HZJ75 possible fuel starvation problem? Or something else

[EsbenDenmark]

I have a hzj75 1994 with the 1hz non turbo.
I got it a few months ago and been going through everything.... removing rust, changing fuel lines, changing all liquids, installed a Flash lube prefilter, installed snorkel, changed oem fuel filter and air filer. Cleaned the fuel tank and changed the fuel vent check valve.
And a million more things......


I just got it back on road and did a longer drive today.
When going down the highway between 70 og maybe 90km/h.. keeping the same speed. Sometimes it felt like it was pulling just a little less than normal.
Like I suddenly had a stronger headwind (the was absolutely no wind today) or the brakes was dragging a little (I checked and the wheels are spinning freely)
Not enough to see a speed change on the speedometer......., just a slight feeling.
And yes I was holding the throttle in the same position.

I also tried to give it full throttle to see what that top speed would be. I hit 115km/h and then nothing more happened.. is that a normal too speed for a 75?
I should maybe mention is was something like minus 5 celsius.

Any ideas? What should I try and check? No idea where to start...
Air in the fuel line? Not enough air?

 

[Squash]

5speed or auto tranny!
These engines have their sweet spot. The trick is to find that area and maintain rpm. Drove mine from Vancouver BC to Sudbury Ontario this summer. 4000kms. Lots of gear shifting.
Watch the rpm's and listen to the engine.
What size tires are you running?
I will admit winter fuel is not like summer.

 

[EsbenDenmark]

It's a 5 speed manual.

There is unfortunately no tachometer in mine. So no idea if the rpm is changing.

 

[Squash]

Sounds like you've covered most bases.
What rpm do you mostly drive at.
I find that when approaching a hill I will speed up and then pay attention as speed/rpm drops and then shift accordingly. These units can lose speed quickly if you don't pay attention.

 

[Squash]

No problem!
Mine does 80kph at 1800 rpm, 100kph around 2200 rpm.
Best to not lug a diesel engine at low rpm and of course don't make her scream. If you can run through the gears and she steadily increases speed then you should be OK.

 

[EsbenDenmark]

Sounds like you've covered most bases.
What rpm do you mostly drive at.
I find that when approaching a hill I will speed up and then pay attention as speed/rpm drops and then shift accordingly. These units can lose speed quickly if you don't pay attention.

This happens when going about 80km/h, on a flat road, no wind.
So it happens when maintaining a steady speed.

Then for a few seconds it feel like it is struggling a bit and then pulling as usual.
Just really strange feeling and not enough that I can see any change in speed on the speedometer.

I figure I will try and check

Leaks in the fuel line. (I did change all fuel lines but maybe one of the connections is bad.)

Primer pump.

Fuel tank cap (sounds like those sometimes clog up)

Fuel tank check valve.

Air filter is new but I did add a snorkel with cyclone prefilter.. not sure if this could be a problem.

Any other ideas?

 

[Squash]

If you are worried about air in the fuel line get a section of clear hose and bypass the filter by going straight to the injection pump.
Bubbles of course mean air. If you have bubbles work backwards towards tank. Leaks are hard to find as the ip creates a vaccum sucking air in.