1996 F-150, 5.0, 4x4, 113,000 miles, Battery is new and good

Ok, so when the temps drops to about 20f outside and colder the truck will not start if it is not plugged in with the block heater. If the block heater is on, truck will fire right away even at -10f outside, but no block heater it wont start.

Only way to make the truck start when the block heater is NOT plugged in is to hold the pedal down a bit when cranking it, then it will fire, sometimes with lots of blue smoke and some popping which is telling me that a fuel supply issue does not look like it is the problem. And once you get it going it will be fine rest off the day.

I think it has to either be a fuel or air supply problem as when you push the pedal down, the further you go the more you increase the both of them. And with getting a lot of blue unburnt fuel when doing so that tells me it is getting fuel, which leaves air. Air filter is good, Once running it idles great and runs great.


Now today it is about 20f out tired to start the truck twice did not start, I took the air intake tube off and then started it and it fired right away.....

EDIT: I should also say that once the temp is above 20-25f the truck will start just fine, no problems at all.

Any help guys or suggestions?

Thanks
Josh

 

i was having the same problem with my 92 5.0, it would take a very long time to start or no start at all. but only when it was cold outside, if it was warm it had no problem starting. i replaced two sensors your truck reads fuel/air ratios, air intake temp sensor, and coolant temp sensor. Nothing seemed wrong the the coolant one, but the air intake one was pretty gummed up. You might wanna give this a try since there only like 10 bucks a piece. Not much of a mechanic, but just giving my 2 cents with my past experiences.

 

No, that's not true of EFI. On a carb, pumping the pedal operates the acceleration pump to spray gas into the intake, but on EFI, it just screws up the TPS calibration & IAC adaptation. If you hold it to the floor during cranking, it turns off the injectors to clear a flood, just like a carb.Unburned fuel has no color. It would stay liquid at that temperature, and simply coat the insides of the exhausht manifolds until the engine warms up, and it evaporates (which is also invisible). "Blue" is usually how people describe the smoke from OIL burning - does your oil level drop between changes? What do your spark plugs look like? But in such a cold climate, the sooty smoke from too much gasoline burning might appear blue, so pull the red vacuum line off the FPR & inspect it for the presence or odor of gasoline.

It's virtually impossible for airflow to be a problem, unless the throttle cable breaks (which obviously isn't the case), or someone has messed with the throttle stop screw.



I'd start by testing the ECT & ACT/IAT as described in this diagram & its caption:



Then get a Haynes manual, a digital multimeter, & a fuel pressure gauge, and test the ignition system & fuel pressure.

.

 

Well I thought I was getting somewhere but I guess not lol. See BOLD below

Thanks for the help! I will see what I can do in the next couple of days

 

Not good. The plugs should have been replaced LONG ago (probably 2x). Read the tune-up specs on the VECI label under the hood. I recommend high-quality 9mm silicone wires, and cheap normal Autolite plugs from WalMart. Read these:

. . . . Good, but don't buy or replace any other parts until they fail a test. Changing anything else will make the REAL problem that much harder to diagnose.

 

I know...Got the truck about 10 months ago and that was one of the first things I saw when I looked at it, were the plugs/wires. Hope to get them changed out this spring when it gets a little warmer out.

 

Do you think/ could it be possible that the IAC is causing the problem?

 

It could, but get the ignition system up to speed first! Plugs, wires, rotor, and cap aren't that expensive. From Rock Auto:

Autolite copper plugs - $1.08 each
OEM Motorcraft wires - $39.89, other brands are cheaper. Dunno what the 9mm's that Steve recommends cost.
OEM Motorcraft cap - $25.79, other brands are cheaper.
OEM Motorcraft rotor - $10.25, other brands are cheaper.

 

UPDATE:

Pulled the IAC the other day and it looked very dirty and covered heavily in soot. Could of cleaned it perhaps but decided to drop the 40.00 bucks for a new one.

Guess what? PROBLEM SOLVED!

Air temp was 6 above this morning it it fired right up with not being plugged in!


As soon as I replaced it I could already tell a difference in how it started, like it had more air.

Still going to do plugs/wires/cap & rotor...parts are on order from rockauto.com. I think I will wait til it warms up a bit though before doing them....would be nice to do them in the driveway when it gets a little warmer then 6 above out!