Fuel starvation, '92 TD42.

[yossie]

I'm new to the world of Nissans and diesel motors so I may ask the odd silly question, but I'd appreciate some help. I have recently acquired a '92 GQ Patrol, in very good condition, only 139K kms, but with ocassional lack of response when I want or need to accelerate hard. When the problem occurs, the response can be varied - ultra slow pickup, or pickup OK to a certain point then falls away sharply (with the kind of groan you might get if you were in a petrol vehicle and suddenly pulled the choke on full), or pickup OK then engine "missing" (like bad/dirty points or a cracked distributor lead might do in a petrol vehicle - for those of you old enough to remember cams, points and condensers!).

If I drive conservatively (which I do most of the time anyway) there's no problem. Only when I go hard on the accelerator, and I notice it mainly in 2nd and 3rd gear. I suspect that's because the higher gears don't cause the rapid increase in revs that you get at the lower gears, and so the fuel supply can keep up.

I've read forum posts about the main fuel filter (replaced, bled, last weekend), and the scintered wire filter in the banjo fitting at the front of the injector pump (checked - mine doesn't have one, might've been removed by previous owner?) and I even took the plate off the top of the fuel tank and checked the fuel pickup line to make sure there was no obstruction. I'm now looking at other potential problem areas.

Air in fuel line? - I notice that the priming pump on the main fuel filter will always take 5 or 6 pumps to harden up when the motor has not been running. Is this normal? Just today I parked for 20 minutes, facing up on a very steep drive. When I took off, I traveled about 50 metres and the engine then dropped to a rough idle, no response at all to the accelerator, and then evened out. To me, that lends weight to the idea that fuel in the line was able to run back away from the engine. Do these things indicate that the fuel line is dragging in air somewhere and possibly creating low fuel spots in the line? Could this starve the injectors under heavy acceleration?

The injector pump? - Am I right that this is the only fuel pump? Without any knowledge, I expected that there would be an electric pump up the back of the vehicle somewhere, but other posts I've read indicate that fitting an electric pump is something some keen people do - possibly to alleviate the problem I'm having. Anyway, at 24 years old and despite the low kms, could the pump be tired and not able to keep the fuel up to the injectors under heavy acceleration?

I look forward to any pointers and advice you people of the interweb can offer.

[MudRunnerTD]

Hi Yossie,

Firstly please head over to the intro section and post an introduction thread, we like folk to say g'day.

There is only the mechanical pump and suction. There is no electric secondary. The guys fitting the inline electric pump are chasing bigger HP generally out of bigger pumps starving. I doubt this is you problem on an unmolested car.

It could well be the pump but that would be unfortunate! Others might give you some tests to run.

Air in the lines certainly sounds feasible too. Do you have trouble starting it after it's been sitting for a few minutes? If there is air getting into the line between the tank and the pump the fuel will drain back and it will be a dog to start.

How does the Air filter look? Air starvation will present like this too.

[Cuppa]

Sounds like an air leak could be a possibility. Your description of taking off, faltering, & then coming good supports this. Vacuum in the line at larger throttle openings could reach a point where it's enough to suck air in, but not at moderate throttle openings. I reckon your pump will be fine.
Is there any difference in re-starting after the engine has been switched off for a short time compared to when it has sat overnight or longer?

A short story. On a previous vehicle (4 cylinder Nissan diesel) I had it would run fine a low to mid revs, but ran out of steam & could only manage 80kph flat out, whereas owners of similar vehicles reported a top speed of 100 to 10kph. I just thought they were exaggerating! When I then had what I thought was an air leak problem in the fuel supply line (it wasn't it was a sticky exhaust valve letting air in) I discovered a previous owner had fitted a non return valve in the fuel line, a not uncommon solution to prevent the 'loss of prime' caused by an air leak between fuel tank & pump. The problem in my case was that the non return valve was too small & restricting fuel flow at full throttle. Removing it gave me an increase of 20-25kph. Reason for the story - it is worth checking that you have no restrictions in the fuel line as well as checking for leaks.
FWIW leaks are not necessarily easy to see, if there is one a light dusting of talcum powder on the hose may reveal some dampness, but it isn't uncommon for air to be sucked in , but no fuel to leak out. Once access to the fuel line is achieved, it's far easier just to replace it with new hose.

But like MR suggests - check the air filter too.

[jff45]

Is it possible the little gauze strainer under the fuel line banjo is slightly clogged?

[Avo]

Is it possible the little gauze strainer under the fuel line banjo is slightly clogged?

check this first as it's easy to get at and is an easy fix,if it the problem

[Rossco]

Is it possible the little gauze strainer under the fuel line banjo is slightly clogged?

I think he checked and doest have one on the pump. Sounds like exactly what mine was doing. Mine was the pump but sounds like air getting in from somewhere could be the case too especially if it feels like its lost its prime. Could be the primer mechanism too letting it drain back as well.

[MudRunnerTD]

Is it possible the little gauze strainer under the fuel line banjo is slightly clogged?

It is not fitted. Has been checked.

[jff45]

Sorry, should have read it a bit better.
I wonder why someone would remove it from a low mileage engine. I've read of several cases where people were sure there was no gauze filter there but found it was a bit deeper than they first thought.
When I first checked mine I also thought there was nothing in there..

[Bushy674]

Early model TD42 didn't have a gause filter in the banjo fitting

[MudRunnerTD]

My 2005 GUIVTD42Ti did not have a Banjo gauze filter fitted, still doesn't. Never checked the GQ. I had very similar fuel Starvation issues with the GUIV a couple of years ago. Took 6 months to figure out and had lined up a pump rebuild, was a week away from putting it in to get done!!

Went and filled up the car then parked it in the sun at the supermarket, on my return I found a patch of fuel on the ground!!! First time it has ever presented!6 months of symptoms!! Turned out to be a split fuel line on top of my rear spring tower. Easy fix!!! Glad I didn't spent $2000 on a rebuild pump as it would not have fixed my problem!!

Mine would loose prime when sitting. If I sat on the side of the road idling it would stall when taking off too! Was a bastard!