Engine will not stay running?

Tiny
JOEY GANN
  • MEMBER
  • 1997 TOYOTA T100
  • 3.4L
  • V6
  • 2WD
  • AUTOMATIC
  • 212,000 MILES
I used my OBD-2 diagnostic code scanner trying to pull any code that might steer me in the right direction to get my truck running but had no luck as no codes were stored in ECU. So, I went under the hood to the data link diagnosis connector and jumped E1 to TE1 with a solid piece of copper wire. I then went to the driver's seat where I then turned the key to the on position. No orange check engine symbol lit up. It did not flash or anything. Does this mean that I need a new ECU?
Monday, November 14th, 2022 AT 3:59 PM

12 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

Not necessarily. When you say it won't stay running, explain what is happening. For example, does it start and then stall as soon as you allow the key to return to the run position? Or does it start for a while and then stall? Also, does the vehicle restart right away? Does the check engine light turn on when the key is first turned on?

Do me a favor. Take a look at the wiring schematic below. Make sure the OBD fuse in the fuse box under the dash is good. Additionally, make sure there is power to and from it.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If the fuse is good and has power to and from it, check pin 16 in the DLC for power. It should have power at all times.

If that has power, confirm fuses 4 and 5 have continuity to ground.

Let me know what you find.

Take care,

Joe

See pics below.
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Tuesday, November 15th, 2022 AT 9:11 PM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
Yes, it dies as soon as I allow the key to go back to the run position and yes it will do the same thing over and over again until battery dies. No, the check engine light never comes on. Even when I got the truck and there was 2 stored error codes the light was still not present. I just noticed tonight that the radio stations that the lady had set from 2019 are still set. This truck sat for 3 years with a dead battery and since I have had it I know I have had the battery disconnected a couple of times for more than 24 hours. One of those times the EFI fuse was pulled for the whole 24 hours as well because I changed the fuel pump and fuel filter. I even pulled the ECU recently to do a visual inspection thinking that a capacitor may have went bad and had it unhooked for over 24 hours. It is not possible that someone could have played a prank on me either because I am the only one here. Both legs of the fuse for the ECU are good. 16 has power. 4 and 5 have continuity. I also straight wired my fuel pump and truck ran just fine.
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Thursday, November 17th, 2022 AT 12:27 AM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
I would still like to figure out what is wrong because I don't like the thought of being burned alive if some freak accidents were to happen. I hooked multimeter up to blue fuel pump wire underneath driver seat and it's only getting 10 volts while cranking instead of 12 volts then goes back to 0.22 volts with key in the on position as well as 0.22 volts when key is in the off position. It seems when I straight wire fuel pump with positive and negative wire coming straight from the battery to the electrical connector on top of the gas tank my truck runs fine but when I splice into the blue fuel pump wire underneath the driver's seat with only a positive wire straight from the battery I have to feather the gas pedal and it only runs for a few seconds before it bogs down and shuts off. If I try again, it will do the same thing. There's about 7 gallons of gas in the gas tank. Along with a can of seafoam, a bottle of Chevron Techron complete fuel system cleaner and a red bottle of
heet + injector cleaner.
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Thursday, November 17th, 2022 AT 12:55 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

I think we have an issue with the ignition switch. As far as the 10v when cranking, that is because there is a heavy draw on the battery by the starter. I was always taught it needed to be a minimum of 9.6v for the engine to start, so that is okay. However, when you let the key return to the run position, the voltage should then go to 12v.

This is a theory, but I feel the ignition switch itself has failed internally. If you look below, the switch should be providing power in both start and run positions. See where I highlighted. It does get it in the start position, but it returns to the run position, we lose power. This is where I believe it is happening. Also, with the key off, there should be no power from the switch. There will be power to it, but once off, nothing should come from it.

Disconnect the ignition switch and see if the.22v is gone. At least we will confirm there isn't a short to power from a different source.

Let me know your thoughts.

Joe

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Thursday, November 17th, 2022 AT 4:03 PM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
My fuse box doesn't have the two metal contacts inside of the ECU-IG fuse spot. I attached an image of what my fuse box looks like.
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Thursday, November 17th, 2022 AT 4:34 PM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
From what I understand the only way that the fuel pump wire would be receiving 12 volts when key is in the Run position is if the ECU receives run signal from either the camshaft positioning sensor or the MAFS. I have replaced the MAFS and I'm about to go check the camshaft positioning Sensor now. I'm not saying that it's not the ignition switch, I'm just trying to put all possibilities out there.
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Thursday, November 17th, 2022 AT 4:41 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

You are correct. It receives power to prime the system for a couple of seconds at first. At that point, there has to be an ignition signal for it to be powered. If the engine starts and then stalls, the signal when it starts is present when needed and the pump should be energized.

Joe
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Thursday, November 17th, 2022 AT 5:00 PM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
Okay, I am lost now, so what should I check?
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Thursday, November 17th, 2022 AT 5:16 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

I hope I'm not confusing you. If I had the car, I would locate the ECU/IG fuse in the fuse box. With the key off, it should have no power. Have a helper turn the key to the run position to confirm there is power present. If there isn't, turn the key to the start position to see if it is present then. If it is, the ignition switch is my first suspect.

Let me know.

Joe
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Thursday, November 17th, 2022 AT 8:39 PM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
Key off- no power.
Key on acc- power.
Key in starting position- power.
Key in run position- power.
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Monday, November 21st, 2022 AT 10:59 PM
Tiny
JOEY GANN
  • MEMBER
  • 8 POSTS
I appreciate all your help, but I am about to put everything back in order on the T100. I am about to call a tow truck driver and have him come get it in the morning and take it to Springhill Toyota dealership. It's going to cost me $150.00 for a diagnosis but that's okay. I can't put a price on my sanity, but I know it's worth more than $150.00. Thank you
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Tuesday, November 22nd, 2022 AT 2:33 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

Thank you for the update. And I totally understand what you are saying. Not being there with you makes my job ten times harder, but you did a good job with the diagnostics. We are likely missing something simple.

If you can, let me know what they tell you. I'm interested in knowing.

Take care of yourself and I hope you have a good Thanksgiving.

Joe
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Tuesday, November 22nd, 2022 AT 6:44 PM

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