96 Fj80 running bad climbing up hill ,help??? (1 Viewer)

[sledge916]

Hello All

I have a 96 fj80 and it runs like a top, just recently I was climbing a steep incline and it ran horrible , seems to cut back to 3 cylinders or something, very under powered and even pops or backfires a little, acts like it is running out of gas, runs fine when on flat ground, It just started doing this as I have always been able to climb a wall when I wanted too, any ideas??


Thanks

Sethro

 

[fishwater]

plugs/wires? do you know how many miles yours? others will chime in.

 

[sledge916]

no its not that, it runs fine on flat ground, I replaced that stuff not to long ago, I have 135000 on the clock

Thanks
Sethro

 

[sledge916]

I was thinking fuel pump, anyone else??

Sethro

 

[Atticus]

I was thinking fuel pump, or possibly wiring harness. Going up hill puts a load on the engine, which causes it to torque a little, which can cause wires in the harness to ground out if they are frayed. Give the harness a look, especially near the intake manifold.

 

[Tools R Us]

Sounds like it's fuel starving under load? The most common culprit is a clogged fuel filter, second would be a weak pump, both pretty rare events on an 80. Two tests that I use to confirm, starting stopped nail the throttle, hold down to highway speed, does it do it? When it does it on a climb, shift neutral, allow to coast at idle for a few seconds, shift drive and accelerate, does it run correctly for a few seconds then start missing?

 

[sledge916]

Sounds like it's fuel starving under load? The most common culprit is a clogged fuel filter, second would be a weak pump, both pretty rare events on an 80. Two tests that I use to confirm, starting stopped nail the throttle, hold down to highway speed, does it do it? When it does it on a climb, shift neutral, allow to coast at idle for a few seconds, shift drive and accelerate, does it run correctly for a few seconds then start missing?

I will give this a try and get back to you

Thanks
Sethro

 

[irondalefj80]

sledge916, my fj80 3fe is doing the exact same thing, please pm me when you find out what it is. i have new fuel filter, plugs, wires, button, cap, it only does it when i am under a load (pulling someone up a hill) when i dont have much wheel speed. like it is starving out / not getting enough air out. no codes, just VERY BAD lack of power.
thanks
charles

 

[Michael Hanson]

Fuel filter in gas tank been replaced? Mike

 

[jeremy000]

Clogged Cat??? And you're also in Head Gasket mileage. Please post if you figure it out.

 

[sledge916]

Sounds like it's fuel starving under load? The most common culprit is a clogged fuel filter, second would be a weak pump, both pretty rare events on an 80. Two tests that I use to confirm, starting stopped nail the throttle, hold down to highway speed, does it do it?




When it does it on a climb, shift neutral, allow to coast at idle for a few seconds, shift drive and accelerate, does it run correctly for a few seconds then start missing?

yes it does run right when I do this, runs great under load on flat ground, what you think Keven?

Sethro

 

[sledge916]

I will post when I get this figured out

Sethro

 

[Tools R Us]

So, when you shift neutral, then back to drive on a climb power is restored? This usually confirms fuel starvation, the best way to be sure is do the test with a fuel pressure gauge and look for pressure drop. The theory is, it takes lots of power/fuel to climb, if the system can't deliver enough allowing the motor to idle for a few seconds allows it to catch up and power is briefly restored. If the hill is long enough the problem should repeat.

If it runs well, makes full rpm on flat ground, it usually rules out plugged exhaust. It's more about rpm, less affected by load.

Is the check engine light on, any codes? It's difficult to diagnose a problem over the net and these tests are interpretative, but from behind my desk it sounds like a fuel delivery problem. If so it could be fuel filter, sock in the tank and/or main filter or a weak pump.

 

[sledge916]

So, when you shift neutral, then back to drive on a climb power is restored? This usually confirms fuel starvation, the best way to be sure is do the test with a fuel pressure gauge and look for pressure drop. The theory is, it takes lots of power/fuel to climb, if the system can't deliver enough allowing the motor to idle for a few seconds allows it to catch up and power is briefly restored. If the hill is long enough the problem should repeat.

If it runs well, makes full rpm on flat ground, it usually rules out plugged exhaust. It's more about rpm, less affected by load.

Is the check engine light on, any codes? It's difficult to diagnose a problem over the net and these tests are interpretative, but from behind my desk it sounds like a fuel delivery problem. If so it could be fuel filter, sock in the tank and/or main filter or a weak pump.

thanks, I will put a fuel presure gauge on it and test it, no check engine lights are on at all, is the sock in the tank servicable? Cleanable?

Sethro

 

[Tools R Us]

thanks, I will put a fuel presure gauge on it and test it, no check engine lights are on at all, is the sock in the tank servicable? Cleanable?

Sethro

Yes, it's on the pump, some carb cleaner and compressed air is effective, but they are relatively inexpensive, so normally replace them. Another thing to check would be the voltage on the pump circuit at the tank, if there is a bad connection or relay the pump wont make full power. This was a problem on the 3FE rigs, not so much on the later rigs.

 

[sledge916]

Yes, it's on the pump, some carb cleaner and compressed air is effective, but they are relatively inexpensive, so normally replace them. Another thing to check would be the voltage on the pump circuit at the tank, if there is a bad connection or relay the pump wont make full power. This was a problem on the 3FE rigs, not so much on the later rigs.

ahh, that makes allot of sence too, I will check voltage there as well.

Thanks Again, maybe see you on the trail someday

Sethro

 

[Tools R Us]

... maybe see you on the trail someday

Sethro

Sounds good, but I heard your selling the '80 to get a mini van?

 

[sledge916]

Sounds good, but I heard your selling the '80 to get a mini van?

Ha, no kidding huh, no I came to my senses real fast, I will keep the 80 and finish it off, need a turbo or supercharger, rooftop tent/rack, stereo, recover the seats with heaters is the short list, thought I wanted the MiniVan but just could not bring myself to do it,

Thanks again for your help
Sethro

 

[sledge916]

Just checked the sock and voltage, the sock was clean for the most part and the voltage reads on the plug in the picture, top left 11.70 v , the bottom left 5.76 v with key on.

Sethro

 

[Tools R Us]

Just checked the sock and voltage, the sock was clean for the most part and the voltage reads on the plug in the picture, top left 11.70 v , the bottom left 5.76 v with key on.

Sethro

Toyota filters hold a bunch of junk, if the sock is clean, it's a pretty good indicator that the main filter probably isn't clogged. Probably, maybe, pretty good, etc all apply, no guarantee!

That voltage is probably good, depending on the running state. The pump is controlled by three relays. First is the main EFI relay, if it was a problem there would be bigger issues, the motor wouldn't run. The circuit opening relay controls when the pump runs, this could be a problem, if the contacts are pitted would reduce the currant available to the pump, this doesn't sound like the problem? Last is the fuel pump relay, it controls the speed that the pump runs. In normal operation it sends power through the fuel pump resistor, reducing the currant to the pump, when the ECU senses motor load it engages the relay to send full power to the pump.

One way to test is, check the voltage as close to the pump as possible, (red-green = power, white-black = ground). Do this under running conditions, look for the voltage to increase under load.

The other is to remove the fuel pump relay and jumper the red-green power supply input to the red-black output wire, this will run the pump at full speed all of the time. If the rig runs well it could be the relay contact is pitted or the ECU output isn't correct, not switching the relay.

Carefully check the wiring at the fuel pump bracket, it's not uncommon for there to be corrosion, bad connection where the wires go through the bulkhead into the tank or connect to the pump.

If you have access to a fuel pressure gauge I would use it. With this type of problem I hook it up and tape to the windshield, so pressure can be monitored full time.