1HZ sputter and loss of power (1 Viewer)

[JDMBC]

Evening all,

Hit a bit of a wall in trying to self diagnose an issue I am having with my 2001 HZJ79. This truck is a conversion from ex-fire service in Japan and just hit 26,000kms on the ODO.

Modifications that were done are a new 90L fuel tank and fuel filler neck from another 70 series. The truck came with a 60L tank that was situated on top of the pump on the rear of the truck fitted by Morita.

For the last 6-8 month or so I have been dealing with what I feel is air in the fuel line. In second gear the truck seems to stutter or lag around 2800rpm and I notice white smoke from the exhaust. Initially this is the only time it would do it and it was not consistent at all. More recently I have been taking the truck up to the Mtn to ski. After a day of skiing I start my truck and let it warm while I load the gear etc. I then start my decent and I notice a significant increase in white smoke and power lag/loss/chug as I accelerate. Eventually it goes away.

I have no issues with initial cold start up either.

I had taken the truck to my local diesel shop and was suggested it could be related to no tank breather valve and a build up of pressure with elevation change. However I notice the lag not only at the mtn but in town, that being said its significantly more noticeable up the mtn. The mechanic recommended adding a breather valve so I did this. There are three hard lines coming off the OEM neck provided with my tank. The main filler, return, and the 3rd was left open with a breather valve. I had noticed prior to adding the breather valve there was some pressure when undoing the fuel cap. I have read others have the same and it is "normal"?

I have yet to change the fuel lines. I have inspected them all and there appears to be no visible signs of deterioration or cracking. Check all the clamps and everything seems as it should be.

Back in the fall I did attach some clear tubing and noticed some air getting through after passing through the fuel primer. So I replaced the fuel primer and filter.

Now that it is winter and no access to a shop I am tempted to take the truck in and get a professional mechanics opinion but wanted to reach out to the LC community before making such a bold move.

Cheers and thanks for chiming in!

 

[mudgudgeon]

In second gear the truck seems to stutter or lag around 2800rpm and I notice white smoke from the exhaust.

Certainly sounds like air in the fuel

I did attach some clear tubing and noticed some air getting through after passing through the fuel primer. So I replaced the fuel primer and filter.

Re-test for air.

If the symptoms didn't go away after changing the primer assembly, then you didn't solve the problem. Re-test to be certain

You may have a hardened fuel hose with a poor seal where it attaches to a hard line. Or split hose.

You don't need a shop to do the clear hose test. I did this in the car park if the hardware store where I bought clear hose

 

[JDMBC]

Certainly sounds like air in the fuel



Re-test for air.

If the symptoms didn't go away after changing the primer assembly, then you didn't solve the problem. Re-test to be certain

You may have a hardened fuel hose with a poor seal where it attaches to a hard line. Or split hose.

You don't need a shop to do the clear hose test. I did this in the car park if the hardware store where I bought clear hose

Cheers!

I am thinking along the same lines. Has to be sucking air in somewhere. My thought though was that if it was sucking air I’d notice the white smoke on the drive up to the mountain with acceleration. Event only happens after I’ve skied and come back to the truck and it’s been sitting for 3-4hrs.

I had done the clear hose test and did note some air bubbles so back to the drawing board but temps are dipping to -24C this upcoming week. Ain’t no way I’m standing in a parking lot doing such a test haha

Thanks for the reply @mudgudgeon

 

[mudgudgeon]

Cheers!

I am thinking along the same lines. Has to be sucking air in somewhere. My thought though was that if it was sucking air I’d notice the white smoke on the drive up to the mountain with acceleration. Event only happens after I’ve skied and come back to the truck and it’s been sitting for 3-4hrs.

I had done the clear hose test and did note some air bubbles so back to the drawing board but temps are dipping to -24C this upcoming week. Ain’t no way I’m standing in a parking lot doing such a test haha

Thanks for the reply @mudgudgeon

If it's sucking in air, the white smoke is because air compresses in the injector line. The nozzle in the injector doesn't open as promptly as it should because some of the hydraulic pressure is lost to compresssing the air bubbles, so spring preload isn't overcome when it should be, this delays injection of fuel into any cylinder that gets air in its injector line, injection happens too late, and the fuel doesn't burn fully in the cylinder, if at all. The white smoke will smell strongly of raw unburned diesel.

The stumbling is because you may only get air at one of two cylinders injector lines at a time

 

[roscoFJ73]

Try a separate (temporary) fuel supply with a small container strapped inside the engine bay. This should tell you if its air or not. I think it is air.

 

[JDMBC]

If it's sucking in air, the white smoke is because air compresses in the injector line. The nozzle in the injector doesn't open as promptly as it should because some of the hydraulic pressure is lost to compresssing the air bubbles, so spring preload isn't overcome when it should be, this delays injection of fuel into any cylinder that gets air in its injector line, injection happens too late, and the fuel doesn't burn fully in the cylinder, if at all. The white smoke will smell strongly of raw unburned diesel.

The stumbling is because you may only get air at one of two cylinders injector lines at a time

Appreciate the explanation and detail @mudgudgeon. Constantly learning which is a good thing. With your explanation it certainly sounds like what I am experiencing. Now to find the culprit. There are a few variables given the custom work so will need to isolate each and rule out.

Again I appreciate the response and help!

 

[JDMBC]

Try a separate (temporary) fuel supply with a small container strapped inside the engine bay. This should tell you if its air or not. I think it is air.

Ya that is also on my list of to does. My issue is that it is not a constant issue, its sporadic but none the less I should give it a go.

 

[bcsteel]

Did you get a new fuel cap with the new tank? All new lines from tank pickup to pump?

 

[JDMBC]

@bcsteel Negative. Used the existing Toyota locking cap from the old tank. Had visually inspected the lines and I couldn’t find any obvious so assumed good - shouldn’t have assumed.

 

[bcsteel]

Might be a place to start? You could probably get one easy down there. If needed

 

[Squash]

Looking for leaks is generally pointless because the system is under vacuum, and this is how air in introduced into the fuel system. Fastest way to isolate the problem is the clear hose method.

 

[JDMBC]

Clear hose is the way to go. Though not in -27. Soon as it’s “warmed up” I’ll be tackling it.