Sill No Secondaries

[Marccus]

I followed test guidelines to check why my secondaries were not opening.

I've replaced the solenoid and canister three times and still nothing changes upon starting or above 4,000 rpm

With the key in the start position, the red wire reads 12.5 volts where the black wire reads about 0.3 volts.

When I start the engine, the read wire reads 13.9 volts and the black about the same - 0.3 volts.

When I open the throttle above 4,000 rpm, the red wire reads 14.1 v and the black wire jumped to 1.1 v for a split second.

I guess this means I need a new PCM?

Can anyone advise?

Thanks.

 

[dantheman68]

I had a similar problem. new PCM fixed it

 

[hawkeye18]

Yeah, sounds like the PCM is at fault. That red wire should drop to 0.0 volts when the engine crosses 4Krpm, when the PCM shuts it down to close the vacuum down.

 

[Marccus]

OK. I'll replace the PCM.

I honesty don't know how these PCMs can keep failing.

They are just a circuit board.

How the heck can a pin or circuit board component fail so easily when they've been refurbished with new parts.

The boards are just stuffed with passive components (resisters, capacitors, coils, inductors, op amps?, etc.)

I've gone through three or four PCMs in my cart ('89, 426,000 mi).

The last two, it seems, just several years about apart.

I think the original unit lasted about 12 years!

They sure wouldn't pass any Mil Spec testing.

I'd like to take one apart, find out what failed, and restuff the board with what I am able top replace.

:thankyou:

 

[techi14]

Maybe the heat factor where you live and possibly dust or whatnot could have contributed to the failure.

 

[Devin]

I doubt too much dust gets in there. The PCM is in a crimped metal box.

To the OP, obviously something is wrong somewhere to make you go through PCMs. The tough part is figuring out what.

What stuff died before that caused you to switch?

 

[AREA 91]

OK. I'll replace the PCM.

I honesty don't know how these PCMs can keep failing.

They are just a circuit board.

How the heck can a pin or circuit board component fail so easily when they've been refurbished with new parts.

The boards are just stuffed with passive components (resisters, capacitors, coils, inductors, op amps?, etc.)

I've gone through three or four PCMs in my cart ('89, 426,000 mi).

The last two, it seems, just several years about apart.

I think the original unit lasted about 12 years!

They sure wouldn't pass any Mil Spec testing.

I'd like to take one apart, find out what failed, and restuff the board with what I am able top replace.

:thankyou:

If you accidently plug in the EATC wires into the secondary circut and vice versa, it WILL DESTROY the secondary circutry in the PCM. I have done it, and damn ford for putting the plugs within reach of each other with the exact same plug ends.

 

[dantheman68]

If you accidently plug in the EATC wires into the secondary circut and vice versa, it WILL DESTROY the secondary circutry in the PCM. I have done it, and damn ford for putting the plugs within reach of each other with the exact same plug ends.

WOW! Great to know, thanks a million!