I think the battery voltage is good since the truck cranks for a long time off of the battery. Any ideas where I might check for bad ground or poor voltage connection. All of the accessories in the truck work just fine. I see no indication of a bad ground. Are there any checks that you can suggest so that I might be able to isolate. If I have to get yet another ECM, I have two weeks to get it and install it before I have to get back to work.

 

dezertdirt:

I do not know what year the truck is so I can not give you any ground locations. Pins 6, 40 & 60 are the ground pins at the computer plug.

But you can check the plug at the computer as a lot of the posters have fixed such problems by just unplugging the computer and plugging it back in. Make sure no pins are pushed in.

Did you use a lot of dielectric grease on the plug when you replaced the computer?
If not that alone causes a lot of computers to go bad around wet conditions and engine washing as the old grease dries up.

Also check the red wire going to the injectors from the power relay for voltage while cranking as it is the same red wire that powers the computers pins 37 & 57.
Pin #1 gets it its power from another location.

 

A little follow up on the ole F250. Although the battery was brand new (3months old) the voltage on it was just under 12 volts. i charged it with a trickle charger and the next morning the fuel pump behaved properly (it shut off after a second or so). I got it running and went out and ran it daily and that seemed to help. I did notice that when running the voltage from the alternator is a bit high, running at about 15 volts (although it will got down to 14 after an hour or so of running) where most vehicles I've worked on run about 14 volts. I'm not sure what that's all about. The power is pretty good although I think I have a miss on one of the cylinders. I don't think it's spark as all cylinders light a timing light. I guess it could be a fuel injector or a vacuum leak as some of the small vac tubing for heater controller is all cracked fromm sitting. It almost sounds like an exhaust leak at the manifold but I checked for that and couldn't find a leak.

Anyway, the next round of diagnostics is set for April when I go back up to check in on father in law. cleaning fuel injector, fixing vacuum leaks and whatever else needs fixing is in the plan. I suspect the truck won't get many miles between now and then but I'm feelin pretty good about myself as when I went up there he had an unusable vehicle and now its running ok. Starts fine, plenty of power for what he needs. Thanks for all the help. This is really a terrific helpful forum. I have another non-ford truck and their forums are not nearly as clear, supportive or helpful.

Oh, and subford, I did use dielectric grease when I put the new ECM in last Christmas. Thank you for all your help

 

I realize this is an older thread and the OP never came back with a resolution, but the one additional thing to consider here is a marginal PCM relay - the one that sits right next to the fuel pump relay.

 

I believe the resolution was either a slightly too low battery voltage for no use and or a marginal fuel pump relay from the same combined with sitting out in the winter weather. When I left at New Years she was running ok with the exception of this miss (that has the sound of an exhaust leak when it's under load. This issue has existed for at least 10 years and no one has been able to diagnose it. However, now that I own another properly running six, I know the ford just isn't right. Like I said earlier, I have my work cut out for the next round of diagnostics...it's either spark, a fuel injector not getting grounded or a bad fuel injector...or the exhaust leak I've never been able to find. Thanks to all

 

Well, i know I'm bringing up an old thread but i talked with my father-in-law today about the truck. He says that its taking about a minute for the fuel pump to bring the system up to pressure and then the truck starts fine. Until that time, the truck won't start. I guess I'll check the grounds next time I'm there, regrease the computer plug, change the fuel filter and maybe have the alternator checked. i was also thinking about taking a look at the fuel injectors to try to address the miss that the engine has had. I had hoped it tough starting from lack of use but i guess that wasn't it.

 

Did anyone think to spray a little starting fluid into the eng. intake to see if it would run even just for a moment. This would tell you if the computer is able to start your eng. It might be a great idea to make sure there is fuel in the tank, stranger things have happened before. Good luck, that's my two cents, if you want more you'll have to ask.

 

If the fuel pump runs for a minute and then it starts it is the computer that is keeping it from starting in that minute.
More than likely a bad computer but read on.
It is taking a minute for the clock to start running in the computer.

It may also be low voltage or a bad crystal in the oscillator circuit of the computer. This is taking for granted that the replacement computer has the right spec replacement caps in it that they changed out when they worked on it.
At any rate the oscillator circuit in the computer is not starting up for a minute or so.

 

Note Bill's comments above. We really need to know, very specifically, what you mean by your statement above. There are several ways to interpret what you wrote.

 

I didn't read the entire thread as I left for work but from now on I will. Excellent observation on your part. You keep talking and I'll keep listening.

 

Normally, when you start the truck, you would go out turn the key to the "on" position. You could hear the fuel pump fire up and humm for a couple of seconds and then shut off. Turn the key to "Start" and she fires right up. Recently, at Christmas, I went up with my family to visit my wife's mom and dad so that I could fix up whatever needed fixin and to share the holiday. This time, the truck when the key was turned to "on", you could hear the fuel pump humm but instead of shutting of after a couple of seconds it would continue humming. When I tried to start the truck, it would just continue to turn over but not start. When i sprayed carb cleaner in the tb, it started and continued to run, a little rough at first but then normal. When I drove down the road (country highway) a few miles, it ran fine mostly but did cut out a couple of times for a second but then continued to run. It did this for about a 10mile round trip. When I got back, I charged the battery good as I noted the battery voltage was a little low (about 11.5 volts) on a battery that was 4 months old (I bought it in August. After that I ran the truck nearly daily during the visit, including one off road expedition on the sand dunes, and it ran ok the whole time.

It's now been a few weeks and my father-in-law says its starting to do the same thing again, although he seems to be able to start it after about a minute. The computer is only a couple of years old (at most) and it was the same part number as the one it replaced (a California-based 4.9L with a manual transmission. It worked good for a couple of years.

So now we're plannig a visit at spring break and am hoping to get the truck running reliably again (I'm actually considering new fuel injectors as I think I have one bad one). Anyway that's my story. I looked for another computer from parts geek and the one model that it is out of stock is the one I need ("Y" in the engine code in the VIN, California based 4.9 with a manual). Thanks

 

Normally, when you start the truck, you would go out turn the key to the "on" position. You could hear the fuel pump fire up and humm for a couple of seconds and then shut off. Turn the key to "Start" and she fires right up. Recently, at Christmas, I went up with my family to visit my wife's mom and dad so that I could fix up whatever needed fixin and to share the holiday. This time, the truck when the key was turned to "on", you could hear the fuel pump humm but instead of shutting of after a couple of seconds it would continue humming. When I tried to start the truck, it would just continue to turn over but not start. When i sprayed carb cleaner in the tb, it started and continued to run, a little rough at first but then normal. When I drove down the road (country highway) a few miles, it ran fine mostly but did cut out a couple of times for a second but then continued to run. It did this for about a 10mile round trip. When I got back, I charged the battery good as I noted the battery voltage was a little low (about 11.5 volts) on a battery that was 4 months old (I bought it in August. After that I ran the truck nearly daily during the visit, including one off road expedition on the sand dunes, and it ran ok the whole time.

It's now been a few weeks and my father-in-law says its starting to do the same thing again, although he seems to be able to start it after about a minute. The computer is only a couple of years old (at most) and it was the same part number as the one it replaced (a California-based 4.9L with a manual transmission. It worked good for a couple of years.

So now we're plannig a visit at spring break and am hoping to get the truck running reliably again (I'm actually considering new fuel injectors as I think I have one bad one). Anyway that's my story. I looked for another computer from parts geek and the one model that it is out of stock is the one I need ("Y" in the engine code in the VIN, California based 4.9 with a manual). Thanks

 

It would probably be worth a shot to pull out the existing PCM (computer) then inspect the circuit board for signs of burning or pitting from leaking capacitors. Leaking caps are a VERY common problem and can be repaired for a few dollars in parts.

 

All I can say is re-read my post #23 above.

 

The other thing you can test is the ignition coil check the power going in and out. Do the same thing to a couple injectors.. If you got the same voltage on both wires, can't pull any codes, and the fuel pump keeps running it's safe to say it's the PCM or these trucks it's called the EEC. And the injectors and ignition coil ground through the computer so if they don't have a ground it's safe to say the computer is at fault. I just went through the same thing with my truck and finally diagnosis is a bad PCM. I got one coming Monday but I'm pretty confident it's the problem. I got a no start got fuel pressure and spark. Fuel pump won't stop running when key is on and I had no communication with a scan tool.