Swapped Tranny, No Fuel Pressure

[JoeShmoe]

Ok, I'm still at work. If the PCM is inside the passenger compartment then I doubt thats bad. I'm thinking very strongly that missing the ground wire by the harness (behind the resorvoir) is culprit. I really hope it is that simple, but what about this guys. If that ground wire is not hooked up, would that cause the whole pcm to not function properly? Like I said, everything else seems to be in working order (including my fuel level indicator.) Thanks for all ya'lls help, I'm going to check it out tonight.

[rhandwor]

Its a ground for the computer.

[rhandwor]

What did you find is it running at this time?

[JoeShmoe]

I haven't put it back together but yes the ground wire was loose. Apparently the screw that goes into the wal was stripped when I was screwing back in. There is about 1/8" gap, making the ground connection loose. I don't want jynx myself but it looks like today I'll have it back together. I'm going to give it one more shot.

[rhandwor]

I'm glad you fixed it a loose ground is hard to find.

[JoeShmoe]

I have to cut the screw tonight and get it nice and tight. I hope that will give me power to the realy. I'll let ya'll know.

[JoeShmoe]

Ok, so grounded the wire properly leading to the PCM harness and still a no go. I think its time for new PCM. Do you fellas agree? Is it a simple swap with another?

[rhandwor]

Their is an inerta fuel shut off switch behind the left kick panel. Putting in a transmission you might have bumped the car hard enough to trip this. Push in the push button and try to start. According to the wiring diagram if I'm reading it correctly. Get a piece of no.12 wire and make a jumper hot wire it will supply the feed to the fuel pump.Either a PPL/BLK or a PPL/ORG they go to a splice and it appears to be a PPL/BLK but both wires go to the splice. If it runs trip the inerta switch and make sure it trips off the pump.
If this works go to the parts store and buy a Dodge starter relay they are metal. Use a self tapping screw and screw it to a metal place that is not rusty. Buy a inline fuse holder and wire it from the battery using a 20 amp fuse. Use a female splice connector and a male splice for the hole where the fuel pump relay goes. Find a place in the fuse panel where you can hook up a small wire to turn on the relay. The relay is always grounded and when you shut off the ignition switch it will shut off.
Go to the ignition switch should be on the column. Check the green wire for power. This will get it running and if you send me a private email I will copy a 1997 wiring diagram to you. Also send a fax if I have trouble making an email. Put your fax number and a private email and I'll try to get it to you.
Either you have a wiring problem or it is a control circuit. Possible a computer but I doubt it.

[beyondloadedSE]

Originally Posted by JoeShmoe

Ok, so grounded the wire properly leading to the PCM harness and still a no go. I think its time for new PCM. Do you fellas agree? Is it a simple swap with another?

I personally doubt its the PCM. It was working before you replaced the trans.

If you do decide to replace it, I would find one from the same year. A 98-00 PCM won't work due to PATS. 95 won't work due to a few odd ball things like vacuum operated secondaries and cable driven speedo. 96 would probably work, but your best bet is to find one from 97 and if possible with the same PCM code.

[JoeShmoe]

My fuel cut off is working properly. I'm sending you a PM rhandwor, If I'm not mistaken this is a relay getting power form another source right?

[Selectron]

The fuel pump circuit comprises of two separate circuits, so you'll probably find it helpful to think of it that way when you're reading the wiring diagram. First there is the circuit which drives the fuel pump relay coil, and then there is the circuit which drives the fuel pump itself, via the switched contacts of that relay. I'll describe both circuits, in case that might be of some help.

============================

Coil circuit of Fuel Pump Relay:

12V is fed to the high end of the Fuel Pump Relay coil via the following path: Fuse 9 (20A, hot at all times) - to switched contacts of the PCM Power Relay (contacts closed when ignition switch is in Run or Start positions) - to high end of Fuel Pump Relay coil.

The low end of the relay coil then connects to the PCM, and when the PCM wants the relay to operate it will ground the low end of the coil - current will then flow through the coil - the switched contacts of the Fuel Pump Relay will then close, and feed current via those switched contacts to the fuel pump motor via the following circuit:


Switched contacts circuit of Fuel Pump Relay:

The input terminal of the switched contacts within the relay is connected to 12V at all times. When the PCM activates the relay (as above), current flows via the following path: through the relay's switched contacts - then through Fuse 14 (15A) - then through the closed contacts of the Inertia Fuel Shut-off switch - then through the fuel pump motor - and finally to ground. When that circuit is complete, the fuel pump motor will operate.

(Note that at the 'cold' end of fuse 14, a 12V feed is also fed back to the Fuel Pump Monitor input terminal of the PCM, to inform the PCM that the fuel pump has been successfully activated).

============================

For troubleshooting purposes, voltages in the coil circuit should be:

When the ignition switch is first switched to the Run position, 12V should be present at all points along the path described in the coil circuit, above, except the low end of the relay coil, which will be held at 0V (i.e. grounded) by the PCM. After a few seconds has elapsed and the PCM has primed the fuel system, 12V will remain present at all points along that path but additionally, the low end of the coil will then rise to 12V. So, 0V at low end of coil = relay on, and 12V at low end of coil = relay off.

And the voltages in the switched contacts circuit should be:

With ignition switch at the Run position, 12V should be present for a few seconds only, at all points along the path described in the switched contacts circuit, above, all the way through the circuit as far as the motor positive terminal (the motor negative terminal will always be at 0V potential). After a few seconds, only the input terminal for the relay's switched contacts will remain at 12V, with all other points from the relay's output terminal through to the fuel pump dropping back to 0V.

Perhaps you're already aware of that but if not then maybe it will help. Let me know if you don't follow any of that.

[JoeShmoe]

Originally Posted by Selectron

The low end of the relay coil then connects to the PCM, and when the PCM wants the relay to operate it will ground the low end of the coil - current will then flow through the coil - the switched contacts of the Fuel Pump Relay will then close, and feed current via those switched contacts to the fuel pump motor via the following circuit:

Thats where the problem lies IMO. I'm not getting power from the PCM to my relay. I understand the concept (props on the wright up) but for some reason I can't get power to the relay itself. Wires are not knicked, cut, or anything of that sort. I honestly feel like getting an atutomotive electrician to look at it, even if it costs an arm and a leg.

[beyondloadedSE]

Originally Posted by JoeShmoe

I honestly feel like getting an atutomotive electrician to look at it, even if it costs an arm and a leg.

Or get a Contour with an MTX-75 and kill two birds with one stone.

[Selectron]

With the ignition switched off, I'd unplug the Fuel Pump Relay and check for voltage at terminal #3 of the empty relay socket. That should have 12V at all times, so you can leave the ignition switched off while you do that, and you can use either a meter or a 12V test lamp.

Then switch the ignition on and check for voltage at terminal #2 of the empty relay socket, which again should have 12V, but only with the ignition on.

What happens next would depend on the results of those tests.

If 12V is present at terminal #3 then that tells you that power is available for the switched contacts side of the circuit.

If 12V is missing at terminal #3 then (with ignition switched off) check for voltage at fuse #9 (20A, in battery junction box). The current for the relay's switched contacts doesn't actually flow through the fuse, but the current is tapped-off of the feed for fuse #9, so if 12V is missing at terminal #3 then it might well also be missing at that fuse.

If 12V is present at terminal #2 then that tells you that power is available for the coil side of the circuit.

If 12V is missing at terminal #2 then (with ignition switched on) check for voltage at fuse #13 (20A, in battery junction box). Leave the fuse plugged in while you check for voltage, and probe first onto one leg of the fuse, then the other, through the small holes in the top of the fuse's plastic casing.

If 12V is missing at fuse #13 then the PCM Power Relay would be the next item to investigate.

If 12V is present at both terminals #2 & #3 then (after plugging the relay back in), have an assistant switch the ignition on while you check for voltage at either fuse #14 (15A, battery junction box) or at the inertia switch (whichever is easiest) - you should have 12V for just a second or two as the key is turned.

Those would be my initial tests - they're quick and easy, and would shed a lot of light on the source of the problem.

I'm reluctant to mention this, but this is a '98, isn't it, so I just hope it isn't one of the early '98s with the nightmare wiring harness problems. I'd start by unplugging the relay though and find out what's happening at terminals 2&3.

[JoeShmoe]

12V is not present at the realy, not even a small jolt to prme the pump. Don't know about the other smaller fuses, I'l have to check tonight. Thanks for all your help guys, I hate automtive wiring!!!