P0740

[Sherrinan56]

I recently bought a 1997 Chevy Blazer. I was going to drive it to work yesterday and it would not turn over. I had my mechanic come and check it out this morning. The code P0740 came up. Will this stop the vehicle from starting? My mechanic says that I am not getting fuel. He's going to come back and check my fuel pressure. The gentleman that I purchased the vehicle from says that he has put a new fuel pump on the vehicle. I recently watched the video about the five codes and checking fuse 47. It was the video that prompted me to register at this site. I look forward to any suggestions to tell my mechanic when he returns. Thank you in advance.

 

[christo829]

Um....you mean a 1997 "Blazer", I'm assuming? They didn't make Trailblazers in 97.

P0740 is "Torque converter clutch circuit malfunction". Might make it stall when you try to put it in gear
but shouldn't keep it from starting.

You mention five codes, but don't list them. One of *those* might be the diagnostic for why you're not getting
the truck to start.

Is it actually cranking, just not firing?

What engine, how many miles, any maintenance records? Was the new fuel pump put on for a "no start" condition
as well? Might be fighting something else besides just the pump. Fuel filter changed? Is fuse 47 in that vehicle part of the
fuel pump circuit?

Good Luck!

Chris

 

[Sherrinan56]

Um....you mean a 1997 "Blazer", I'm assuming? They didn't make Trailblazers in 97.

P0740 is "Torque converter clutch circuit malfunction". Might make it stall when you try to put it in gear
but shouldn't keep it from starting.

You mention five codes, but don't list them. One of *those* might be the diagnostic for why you're not getting
the truck to start.

Is it actually cranking, just not firing?

What engine, how many miles, any maintenance records? Was the new fuel pump put on for a "no start" condition
as well? Might be fighting something else besides just the pump. Fuel filter changed? Is fuse 47 in that vehicle part of the
fuel pump circuit?

Good Luck!

Chris

Hello Chris,

Thanks for the quick response. It is a Blazer. The YouTube video was (Trailblazer/Envoy P0740, P0753, P0758, P0785, and P1860 - first test).

The P0740 code is the only one that came up. It is cranking and not turning over. Engine - VORTEC 4300, V-6, 156,000 miles. I am not sure if the fuel the pump was purchased for that reason. I don't know if the fuel filter was changed. I will check with my mechanic when he returns this afternoon. I am not sure if fuse 47 is in that part of the vehicle since that was in a Trailblazer and this is a Blazer. Is there a way for me to check?

Chris, I really appreciate you assisting me. I look forward to hearing from you soon.

Thanks

 

[christo829]

Fuse #9 I'm pretty sure was part of the fuel pump relay circuit on the late 90's blazers. Might want to give that and the fuel pump relay itself
a check. It's been awhile, but I think on that model (my father had one) the fuel pump relay and the horn relay could be swapped for testing,
but please don't take that as gospel.

Ah..the other codes you were referring to were the ones in that video? OK. I misunderstood.

Cheers-

Chris

 

[Sherrinan56]

Fuse #9 I'm pretty sure was part of the fuel pump relay circuit on the late 90's blazers. Might want to give that and the fuel pump relay itself
a check. It's been awhile, but I think on that model (my father had one) the fuel pump relay and the horn relay could be swapped for testing,
but please don't take that as gospel.

Ah..the other codes you were referring to were the ones in that video? OK. I misunderstood.

Cheers-

Chris

Thanks Chris,

It is #9. That fuse is good. I don't know where the Relay fuse is, but I will have my mechanic check it when he comes back. The seller did replace the fuel filter.

Thanks for all of your assistance. I really appreciate your help.

Sherri

 

[christo829]

Mmm...dredging up old memory cells, I think it's in the glove box. If so, it's the relay on the left. Hopefully
I'm not getting that conflated with another vehicle.

If you get in and just turn the key to start, *not* to run, do you hear the fuel pump prime up for a couple of
seconds, then stop?

It's always possible that the replacement pump has gone bad, even with OEM equipment. Hopefully that's not
the case, but you should be able to check most everything prior to that before having to drop the tank.

If you *do* have pump function, the next check would be the fuel pressure. The pump could be running but not
supplying enough pressure. If the pump is supplying enough pressure, the fuel pressure regulator could be acting up.

And I do not remember if the older blazers were prone to ignition switch failures or not, like our GMT360 line seems to be.

Cheers-

Chris

 

[Sherrinan56]

Mmm...dredging up old memory cells, I think it's in the glove box. If so, it's the relay on the left. Hopefully
I'm not getting that conflated with another vehicle.

If you get in and just turn the key to start, *not* to run, do you hear the fuel pump prime up for a couple of
seconds, then stop?

It's always possible that the replacement pump has gone bad, even with OEM equipment. Hopefully that's not
the case, but you should be able to check most everything prior to that before having to drop the tank.

If you *do* have pump function, the next check would be the fuel pressure. The pump could be running but not
supplying enough pressure. If the pump is supplying enough pressure, the fuel pressure regulator could be acting up.

And I do not remember if the older blazers were prone to ignition switch failures or not, like our GMT360 line seems to be.

Cheers-

Chris

Chris,

The relay is exactly where you said it would be. I do hear the pump. I am waiting for my mechanic to come back and check the pressure. I will ask him to check the other things before I get another pump. I am currently waiting on the information from the seller regarding the fuel pump. Again, thank you for all of your help. It is very comforting to know that this site is here.

Sherri