Yeah, that's the one. The ECM is very reliable and seldom fail so if you could find one in a local wrecking yard it should work just fine and for a lot less $$$

When your engine is running it's because the ECM is telling the injectors to fire, the spark plugs to spark and the fuel pump to run.

When the ECM is acting stupid it is only telling the fuel pump to run.

Probably a bad connection in the ECM internal wiring and when it warms up the connection is temporarily good again.

 

Today when getting home from work the Bronco surprised me by starting right up on the first try, good pressure in the lines after just the 2-second prime from the pump.

So it might mean that the check valve gets stuck sometimes, but not always. Of course, I don't know how the check valve works... Is it possible that it gets stuck and may get unstuck later, or will it just break and never work again?

Of course, the symptoms can just as well be exactly what you just wrote: it might be that there is good pressure in the lines, but the ECM is not firing the injectors and not giving a spark, just running the pump... The funny thing is that when the pump keeps running, there is a click, like a relay, when it stops running and after that the car will start. It felt very obvious that it had just pumped enough pressure to empty fuel lines...

I ran the self-diagnostics using the check engine light, and only got 11, everything OK. Would a faulty ECM give that?

I wish I'd known all this before ordering the new pump, but hey, at least I'll have a new pump. If that doesn't solve the problem, then it can't be anything but the ECM. RockAuto.com has pretty much everything for the little Bronco, very reasonable prizes and will ship to Finland. They sell the cardone remanufactured ECMs for less than half the price than any I saw on eBay. Thanks for the tip! I had actually forgotten about RockAuto, AMC hobbyist here use that to get all their hard-to-find AMC car parts.

 

The ECM is just a simple on off switch for the fuel pump it does'nt care if the check valve is working or not.

The check valve simply prevents fuel from running back into the tank. This allows quicker starts.

When your ECM is working properly , yes you will get the 11 system pass code. The problem is it isnt always working properly. Congrats on knowing how to pull the codes. Some guys seem to be afraid of pulling the codes??? Go figure

When everything is working as it should the fuel pump sends fuel to the FPR..

The ECM opens & closes the injectors and fuel is fed to the injectors from the FPR. Any fuel that is'nt needed by the injectors flows back to the fuel tank.

When your ECM is acting stupid and running the pump for 60 seconds with the key on engine off the fuel has no place to go except right back to the fuel tank.When this is happening you wont be able to pull any codes at all.

 

Glad to hear you found the ECM for much less. BTW what is an AMC, I'm guessing thats not an American motors corp. hornet or Pacer. Maybe a high buck Mercedes??

 

Thanks for all the info you've shared! I'm sure I'll have a beautifully working Bronco in a couple of weeks. Now it's just a long wait for the parts to start arriving...
AMC is American Motors corp. There is a small but active club in Finland, AMCCF. I used to own a -65 Rambler American, and I've had three full-size Jeeps from the 70s, with AMC engines.
I guess I could start a project thread about the Bronco to share my progress with it. I have a million questions about it, and that would be a good place to pick people's brains.

Here she is, just arrived home on the weekend.

 

It might well be that I've ordered a lot parts in vain... Today I just started going through some bad-looking things in the car after getting the new tires. I dismantled the power distribution box cause it looked dirty and broken. I cleaned everything as well as I could, took out the EEC and Fuel Pump relays, cleaned them and sprayed plenty of CRC into the connectors. Especially the relay connectors were full of yellowish gunk. I put everything back together, turned the key, and no fuel pump... Tried a few times, no pump. I took the box apart again and noticed that one of the female connectors of the fuel pump FUSE had been replaced with crimp-style female terminals (whatever they are called in English, we call them Abiko connectors) and it had come loose the previous time I took the box apart. I put it in securely, put everything back together, and the car has never acted up on start-up since! Every time the pump runs for two seconds and the car starts right up. So, unless it starts acting up again, I can store the new pump assembly and ECM in the garage for a rainier day... Unfortunately, the radiator leak hasn't miraculously disappeared, so I still have some work to look forward to.

 

Had I had more time, the first thing I should have done is get a fuel pressure gauge... On that subject, can someone point me to the location of the fuel pressure release valve on the 1990 2.9 liter engine? I've understood that it is where you would plug in the pressure gauge. A picture would be nice.

 

Yeah, pretty soon you're going to need to put up a sign "Ford parts distribution center-Finland."

Sounds like you're making some good progress with this, i don't see how fixing the fuse connection could cure the pump problem, but you can't argue with success. Hopefully that problem is solved.

It was my turn for problems yesterday when the PC crashed, but now i'm up & running much better on a different browser.

Thats a nice looking B-2 & if you're not afraid to put your foot in it and keep the revs up you are going to love the way it drives, especially with the 5 speed manual trans. i've been driving mine like i stole it since i bought it new in 1987. The 2.9 loves to rev, & i love to rev it.

Interesting that theres an AMC club in Finland. A former neighbor of mine had a beautifully restored Javelin & Rambler american rag top. The Javelin had a 360 4 barrel & 4 speed trans & it was quick.
Good luck with the project

 

I think cleaning the relays was the solution, the fuse slipped out of its socket on the first go. Still starting great this morning.

 

I see we were typing at the same time. The schrader valve is 5 inches from the FPR, unscrew the rubber cap & screw on the pressure gauge.

 

If the fuel pump ever again keeps running when it should'nt turn the ignition off, if the pump keeps running the contacts in the pump relay are stuck closed

 

So far, the car has started without hickups every time. However, today the morning was cold and foggy, really damp. I started the car to drive to the train station. After a couple of seconds, it died, but started right up again. I figured this is OK for the weather. Then 2 minutes later, almost at the station, the engine suddenly died on a straight, doing 40kph. I pulled over, turned the ignition off and tried to start, and it started right up. I think the fuel pump primed a little bit longer than it is supposed to. Anyway, it seems that there is still a bad connection in the relays (or a broken relay), or the ECM is acting up. Now for the relays: which should I replace and what type are they? In the rockauto catalog it says there is a Fuel Pump / Circuit Opening Relay (RY610), a Fuel injection relay (RY71/RY71T) and a Computer Control Relay (also RY71/71T). Now, I saw two similar looking relays at the bottom of my power distribution box, one with a brown base and one with a green base. They both had the same 5-pin arrangement. Then there is one attached to the passenger side fender right next to the power distribution box, which is just black. I assumed (looking at Google) that the brown is the Computer control relay and the green is the fuel pump relay. Or is it the fuel injection relay? And what is the third relays outside the power dist. box?
The relays are the one thing I haven't ordered, yet...
A related question: what is the difference between RY71 and RY71T relays. The 'T' seems to be cheaper, so is it just an inferior quality version? I need to get hold of a repair guide for the Bronco II...

 

There should be a relay for ECM, fuel pump, starter (positive battery cable attaches to it) and door locks. I have no idea what a "fuel injection relay" would do. The fuel injectors (and many other things under the hood)are powered by the ECM relay. The voltage flows thru the injectors and then to different pins on the ECM. The ECM pulses a ground to fire each injector.

IIRC you are correct that the green relay is fuel pump & brown is ECM relay.

When it stalled did the idiot lights come on? If not the ignition switch might be the problem. It would be much better if it would quit running and stay that way.
I have no idea what the difference is between RY71 & RY 71t would be.

If you google "1990 ford bronco 2 EVTM" you will find a used version on EBAY for $19.47. This is an incredibly helpful manual. It will show you how every electrical circuit on your B2 works with easy to understand diagrams & it will give you the location of every splice/ground/sensor/fuse/connector/relay on your B2. For fixing electrical problems this manual is worth a hundred times the $19.47.

 

Yes, all the lights came on indicating that the engine had stalled. I'm pretty sure it was a dampness issue somewhere in some connectors, probably the relays, as they had already been "cured" once from the original problem by wiggling the wires...
Well, I'll just get change the relays as well as the actual ECM once it arrives. I've had many electrical problems with many of my cars that just happen on cold and damp mornings and disappear as soon as the car and all the electrical connections warm and dry up...
I just got the Haynes book, which will help me with some things. It even has electrical wiring diagrams, although it is missing the 1990 2.9 liter one. I guess the '89 is close enough. I've seen the shop manuals (the 2 volume book) for sale for $80 in a couple of places. I'll invest in that later on.
Thanks again!

 

I jusr read your first post again & the symptoms you described there are a perfect match for a flaky ECM. Replacing the ECM might also solve your stalling problem.

The wiring diagrams in a Haynes or Chiltons are PATHETIC, what they try to cram into 2 or 3 pages is not really usable.

I think the reason most guys are afraid of electrical problems is that they have only looked at the useless diagrams in a Haynes or Chiltons manual.

The EVTM is about 130 pages and very easy to understand.

The shop manuals are an xlnt investment, but wont help much with electrical problems.