Will engine w/bent crank turn over?

[Izzy]

Hi,

I recently purchased a '94 B4000. The seller told me it had a bent crank otherwise all else was fine ... when looking over the battery was dead, so I didn't check anything, just towed the truck home.

This weekend I charged up the battery and turned the key ... to my surprise the motor cranks quite nicely, but would not start. I would have expected a motor with a bent crank to either not turn or make some kind of noise. But being a novice (but trying to learn) I thought I'd ask you all ... would a 4.0 motor with a supposed bent crankshaft crank like a normal engine?

BTW, I did check for spark by putting a spark tester in line with one of the sparg plug cables ... no spark.

TIA
-Izzy

 

[97ranger4x4]

HMM, well that has a coil pack in it right? Is there any way you can check the coil pack to see it its getting anything. I would imagine a bent crank wouldnt turn or would make a lot of noise. BTW, how do you bend a crank without killing a motor?

 

[Izzy]

HMM, well that has a coil pack in it right? Is there any way you can check the coil pack to see it its getting anything. I would imagine a bent crank wouldnt turn or would make a lot of noise. BTW, how do you bend a crank without killing a motor?

I am far (very far) from an expert but I too believe if the crank was bent, the motor would be destroyed or at least make some kind of odd noise, vibration, etc. The sound of this motor cranking with the starter is very smooth. I purchased this truck for parts thinking the motor was shot but it is so clean I am going to see if I can't fix it instead.

I ordered a repair manual which I'm hoping will help me troubleshoot the problem. In the mean time can anyone suggest what I should check? Like I stated in my original post, I did put a spark tester in line with one of the spark plugs and did not see a spark. That is as far as I have tested so far.

 

[Stranger ranger]

Someone with some knowledge please chime in here...

 

[woodyedmiston]

Sure a bent crank will turn over. Crankshafts flex in every motor to a minor degree. Commonly the very end of a crankshaft will bend a couple of thousandths at the flywheel and continue to run until the rear main and seal are wiped out. The same can happen on the front if too much load it put on the front harmonic balancer. In a reall high rev motor the thing will probably self distruct, but a lower reving motor could last for quite a while.

If you have a dial indicator it's pretty easy to check out. The motor should turn over unless something drastic has already happened. If the motor is not damaged otherwise - put in a new crank and bearings and run it.