My 99 Express will not start so I assumed it was the fuel pump as I could not hear it prime after turning the ignition to the on position. After dropping the tank I straight wired the pump and it worked fine. Now I am stuck. I have replaced the CAM Position sensor as many told me it would kill the fire to the pump if bad. I also have the CRANK position sensor. 2 things I have noticed. 1, using my test light, the fuse for the CRANK has no power. 2 my scan tool seems like it's not connecting to the computer. It continues to read linking. I have tried it on my S10 and it works fine there. Suggestions please. This is my money maker.

 

check power to the fuel pump fuse, and also fuel pump relay. a quick easy way would be to listen\feel for it to click
Stop replacing sensors as those will not effect fuel pump operation

 

I have checked all the fuses and replaced the relay to the pump to no avail. That was step 1. I have tested the fusable link today up until where it goes into the fuse box under the dash. I can get 12V up until the connector on the fuse box. The connector does not give any power on the test light. I tested the wire going into the MAP sensor and did not get anything on my test light and only .1 on my multimeter. Computer? PCM? Help. Losing money and time.

 

Also, I am getting fuel or fire. Fuel pump not pumping, not power to connector and no spark to spark plug wires.

 

check the ECM B Fuse....its in the underhood junction box rate for 20amps. It is the fuse for the fuel pump, ecm, among other things. You said you replaced the fuel pump relay, but did you check to see if there was power going to it? You should have a hot, prime\run(b+), ground, and the pump wire(usually grey). If you are not getting 12volts for the prime\run wire, it is very possible that you may need a ECM. As long as your ign switch is feeding the proper circuits. I have in the past, conected my own relay, or even re-wired the stock one to come on constant with the ignition. Now this was of course by request of the costumer as he didn't want a new ecm, but this was a cheap fix. He just cannot leave his key on without the engine running.

The more a ramble on about this the more i'm lleaning towards the ECM as the culprit. you say there is no spark, no fuel, and no communication with your scan tool?.......i'm gonna say it agian because its so easy to overlook...check fuses, makre sure there is volage on the ecm fuses, check for power, ground, ign, at the ecm itself,check to see if the map, cam, crank sensors have a 5v referent signal from the ecm..........

 

Ok, I replaced the ECM. The dang thing had a hole in it. Got it in and now the van will not run. It will start occasionally and run rough until you hit the accelerator. Most of the time it will only run for 2,3,4 maybe 5 seconds.

 

Keep an eye on your ignition coil. I have had 2 of these that developed tiny cracks and send the spark voltage to nearest metal item.