No evidence of spark. Tested the fuel rail and there was no pressure. I pulled the fuel pump relay and jumped the relay contacts and fuel pressure was then normal. I then decided to check for error codes using the check engine light. But that light never comes on. The bulb is good. I then decided to check the fuses. I turned the ignition switch to run and tested fuses. All were good except f13 which i think powers the lights on the instrument panel including the check engine light. My Haynes manual seems to show that the ignition switch supplies power to f13 and the asd relay when in the run position. The asd relay seems to get power but not f13. Im currently trying to drop the fuse panel inside the truck to examine the wiring to f13. There are two bolts holding the panel in place. The bottom one came out ok but the upper one just spins in place. Im still trying to get the upper one loose but i thought i would check here for suggestions. Thanks for any advice you give.

 

Suggestion 1: Dump the Haynes manual for wiring; grab a copy of the factory service manual (hint: It ain't a Haynes Dakota!) which has much more accurate wiring, and for just a 1993.

Have you checked the socket to see if it's getting power when you turn ignition on? Easiest is with a ATO style fuse (fingers exposed on the top), instead of the ATC (fingers insulated on top); with the ATO, you can ground a trouble light and see if both sides have power with ignition on. (If only one side does, the fuse is bad. If neither one does, it's a problem with the ignition switch or the wiring.)

I've attached the wiring to that fuse; no, it's not downstream of the ignition switch on a 1993 (hence my recommendation to forego the Haynes - or the Chilton's! - because, frankly, for wiring on these trucks, they don't even make good toilet paper ... )

The MIL (Malfunction Indicator Light, or Check Engine Light) itself gets power from the ECU.

RwP

 

And BTW - when you say, "The ASD gets power", on which pins? There should be one that goes hot when you turn the ignition on and another one that the ECU will make hot; the ECU will ground the relay to turn it on, so you should have power to two contacts (contact A is the switched contact for the coil, and it's in parallel with the coil for the fuel pump relay for a 3.9/5.2; contact C on both relays are switched by the ECU; contact B is switched on and off by the ECU itself, but feeds through a 10 pin connect, black, by the rear of the battery; contact D is the switched output and runs to the HEGOs, the injectors, the coil, and a few other circuits on the ASD; to the fuel pump on the fuel pump relay. That's the only contact that's NOT wired in parallel; if you have a multimeter, pull the negative battery cable from the battery, and see if A, B, and C have continuity between the two sockets. If so. that's probably good .. and no, that's not under the dash!)

RwP

 

Follow up test

 

I sent a follow-up earlier but i think it got lost so please excuse this message if you get both. Anyway, my first question has to do with wiring diagrams. Used factory service manuals sell for $100 or more on ebay. Is there a web site that can give you an accurate diagram at a reasonable rate?
Next question you said the check engine light gets its power directly from the PCM and not fuse f13. Everything I have read so far seems to indicate that from 1991 to 1995 all PCMs are the same and similarly so is the wiring. Supposedly pin 32 of the PCM grounds one side of the check engine light to turn it on which implies the other side is powered with 12V either by a fuse or the ignition switch. Is this correct or not? I disconnected the PCM connector and grounded pin 32 of the wire bundle with the ignition switch in the Run position and the check engine light did not come on. It is my understanding that the check engine light as well as other dashboard lights are supposed to light up when you first turn the key to the run position. They do not. Is this an indication that the PCM is bad? Or is this an indication of power loss to the dashboard lights. My main concern is whether the PCM is bad. If i could get the PCM to flash error codes with the check engine light then i would think the PCM is ok. Am i looking at this correctly?

 

The CD of the PDF is available. Bishko Publishing ( http://www.autobooksbishko.com/ ) has them; I found one copy of it on Ebay for less ( https://www.ebay.com/itm/1993-Dodge-...D/152790385047 )

The 1991 FSM is for a TBI unit; 92/93 is a MPFI injector design, 94/95 is also MPFI, but there are differences still. So no, they're not all the same. (They may be wired the same here; I can't be arsed to check again myself right now.)

Now. Checking the 1993 FSM, the CEL is powered by the fuse at 16, a 5A unit. I'd check that one also. Shucks, due to age, I'd check ALL the fuses. Possibly replace them all as a nod to your cousin and mine, Justin Case.

The PCM has nothing to do with the 'Lamp Test' function of the ignition switch; that's entirely within the ignition switch.

I'd triple check, but there's also a chance the ignition switch has failed ...

And what I said, and I quote:

You may notice I never EVER mention the MIL / CEL is powered in that sequence; I was talking about the ASD and fuel pump relays!

So no, you're NOT looking at it correctly.

Pin 32, a black and pink wire, should ground the CEL/MIL indicator; if it doesn't turn on, the problem isn't the ECU. This does not mean the ECU is in perfect shape, but it means you've got another problem.

Time to check fuse 16 with the ignition turned on (both sides!), and also check the L pin on the red instrument cluster connector; that's where the ground is fed into the cluster for the CEL/MIL. If that is grounded when you ground pin 32, it's not the wiring there. Do consider it may be old enough that the BULB has failed; it's a 1993, after all! (Suggestion: Replace ALL the 194s with new ones. Or go LED; go warm white and good ones, not the cheapest ones you can find on Amazon or Ebay.)

RwP

 

It might help if I understood how the ignition switch performs a lamp test of all the lights on the dashboard. I pulled out the dashboard and tested each bulb individually. I had to clean the contacts on some bulbs with an emory file but all bulbs were good.
Also in reference to your quote, is the wiring diagram below accurate for this vehicle? If yes, it appears pin B of both relays are always powered by PDC- fuse D. In addition, pin 3 (battery) of the PCM is also always powered thru that 10 pin connector supposedly located behind the battery which i can't find. Pins A of both relays receive 12V when the ignition switch is in the Run position. My suspicion is the ASD pin 51 of the PCM is not grounding pins C of both relays and that is why the engine cranks but won't start. The question is how do i prove or disprove my suspicion. The CEL not working is one clue that the PCM may be bad. I will try checking fuse f16 today. I will also check pin L on the red display panel connector. Thanks again for your input.
Louis

 

Easiest would be to pull the relay; connect a test light to 12V on the battery and to pin C of either socket, and see if it lights during crank.

If it doesn't, disconnect the negative battery cable, disconnect the ECU, connect pin 51 to ground with a jumper; reconnect the negative cable; and see if the relay kicks on when you try to crank (it won't start, but it should kick on.)

While doing this, when reconnecting, remove/replace the ECU connector three or four times with the negative battery connector off, then see if it helps any.

As to how does the ignition switch do a lamp test? It has a section that's grounded to the steering column; on start, it grounds the return side of several of the warning lights to light them up, the CEL amongst them. But you can again check by grounding the CEL/MIL output wire with the ECU disconnected and verifying it does, or does not, light up. Again, that's pin 32, a black/pink wire, as I referenced earlier. If the MIL/CEL doesn't light up with that grounded, the light not lighting up is NOT due to the ECU malfunctioning.

Last but not least, CHECK ALL YOUR GROUNDS. At this age, every vehicle is suffering from random ground failures if it hasn't been properly maintained.

Or *shrug* You can order a reman'ed ECU; or order a used one. car-part.com shows at least one down to $35 (!!) and a lot of $CALL for prices.

RwP

 

Every fuse seems to be good especially f16 and even f13 which becomes active when the headlamp switch is turned on. I connected a test light to 12V and attached it to pin C of each relay (asd & FP) one at a time but the light never came on when I cranked the engine. I grounded pin 51 on the disconnected PCM cable with the ignition switch in the Run position and both relays clicked. I also tested each relay separately and they clicked. Grounding pin 32 of the PCM still does not light the CEL. If fuse 16 powers the CEL light what pin on the red or grey dashboard connectors is that fuse connected to. If I can get the CEL to light when grounding pin 32 then it would seem getting a rebuilt or used PCM would be my next course of action. Do you agree? Also do the wiring diagrams show how the ignition switch lamp test works? Thanks again.
Louis

 

The wiring diagrams show the section in the ignition switch used for the lamp test; it also shows the connector pinout at the instrument cluster.

As to which wire the CEL is on ... it's the L position of the RED connector.

I'm not sure the PCM is dead; I'd also check 12V into pin 3 of the ECU, to make sure that the ECU is getting power. If that wire is open at the black connector by the battery, you won't get squat.

Also - have you checked the infamous splice by the washer fluid container? There's a 3 wire splice there that's bad about corroding, and that will kill various portions of the circuitry when it fails.

RwP