Reviving a 1993, 4.9L-Engine issues
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Junior Member
Joined: Jan 2018
Posts: 7
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Reviving a 1993, 4.9L-Engine issues
We have a 1993 F-150 reg cab, 4.9L, E40D auto, 2x4, 8ft bed that has been sitting for about 5-6 yrs. My son decided when he turns 16 he wants to drive this thing.
To start with I attempted to drain the tank and put fresh gas in. New battery. Cranked a little and the little wire on the starter would not make good connection. Ended up replacing starter under warranty. Next, would crank, but not fire. Took breather box off, was mouse nest packed all the way from outside intake to filter. Replaced wires, cap & rotor. The plugs were not too old when it was parked. Put a new gas tank on the front tank, new pump, and inline filter in the frame rail.
Cranked a little, no fire. Took the plastic off air filter to throttle body and shot a little ether in the throttle body area. Fired and ran VERY rough. It seems to idle not terrible, but when I put it in gear to get it into the shed it would die as soon as it felt a load. Restarted, held the idle higher and quickly shifted into gear. I could keep it running enough to move it 20ft. Once i got it inside I quickly put it in park, let off the throttle to let it run on its own. At this point it idles w/o dyeing but the motor is rocking on the mounts pretty good. I'm curious if I should be looking at injectors now. Would clogged or faulty injectors cause this type of idle and motor to run this way?
Thanks for the info, I'm new to trouble shooting this type of issue. I've been using YouTube, and the Hynes book as a source for repairs, but I haven't seen anything that related to my issue.
To start with I attempted to drain the tank and put fresh gas in. New battery. Cranked a little and the little wire on the starter would not make good connection. Ended up replacing starter under warranty. Next, would crank, but not fire. Took breather box off, was mouse nest packed all the way from outside intake to filter. Replaced wires, cap & rotor. The plugs were not too old when it was parked. Put a new gas tank on the front tank, new pump, and inline filter in the frame rail.
Cranked a little, no fire. Took the plastic off air filter to throttle body and shot a little ether in the throttle body area. Fired and ran VERY rough. It seems to idle not terrible, but when I put it in gear to get it into the shed it would die as soon as it felt a load. Restarted, held the idle higher and quickly shifted into gear. I could keep it running enough to move it 20ft. Once i got it inside I quickly put it in park, let off the throttle to let it run on its own. At this point it idles w/o dyeing but the motor is rocking on the mounts pretty good. I'm curious if I should be looking at injectors now. Would clogged or faulty injectors cause this type of idle and motor to run this way?
Thanks for the info, I'm new to trouble shooting this type of issue. I've been using YouTube, and the Hynes book as a source for repairs, but I haven't seen anything that related to my issue.
Senior Member
Joined: Jul 2007
Posts: 3,805
Likes: 480
From: Cape Girardeau MO
Suggest given the time setting and the apparent slight improvements as things progress - yes, injectors are one of the several primary suspects. May try a max dose of in-tank cleaners, or splurge for the 'professional' injection cleaning shot in through the fuel rail. Consider the original fuel injectors have been proven as very reliable with few failures - so don't go replacing them on a whim without efforts to clean them first.
Would also check and verify fuel pressure on the rail - for the 4.9L, looking for 45-60 psi. If not there, consider the fuel filter, fuel pump, fuel pressure regulator, and tank pickup screen as leading suspects.
Consider pulling the computer codes to see whether the computer has flagged anything.
May pull the plugs to inspect for any crudding up as well as just verify the correct plug wire firing order to cross that off the list of possibilities.
Would also check and verify fuel pressure on the rail - for the 4.9L, looking for 45-60 psi. If not there, consider the fuel filter, fuel pump, fuel pressure regulator, and tank pickup screen as leading suspects.
Consider pulling the computer codes to see whether the computer has flagged anything.
May pull the plugs to inspect for any crudding up as well as just verify the correct plug wire firing order to cross that off the list of possibilities.
Senior Member
Joined: Apr 2023
Posts: 4,301
Likes: 1,394
From: Near Salt Lake City
I think you will need to replace the gas tank
Find, rent, or buy a borescope and check the condition of the inside of the tank
Back in the old days you could clean one out
Fill it with BB's and some solvent and you and a buddy shake the hell out of it
These days: tanks are cheap, and labor is expensive
I'd replace the tank, so you know at least that part is good as you work through any further trouble
Find, rent, or buy a borescope and check the condition of the inside of the tank
Back in the old days you could clean one out
Fill it with BB's and some solvent and you and a buddy shake the hell out of it
These days: tanks are cheap, and labor is expensive
I'd replace the tank, so you know at least that part is good as you work through any further trouble
Thread Starter
Junior Member
Joined: Jan 2018
Posts: 7
Likes: 1
Suggest given the time setting and the apparent slight improvements as things progress - yes, injectors are one of the several primary suspects. May try a max dose of in-tank cleaners, or splurge for the 'professional' injection cleaning shot in through the fuel rail. Consider the original fuel injectors have been proven as very reliable with few failures - so don't go replacing them on a whim without efforts to clean them first.
Would also check and verify fuel pressure on the rail - for the 4.9L, looking for 45-60 psi. If not there, consider the fuel filter, fuel pump, fuel pressure regulator, and tank pickup screen as leading suspects.
Consider pulling the computer codes to see whether the computer has flagged anything.
May pull the plugs to inspect for any crudding up as well as just verify the correct plug wire firing order to cross that off the list of possibilities.
Would also check and verify fuel pressure on the rail - for the 4.9L, looking for 45-60 psi. If not there, consider the fuel filter, fuel pump, fuel pressure regulator, and tank pickup screen as leading suspects.
Consider pulling the computer codes to see whether the computer has flagged anything.
May pull the plugs to inspect for any crudding up as well as just verify the correct plug wire firing order to cross that off the list of possibilities.
Thanks for the suggestions. I took the cap off the Schrader valve on the rail to poke the valve stem with a screw driver to see what kind of squirt it made. It was pretty decent, but not an actual pressure reading. I should borrow or get a pressure gauge to check it.
Where would you check the codes on a 93'? I have the code reader for the 96' and older vehicle.
Senior Member
Joined: Jul 2007
Posts: 3,805
Likes: 480
From: Cape Girardeau MO
Definitely put a real gauge on the fuel rail, many recommend a gauge with a hose long enough to secure in place to monitor while driving. The hose thing perhaps not an immediate concern with your current situation, but yes, get a gauged numbers measurement to know rather than guess and speculate.
Memory fades, but pretty sure the '93s were still the OBD-1 protocol, which required a manufacturer specific reader. Some are still available through Amazon or the like, however many users have reported issues with these units. Perhaps a parts store has an older one tucked away they would loan out? There are a couple of Sticky Notes on the main '87-'96 page on how-to with a voltmeter and a paper clip, or the like. One linked here - How-To: retrieve trouble codes- OBDI - Ford F150 Forum - Community of Ford Truck Fans
Memory fades, but pretty sure the '93s were still the OBD-1 protocol, which required a manufacturer specific reader. Some are still available through Amazon or the like, however many users have reported issues with these units. Perhaps a parts store has an older one tucked away they would loan out? There are a couple of Sticky Notes on the main '87-'96 page on how-to with a voltmeter and a paper clip, or the like. One linked here - How-To: retrieve trouble codes- OBDI - Ford F150 Forum - Community of Ford Truck Fans
