I recently aquired a 1994 F250 at a local title loan company silent auction. now by silent, i mean in the usual way, no auctioneer, but also in the risk taking way of you cant crank the vehicles. Once you win, they get the key and tell you good luck. This particular truck has a 460 with a 5spd, and had no radiator. I inquired, and was told it was repo'd while the owner had it in the shop for repairs. Using some risky figuring, i thought "who would put a new radiator in a truck that doesn't run well?" Answer: The previous owner.

Anyway, fast forward a week, and the truck is sitting in my shop, and i'm out of ideas. The thing will crank a brand new battery dry, and sometimes will hiccup like it wants to start, but can not get there. I have tried:
- new plugs, wires, cap, button, coil
- tested the injectors
- tested the fuel pressure (40psi, wobbles a little when cranking)
- New IAC valve
EDIT: I am getting spark.

This is where it gets fun. All that, no luck, tried to read the codes and the CEL flickers. Along with the CEL flickering, if I put a stethoscope to the new IAC valve, it ticks in time with the CEL flicker.

Im boggled. completely. Please help.

G

 

at some point during all this cranking, you will need to put a compression gauge on it.

 

Are you getting good compression? Since they had it torn apart you can't be certain the cam timing is correct.

Other things to check if you haven't already;
-ignition timing(distributor position)
-spark plug gap(0.044or 0.046 is stock)
-the flashing CEL is bad. Could be a bad PCM

 

Ill do a compression test tomorrow. I have been thinking PCM, just as a 'lets try this' I disconnected and reconnected the PCM, and it cranked up, but it just sputtered and spat before dying seconds later.

Also, i noticed that when the CEL is flickering, and the IAC is clicking, the fuel pump is also activating. Im really thinking its something stupid like a ground. The ground always gets me. Will check compression, timing, and ground tomorrow and report back. I've got the battery on the charger, so we shall see what happens

G

 

how old is the gas it it, and what does it smell like? it may just be old gas .

 

First things first, you have to get the PCM working correctly (which it isn't). That means its power and ground need to be verified to be good. Makes certain that the Vref output of the PCM isn't shorted to power or ground. Once that is done and if the erratic PCM-related symptoms continue, then it's time for a new PCM.

Once the PCM is operating correctly, then it's time to address any remaining symptoms.

 

Pop open PCM and look at the capacitors

 

Oh boy... a half-disassembled pile of Somebody Else's Problem.

Check the exhaust for restrictions... who knows what might have crawled in there. Same with the intake ducts.

Also high on my list of things I'd do is what was already mentioned by others: compression test, see if the fuel is any good, check ignition (and valve) timing.

Does it fire on starter fluid?

Are the plugs wet with fuel after you've been cranking it?

 

Seriously, he has to get the PCM working FIRST. Everything else comes after.

Checking the caps is a very good idea.

 

First, to answer some thoughts above:
- no exhaust restrictions that I can locate.
- Unfortunately, it was a deceptively assembled pile of someone else's problem.
- Gas is good. Just to be sure I added 10 gallons of ethanol free 89 octane, as well as about half a shot of HEET
- timing seems to line up, I threw the timing light on it today just for kicks, and seems set at TDC. Ill try it the old fashioned thumb-on-cyl1 way Monday just for kicks, but its good.
ALSO, I did not mention this above - I cranked the truck and drove it on the trailer when i bought it. However, the truck had absolutely ZERO brake pedal, and once it was on the trailer, just for kicks I cut the A/C on. When the compressor kicked in, it stalled and all of my problems started. It sat on the trailer hooked to my dually for a week, and I came back to it Monday. Sorry, should have mention that sooner.

SOOO, last night, about 2AM I got tired of late night cable (Im a bit of an insomniac) and went out to the shop to beat my head against a fender in frustration. I cleaned the ground on the Rt front fender, and truck fired right up, with inconsistent idle and surging at W.O.T. I thought it was odd, but I didn't pursue, it just acted like maybe it had been flooded from constant cranking, and the TPS was bad. So, I ordered a new TPS and threw it in this morning. Nothing. Crank no start. I did notice that the fuel pressure gets up around 35psi now, and when the truck tries to start it drops to around 20psi, and the fuel pump never shuts off. It will literally run until I can smell fuel in the whole shop. I removed the FP relay (which is new, along with the other relays) and cranked the truck at W.O.T. It fired up, and then sputtered after about 8 sec of idling, because it was out of fuel. Re-install relay, same thing.

On a side bar, compression gauge showed 130-135 across all cylinders. Not great, but I have another truck pumping 90-100psi on all cylinders and running like a champ, so I find it hard to believe the compression is the source of my heart aches. Cleaned out the air ducts, air box was de-critterized, new filter installed, did not help. Also, the CEL still flickers when the fuel pump runs. Not flashing, but flickering. Sometimes it illuminates fully, sometimes barely noticeable. id say 5-7 flicks per sec, usually 5-10 sec at a time. I'm almost convinced at this point the PCM is shot, but how do I test it to verify? I'm not finding one in a pick&pull to match my motor trans combo, so a cheap shot in the dark isn't really an option.

Sorry for the long winded post, just trying to get as many details out as possible, hoping you guys can keep my hope up enough to avoid me using it as really expensive target practice.

G