1986 F-150 won’t start
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2nd Gear
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1986 F-150 won’t start
I’m hoping for some advice from y’all. I have a 1986 5.0 F150 that has a code 21 and a code 24 that won’t start. I replaced the intake air temperature sensor (with an air charge temperature sensor because that’s what they show is for the IAT, but it looks slightly different) and the coolant temperature sensor. It won’t start with carburetor cleaner sprayed into the throttlebody either. There is 40 pounds of pressure to the fuel rails. When it was running, it would just stop at random times when driving. Now, it won’t start at all and the one time we could start, it was when the gas pedal was held all the way to the floor and it barely ran for a few seconds while spitting out black smoke. This was before I replaced both the sensors. I’ve also replaced the MAP sensor as I cannot detect a signal coming out of the old one. I’m totally out of further thoughts on what this could be. Has anybody experienced the same thing? Thanks for any help y'all can provide.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Welcome to FTE
I dont know much on the EFI trucks so think of this as a bump.
I dont know what any of the codes mean so someone will have to tell us.
I can tell you when you held the throttle wide open it tell the system the motor is flooded and not to open the injectors when cranking.
You also say at this time it puffed out black smoke another sign it was flooded.
If you pull the vacuum hose off the fuel pressure regulator is it wet with fuel?
If so it would be bad and is not cutting back PSI when it needs to.
Dave ----
(bump)
I dont know much on the EFI trucks so think of this as a bump.
I dont know what any of the codes mean so someone will have to tell us.
I can tell you when you held the throttle wide open it tell the system the motor is flooded and not to open the injectors when cranking.
You also say at this time it puffed out black smoke another sign it was flooded.
If you pull the vacuum hose off the fuel pressure regulator is it wet with fuel?
If so it would be bad and is not cutting back PSI when it needs to.
Dave ----
(bump)
Lead Driver
Joined: Nov 2013
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One thought about your test results. If your carb cleaner spray was indeed the good (flammable) stuff, the lack of response would indicate no ignition, not necessarily a fuel problem. The only catch is if the plugs are flooded with fuel, they won't fire, so don't let that confuse you. I'd hate to see you chasing a non-existant fuel problem if ignition was really at fault.
FTE Legend
Joined: Nov 2015
Posts: 30,917
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From: Angier, NC
Karl, He did say when he held the throttle to the floor and tried to start it fired for a short bit with black smoke out the tail pipe.
IIRC on EFI motors when held to the floor it tells the computer it is flooded and dont let the injectors spray fuel.
If that is the case and was flooded I think I would pull the fuel pump relays so they cant run.
Get a can of starting fluid and see if it will run on the fluid with out the black smoke.
If it dose run clean on fluid then I would look into why it was flooded and go from there.
Dave ----
IIRC on EFI motors when held to the floor it tells the computer it is flooded and dont let the injectors spray fuel.
If that is the case and was flooded I think I would pull the fuel pump relays so they cant run.
Get a can of starting fluid and see if it will run on the fluid with out the black smoke.
If it dose run clean on fluid then I would look into why it was flooded and go from there.
Dave ----
FTE Legend
Joined: Nov 2015
Posts: 30,917
Likes: 4,123
From: Angier, NC
Then again being new to old trucks with EFI that is not starting he may have been trying anything to get it to start and why throttle to the floor?
Dave ----
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Lead Driver
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I have the 86 owner's manual. For EFI do not touch the gas pedal. I can post a photo of the EFI starting procedures if the OP needs that. The only differences are between cold starting below and above freezing and warm engine. In no case should the accelerator be used until after the engine has started.
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Lead Driver
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Won't blow up. But might not start. The instruction for cold. Above freezing cranking, no touchy the gas pedal, is 4 seconds. If it does not start wait for a few seconds and repeat. I forget how much wait time but not too long. Under 32 degrees you crank more, wait more between attempts. They say no gas pedal. That's been the case with every EFI I have had some experience with. Actually they all fired straight up.
Lead Driver
Joined: Jun 2013
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From: Tolland, CT
Correct, for a 86' 302EFI, DO NOT touch the gas pedal for starting. Turn the key to on for a couple of seconds, to let the fuel pump prime, then start engine. You only hold the pedal to the floor if you somehow flooded the engine with fuel. They say holding the pedal to the floor, shuts off the fuel supply.
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