can't get it started

[V6cious]

How can I check my cam and crank sensor I have tried using a voltmeter and cranking the engine but the needle only swing between 4to 5 when it should be 1 to 9 please any help will be appreciated I've had my car sitting up for 10 months and I need to get it going it started missing real bad and now it backfire really hard sometimes when trying to start so I THINK that it it is not firing all the time
PLEASE HELP

 

[TurboBuickSix]

some other Backfiring causes...

Timing chain bad maybe? or firing order goofed up? Fouled plugs,plug wires bad to the point where they are crossfiring sometimes,cam sensor timing set procedure can be found on www.gnttype.org

 

[V6cious]

Hey I think that I'm on to something can some one tell me what happens when the cam sensor goes bad and what arethe symptoms

 

[703crewchief]

To check your cam and crank sensors you will need an osciliscope.
Your volt meter is buffered and will not show real time readings, but a scope acts as a graphing volt meter and you can actually see the signal your sensors are creating(or not creating). These scopes are pretty expensive so it might be in your best interest to just have a technician check it out.

 

[S10xGN]

If it's trying to start, the crank sensor is most likely OK. If the cam sensor is "off", it'll backfire out the tailpipe about every 5th or 6th revolution. You can also tell by the sound the engine makes while cranking: If it sounds like it has 15:1 compression ratio while cranking, try disconnecting either the crank sensor or cam sensor harness - now it should ound like it's cranking normally. If so, your cam sensor is either bad or just off a little. I found that I was setting mine on the wrong "edge" of the window. Just a little adjustment, most likely...

 

[Darrell Jackson]

A cheaper alternative is to use a logic probe. They usually have 2 settings--- TTL/CMOS. In this case you would CMOS---- used for circuitry up to 15 VDC. The TTL is used for 5VDC circuits. Just use a service manual to find the various points where you can see the return signal from either the cam or crank sensor and follow the directions on hooking up the logic probe and each time LOW is sensed the probe will show a pulse LED light up. There are different posts throughout here that will help with the signal tracing. Do a search under COPO TOM, (I think). Jim Testa and me helped him with a no start condition and we went pretty deep into the signal tracing with a logic probe. They usually cost around $20 at Radio Shack. This is a good tool for future use if you ever have a total no-start condition.

Darrell Jackson
'87 GN