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RIP, Lead Technician
Category: Car
Satisfied Customers: 5591
Experience:  A.S.E. Master Technician, Advanced Level, Smog - European, Domestic, & Asian -- Car Category Mentor
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will the crank sensor cause my car not to start

Resolved Question:

i have changed spark plugs and the ignition module and the qoil packs i have good fuel and some spark on all 4 cylenders will not run
Submitted: 11 years ago.
Category: Car
Expert:  RIP replied 11 years ago.

The crank sensor can definitly cause the engine not to start, but it has to be diagnosed thru a factory level scan tool or automotive oscilliscope. So we can determine if it may be at fault, by testing some basics. You say you have "some" spark.

Is there intermitent spark on all cylinders?

Or is there only spark on 1 or 2 cylinders?

How are you testing for spark?

And how have you tested for fuel?

Was there a Check Engine Lamp illuminated, when it was running?

Customer: replied 11 years ago.
Reply to RIP's Post: there is spark on all 4 cylanders its kinda weak and the fuel is soaking the spark plugs when trying to start testing the spark by pulling the plug and checking for spark the check engine was on and changed the knock sensor that was on the code and the mass air flow sensor was changed and now there are no more codes i have had it in a shop and paid them 265 to diagnose they said it was my ignition module so i changed those and the coil packs still not working the mechanic also checked the compression and they said it was good so the timing chain is still good too they said getting expensive!!
Expert:  RIP replied 11 years ago.

The unusual part of your description is that there is "weak spark." The CKP (crankshaft senor) only creates a signal for the computer to use to tell the module when to fire, and on what cylinder. It has no affect on the magnitude of the spark. The components that create spark are considered 'secondary ignition components.' These include, the plugs, wires, coils, and module. So if your getting spark on all the cylinders, this would entail that the computer must be recieving the CKP signal, and that somewhere between the module and the spark plug it's being lost. We need to get a better look at the spark, at the coil end. This is done with a generic automotive test lamp, do you have one of these? Before anything, make sure the battery cables are tight and clean. If they are not this will casue a voltage drop, and the ignition components may not get full voltage to operate, even if the engine cranks fine. Let me know if you have a test lamp, and i'll give you instructions on testing for spark strenght.


Customer: replied 11 years ago.
Reply to RIP's Post: yes i have a test lamp and a voltage meter the battery cables are tight i have changed allmost all the components of secondary ignition components with new parts.
the ignition module and both coil packs i have even put another computer in the car from a junk yard car still the same. before it shut down it was running crappy like the cat was clogged but it wasnt and the exhaust was getting really hot and when you step on the gas it would bog down the it got the exhaust real hot and just died and it hasnt started since maybe is there a temp sensor that could have been fried? if ya answer 1 more time ill accept thanks for the help oh yeah i changed the oxegen sensor cause i thought thats why it was running like that i have put clean new plugs in tried almost everything except this crank sensor i took the crank sensor out and it has black residue on it its brass one not the plastic
Expert:  RIP replied 11 years ago.

How about you can accept when we've gotten as far as we can?

#1, I'd like to show you haw to use the test lamp to check for the strenght of spark, this way I can get an idea if it truly is a spark issue or do we have too much fuel, putting the spark out. Clamp your test lamp to good engine ground, near the coil pack area. If this model has the coil packs under the intake, it'll be difficult to do the test, unless you can get the car up on jack stands. Pull one coil wire off, and keep the tip of the test lamp approx 1/2 inch away from the coil tower. Have an assistant crank. Will the spark jump to the tip? If so what color is it - orangeish or blue? Do the rest of the coil towers, one buy one, replacing the respective wire on the previous one as you go, so that you will not get shocked. If the spark does not jump 1/2", move the tip of the test lamp closer and closer until you can see where it arcs to the tip. And let me know your results. Also, did the exhaust ever get red hot??


Customer: replied 11 years ago.
Reply to RIP's Post: I will test the spark tomorrow morning when i have a helper yes the exhaust did get really red hot right before it stopped on its on and now wont start talk to you more tomorrow morning
Expert:  RIP replied 11 years ago.

If the exhaust got red hot, this concerns me. It either means that the ignition timming (computer controled) is excessivly retarded, or the cam timming has changed (timming chain). Or it could mean that too much fuel is entering the intake. Are you sure you don't have any more codes in the computer? Do you know how to check for codes? If you still have a knock sensor code - this may mean something. I want you to still check the spark strenght, but just so you know, we're going to have to make a few more checks before comming to a determination.

How many miles are on this car?


Customer: replied 11 years ago.
Reply to RIP's Post: it has 70,000 miles
i use the computer from shucks to read all the codes and after everything it has no more codes in it now also my friend is a tech he used his code reader on it cant find any codes the code with the knock sensor was back when the car was still running but running crappy it had a few things with it and those parts were all changed dint not make a differance. and now no codes at all but wont start
Expert:  RIP replied 11 years ago.
The thing that bothers me is the Knock Sensor code, since the
Knock Sensor is there to signal the ECU when is hear's a ping or knock,
than the ECU will retard the timming to alliviate it. If the
circuit isn't working properly it could be retarding the timming so
much, it could cause your problem. This is a rare occurance, and the
most likely fault would be the ECU itself, which you mentioned you had
already changed. So, after verifying the spark strenght, I want
to see if we can tell if the engine is getting too much fuel. To do
this, you'll need to remove the fuse/relay for the fuel pump, to
prevent fuel from getting to the engine. Than pull out all the spark
plugs, and place rags over the holes. Have someone crank the engine,
holding the rags over the spark plug holes to catch any fuel in the
combustion chamber. Remember to keep the disconnected spark plug wires
away, or covered up so that the fuel escaping the cylinders, doesn't
ignite. After cranking, dry the sprak plugs and reinstall them. Remove
the intake boot, spary some carburator cleaner in there, and replace
the boot. Crank the engine, and see if it will momentarily fire. If it
does, repeat the test, infact you can attempt to keep the engine
running by spraying carb cleaner into the intake while someone is
cranking, but you have to use a liberal amount, too much will just
flood it, and too little will not let it run either. If it runs on the
carb cleaner, it's possible the engine is recieving too much fuel,
possibly from a restricted fuel pump return line, or bad fuel pressure
regulator.If it doesn't run, we know it's either a ignition timming
issue, or cam timming. Let me know your outcomes onthe above

Can you disconnect the crank sensor, and measure the resistance accross the terminals with your multimeter?


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