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Lj80 Acceleration problem
https://auszookers.com/forum/viewtopic.php?f=5&t=57129		 Page 1 of 1
Author:  Jeepmalta [ Sun Dec 05, 2021 1:45 pm ]
Post subject:  Lj80 Acceleration problem
Hi everybody
Popped in for some brainstorming from the group.

Some years ago I bought an LJ80 fitted with a Toyota 1.5 diesel non turbo engine with the intention of restoring it to factory specs.
So I pieced all the bits and pieces, and got the LJ is on her feet with an original F8a engine.

However the acceleration, I cannot get right.
Have two carbs, one original, cleaned it to the best of my knowledge, removed everything jet, checked and cleaned. She goes fine till 50km/h, then with pedal to the floor reaches 70 on flat ground. Bought a new Chinese carb which is a direct bolt on,.. goes well up to 60 reaches 80-85 on flat, then closes.

Compression ok
Fuel pump ok
New plugs, plug wires, almost everything new.
Distributor obeys left and right.

So what am I missing? Maybe both carbs are crap? I tried another 2 in between which gave me even worst results.

May it be that the rear diff gearing is from another model? Perhaps po changed it to re gear the TOY Diesel engine it had on? Are there other diffs that fits and lj80 producing less km/h? I am not much into gearing and never messed up with gearing myself.

I can feel it’s a small bug, just can’t find it…
Author:  Gwagensteve [ Sun Dec 05, 2021 2:29 pm ]
Post subject:  Re: Lj80 Acceleration problem
Well there's potentially two very different issues going on here.

I also think you're talking about two different things - acceleration and top speed.

Is the car accelerating well up to 70-85km/h, then won't gain any more speed, or is it very slow to accelerate?

You need to confirm your gearing.

What tyre size are you running? I've assumed stock, so ~28"

If you have standard LJ80 gearing, (1.57 high range in the transfer case, 4.556 diff gear) 85 km/h in 4th gear is 4500 rpm. A F8A will happily rev much higher than that.

If the previous owner fitted LJ50 diff gears, 4.88:1, 85 km/h would still be 4880rpm, easily achievable.

Are you sure you are in high range?

85 km/h would be just under 7000rpm in low range, and at that point I'd expect the engine to not rev much faster.
Author:  Jeepmalta [ Sun Dec 05, 2021 7:00 pm ]
Post subject:  Re: Lj80 Acceleration problem
Thanks for your input Steve.
Yes talking about bad acceleration, and unreachable top speed. I can reach top speed only down a hill.

Drive mode set on HIGH2. (If this is what you mean asking if I’m in high range?)

Wheels are +-28”

Car accelerates nicely up to 60km, then struggles to reach 85km top speed on straight ground.
Uphills,.. uughh …. she is like an old lady.

One thing this car is managing - that is driving me crazy….
Author:  sideways [ Sun Dec 05, 2021 9:04 pm ]
Post subject:  Re: Lj80 Acceleration problem
Jeepmalta wrote:
Hi everybody
Popped in for some brainstorming from the group.


A healthy LJ80 should be able to break 100 quite comfortably but it's not gonna be any rocket ship on its way there.

First things;
Check vacuum leaks, spray something around the manifold flanges/vacuum ports/carby and see if the revs change.
Check timing, both base timing and advance when revved.
Check timing belt marks line up. While you're there check the timing mark on the flywheel says TDC when the timing belt marks are lined up, it's possible to put the flywheel on wrong. Some cam sprockets have multiple keyways, all the ones I've seen have been on the one with a single dot.

Fuel flow. Put a clear filter between the pump and carby, see if it empties when trying get up to speed. Could be blocked pickup/lines ect.
Blocked exhaust. I had this once, it felt like I was driving into an extreme headwind. I could hardly do better than 80km/h.
Could be 2 dud carbies. Mine runs flawlessly with it's china carby but it does have a bit less power than with the original carb, still I've got the power to cruise at 110 but that's an F10a.

There's various ratios that fit the diff from 4.11 to 5.375. They could have fitted some other diff with a taller ratio for the diesel which could cause you problems. You really do need to confirm the ratios. It was possible to get high ratio transfer cases back in the day so it would be worth confirming that ratio too.
Author:  Jeepmalta [ Sun Dec 05, 2021 10:53 pm ]
Post subject:  Re: Lj80 Acceleration problem
Thanks for this Sideways.
Yes I know the feeling of acceleration on an LJ. My LJ feels far from healthy.

Following your suggestions- there are some things I will check out.
For instance I put on a complete new exhaust on it. So I’m thinking What if it was badly manufactured in the first place? So I will see how will it do without.

Fuel seems coming out okay out of the pump. Fuel filter is fitted as stock, few inches away from fuel tank. Never was a fan of this. So adding a filter in between is a good idea. I will do that too.

Transfer case came from Germany, and went out of an untouched LJ. The only thing I have not touched is the rear axle. Seems i will need to get it out of there and have a look too.

Original Carb mounted yesterday not holding without choke or some advance tweak. However with it the engine revs and howls much better then with the Chinese carb.

It would be really helpful if a friend with an another LJ is around. Could ask him to try my carb on his car…. But unfortunately only a handful around here…

sideways wrote:
Jeepmalta wrote:
Hi everybody
Popped in for some brainstorming from the group.


A healthy LJ80 should be able to break 100 quite comfortably but it's not gonna be any rocket ship on its way there.

First things;
Check vacuum leaks, spray something around the manifold flanges/vacuum ports/carby and see if the revs change.
Check timing, both base timing and advance when revved.
Check timing belt marks line up. While you're there check the timing mark on the flywheel says TDC when the timing belt marks are lined up, it's possible to put the flywheel on wrong. Some cam sprockets have multiple keyways, all the ones I've seen have been on the one with a single dot.

Fuel flow. Put a clear filter between the pump and carby, see if it empties when trying get up to speed. Could be blocked pickup/lines ect.
Blocked exhaust. I had this once, it felt like I was driving into an extreme headwind. I could hardly do better than 80km/h.
Could be 2 dud carbies. Mine runs flawlessly with it's china carby but it does have a bit less power than with the original carb, still I've got the power to cruise at 110 but that's an F10a.

There's various ratios that fit the diff from 4.11 to 5.375. They could have fitted some other diff with a taller ratio for the diesel which could cause you problems. You really do need to confirm the ratios. It was possible to get high ratio transfer cases back in the day so it would be worth confirming that ratio too.
Author:  Jeepmalta [ Mon Dec 06, 2021 2:36 am ]
Post subject:  Re: Lj80 Acceleration problem
Has anyone came across a picture which was posted showing were this guy drilled a hole in the carburetor in order to reach for a ball which seems to get stuck if carb was not used for a long time.
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