HJ75 will only do 80kmh for first 30k's

[marcinoz]

I have a 85 HJ75 series ute with a 3 ft chassis extension and an Akhana Aluminum pop top camper body.

When you go on the highway it won't budge past 80kmh for about the first 30k's, it also takes quite a few k's to reach 80 and any incline in the road and its down to 3rd and 50kmh. All of a sudden it just takes off and your doing 110kmh and driving beautifully with no downshifting etc. It will drive like that until you pull over. As soon as you stop (without even turning engine off) take off again and its back to 80kmh.

The truck drives great, it doesn't blow smoke it doesn't use oil it doesn't miss a beat, just this highway problem. I have done new filters, drained the fuel tank, tried injector cleaner.

I have had 3 mechanics look at it they have no idea as it runs so well.

Any help would be GREATLY appreciated.

 

[Entaran]

Exhaust is blocked more than likely. Check the mufflers and if you have one, the Cat.

 

[roscoFJ73]

Exhaust is blocked more than likely. Check the mufflers and if you have one, the Cat.

Why would a muffler cause intermittant loss of power.

I was thinking something more like fuel starvation.
If you have dual tanks ,maybe one of the solenoid valves is partially blocked.(there was a case like this on Overlander recently, some plastic stuff was blocking the valve and had algae or something around it as well from memory).

I would set up a temporary,alternative fuel system and plug it to the fuel pump directly.

You could also disconnect the fuel lines at each section/end and blow them clean with compressed air.

If all that fails I would take it to a proper diesel shop and let them have a look at the pump.

 

[brownbear]

does the 2H use a pneumatic governor like a B? if so could it have an issue there in the diaphragm not allowing throttle actuation..

Or maybe in an altitude compensation device, holding back the fuel.

I second the fuel injection shop having a look.

 

[crushers]

definately sounds like fuel delivery issues..
but even fuel issues should not take 30K to clear up, the engine should be at operating temp before that... to check try plugging the truck in so the engine is at operating temp befor eyou go to start the unit... if it runs good right away then it will be something heat related, if not then go to the next step...

curious, do you have a factory shop manual for that engine? if not go buy one they have a decent self diagnostic section...

 

[marcinoz]

Thanks everyone

Great "alive" forum and thanks for all the replies.

I do have dual tanks, but the second tank is merely a holding tanking, you have to pump the fuel into the main tank (electronically). Could there be a pressure issue? or if the line from from the second tank was blocked could that be causing a problem.

About the heat issue, I actually went out yesterday afternoon to recovery a New Pajero out a serious bog (to the sills!) it was 110k's out of town and the first 50k's were bad and then it went ok. On the way back it went great for about 80k's and then bogged down again. I never turned the engine off the whole time.

I have a great manual but nothing is pointing to the issue. It's a real baffler becuase it does drives and runs so well.

One other point I didn't make initially is that when it runs at the 80kmh is runs quite a lot hotter than when it does 100kmh, it sits over half way on the guage and when it picks up and runs well again it drops to 1/4.

 

[roscoFJ73]

Great "alive" forum and thanks for all the replies.

I do have dual tanks, but the second tank is merely a holding tanking, you have to pump the fuel into the main tank (electronically). Could there be a pressure issue? or if the line from from the second tank was blocked could that be causing a problem.

Try going for a drive without the fuel cap

One other point I didn't make initially is that when it runs at the 80kmh is runs quite a lot hotter than when it does 100kmh, it sits over half way on the guage and when it picks up and runs well again it drops to 1/4.

This could be something restricting the air intake,makes them run hotter

 

[Entaran]

The reason I said check the exhaust is because mine coked up like crazy inside and took about 600km on one trip to blow all the crap out of it. did it a couple more times soonish after that.

Probably not entirely relevant here tho.

 

[marcinoz]

Fuel cap didn't work

Tried a drive without the fuel cap, no change...........damn!! thought it was going to be a quick fix!!

 

[Ron R]

Looks as if you get air in the system.
Can you put a clear hose just in front of the injection pump in the fuel line?
If so, run it in a curve, that way that part of the curve is above the inlet level of the pump. Purge the system so it's clear of air.
Now start the engine and watch or air is collecting in the top of the curve.
This way you can make sure that the line is airtight. If not....find the airleak.
Can be your filter not being tight or a crack at someplace in the line or even the pipe in the tank that has a crack.

 

[brownbear]

if he had air would it not be very rough running and hard to start? he only says it is loosing power.

 

[Ron R]

Not necessarily.
I once had a very minimal airleak in the fuel line. Had troubles for months.
Could not locate it. Later I found it was the weld in a 'banjo' bold ( a kind of hollow circular connector fitted with a hollow bold - I don't know the english word for it).
The engine showed bad power and was running hot, but started without any problem.
Depending on the ambient temperature the airleak was present or not or very minimal.
Once I found it, it was fixed within a minute. Sand it, solder it. Go.

 

[brownbear]

banjo is the right term.


Was there any fuel leaking out?

I wonder if we put low pressure(7 psi or less) electric pumps at the back near the tank and helped push fuel to our engines it might be easier to find problems. As the pressurized fuel is going to show the leaks. Where as a small leak under vacuum might not be evident for a long time. Other than running issues.

I planned to install a small pump to overcome vacuum from a large racor in the system. As I did not want the fuel pump to have to work so hard to draw thru a large filter to get the fuel.

 

[Ron R]

banjo is the right term.

Hm, more clever than I thought

Was there any fuel leaking out?

Nope. It was the connection at the fuelfilter, leading to the IP. After I found it it was obvious what had happened, but before that it was driving me mad. I had been searching for it for months (litteraly).
After I put in a clear hose I saw airbubbles every now and then but just a few. Running the engine at higher RPM often made these bubbles disappear.
Why? Because the engine shifted a bit, putting a light strain on the banjo and thus closing the very small gap of the badly connected hosepillar.
Maybay I have to explain this a bit for those who don't quite know how a banjo looks like.
A banjo consists of a hollow 'ring' with a pillar soldered (welded) to this ring. The hose is put on this pillar, whilst the ring is connected by a hollow bold. Fluid gets through the hollow bold into the ring and then through the pillar.
It was the connection that had a very fine crack.
If there was a little strain on the pillar, the crack closed, but every now and then it would open, letting some air into the system, the engine loosing power and running hot.

I wonder if we put low pressure(7 psi or less) electric pumps at the back near the tank and helped push fuel to our engines it might be easier to find problems. As the pressurized fuel is going to show the leaks. Where as a small leak under vacuum might not be evident for a long time. Other than running issues.

I planned to install a small pump to overcome vacuum from a large racor in the system. As I did not want the fuel pump to have to work so hard to draw thru a large filter to get the fuel.

If the system is tight, no pump is needed, but the pump will mask small airleaks because the system is under pressure now. I doubt or it will show (very) small leaks. Fine cracks will allow air to seep through but will block fluids like water or fuel. A fluidtight container is not necessarily airtight.
On the other hand, a pressurepump might cause some risk. If a line gets damaged, fuel will be pumped overboard. Best case scenario is fuelstarvation, worst case? Fuel on fire?
Without fuelpump? Air getting in the system, bad running engine?

 

[cheeckyboy31]

could be a sticking timing advance piston in the fuel pump?? its a maybe, those pumps do not like water, if some gets in it will settle in the bottom of the injector pump. if you want to check for a suction leak carefully presurise the tank (engine off) with a bike pump through the breather tube, you might have to tape up the cap depending on what type you have.

 

[marcinoz]

Going to the specialist

Hi All, I'm taking the old girl in to the "specialist" on Monday, I'll let you know how I go. Had a chat with them over the phone and it looks like it could be the air in the fuel. Fingers crossed!

 

[roscoFJ73]

Hi All, I'm taking the old girl in to the "specialist" on Monday, I'll let you know how I go. Had a chat with them over the phone and it looks like it could be the air in the fuel. Fingers crossed!

Try bleeding it yourself ,its not hard. I had a slightly longer crank time after I emptied one tank. I managed to switch over to the other but still had starting problems.
I bled the lines from filter to pump and everything was fine.

Looking forward to the result one way or another.

 

[marcinoz]

**************the Result*****************

Well the old girl is back and faster than a Ferrari. Problem......Master cylinder!!! The front brakes were not releasing. I am a little dissapointed that the last mechanic didn't pick this up as they fitted new front discs and should have seen this. Good news though, engine purrs like a kitten and now she's going in for a new pop top and interior fit out. Will load up some pics if anyone is interested , its quite a machine!

 

[roscoFJ73]

Well the old girl is back and faster than a Ferrari. Problem......Master cylinder!!! The front brakes were not releasing. I am a little dissapointed that the last mechanic didn't pick this up as they fitted new front discs and should have seen this. Good news though, engine purrs like a kitten and now she's going in for a new pop top and interior fit out. Will load up some pics if anyone is interested , its quite a machine!

Good news.Are you saying it was the seized MC slowing the cruiser down? I thought that would have been obvious when you eased off the accelerator.



Pics are always welcome

 

[marcinoz]

You didn't really notice when backing off or stopping as its quite a big rig. The MS wasn't letting the fluid back in, but after those 20 or 30k's it worked its way free, thats when it went ok and of course when i stopped, applying the brakes, then taking off again they would stick. So simple really, I had actually said a couple of times that it feels like the brakes were on. Only wish a i had of jacked the front and tried to spin the wheels, problem would have been solved a long time ago!!

Very happy anyway, had a great trip home after awesome camping weekend on the beach, just had to pull over after you braked and bleed the front! Drove like a dream. Couple of pics below of the weekend.