ECM Code Issue

[Mechrick]

I'm getting a 1.4-2.1V signal across the EEC relay

The PCM pins are 85/86 (coil) and 87/30.

Whet voltages do you get referenced to battery ground in the relay socket with key on/engine off?

 

[rusty ol ranger]

12V to the pump has been tested, but I'm not getting it through the relay. Not burning up pumps, the pump works perfectly fine when I put a 12V lead to the inertia switch. Inertia switch does pass voltage, I've tested all the leads and I'm getting continuity throughout the wiring harness to the pumps, both low and high pressure, right up to the fuel pump relay.

At this point, its either a broken ECM or a bad relay connector. Should be the only two options left.

To recap: with just my key, fuel pumps don't prime or run when engine is turning. When I connect 12V directly to the inertia switch, fuel pumps run. This indicates either a PCM or a connector issue, as I've replaced the relays. When fuel pumps run and engine is cranked, it doesn't fire. Could also be a spark issue with the distributor, but that could be a symptom of a failing ECU or a relay connector that doesn't pass voltage.

ah ok...i think i misread your post before i asked that.

 

[franklin2]

I'll check the distributor, but it doesn't prime the pump when the key is turned. In addition to that, I don't think the fuel injectors are opening, because when I have the pump manually hooked up, fuel just sprays out of it. I think the rail is completely pressurized and more fuel just can't fit.

There is something wrong here. Fuel should not spray out, even if the injectors do not open. Fix the obvious things first.

 

[BoomTexan]

Alright, finally got around to trying to fix my Ranger this week, replaced the relays, checked for connections across the relay connectors and turned out all the connectors were working fine. Replaced them anyways, recharged the battery to make sure it wasn't a low voltage thing, still no start. Replaced the PCM with a reman one and nothing changed either.

At this point I'm assuming that it's a broken wire somewhere in the harness, should be between just a couple things, but was wondering if anyone had a good wiring diagram for a 2.9L with a PCM pinout so that I can diagnose it at the PCM connex pretty quickly. With the spaghetti wiring in there, I'd rather not have to trace stuff back through the firewall.

 

[franklin2]

Ford went to the effort (believe or not) to give you a test port for the fuel system. It's on the plug where you plug in the code reader. With the key on, you can ground this test port and the fuel relay should click and the fuel pump should run.

If the fuel pump relay will not click, you need to do some checking with a testlight at the relay.

If the fuel pump relay clicks, then you need to check the crash switch wiring and the wiring back to the pumps. You can leave that test port grounded at all times with a alligator clip grounding it out, and it will hold the relay in and send power to the pumps at all times so you can take your testlight and start testing the wiring at the frame rail pump to see if you have power. And also the crash switch.

Once you get it narrowed down some, we can pull out the diagrams and see what you have going on, such as the relay wiring and what should have power and what will not have power.

 

[franklin2]

Here is the port for the fuel pump test.

 

[BoomTexan]

Ford went to the effort (believe or not) to give you a test port for the fuel system. It's on the plug where you plug in the code reader. With the key on, you can ground this test port and the fuel relay should click and the fuel pump should run.

If the fuel pump relay will not click, you need to do some checking with a testlight at the relay.

If the fuel pump relay clicks, then you need to check the crash switch wiring and the wiring back to the pumps. You can leave that test port grounded at all times with a alligator clip grounding it out, and it will hold the relay in and send power to the pumps at all times so you can take your testlight and start testing the wiring at the frame rail pump to see if you have power. And also the crash switch.

Once you get it narrowed down some, we can pull out the diagrams and see what you have going on, such as the relay wiring and what should have power and what will not have power.

I actually tried all of this earlier in the thread.

Crash switch was unhooked and wires were spliced together from a previous owner. Tested applying 12V directly to the crash switch, the pump ran. Also, considering that not only does the fuel relay not start, but the injectors aren't going as well, I think that the problem can be narrowed down to that harness.

I can give the fuel relay a try with that method, but having replaced and tested for continuity at those places, replaced the connectors, replaced the fuel relays, and replaced the PCM, I think that my issue stems from that PCM wiring harness.

 

[franklin2]

If the relay clicks and the fuel pump runs with the test port grounded, then I agree, it might be a wiring issue to the PCM. That is all the PCM does, is ground that same wire that is going to the test port.

One other thing, not sure if it was covered earlier. Will the engine run on ether sprayed in the intake? If there are no pulses from the ignition system, then the PCM will think the engine is not turning and it will not ground the fuel pump relay and fuel the engine on purpose. Safety feature.