Ground wire from the negitive terminal was just replaced this week. Terminals are clean and in good shape.

 

i'm sorry i wasn't very clear.
what i ment was when my truck hits the speed limiter it completly cuts out like you turned off the ignition then once u've slowed down the engine kicks back in.
Im pretty sure it does that buy cutting power to the coil or fuel pump.

you said it acts like its completly shutting off and coming back on causing bucking.
so i just thought that maybe power was getting interupted to the coil or the fuel pump

but unfortunatly that doesn't explain the lean reading ur getting off of ur O2 sensor or why ur getting a -0.5V when the lower limit should be 0.0V
That sounds like a crossed wire, but u said the reman engine ran great till this last spring so i dont see how a wire could get crossed.

that leads me back to the fuel diverter valve i think that is your best bet right now.
I had a 1987 F-150 302 4x4 XLT Lariet that i worked on that had a very similar problem, it would run great for about 30 sec to a minute then it would spit, backfire, cough, buck the whole 9 yards turns out i had 2 porblems
1. the intank fuel pump was bad
2. the fuel diverter was actually sending the little fuel it was pumping from the rear to the front tank.
Now since you just replaced the pump i think whats happening is the FDV is the check ball is messed up and not allowing the fuel to go the the right place.

Now i know what ur thinkin in that if its cutting off fuel why does it look rich and the O2 says lean? well im not sure about that but mine had enough black smoke come out of it to make a cloud behind the truck and it WAS starving for fuel.

what we eventually did is use a cheap fuel filter and use that to make the connection becase it has the ford fuel line ends on it

sorryfor the long winded post :P

 

oh and i forgot to mention the same truck had another problem where the engine would cut in and out for no reason and it turned out to be the ignition control module that was overheating and cutting out.

I have read all 20 pages but i dont remember if u replaced it or not. And if you dont want to spend the money O'Reilly's will test it for free.(Though i dont know if it'll act up till its hot)

 

The ignition control module was replaced with the new distributor.

No black smoke.

The plugs look like it is running lean but it is using gas like crazy. (7 - 8 mpg) They look white. If it is indeed running lean then where is all that gas going?

The FDV - the cutting in and out doesn't seem like when you are running out of gas. No spitting or spuddering. Maybe it's time to bypass that thing like Chas suggested just to rule it out.

Fuel pressure is good. New pumps. New injectors. New filters.

Just seems to be electrical. What exactly does the ignition actuator do?

Todd

 

if the FDV is completly 100% shutting off the fuel to the engine it will do that.
i had another ford (1987 F-150 300 4x4) that the fuel pump relay was bad. and when it got bumped just the right way the truck would just die no sputter or nothin
and it was sensitive enough to where Literally you could slam the drivers side door and it would come back on.

and im sorry but i never took the computer or fuel pressure readings on etheir truck when this was happening

But i know when you think a sensor is bad just unplug it reset the computer and see if it runs any better. worked for me with my TPS and IAC

when my TPS went out it would act like it was cutting out at partial throttle after i unplugged it it ran Great,
and when my idle was messed up (it would hang at 2000 RPM after letting off the throttle and the RPM would go up and down for no reason when it was cold) i unplugged the IAC and screwed in the set screw on the Throttle Body so it wouldn't die and its running much better. it just wont warm up in the morning

 

oh and experimenting buy unplugging is free

and i like free

 

when you turn your key you move a rod that moves the actual electrical connector called the ignition actuator.

advanced search will come up with more details and how to replace it.

 

Chas87F150, by DFR do you mean that 6 port valve on the frame rail under the driver side door? If so it made mine cut out just like Kart18 is doing when i was driving down the road. this was about a year ago. Replacing my fuel filter and 6 port valve fixed mine. It would run fine for a while then all of a sudden act like the key was being turned on and off or bucking like a plow mule. It would flat out die sometimes but would start back up after setting a few minutes. Replacing the computer would have just fixed the rich signal he was getting from the negative 0.5 bias.

 

Nextal, my fuel relay went out on me like you are takling about. pop the hood thump it and crank it back up. Of course sometimes it wouldnt crank back when i thumped it. I called the tow truck. when he got there about 2 hours later, he told me to try it again for grins. I did and it cranked. It didnt make mine buck and jump, it would just die. but the six port fuel diverter valve thingamajig did make it buck.

 

ya i hear ya gpedens but im just sayin if the relay was shortin out it may cause it to buck.

it may explain why it does it after a couple of miles too, when the relay gets hot the contact may expand just enough to cause it to short out and cause the fuel pump to turn on and off

 

Shorting some or a lot of the turns in a dc relay typically wont keep it from working. It will just draw more current to make the contacts. They do run hotter. I have seen dc relays with the covers melted and they still function. once picked up you can drop the voltage to about 4 volts before they drop out. I think you mean opening rather than shorting. A loose wire connector or broken wire can cause it to chatter. most of the dc relays in a car do have a resistor, or reverse bias diode, or transzorb, or combo resistor and diode across the coil. this is for transient or high voltage kick when the relay is turned off. it protects the computer inputs or outputs from getting fried from the high voltage surge. the reverse bias diode can fail and short the coil briefly but even then the diode just burns open or pops the fuse to the circuit. Those with the reverse bias diode have to be connected to the battery correctly or it will destroy the diode if you connect it forward biased. They are usualy just 1 amp diodes. If the diode fails before the fuse and you reinstall the relay, it will probably fry your computer. The contacts can get an oxide film from out gassing of the plastic or other relay parts. this can cause the contact to not make when the relay is energized. The symtoms you describe above are caused by an intermittent open circuit. this would cause both fuel pumps to stop, then when the door was slammed it remade the loose connection and picked the relay back up. thus starting the fuel flow again. the transient voltage created by some of those little relays can be several hundred volts.

 

So let me ask this - where can you get a FDV? How much are they? Would one from the junk yard be ok to put on? I can probually get one for $20 or so and put on. I could bypass it to check it but those lines are a pain in the butt to get to and work on. I can say that the fuel pressure was checked while it was running and acting up and it wasn't changing while it was cutting out. Maybe that don't mean anything.

Todd

 

It was also suggested to unhook the alternator and see if that made a difference. That maybe the thingy that controls the voltage may be causing the problem. What about that?

 

Hi Gpedens - yes, if you have dual tanks then your DFR will have six ports (two from each tank coming into the rear and only two exiting the DFR forward). The symptoms of a faulty DFR (Dual Fuel Resevoir) are varied, but usually include idle loping, bucking, exhaust smoke and stalling. I have some detailed posts in this thread that explains my thoughts on this. It is not difficult to bypass but for some reason Todd doesn't seem to give the idea any credibility. The test in the various aftermarket manuals is not adequate. The DFR must be fully bypassed.

 

i found this but it says it will work on all makes and models?
1988 Ford F-150 Fuel Tank Selector Valve | O'Reilly Auto Parts

also i would not recommend something from the junkyard.
what if u happen to get another bad one? u wouldn't get anything accomplished

i still think u should bypass it first instead of throwing another part at it

oh and for the fuel pressure thing i think that what is happening is that the valve is blocking off the fuel so the truck is not getting enough Volume but is still somehow maintaining pressure. Remember the components in our fuel injection systems are stupid, all the FPR knows how to do is maintain pressure not volume. So you may have 30-40 PSI but it may be being pulled/pushed through a very small spot so the truck cant get enough volume witch will cause it to run lean and cut out.

at least thats my theory