Today I managed to get most of the stuff done. I replaced the radiator, the coolant temp sending unit, the ECM, the fuel pump and the fuel and air filters. Lots of new shiny stuff in the car now, so I had to follow up and give her a good wash.




New radiator, no more leaking.





New pump in place. The fuel tank was really clean inside, compared to the outside.





The old pump was covered in some kind of black soot and the filter looked really dirty.

One thing I immediately noticed was that I can no longer hear the fuel pump. The old one was making a loud whizzing sound. The old ECM was rusty on the backside, but I didn't open it. The air filter was filthy and the fuel filter was covered in a thick crust of dirt.
Let's hope the problems are gone now... I guess I'll still get my hands on some new fuel pump / EEC relays, just to make sure. I've also read a lot of forum posts and there seem to be other possible explanations left for my problems. So, if the trouble continues, next on my list are the relays, then the inertia switch, then the ignition control module.
Before I did all the fixing, the car stalled once on a straight road doing 60kph. I stopped, tried to start a couple of times, then had the pump again stay on for a long time, after which the car started. The stalling when hot matches with the ICM overheating problem that I read about somewhere, but the fuel pump staying on is something else. It had done the same 400 yards from home, so overheating wasn't possible that time. Anyway, let's hope it doesn't happen anymore.

 

Well, no luck... This foggy morning, really damp and cool, the car died 100 yards after leaving the driveway. The same old symptoms: the car just dies and when I turn my key to off and then on, the fuel pump runs for a very long time, and maybe a minute later I hear a click, the pump turns off and the car starts right up. Next step, relays...
I read this great article on the EEC relay. According to the text the EEC relay controls the power to both the fuel pump and the ignition. So if that relay feeds power to the fuel pump relay, it is at the same time feeding power to the ignition. I don't understand what's going on... Why do I get power to the fuel pump for over a minute but not to the ignition? And it seems that there is a relay that clicks somewhere and after that the car starts. Is there another relay that controls ignition behind the EEC relay? At least Rockauto lists a "Fuel injection relay" for my car separate from the fuel pump and EEC relays, but I cannot find any mention of that anywhere. I cannot get my hands on a fuel pump relay before my 1000-mile trip to the north, but I can get an EEC relay. Somewhere on the internet I read that I can just use the same relay for both, but I'm hesitating with that. Also, I saw somewhere some instruction on converting to modern and reliable Bosch relays, which is something I might do.

 

So that damned pump is still running when it should'nt even with the new ECM.

As they say it takes a 1,000 words to explain a simple picture/wiring diagram.
When you turn the key to run, voltage from the ignition switch flows thru the coil side of the EEC relay to ground. The relay closes & sends 12 volts to the coil side of the fuel pump relay and to a pin on the ECM. The ECM grounds that pin, the pump relay closes & sends 12 volts to the inertia switch & on to the fuel pump.

The only way i can see this acting the way it is is if theres an intermitant short to ground on the pump trigger wire between the pump relay & the ECM. The fuel pump pin is 22. If you pull the connector off of the ECM & look toward the fuel pump relay you should see some amount of resistance. Yank the relay & should see a clean open.

The fuel pump trigger wire is tan/light green stripe.

 

The fuel pump running isn't exactly a problem per se, but it is another symptom of the stalling-and-not-starting-again-until-the-pump-stops-running problem. They seem to be connected, as the fuel pump issue occurs when the engine stalls and won't start. So, whatever causes the pump to keep running, also seems to cause an ignition failure at the very same time. And I'm pretty sure I hear a relay click when the pump finally stops running and the car can be started...

Another related observation: when the pump runs continuosly with KOEO, the sound of the pump seems to be oscillating a little, like it wasn't running well. Could this be a voltage drop issue with a poor contact in the relays? If the relay is stuck closed, but the connection is poor, then the pump would turn at a lower speed and the voltage might not be enough for ignition. Or maybe JUST the voltage to the pump is sometimes low (bad throughput in the relay), and it can't pump enough fuel to keep pressure in the system, and it actually stalls because of lack of fuel due to poor pump voltage? Just wildly guessing here... This is really hard to test, because the problem is rare and I'm on the road when it happens.
Actually, occasional poor voltage could also point to a faulty inertia switch. I can test bypassing that if the new relays don't fix it. However, now it all points very much to the relays. I mean, the problem was far worse originally; I couldn't even start the car without waiting for the pump to do it's thing. And that was cured by yanking the relays...

I wouldn't like to go on a 1600 km round trip with a car whose engine can die randomly. Electrical problems like this usually get worse, and this most certainly is an electrical problem. Also, so far it just occurs in cold/damp conditions.

Anyway, I'll rebuild the relays from new standard 4-pin relays with diodes. I don't know if the diodes are needed, but since the original EEC relay has a diode, I'll get one that has it, too, cause I don't understand the workings of the relays well enough. I've understood that the two circuits in the relay are never mixed, so the current that is activated by the relay should never enter the circuit that does the activating, but I guess the diode is there to somehow protect the ECM from potential power spikes anyway. I'll have the new relays in tonight, and once again hope the problem goes away...

 

Yeah, hopefully the new relays will fix it.

Heres something you can play around with. Do a google search on "EEC-4 test connector."
Look at the picture of it and you will see the "fuel pump pin". When the key is on and you ground that pin you should hear the pump relay click & the pump will run for as long as you keep the pin grounded. This pin is spliced into the pump trigger wire between the ECM & the pump relay. I'm not sure if the engine will run when you do this.

You could also hook up a scanner & see if there are any trouble codes that might give a clue on this.

The EEC-4 test connector is under the hood/passenger side & on some Fords it just hangs at the end of it's wires. Might have to fish around to find it.

 

OK, I took apart the whole power distribution box, installed all new fuses there, cleaned the main power wire connections, and of course built the new relay system. I sprayed everything with electronic protection spray and put the box back together. I even sealed the box with some gorilla tape, because the latches are broken and the cover doesn't stay on well.
There was a scary moment after installing the new relays; the brand new 60 AMP ignition fuse burned in two seconds when I turned the key to on! After a little head-scratching I realized I had the wires that activate the relay through the diode installed backwards. Luckily, nothing else was damaged and after swapping those wires in both new relays and installing an old spare 60 AMP fuse, everything worked as they should. Now I'm just waiting for tomorrow morning, so I can test if the car still stalls in cold and humid conditions. At least there was nothing wrong with the car when I let it idle to operating temperature to read the codes again. The CEL said 1 1

 

Yeah, that blown 60 amp would sure enough give a guy a good scare, glad you got that sorted out real quick.

I see that your ECM is happy with the 11 code.

Nice job with the shiny new relays. I've got my fingers crossed that your problem is solved.

 

If the pump does start acting up again, look for a bare spot in the pump trigger wire insulation that might be grounding out to sheet metal.

 

Two mornings and one day of driving around later, and the little Bronco has been on her best behavior We're now building trust into the relationship, and tomorrow we take the road to Lapland, for some grouse hunting. Thanks for all the help! Even though the whole problem was solved in the end by a hardcore version of "wiggling the wires", I feel much better with all the new parts in the car. Plus I learned a ton about the car in the process. After all, this is the first EFI car I've dealt with, and the whole fuel pressure/ignition control system was totally alien to me.

 

Yeah, it sounds like you nailed it this time, glad to hear it. Good luck on the trip, i hope you get your limit.

 

No luck with the limit, awful weather for the entire trip. On the extremely positive side, absolutely no trouble with the electronics of the B2 despite the daily rainfall. Just some new trouble with the transfer case, but so far only on 4wd high.