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Have a 2002 Blazer. Spark-ok, Fuel pump just replaced and delivering. No injector pulse when harness plugged in. Un-plug injector harness and have negitive pulse. plug back in, no pulse. ?????

Submitted: 53 days and 9 hours ago.

Category: Chevy

Value: $15

Status: AWAITING CUSTOMER ACTION

Year : 2002
Make : Chevrolet
Model : Blazer
Engine : 4.3

Already Tried:
tested for grounds, pulse from crank sensor--getting negitive pulse, fuses, relays

Posted by BigBlock434 53 days and 8 hours ago.

Info Request

Do you have power to one side of your injector plug when you turn the ignition key on?

53 days and 8 hours ago.

Reply

yes there is power when ignition on. I get a negitive pulse when unplugged, plugged in all injector wires show positive with no pulse

Posted by BigBlock434 53 days and 8 hours ago.

Answer

Disconnect the injector harness and measure resistence on each injector. A good injector will read 11-14 ohms.

53 days and 8 hours ago.

Reply

Injector readings are ok--this started when the fuel pump failed. Did it a week prior to total failure but unplugged MAF, plugged in and started. All was fine. I'm trying to shy away from the ECM because I have pulse when disconnected, and spark. In addition I'm getting a pulse from the Crank Sensor so I eliminated that.

53 days and 8 hours ago.

Reply

Back in a minute, I'm going to unplug the MAF and see what I get when crank. But a shorted MAF should not prevent it from starting, I'll try anyway---BRB

Posted by BigBlock434 53 days and 8 hours ago.

Info Request

OK

53 days and 8 hours ago.

Reply

No good, no effect

53 days and 8 hours ago.

Reply

Oh, just thought of something. Fuel pump does not activate until in crank mode---relay changed but no difference

Posted by BigBlock434 53 days and 8 hours ago.

Answer

At the beginning of your post you stated you had fuel pressure. Could you test fuel pressure again. The pump will activate for two seconds with the key in the on position.

53 days and 8 hours ago.

Reply

Yes during crank mode I have fuel pressure--if I remember right it was 35-40 lbs. But it does not activate for the 2 secs when key first turned on. interrelated somehow??? My thought was the relay but after changing it, no difference

Posted by BigBlock434 53 days and 8 hours ago.

Info Request

Will your vehicle start and run when you spray carb. cleaner in the intake system?

53 days and 8 hours ago.

Reply

Yes

Posted by BigBlock434 53 days and 7 hours ago.

Answer

OK you say you have battery voltage at each injector(making sure you still have voltage when you plug the connector back in). You say you have injector pulse on each injector when you turn the engine over with the injector plug disconnected. You say you have checked the resistance on each injector and they are in spec. Then you plug the connector back in and lose pulse. You have one of two problems. You have a injector grounded on each driver or you have weak injector drivers. In that case you have to replace the Engine Control Module.

53 days and 7 hours ago.

Reply

OK, I'll go down that avenue. I will isolate each injector to test for an possible grounded injector backfeeding. If that doesn't do and good then I will have to condemn the ECM. Do you concur??

Accepted Answer

If you have made sure you have checked all the specs. then I do.

Accepts:
Expert:	BigBlock434
Pos. Feedback:	97.1 %
Answered:	10/1/2009

Chevy Mechanic

ASE Master certified and 100% General Motors trained in all fields

53 days and 7 hours ago.

Reply

ok, thank you for your input. I was hoping it wasn't that, but I was leaning that way but needed another opinion before I went to the expense. Thanks again

Posted by BigBlock434 53 days and 7 hours ago.

Answer

Your welcome and Thank you.

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Question

Have a 2002 Blazer. Spark-ok, Fuel pump just replaced and delivering. No injector pulse when harness plugged in. Un-plug injector harness and have negitive pulse. plug back in, no pulse. ?????

Optional Information

Year : 2002Make : ChevroletModel : BlazerEngine : 4.3 Already Tried: tested for grounds, pulse from crank sensor--getting negitive pulse, fuses, relays

Info Request

Do you have power to one side of your injector plug when you turn the ignition key on?

Reply

yes there is power when ignition on. I get a negitive pulse when unplugged, plugged in all injector wires show positive with no pulse

Answer

Disconnect the injector harness and measure resistence on each injector. A good injector will read 11-14 ohms.

Reply

Reply

Back in a minute, I'm going to unplug the MAF and see what I get when crank. But a shorted MAF should not prevent it from starting, I'll try anyway---BRB

Info Request

OK

Reply

No good, no effect

Reply

Oh, just thought of something. Fuel pump does not activate until in crank mode---relay changed but no difference

Answer

At the beginning of your post you stated you had fuel pressure. Could you test fuel pressure again. The pump will activate for two seconds with the key in the on position.

Reply

Yes during crank mode I have fuel pressure--if I remember right it was 35-40 lbs. But it does not activate for the 2 secs when key first turned on. interrelated somehow??? My thought was the relay but after changing it, no difference

Info Request

Will your vehicle start and run when you spray carb. cleaner in the intake system?

Reply

Yes

Answer

Reply

OK, I'll go down that avenue. I will isolate each injector to test for an possible grounded injector backfeeding. If that doesn't do and good then I will have to condemn the ECM. Do you concur??

Accepted Answer

If you have made sure you have checked all the specs. then I do.

Reply

ok, thank you for your input. I was hoping it wasn't that, but I was leaning that way but needed another opinion before I went to the expense. Thanks again

Answer

Your welcome and Thank you.

Related Chevy Questions

Year : 2002
Make : Chevrolet
Model : Blazer
Engine : 4.3

Already Tried:
tested for grounds, pulse from crank sensor--getting negitive pulse, fuses, relays