Previously, When I jumped the Data Link Connector with a paper clip, I was able to read the trouble code which flashed, and replaced the bad part. Later I just wanted to see if I had any problems, I jumper the DLC again and it flashed the 12 and nothing else, so I was in good shape no trouble codes.
Some time ago I needed a relay, went to the junk yard for relays, I cut all the wires off all of the relay connectors on the junked car ,and then replaced the relays on my car matching the wires on each relay with the color coded wires on my car. All seemed to be OK.
I had to replace the harmonic balancer, and the fuel filter, all was fine.
I had then ran into my engine starting to stumble when starting, but it would clear up after idling within 30 seconds, and would then stumble on acceleration intermittently, but if I floored it, engine would run "like a race car", and would do good.
The last time the car was started I had to feather the gas pedal to get it to start. It then continually to stumble at low speeds when giving it gas, but again, when I floored it would have extremely good power. Pulling into my driveway it continued to stumble, when I gave it gas it died and upon restart running bad stumbled and backfired.
Now, I have a crank but no start, it tries to start but will not run. I sprayed starting fluid in intake, it backfired big time no start., I have no checking light on, Post from pogo69March 7th, 2015, 09:53 PM Suggested Bank Crank Position sensor.

I have spark, Checked with new Plugs 1 and 3. they have fire but old ones are black, I hear Fuel Pump, cat conv and exhaust clear then, tried to start with pedal to floor no start and tried to obtain trouble codes it will only flash a 12, and the engine coolant fan runs continually with the jumper in the DLC.

Due to the fact that the engine coolant fan ran when I jumper the DLC, just to check ,Disconnected Battery, I pulled the o2, and the MAF Sensors off and retested with the jumper in the DLC, Same results, it will only flash a 12.

So, (1) I guess I may have screwed up with the junk yard relays?
One or more have something to do with the engine coolant fan? could this be why the fan runs when I try and get codes?
(2) any other ideas on the crank but no start?
Thank you all for your help

 

you almost need to get a gm olds manual and go step by step and check things as you go.i had a problem with my old 89 pontiac.it started running like crap then one day crank but no start .i got a manual with the car so started going thru the list.everything checked out.still no start,the last item was the control module under the coil pack.so i got a borg warner umit.still no start but before i replaced it it acted like the timing was really retarded.with the b/w unit it cranked like it didn't have plugs in it.which i thought was weird.after a couple days of checking everything again i decided to get a GM module.car fired right up.

 

Thank you for your reply, any ideas as to why engine coolant fan runs when I jumper the DLC to try and get a code?

 

i dont know but i seem to recall mine did it too.

 

Starting problem resolved by replacing engine coolant temp. SENSOR.