Idles fine, barely accelerates
 

Hey guys, newbie here.

I do not know much about carburetor systems except they are old.

The truck is a 1984 F150(Non Cali) 2WD Auto. The engine has been swapped to a 1977 Ford engine. I believe it is a 360 Windsor. It was taken out of a motor home, or the platform they built the EMS truck on.

The problem I am having: The truck starts fine after a few pumps and will run great in park. When you put the truck in gear and try to accelerate it will take off and then immediately lose power and usually stalls.

If you let off the gas it will run normally, but if you give it gas it will stumble or barely run and just sit there until you let off the gas. It is currently very hard to go over 20MPH.

Here is a recap of what has happened to the truck:

1.Truck sat up and motor died; replaced with the 1977 engine
2. Truck sat up again; fuel tanks were replaced
3. Truck runs good with no issues
4. Dipstick breaks off. No way to check oil level.
5. Truck starts missing and often dies while driving.
6. Carburetor from original engine installed no changes.
7. Current issue surfaces. Engine stalls when at a stop in gear
8. Another issue; engine stalls when trying to accelerate
9. Take truck to my wrench. Discover accelerator pump primer was not touching the pump. Primer now touches pump and can accelerate with no issues.
10. Same day. After 1 hour driving; engine misses and starts stalling.
11. The wrench adjusts carburetor, says the ignition timing is off and cannot accurately dial in without his tools. Wrench notices ignition module is leaking on the fender. struggled to make it home
12. I install new Motocraft ICM same issues except engine will not miss after running for a while
13. Currently: Cannot bring truck to wrench as truck will not accelerate without dying.

I hope that was helpful.

Also; if I give it some gas the engine will stumble and continue to run, but if I floor the pedal after it has built some speed the truck will accelerate but as if it only has 3 or 4 cylinders. Technically I could get there driving this way but I don't want to hurt the motor.

Any help at all appreciated guys.

Thanks.

Rule out basic issues;

Spark OK?
Plug Condition?
Fuel Good / Clean Fuel Filters?
Good Air Flow / choke settings?
Vacuum Leaks?
Air/Fuel Mix correct?

Engine just needs air, fuel and spark. It all the above are good, I'd be looking at timing, compression, and carburetor condition (accelerator pump, jets, varnish, etc)

The bottom line from my perspective, is that if it has good fuel, air and spark, compression is good, no vacuum leaks, air/fuel mix is set correctly and timing is correct, it's time for a carburetor rebuild or replacement.

It also might be a restriction in the exhaust, plugged convertor, or muffler.

I am familiar with the first 5, but not the last one. How can I check the Air/Fuel mix?

The wrench said he thinks it is running rich.

The wrench also said that the timing was off at the distributor. I plan to take it to his shop so he can time it.

To maytag: This truck was heavily used. It was a farm truck for a large part of its life. It had a 5th wheel and hauled horses. The original motor had over 300,000 miles on it. The current motor that came out of a motor home has who knows how many miles. It was a motor home so it could be over 500,000.

I have never heard of a 360 Windsor. Is it a 351w? A FE 360 would not have fit very well in this truck.

Do a test; Take the dist cap off, leave all the wires on it and put it to the side. See if you can turn the engine by hand by grabbing the belts. If you can't, find a socket that will fit the large bolt in the middle of the crank pulley. Turn the engine so the rotor turns in the dist. Stop, and see how much you have to turn the engine the opposite way before the rotor starts turning again. If you can turn the engine a lot before the rotor changes direction and moves, you have a lot of slop in your timing chain, and it may have even jumped a tooth. This would explain why the timing is way off also.

Air/Fuel mix is what the mechanic was talking about when he said it was running rich. It can be caused by an improper idle mix setting, but also EGR issues or anything that messes with the air / fuel ratio.

Timing is easy to set using a vacuum gauge and in older engines, sometimes the best way as it compensates for carbon build-up and wear. The factory settings assume everything is, well, like factory.

I am definitely going to let the wrench correct the AFR, just need to get it to him.

I just drove the truck around my neighborhood and I may have a more accurate diagnosis now.

While the truck is in gear if you blip the throttle you will have normal acceleration for about 1 second and then it will bog down and lose all power.

If you blip the throttle and hold it in the same position the engine will continue to run but barely pulls. It will eventually chug its way up to 20MPH.

If you blip the throttle and continue to press the gas it will bog down more and more until it stalls.

Is this too much air, or not enough fuel?

The accelerator pump primer keeps sliding up the face of the pump. I am thinking of making a groove for the primer to rest in.

Sounds like a clogged fuel filter causing fuel starvation. Happened to me last spring. Idles and revs fine, but no power under a load.

If it feels like it's running out of gas...it's because it is.

Sounds like your running rich (too much fuel). What color is the exhaust?

Lol, so one of you have to be right haha.

My dad installed one of these: Dorman® Help!™ 55240 - Glass Fuel Filter | O'Reilly Auto Parts

So he could see if what was coming up the line. I am not sure if this was a good move as the stock fuel filter is huge compared to this glass filter.

I watched the filter while it ran and noticed that it is almost bone dry. If you rev it up it will fill up about 1/8ths full.

I also noticed there were air bubbles entering the fuel filter from the fuel pump side. Could this indicate a problem?

I checked the exhaust pipe and is was clear air. From the sound it makes it is missing on a cold start.

An update:
I tried to take the truck to my mechanic and got better understanding of what it is doing.

If I massage the gas pedal(press a little, let off, press a little; repeat) I can get the truck up to 25MPH. When the truck is at those speeds I can press the gas pedal and the truck will not stall. It will accelerate but with very low power.

If I press the gas to the floor it will downshift and the engine will build up revs and accelerate very slowly.

I was not able to get the engine timed , but now I know how to get the truck around.

Does this sound completely like fuel starvation or do I have a carb issue?

Okay, now your getting somewhere.

Do you have a mechanical fuel pump? If so I'd guess you have a cracked bit of rubber fuel hose somewhere between the fuel tank and fuel pump. A rotten bit of fuel line will cause the fuel pump to suck air instead of fuel.

Carefully inspect all your fuel lines between the tank and pump. Start with the fuel pump inlet line, they often fail there.

It's possible you have a bad fuel pump as well and it's not operating as efficiently as it should. Simple to replace and not expensive at all..

I had this exact same problem. The hose was cracked at the tank selector module but on the side that went to the pump. When it dried out it would seal and the truck would start and run for a bit. As soon as I got down the road the wet hose would allow air in and ruin the suction the pump was trying to produce. After I repaired that bit of hose, it works great. Make sure you check your hoses carefully. The old rubber hoses get very stiff and brittle after a while. It may be somewhere in the middle that you have a hole or crack and not just at the ends.

We are planning to overhaul the fuel system from the carb to the tank. We plan on changing the fuel pump and inspect for damage to the pump itself and for leaking hoses.

My Dad spoke to a wrench, and he mentioned converting to an electrical fuel pump instead of the mechanical one. I searched the site and only found mentions of the conversion on diesel.

Do you guys know of a conversion kit that will work for my truck?

There was a guy here posting a bit ago about how his truck wouldn't run right. We never heard back from him, but he wrote about 'talking to a wrench' as well.

Odd term for me; I figured if I was doing the work, I was the 'wrench' and talking to myself never does any good...

ROFL