Engine/Transmission (1994 - 1998) 97 problems

[JacobsD]

Okay, my buddy's truck (97 12 valve automatic regular cab/long bed SLT) was having problems cranking in cold weather. So he replaced the batteries on it, and then it was cranking over well for a while, and now it will sometimes start, sometimes not. Also now when it does run, it has low power, the tach and speedo doesn't work, and the volt meter is reading real low. The batteries are reading full charge with a regular handheld tester, and all the fuses appear to be good. Any idea what could be going on here? I was thinking it could be a computer.



Thanks in advance.

 

[DonTX]

I think I would want to see a digital voltmeter hooked up when it does that for further troubleshooting.

 

[JacobsD]

Reads 12 volts and 14 when running. He's saying now that his terminals are loose on the posts so we'll have to put new ones on first. I don't know why it would mess up the tach or speedo though?

 

[Joe G.]

Check the engine speed sensor on the crank pulley. If it is not working then the PCM does not react as it should when the engine is running. So the alternator, tach, and speedo won't work.

 

[JacobsD]

Thanks, we'll try one of those tomorrow when the parts stores are open.

 

[Fordiesel69]

When you say low power, do you mean low electricity (volts) or low engine power (feels gutless)?

 

[JacobsD]

Engine Power, but it could be just in my friend's head, I'm gonna try the sensor and terminals first.

 

[Hammer]

Sounds like the fuel system is sucking air someplace if its a low power/hard to start deal... ... Andy

 

[Joe G.]

If it's still hard to start and low power then email me at -- email address removed -- for my 12 valve fuel supply system write up, how it works and how to fix it.

 

[JacobsD]

Well the low power issue is because it's in limp home mode. Would that also be caused by a bad crank sensor?

 

[Joe G.]

It's a 12 valve. I don't think there is such a thing as "limp home mode" for that truck. The entire fuel system is mechanical except for the fuel solenoid.

 

[JacobsD]

The transmission doesn't have a limp mode?

 

[Joe G.]

I've never heard of a limp mode for a 47RE. Maybe if I'm wrong someone will chime in. I don't recall a limp mode ever being mentioned on any of the 12 valve forums.

 

[Vaughn MacKenzie]

Never heard of it either. The only thing the auto does out of the ordinary when electrical issues occur is not go into OD and/or lockup. . . that's as "limp mode" as a 12-valve gets.

It sounds like something else going on with the engine not related to the electrical issue. One idea I have is maybe the shutdown solenoid is not fully latching to the Run position & restricting fuel. Other problem could be slipped or retarded timing- does it sputter and smoke a lot? Last idea, maybe the grid heaters are not kicking in. How cold of temperatures are we talking about at startup?

Vaughn

 

[Joe G.]

If it runs ok in spite of the electrical problems, but is gutless take a look at the AFC. If it's not working it will act like that.

 

[JacobsD]

We're going to do the crank sensor and the battery terminals tomorrow night. Hopefully that would cure it. The shut down solinoid was a consideration of mine. I will check it out when I drive down there to help him out.



How cold? 20's... but it does it when the motor's warm too.