fj40 low acceleration at high rpm . and engine don't work smoothly (1 Viewer)

[shahab]

hi .
my 1978 fj40 have a good acceleration in low and medium rpm
but poor acceleration in high rpm

and engine don't work smoothly in high rpm (may be some cylinder not work in high rpm) and engin and car vibrate in high rpm .

in 4th gear engine haven't a good power .
but in 1st and 2nd gear have a good acceleration and power .

this item checked since now ...
1 - spark is new
2- spark wire is new
3- distributor is adjusted exactly..
4- vacuum advance is worked
5-my carb. is a new ...
6- second car bar diaphragm open when rpm is too high
7- contact breaker is new
8 - fuel pump is new
9- fuel filter is new
10- ignition coil have a good condition
11-i have not a clutch fan

 

[csd1982]

Had a similar problem as well and went through all the checks. It was a vacuum leak for me.

Have you hooked up a vacuum gauge to the manifold where the brake booster connects? There is good info in the forum about vacuum readings and what it means.

 

[Curt]

what is high rpm range for you? what speed is it running rough?

 

[John Smith]

Did the old fuel filter you replaced contain any rust particles?

 

[edwjmcgrath]

Sounds like a problem with fuel flow. Usual cause is clogged fuel filter. You say it is new but with a rusty fuel tank, it can clog again quickly.
Another possible cause is the pickup in fuel tank or fuel lines clogged.

To test, use a small fuel tank with new fuel.

 

[shahab]

Had a similar problem as well and went through all the checks. It was a vacuum leak for me.

Have you hooked up a vacuum gauge to the manifold where the break booster connects? There is good info in the forum about vacuum readings and what it means.

hi
I didn't vacuum test before
I have to do that at soon as possible...

 

[shahab]

what is high rpm range for you? what speed is it running rough?

hi
after 80 km/H at 3rd hear ..
I have not tachometer...

 

[skidplate]

I installed a used gas tank in mine and had to clean the fuel filter many times because of rust from the tank was plugging the fuel filter. Install a clear glass or plastic fuel filter so you can see the debris. Also check for a vacuum leaks around your carb base.

 

[csd1982]

hi
after 80 km/H at 3rd hear ..
I have not tachometer...

You aldo should get a tach meter to help figure this out and tune your carb right. Just get a timing light.

 

[csd1982]

hi
I didn't vacuum test before
I have to do that at soon as possible...

Read this

Vacuum 101 - Land Cruiser Tech from IH8MUD.com

 

[65swb45]

I have a hunch. Since you're not experiencing bucking associated with fuel starvation, I'm inclined to suspect your mechanical advance in the distributor is not working properly.

You can test your mechanical advance with the truck parked by disconnecting the vacuum advance and checking timing thru the RPM range with an advance timing light.

Best

Mark

www.marksoffroad.tripod.com

 

[shahab]

Read this

Vacuum 101 - Land Cruiser Tech from IH8MUD.com

very very useful info .....
so thanks ...

 

[shahab]

I have a hunch. Since you're not experiencing bucking associated with fuel starvation, I'm inclined to suspect your mechanical advance in the distributor is not working properly.

You can test your mechanical advance with the truck parked by disconnecting the vacuum advance and checking timing thru the RPM range with an advance timing light.

Best

Mark

www.marksoffroad.tripod.com

hi .
I checked my mechanical and vacuum advanced before and they worked properly . I checked with timing light .

 

[shahab]

Did the old fuel filter you replaced contain any rust particles?

yes.

 

[shahab]

Had a similar problem as well and went through all the checks. It was a vacuum leak for me.

Have you hooked up a vacuum gauge to the manifold where the brake booster connects? There is good info in the forum about vacuum readings and what it means.

this is a my vacuum test ...
here altitude is about 4500 ft

you can download test result video from

TinyUpload.com - best file hosting solution, with no limits, totaly free

 

[John Smith]

yes.

Then I believe your problem may be that your supply line is partially clogged with rust particles. As you have found at low speeds there are no issues. However, once you try to reach speeds above probably 40mph, you experience fuel starvation and problems.

I had this exact issue with my truck and had to replace my rusted fuel supply hard line and tank. To test my theory, rig up a temporary fuel supply to your fuel pump. Take a samll gas can and run a long supply hose to your fuel pump intake port. Have your passenger hold the gas can so you don't have any accidents and take a test run.

You also have low vacuum based on your video. You should be at 20 at idle. It looks like you are at 15.

 

[78FJ40CALI]

I am having similar issues with my 78 California FJ40. I am getting so sick about it, I sometimes consider ditching it over a cliff.

I'm having the following issues; somewhat difficult to start when cold - seems to crank slow, seems to run great at idle and low speed, sometimes cannot start after driving for 20-30+ minutes, stutters/stumbles at 45-ish+ mph and won't start if I pull over and shut off...

Here is what I have done so far;

Replaced carb, replaced all vacuum hoses, replaced distributor cap & rotor, replaced all spark plugs, checked all plug wires, replaced fuel filter and added clear 'pre-filter', check gas tank and its very clean (no debris and nothing in fuel that was drained), round and repaired kinked vapor line (i think that is what it was.. runs from vapor separator down thru cab to a hard line near rear passenger wheel well, replaced the fuel pump, replaced ignition coil.

Things I have NOT done;

???? I don't know what else to try. Seems like fuel issue, but just cant find the cause.

Distributor is electronic (signal generator).

Love the forum and have gained a lot of knowledge and help - hoping I can get this thing to be more consistent in operating and starting.