1993 Does not charge *HELP*

[Highfinance97]

I have a 93 W250 with a cummins & auto trans,

I am having trouble with the electrical system not charging,

I had the alt. bench tested and it is good

disconected the PCM and tested the system with a Snap On scanner, everything worked on the truck, TPS, AC clutch, all relays and the alt showed charge at the ammeter, the only thing that we did not get a reading on was the RPM's

so the wiring seems to be good as everything worked using the scanner so I got a new

PCM from the dealer and the system still does not charge ?

anyone have some info



Michael

 

[Simplysmn]

try looking on fenderwell there is a relay that controls chargeing system ? thats what I went through when I had same problem . maybe this will help ? hope so

 

[dodgenstein]

Since you had no tach output, I would check the crank position sensor. There is a round plug directly in front of the front valve cover that may have come loose. If that checks out, trace the wires down to the sensor above the crank dampener. It should barely clear the dampener (. 050 clearance IIRC). Does your A/C or OD work? These are also dependent on the CPS.

 

[RTRAM]

I had a similar problem. The insulation on the wires going to the crank sensor had worn through rubbing on the timing cover therefore shorting the circuit and the signal to the computer.



Why you need a crank signal for the alternator to work, I don't know. Maybe someone else can explain this.

 

[DBF]

I had a similar problem. The insulation on the wires going to the crank sensor had worn through rubbing on the timing cover therefore shorting the circuit and the signal to the computer.



Why you need a crank signal for the alternator to work, I don't know. Maybe someone else can explain this.

If the engine isn't rotating, why put a load on it?



DBF

 

[cerberusiam]

No rpm's, no charge. The PCM must see the engine turning to turn on the charging system, AC, etc. Check the CPS wiring and air gap then check with the scanner again.

 

[Highfinance97]

Checked the wires starting from the CPS and followed them back to a plug in the back of the engine. Sure enough the plug was corroded



thanks for all the help guys. my father has been going absolutly crazy these past 2 weeks with this truck:-laf I told him a week ago before he bought the PCM make a write up and ill put it on TDR so finally he did and now he is thrilled Oo.





Thanks, Michael

 

[Highfinance97]

Does your A/C or OD work? These are also dependent on the CPS.

no the O/D was not working



thanks, Michael

 

[GIT-R-DONE]

There is a voltage regulator in the middle of the firewall, right behind (above) # 6 cylinder. I have had problems over the years of water run-off, going down over the regulator, causing the plug-in to rust, thus, not giving good contact to the regulator. Check it out as I have to do this again on mine this week. I bet if you pull the plug off of this and look at the contacts, you'll see what I mean.

 

[dpuckett]

1993 doesnt have said voltage regulator. You can relocate said VR, and keep the same one for more than a month. I moved mine to the left fender on my 91.



Daniel

 

[GIT-R-DONE]

Is the 93 the only one that doesnt have the voltage regulator? I know all my first gens have had them, just assumed the 93 did as well.

 

[cerberusiam]

The 92-93 should have the PCM regulated charge system, possibly some of the late 91. 5 also. 91. 5 to early 92 was the switch over and there are some discrepencies in what is actually installed in the truck.