I need help!!!!! GM mechanic needed please

[NITROSNIFER]

Oh good old SI 2000 when I left GM I sure missed it's simplicity easy to find almost anything GM you going to Al's race this year??

 

[Bob Howard]

Would not miss it.

Bob

 

[NITROSNIFER]

We'll be there to

 

[Joe Warren]

Is there any GM mechanics out their that could please help me?I have a 1997 GMC seria 4x4 with the 5.7 and it wont start!

well this is what happened. yesterday I was driving and it just died. it would not restart right away opened the hood and checked the wiring plugs to see if anything came loose. everything was fine tried to restart and it ran, drove about 5 miles parked the truck for the afternoon got pack in and it started right up drove home no problem. this morning went to leave and it wouldn't fire. checked fuel pressure I had nothing. BINGO bad fuel pump. I pulled the box off and replaced the fuel pump. well guess what it still wont run!!!!!! so I checked to see if I had power to the pump. no power. ok lets change the relay.

new relay. we got power the truck started WHOO HOO, it died no power to the pump again. so one more trip to the parts store new oil pressure sending unit. well guess what it ran idled for about 5 min. shut it off now it wont start again.

no power to the fuel pump. now here's were it gets strange sometimes it will have power and sometimes it wont.

I turn the key on it has power then it goes off. just like it should 5 sec. you crank it over and it will show a constant power.

plug in the fuel pump and it will start. runs about 10 sec and dies. check to see it there is any power to the pump and nothing. what else controls power to the fuel pump?

Thanks for any help.

Terry

Terry, If you know where the BOSCH fuel pump relay is? terminal 85 & 86 are the coil. #30 must be hot all of the time (batt). & 87 is the output to the fuel pump. Now many circuits control inputs to the relay. But you must find out what circuit is opening.( remember if the relay opens Something is missing a hot to the coil or the ground to the coil... This is considering you already know the Relay is falling out after you start it.You can listen into the fuel input neck & you will hear the pump runnig when it starts . You will also hear it stop if the relay falls out.... Also Use a Voltmeter it would show a low voltage or a intermitting voltage problem. Also Check the crank trigger in the front timing cover. Wiring is normally wet with oil & sees a lot of wind hanging under the front of the trk. This is a main input to the ECM. A Stop Running or a No start on a GM Most would check Fuel pressure on the fuel rail. most must be a 55-60 psi or more & Crank trigger sensor wiring first.

 

[Bob Howard]

The fuel pump relay can open when engine is running and fuel pump will still recieve power though the oil pressure switch.

Bob

 

[Daniel's Racing]

The fuel pump relay can open when engine is running and fuel pump will still recieve power though the oil pressure switch.
Bob

The oil pressure switch can't supply power to pump if relay is open. Relay open the pump is off. The relay has the final word if the pump gets power or not. A oil pressure switch doen't even have contacts or wiring capable of running the pump for long. It is only a control circuit. The relay coil must have a ground and a hot.

And the power in side of relay must have power. The oil pressure switch never bypasses the pump relay. It either gives the negative side of relay coil its ground or tells the

computer the oil pressure is present and keep sending a negative usually to the coil(most computer out circuits use negatives to control things so if a wire should go to ground it will not burn it up, the item it is controlling will simply just not shut off) of relay the positive side of pump relay coil usually comes from ignition switch. And power in side of relay is many times hot all the time.

Daniel

 

[jydracing]

Hi Terry I have ran into this on a few Gm In that year range. They used to small of a termnal on the pumps and it coused high load on the wiring and conectors. Look at the conectors at the relay really good. I have pulled the wires out of the relay box and use a 30 amp relay wired in to fix the problems. It is strange that that year does not have the resister chip in the key that is exposed. If it does it can be by passed. Hope this helps Jimmy

 

[Bob Howard]

attached is a copy of the fuel pump wiring. As you can see there is two sorces of power to the pump once running

Bob

 

[NITROSNIFER]

I was wondering about the lack of a immobilizer in his vehicle as well. My Z-71 has it as well as my 98 Yukon

 

[SayMikey]

attached is a copy of the fuel pump wiring. As you can see there is two sorces of power to the pump once runningBob

Is the bed still off? Did you check the ground g104 on the frame? and do you have a way to check power and ground volt ohm meter?

 

[TERMINATOR]

attached is a copy of the fuel pump wiring. As you can see there is two sorces of power to the pump once runningBob

Is the bed still off? Did you check the ground g104 on the frame? and do you have a way to check power and ground volt ohm meter?

and i think there is a ground that is often forgotten at the rear of the frame by the bumper..may want to check all grounds and tightness..jmo

tk

 

[Terry Flynn]

Thanks for all the help guys. I'm proud to say it's running like a champ!!!!!!after spending all most $200 on chasing parts and 8 hours getting no were. I found that the wire to the fuel pump and gauge the gray wire in the tank was burnt bad I am shocked that it didn't catch on fire. the insolating on the wire was melted and so was the plug at that point.

Bob thanks for taking the time to send me the diagrams. All I have to say is the people on here are a class act.

its nice to part of this family

Thanks again

Terry

 

[Joe Warren]

Thanks for all the help guys. I'm proud to say it's running like a champ!!!!!!after spending all most $200 on chasing parts and 8 hours getting no were. I found that the wire to the fuel pump and gauge the gray wire in the tank was burnt bad I am shocked that it didn't catch on fire. the insolating on the wire was melted and so was the plug at that point. Bob thanks for taking the time to send me the diagrams. All I have to say is the people on here are a class act.

its nice to part of this family

Thanks again

Terry

Good that you got the GM feeling back! Seems many more will be Repaired.

 

[Chris Thomas]

You never know what you can learn on this site......