40 mph and the sputtering begins

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Finally Mine

Finally Mine

Joined
Aug 28, 2007
Threads
79
Messages
259
Location
Norfolk, Virginia
I've been dealing with this issue since last week. I have a 1978 FJ40 which I've owned since 2007. It has been a work in progress, and around April I finally got it running after rebuilding the carb. It is basically stock and has been desmogged. Anyways, I took the kids for a road trip down to the Outer Banks in NC. About a 90 min drive from where I live in Virginia. It did great going down there and throughout the week that we stayed. During the week in the Outer Banks, I did notice one time that there was a slight hesitation and sputter during one of our evenings out. So Sunday we packed up and headed back home, and about 30 mins into the drive traveling about 45 mph the engine started sputtering. I decreased my speed to around 40 mph and the sputtering stopped. Well a few more miles down the road it started again. This time more frequently and with some stalling. I tried to nurse it home as much as I could but having the kids with me and traveling on the highway I felt the best thing to do for our safety was to just stop. So I called and had it towed home the remainder of the way.

I have looked and changed my vacuum hoses, put a new set of plugs in, along with rotor and distributor cap. Hopped in it today after work and went for a spin. No problems starting and traveling at slower speeds but once again 20 mins into the drive traveling between 40-45 mph the sputtering began. If I tried to give it gas the sputtering became more noticeable and it seemed to lose power, although it never stalled. Once this started to happen I immediately turned around and went home.

I just can't figure out why 40mph seems to be the lucky number? Any thoughts?

Thanks Steve
 
Fuel System. Check the fuel filter, fuel pump, etc. Just for giggles try putting in a water-remover fuel additive to the gas tank and see if there is any difference. If it's been sittting, you may have condensation and/or rust in the tank making it's way through the system.
 
Fuel filter. Change it out to a clear plastic one temporarily while you're sorting it out to see what kind of crap is coming out of the tank. You might want to drain a little fuel into a glass jar while you're doing it "just for giggles".
 
x2 on the fuel system. Fuel filter won't wait until you hit 40mph for it to act up, fuel pump might, are you SURE you routed the vacuum hoses properly? Could still be a carb issue even after rebuild. Could be some debris in the secondary jet.
 
As others have said, lack of fuel. Usually due to rust clogging the fuel filter because the tank if full of rust particles trying to make their way into your carb to clog that. Used to happen to me after wheeling when I would shake all the rust particles from the bottom of the tank. For me the magic speed was 45 to 50mph. If you aren't going to deal with the tank immediately start carrying around fuel filters to swap out as they clog.
 
Replace your fuel filter and ad a pre filter like this one.
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Rudi
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X2 on fuel delivery... Depending on what carb you have, there may be a small screen where the fuel pipe attaches to the carb at the float bowl.

Off roading may break rust loose inside the tank and the rust will migrate into your pump, lines etc.

I would also recommend new ignition points....:cheers:
 
I had the same problem and it was the gas tank. Take the fuel line off at the carburetor, put it in a glass bottle and see how much fuel you're getting and how strong a flow.
 
I would check all my connections, too. I had not tightened a clamp enough around the filter/pump area after replacing my entire fuel system. Same symptoms as you describe.
 
Will start on changing out the fuel filters and checking out the fuel pump with disassemble. If I should need to change out the metal fuel lines, does anyone know the correct size for rubber tubing to connect from the gas tank forward? Thanks
 
Finally Mine said:
Will start on changing out the fuel filters and checking out the fuel pump with disassemble. If I should need to change out the metal fuel lines, does anyone know the correct size for rubber tubing to connect from the gas tank forward? Thanks
Click to expand...

5/16" when I redid my lines.

It is almost certainly the fuel filter. You probably have rust in your tank. I recently posted up with the exact same symptoms and that was the cause. Debris in the tank isn't always due to rust coming from your tank, but you still need to clean it thoroughly.

Get your tank "hot tanked". Cost me $60. Plus, they repainted it too.
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Also, you should buy a rebuildable / serviceable fuel filter. They're only slightly more than the OEM types, but you can dissassmble and clean them out on the fly in less than four minutes. They are so much better.
ForumRunner_20120620_151532.webp
 
Sputtering

Michael Hanson said:
Thats about the speed when a bad fuel pump gives up. Mike
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What Mike says. On one of mine, I would check the pump at idle or with a little throttle and it seemed fine. Tried every other fix mentioned above with same results under load around 40-45. It would idle or drive fine around 25 mph.

Replaced fuel pump and instantly fixed. The O.E.M. ones are still available online.

I have a sister in Chesapeake and parents live on O.B. Kitty Hawk area. Might drive one of mine down I a couple weeks. Then again its a 6 hr trip with no AC in these temps. Good luck.
 
Hey guys, went out and purchased a clear filter like Rudi posted up. I unhooked the old filter and I could not believe the junk that came out of it. Put the clear filter on and we are up and running past 40-45mph without the sputtering, hesitation and stalling. So now comes the task of draining and cleaning the gas tank. Thanks for all your input. Steve
 
Hi Steve,

Do you have a pic of the dirt that came out?
Here is one of mine. It's not only dirt and rust from the tank. It's also dirt from the gas station and water from filling up in the rain.
DSC06524.webp

Rudi
DSC06524.webp
 
Finally Mine said:
Hey guys, went out and purchased a clear filter like Rudi posted up. I unhooked the old filter and I could not believe the junk that came out of it. Put the clear filter on and we are up and running past 40-45mph without the sputtering, hesitation and stalling. So now comes the task of draining and cleaning the gas tank. Thanks for all your input. Steve
Click to expand...

Glad I found this thread, I picked up my car 2 days ago from a complete restoration and everything was fine until last night I noticed some sputtering at around 60mph, I figured might be the car just hitting the red line limiter but this morning it started happening at 50mph and then got worse and started happening at 40mph. I managed to somehow get the car home and decided to see if anyone had a similar problem before. I guess will get my fuel filter changed out tomorrow, maybe the fuel tank rusted during the rebuild or collected dirt. Will take pics!
 
brooklyn said:
Is there any downside to having two gas filters in a fuel system?
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Two more connection points and potential leaks.

I would think you'd be better off with a larger filter with more media area to absorb more crap before restricting flow. If that is what you are thinking?
 
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