PCM??????????

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Nov 24, 2009 | 01:27 AM

MyMoneyPit

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PCM??????????

I have 89 F350 with 92 engine, I have had multiple issues

. My question is, what issues would a bad PCM cause? Can it burn out glow plug relay and help short wires connected to glow plugs. Also I seem to have excessive amounts of electricity moving through glow plug wires over fused with big 50 amp fuse and blew the fuse. Why what is the reason? It was fine and now its not...? please help me

Nov 24, 2009 | 01:39 AM

David85

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From: Campbell River, B.C.

The only thing the PCM controls is the transmission if you have an E4OD (some 89s still had the older C6 3 speed). If its a 3 speed auto, or stick shift then there is no computer at all.

Nov 24, 2009 | 01:54 AM

MyMoneyPit

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PCM

According to shop manuals the PCM does run the time of wait light, heat level for glow plugs, oil temp sensor, in does have two boxes under dash, one gold colored and one black plastic.
Something is burning up system and relay sets at 144.00 each I cannot afford to replace many more times....... Losing my mind!

Thanks for replying
Eric

Nov 24, 2009 | 05:02 AM

LCAM-01XA

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Eric, the shop manual is wrong, the PCM has absolutely nothing to do with any aspect of engine operation, including the glowplugs - the controller for those is on the back of the intake, behind the CDR valve and under the air box, the relay sits right on top of the controller actually. You're burning the 50-amp fuse because the system can pull about 200 amps when operating properly. Why yours is burning up, I don't know, are you sure the whole system is dying, or is it just glowplugs or relay or controller?

Nov 24, 2009 | 07:22 AM

Lazy K

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Really the only thing that limits the current draw on the glowplug circuit is the resistance of the glowplug and of the wires. So burnt wires either indicate, glowplugs a direct short to ground or wires too light/defective.
Too high a current draw may also damage the relay. So also might a faulty controller or wiring keeping the relay on all the time.
So check glowplugs for direct short, check wires are heavy enough gauge and check that wires are not shorting to ground anywhere.
Just my thoughts.

Nov 24, 2009 | 05:17 PM

Dave Sponaugle

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From: Nutter Fort, WV

Sounds like you are reading the Power Stroke specs.

No oil temp sensor on the IDI engine at all.

Everything that controls the glow plugs is located in this unit.

Resistance feedback from the glow plugs tells the controller how hot the glow plugs are which determins how long they need to be on.

Battery power at the battery terminal at all times.
Ignition power at the ignition terminal when the key is on.
Ground wire to a good electrical ground, usually under one of the mounting bolts.
And the wire to the Wait to Start light.
The only other connection is the glow plug harness.

Nov 26, 2009 | 10:03 AM

JHoffman93

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From: Westfield, MA

If the plastic cover is missing from the the gp controller could you possibly be shorting out the controller by coming in contact with something metal like the air cleaner housing?