No start

[mblackmon]

A customer brought me his 1985 Grand national with a no start. There is no spark and no injector pulse. Crank sensor, cam sensor, and ignition module have all been replaced. The signal wire on both the crank and can sensors have a constant 5 volt output. There is 12 volts coming into both sensors and the grounds are also good. The ignition module has power and ground also. The car has been to several shops with no solution thus far. I can even place a knife blade between the crank sensor and still there is no voltage drop on the signal wire out of the crank sensor when the engine is turned over. If I ground the signal wire coming out of the crank sensor, the fuel pump relay will engage as if it was receiving a request. If either of the sensors (crank or cam) are umplugged, there is 5 volts on the wire coming out of the ignition module. Oh by the way, several crank and cam sensors have been tried as well as 2 ignition modules. There is an adapter connecting the ignition module to the engine harness connector but I even tried connecting the connector directly to the ignition module with no help. Does anyone have a suggestion?
This is my first post and I would definately appreciate any help, Thanks, Mike

 

[DailyDrifter]

The crank sensor should be gapped properly. ECM and Sensor Information. Does the computer have a good ground? Is the check engine light comming on when the key is turned on? Does the chip in the car have a anti theft mode, Double check this one!!!

 

[bmackinnon]

Is the check engine light comming on when the key is turned on? Does the chip in the car have a anti theft mode, Double check this one!!!

ditto....

 

[Busted_87]

This is kind of out there but it happened to me...are the cam and cam sensor gears intact...the person who rebuilt my engine forgot the cam button and spring and i sheared the cam sensor gear. Just a thought.

 

[robertmee]

Does the chip in the car have a anti theft mode, Double check this one!!!

We ask that one from experience, believe me. After Dave and I worked on my car one weekend, we couldn't get it to crank for two days. Until I realized that I had an extender chip that defaults to anti-theft mode if the battery goes dead or the cable is lifted. Anti-theft mode will kill the fuel supply. She'll turn over all day long, but never fire.

 

[mblackmon]

Update

OK, I have an update! I rewired the ignition module (there was a jumper between the module and the connector to the module that was wired wrong).
I then found out that because of the wiring issue, the cam and crank sensors were damaged. The 5 volt signal that was coming out of the ignition module was not being pulled down to zero. I replaced both the sensors, replaced the ignition module and the engine has fire and injector pulse..but still wouldn't start.
I then installed an auxilary fuel supply to the fuel rail test connector(the fuel pump does not work), set the pressure to the correct amount and now the car starts but still won't run very long (2 seconds at the most). I have good spark, injector pulse, but the engine refuses to run for more than a few seconds.
It acts just like the computer is shutting of the injector pulse. To my knowledge, this car does not have a security system on it.
Open to any suggestions. Thanks to all who have responded, Mike

 

[TurboBuRick]

unplug the maf and see if she runs.

 

[robertmee]

Not a security system, but the chip may have a security mode in it. PM sent

 

[TurboBuRick]

Doubt it's a security chip in a stock 85.

Are there any numbers on the chip?

 

[robertmee]

Doubt it's a security chip in a stock 85.

Are there any numbers on the chip?

Who has a stock 85 anymore? :biggrin: I'm guessing an 86/87 ecm replacement w/ chip.

 

[DailyDrifter]

unplug the maf and see if she runs.

Good idea.

Make sure the car doesnt have a security mode!!!!! I cant stress this one enough. If the computer doesnt want the car to run...........its not going to let it run .

 

[mblackmon]

It's Alive!

Ok, after I finally got the spark and pulse, I checked on the security issue. There was no security on this car. There were also no codes in the ECM.
I called the customer and he said he had installed a used cam sensor assembly. So I removed the cam sensor again, installed it correctly and then timmed the sensor using the volt meter method. The engine starts and runs fine now. Thanks to all for the help, MIke :smile:

 

[robertmee]

Ok, after I finally got the spark and pulse, I checked on the security issue. There was no security on this car. There were also no codes in the ECM.
I called the customer and he said he had installed a used cam sensor assembly. So I removed the cam sensor again, installed it correctly and then timmed the sensor using the volt meter method. The engine starts and runs fine now. Thanks to all for the help, MIke :smile:

Looks like Busted 87 wins the prize! Congrats on getting it running again.