Well folks, I'm at my wits end. I have an '85 F150 5.0EFI that will not start. Last time it started, it started and was warming up, but was running rough and at a low rpm and died. It never started again. I changed the usual suspects, fuel filter, pump, pressure regulator to no avail. Starter fluid had no effect so changed plugs, cap, rotor, verified spark, and still will not start. Pulled the fuel rail off injectors to verify fuel is getting there which it is, but not out of injectors. Ordered an OBD-1 code reader from eBay and when it came I read the codes as 21, 24, 31 and 31. These were coolant temp sensor, air temp sensor and EGR sensor, so changed all of the these and EGR valve since it was shot too.

Today, after changing the sensors it still will not start. I re-read the codes and get 21, 24, 31 and 11. At least the constant code is now reading system ok. I cleared the codes and still no start. Re-read the codes, still 21, 24 and 31. I can't imagine why these codes still come up as all of these sensors are changed.

One thing I did notice is that when I turn the key, no idiot lights light up - no check engine light, seatbelt, nothing. I would imagine that should indicate something but I have no idea what!

Man, do I miss the days of my '57 Chevy with the 235 inline and NO COMPUTER!

I have no idea where the fuel injection relays are, does anyone know on this truck? My Explorer has them on the fenerwell in a relay box, but I've never seen them on my truck. I changed the ECM relay to no avail.

Stumped. Totally stumped. Any ideas anyone??

 

Sounds like the ecm may be fried?

 

I had a simuliar problem long ago on an 86 , I did allot of the things you suggested and finally, I took it in.. It ended up being the pickup coil insde the distributer - U need a special tool to get it..

I can't remember about the lights on the dash - you should get them. At this point I would go thru every fuse and check them..

 

I don't know about the ECM, but to try to see if it is, I unplugged the TPS to see if it would kick out a new code, and it did. Seems it will recognize a new problem, so I plugged it back in and on the next code run, that code does not show. So, seems like the ECM is ok, or at least part of it????

This got me thinking. Is the ACT, ECT and EGR sensors on a circuit that might have a fuse or relay somewhere that might be blown so that the ECM gets no signal from them, even though they are good? I have checked all my fuses and they are good unless there are some in a place I don't know of, my fuse box only has 8 fuses or so, but I have lost the fuse block cover that tells me what fuse is what, so I don't know what they are. Any place online I can find the diagram for the fuse block layout?

 

I think I know exactly what the prob is - Your IAC , I remember replacing that as well on time.. On the 5.0 & 5.8's it's in front out in the open..Bolted on the pass. side os the TB.

 

What is the IAC? I can't find any info on that one. Any idea what it is and what it does?

On second thought, I see in my chilton's manual what I believe you are talking about listed as the Air Bypass Valve Assembly?

 

Your right!! The air bypass is the IAC - The second pic is from f150.net and is from a later model - but there simular - when that spring locks up it can't adjust air and fuel.

Funny , I was sure they called it the IAC back then as well..? Oh well, that's it..

 

Thanks j, unfortunately I replaced it with a whole new one and still no fire. I can't figure it out and I'm sick of throwing money down a hole. Tomorrow I'm putting it all back together and yanking it to a shop around the corner. They'll at least have some experience and a clue about what they are doing where I'm just changing parts in the dark. After reading about the IAB, I sure had my hopes up, it being bad or stuck would explain the idle problems and it dying when I come to a stop once in awhile!

I'm afraid the only thing left is the ECM. ECM sounds like a grand down the hole!

 

That sucks, Your lights not coming on in the run position is a definite problem as well, you might want to find that cause..Somethings blown.

Meaning it's not communicating properly

 

You said it had spark though. If it has spark and fuel, it should at least be banging, clattering, popping, something! Not just sit there and crank anyway. Can you smell fuel from the tail-pipe?

I would take a look at the cam chain. It may be worn out and slipped which through it WAY out of time (spark and valves). This is excruciatingly common with older GM's with plastic toothed sprockets.

 

What's up triton? Man this sites bogged down lol - He has an electrical problem as well. A fuse is gone somewhere..

 

Go back to basics. Check spark, fuel, and timing. Try some ether spray in to the intake, if it fires its a fuel problem.
If you need the Computer, you should be able to find a used unit somewhere.
Ford dealer would be the best bet for trouble shooting (they have the equipment).
Remember OBD and OBD2 are just tools and a guide to the problem.

 

Triton, I thought the same thing. After all, fuel air and spark, right? But my issue as far as I can tell is the fuel injectors are not opening. I tried starter fluid (ether) too, it has absolutely no effect. But then I pull a plug wire and plug in a spark plug and ground it to the engine and turn it over and I get good spark. Same off the coil wire.

My dad mentioned the timing chain too. I thought it would be strange since it ran great when I parked it last and then this happened. I guess I can pull the #1 plug and crank until the piston hits TDC and check the distributor to see if it is pointing at the #1 spot on the distributor. Of course, #1 cylinder is the hardest to get to with the smog pump and crap in the way! What keeps throwing me is these same three codes keep coming up.

I'll have to replace the starter solonoid because all the cranking and it and the batter positive cable get mighty hot.

 

That sounds like a plan , check out TDC and that will tell yuh.. This is bringing back the good old days , I haven't had a vehicle you can adjust timming on in along time lol..

 

You don't have to pull a plug to find TDC, just line up the timing mark on your harmonic balancer with the timing tab at 0 or TDC on the front of the engine. Your rotor will point at #1 or 180 degrees away. I should say should point one of those places if the timing chain hasn't slipped.