothing.
 
swedefiend said:
100% agree.
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Again, i agree. But it did make it start so it?s irrelevant whether we think it would effect it or not. I?ve jiggled all wires multiple times.

My theory is that the mounting bracket is bent upwards from someone trying to pry to old sensor out so when I turned it sideways I was able to push the sensor further into the bore and boom, she started.
 
Also, I know that you are convinced that this is a spark issue, but...

Have you verified cam timing is correct?
Have you verified that the battery voltage while cranking is 10+ volts?
Have you metered the fuel coming from the tank?

IIRC, the injectors are wired [1,4] & [2,3]. This may or may not be related to your problem.
 
swedefiend said:
Also, I know that you are convinced that this is a spark issue, but...

Have you verified cam timing is correct?
Have you verified that the battery voltage while cranking is 10+ volts?
Have you metered the fuel coming from the tank?

IIRC, the injectors are wired [1,4] & [2,3]. This may or may not be related to your problem.
Click to expand...

Considering I could watch spark consistently not happen, yes, I am 100% positive there was at least a spark issue. And being that these cars are batch fire, I was less concerned with fuel because 1 and 4 had fuel.

I have verified about 5 times that can and crank timing were fine (again, considering the car came to life with ease after turning the CPS).

I have verified fuel leaves the fuel rail rather quickly when disconnected:lol: car has new pump and filter. Wasn’t going to build a device to measure fuel rail pressure based off of how quickly and forcefully fuel left the rail.

And again, a lack of fuel would not cause a lack of spark on 2 cylinders.

I installed a known good battery and left it on a charger while cranking.
 
PromiseRing said:
I have verified fuel leaves the fuel rail rather quickly when disconnected:lol: car has new pump and filter. Wasn?t going to build a device to measure fuel rail pressure based off of how quickly and forcefully fuel left the rail.

And again, a lack of fuel would not cause a lack of spark on 2 cylinders.

I installed a known good battery and left it on a charger while cranking.
Click to expand...

You can't math?

Stopwatch, 16 oz drink bottle, calculator.

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Broken FPR would normally cause the car to flood while cranking or not crank at all. Coupled with a *loose ground* on one injector set might allow you to not flood start on two cylinders (so stop being a know-it-all)

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Good.
 
PromiseRing said:
Yes and if 2 and 3 were both lacking spark, there?s a pretty good chance they were both lacking fuel as well (which they usually were) which is indicative of a faulty crank signal, since they go hand in hand.
Click to expand...

You said you had two wet plugs...
 
swedefiend said:
You can't math?

Stopwatch, 16 oz drink bottle, calculator.

---

Broken FPR would normally cause the car to flood while cranking or not crank at all. Coupled with a *loose ground* on one injector set might allow you to not flood start on two cylinders (so stop being a know-it-all)

---

Good.
Click to expand...
Oh yeah and would that cause a lack of spark, too?:roll: give it a rest dude. And I cleaned all grounds AND added a dedicated ground directly from battery to both injector grounds. None of this matters anymore, the car runs very well now.
 
swedefiend said:
You said you had two wet plugs...
Click to expand...

PromiseRing said:
l Still weirded out that plugs looked almost dry which would indicate a fueling issue.
Click to expand...

PromiseRing said:
Plugs are dry after pulling them.
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PromiseRing said:
After cranking for 15 seconds or so, i pulled # plug and it was not soaked in gas.
Click to expand...

You accuse me of not being able to math, but at least I can read.

I appreciate the attempt to help, but if you’re going to fail to read and then accuse me of untrue things, just stay out.

And the DS thread ended up fine. Vehicle is nice and quiet and tight and shake free. Not that turbobricks was of any help anyway:lol:
 
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