94 HDJ-80 fuel delivery problem (1 Viewer)

[hskasimir]

last year I started having a fuel delivery problem with my 94 HDJ-80 VX with factory dual fuel tanks. Driving on the big 90l tank the car would at any given level of fuel in the tank suddenly start to run out of fuel and eventually stall. All within a very short time, at first maybe within 30 seconds to a minute then much faster. My first thought was that the respirator/tank ventilation hose was clogged and a vacuum was created which eventually starved the engine of fuel. Driving the truck with the fuel cap off and eventually changing the respirator hose proved that this was not the case. Trying to start the engine a few minutes after it had stalled would take a few turns but eventually it would start idling roughly and then a few seconds later the engine would run perfectly fine, even at high speeds, for up to 100km until the same thing happened again. I decided I would at some point take out the fuel tank and see if I can find the problem there. Until then I would make sure the second 45l tank was always as full as possible and switch to the auxiliary tank whenever the engine started failing. This worked perfectly fine. The auxiliary tank never ever failed. I always filled both tanks at the same, brand new gas station.
Finally, about six weeks ago, I took off the tank and rinsed it thoroughly. There wasn't too much muck in it to begin with and after rinsing the tank was clean. Some slightly rusty spots could be seen inside but nothing that would look anywhere like flakes of rust might chip off at any time. I put a new filter on the pick-up tube, checked the hose that goes to the switch-valve, which was OK and installed everything again. For about 5 weeks or maybe 3 entire tank fillings, I had no problem whatsoever driving on the "big tank" until about a week ago the same thing started happening again, only this time the intervals between failing became shorter (sometimes after 5km) and also the time from starting to fail to eventually stall became shorter, too (no more than 10 seconds). Again, the truck runs perfectly fine until this happens. No power loss or even slightly rough running engine at all... And then it stalls within seconds. I still switch to the auxiliary tank when I realize it's happening again, drive on the auxiliary tank for a few minutes, switch to the big tank again and again it runs as if nothing had ever happened until it stalls again.
This is really weird. Does anybody have an idea what this might be..? I welcome any suggestion

 

[Tapage]

this happen engine cold or hot .. or it does not matter .?

that ever happen idling at home / shop .?

First thing comes to my mind it's the fuel control relay that makes the switch between sub tank and main tank

 

[hskasimir]

this happen engine cold or hot .. or it does not matter .?

that ever happen idling at home / shop .?

First thing comes to my mind it's the fuel control relay that makes the switch between sub tank and main tank

Thanks, I was thinking in the same direction, especially because of the suddenness of how this happens. If it was some kind of dirt or muck that was clogging the fuel system somewhere, it seems to me it would take much longer to finally starve the engine. And on the other hand I doubt it would run so well while it does. The same goes for water in the tank. However, it strangely only affects the large tank, never the small one. And there's never a problem when I actuate the switch. It always works, switching from one tank to the other. There's never been any kind of failure. It's hard to imagine the switch would by itself all of a sudden, with no electrical impulse, turn off one tank but not switch automatically to the other, a function that it wasn't designed for or simply doesn't exist...
I will take out the witch in the next couple of days and test it. I'll let you know what I come up with

 

[dawery]

mate I went through a similar thing, cleaned the tank and ok for a while but started happening again. my tank was a little rusty inside too. When I looked in the tank again, the plastic rectangular bit that the pickup sits in had broken off the tank and blocked the pickup.. Never know, haven't seen it happen to anyone else but you might be the second haha.

 

[Tapage]

Another test would be put a plastic line in the feed so when the problem arise you can watch for air in the line

 

[hskasimir]

Another test would be put a plastic line in the feed so when the problem arise you can watch for air in the line

Yes, you're absolutely right... however, as quickly as this problem appears and disappears again, I'm afraid I have to throw myself underneath the truck while driving it to get to see the bubbles before the disappear again, hahaha
I just took a look at the workshop manual and realized there are actually two fuel shut-off valves. One regulates the fuel going to the engine and the other one the fuel that returns to the tanks. I'm not sure what that really means in regards to my problem but I'll take them out this week and follow the testing procedure from the manual. I'll keep you guys updated...

 

[Squash]

The clear hose is in the engine bay from out of filter to the IP(injection pump) intake.
Should be 5/8"
Air bubbles mean you are sucking air instead of fuel, start at ip and move backwards towards tank fixing any leaks and tightening clamps.

 

[roscoFJ73]

I have seen a few cases like this before. Always HDJ80/81. Sounds like an air problem.

 

[Tapage]

I have seen a few cases like this before. Always HDJ80/81. Sounds like an air problem.

naaaaaa 2H it's an air problem engine .. 1HD-T at least are pretty forgiving ..

 

[mudgudgeon]

I'd also guess at air getting sucked into the fuel system.
Use clear hose to check for air bubbles while driving,



or replace all your rubber fuel supply hoses from main tank to the change over solenoid valve.
If it only ever does it on the main rank, I'll bet on an air leak between the main tank and the change over valve

 

[hskasimir]

Of course you are right Tapage, as Squash was friendly enough to point out: certainly a clear hose between filter and injection pump would show you just as well whether some hose was sucking air... even if it was the hose between main tank and changeover solenoid valve. My thought, however, was that if some hose was sucking air, it had to be exactly that one between main tank and changeover valve, since the fuel supply line of the auxiliary tank also goes through the main valve and the truck was always running perfectly fine on the auxiliary. But now I'm totally confused... So here, step by step, what I did:
After a couple of really busy days I finally got myself a piece of clear hose and set out to do exactly what Tapage and Squash recommended - to put a clear piece of transparent hose between filter/primer pump and the injector pump. I took off the regular black hose and that's where I was baffled first. There was hardly any fuel in that hose when I took it off, although I was running on the auxiliary tank before I shut the engine off last. Strange. I then continued and hooked up the clear hose on the injector pump, and, to fill the clear hose with as much fuel as possible, I held the other end up to the primer pump's nozzle, just so that I could fill it with fuel and still let out the air in the hose. I started pumping and then - the next surprise - nothing came out at all. I must have pumped a hundred times or more - nothing - although I was still connected to the auxiliary tank which never, ever failed...
Evidently this means that either the diaphragm of the primer pump is shot or there is a leak in the line somewhere where it's sucking air or, to be precise, both.
I wouldn't have been surprised if it had happened on the main tank which was failing, but on the auxiliary tank?
I connected the hose to the primer pump's nozzle anyway and started the engine to see what was happening. It started just fine and it took about thirty seconds until it was sucking diesel into the hose. I accelerated the engine and slowly more fuel would enter the engine. However, altogether the hose never filled up more than maybe 40% with fuel. The engine was running fine, even if I accelerated a lot, continuously.
That's where I'm at right now. Any suggestions before I start tearing off and replacing all the supply lines..?

 

[Tapage]

So it died on you when sucking from the main tank with the clear hose on place .?

 

[hskasimir]

Yes. Yesterday it died on me while running on the main tank. I opened the hood to look at the hose and was surprised again because the hose was almost entirely full. Inside the maybe 35-40cm long hose there was only maybe a 4-5cm long bubble of air. I could see how this could maybe be a problem driving at full speed on the highway but I was actually coming down the steep dirt road from the mountain I live on and was going in first gear to break with the engine, so I doubt I was ever revving higher than 1500 or at the very most 2000rpm.
This doesn't follow any logic... At least not my logic, hahaha
Anyway, I have already taken out the second row of seats to look at the fuel hoses or check for anything strange - nothing that called my attention. I live in central Argentina and we have a major storm front moving through, so I can't really work outside and furthermore it's a holiday until Wednesday, so I can't buy any fuel hoses until then. But the plan is to replace all the fuel hoses (which I dread, because the quality of hoses you get here in this backside of the woods is so bad that you have to change them every two years) and check the diaphragm thoroughly (which I might be able to do today, if it stops raining for ten minutes...). If that doesn't do the trick I would then move to the changeover solenoid valve and last take the tank out one more time. I'll keep you guys posted. Thanks so much for your interest and help so far...

 

[roscoFJ73]

Any suggestions before I start tearing off and replacing all the supply lines..?

Maybe you could get the hoses tight with some new clamps. The old finger clamps lose tension with time. I was having long cranking times and discovered the hose to fuel pump was totally empty one morning.
The fuel filter seal can also be a culprit for letting air in.

 

[hskasimir]

Thanks roscoFJ73, that's a good idea to change the clamps before throwing out the hoses. Because they look perfectly fine and as I mentioned before, I will never get anything anywhere near in quality here.
When you talk about the fuel filter seal, do you mean the o-ring between filter and pump assembly? I haven't checked the filter/pump yet but I'm on my way now...

 

[Tapage]

after your engine died .. you crank it again and it ran ..?

guess you were alone at that moment ... it still only happening from the main tank only right ..?

 

[hskasimir]

Yes Tapage, after stalling it starts again right away after a few cranks. I usually just switched to the other tank but I also tried cranking again on the main tank and it does start after 4 or 5 cranks...
Just now I checked the fuel filter/primer pump and it seems to be alright. O-ring between filter and pump is fairly new and I put a new filter in while I was at it. After I assembled everything I blew hard into the filter/pump inlet while covering the outlet with a finger and everything seems to be perfectly tight. Let me know if there's a better way to check this...
Also, I put new clamps on the hose between main tank and changeover valve. I'll try it now and will keep you posted

 

[Tapage]

Blow compress air through the line ..

 

[hskasimir]

Well, I've been running the truck for a while after my latest improvements. I can't say it helped much. The truck stalls every 3-5km. Every time it happens I open the hood and look at the clear hose between filter and injection pump and the results are confusing. Sometimes there is a relatively big bubble of air in the hose, sometimes it's more like a foam and one time it stalled and when I looked there was no air at all in the hose. I don't really see why it should stall with even a bubble of air in it. Recently I've only been running the truck here in the little town I live, which means I was driving relatively slow and the consumption was equally low. When you look at the clear hose, which connects the relatively high fuel filter with the relatively low in the engine bay situated injection pump, the bubble of air - if there is one - logically remains on the highest point of the hose, which is near the outlet of the filter. I've never seen the bubble being any bigger than maybe 10% of the hoses length, so actually, the injection pump looks like it is being fed sufficiently with fuel, especially, one would think, if you're not running at full throttle...
The only constant in the whole matter is the fact that the auxiliary tank never fails.
The plan now is to run the main tank as empty as possible before taking it out and inspecting it. I remember the mechanic who had taken it out and cleaned it before telling me that in lack of an original part he put some generic filter on the pick-tube. I've never seen it because I wasn't here at that time. I'm thinking maybe he didn't connect it well to the tube and now it's blocking the entry. In any case, I will take a look at that and in the meantime I will try to get the original filter and see if I can find some good quality hoses which will be a lot easier to fit once the tank is out...

 

[Tapage]

So every time you are running in the aux tank you have the same bubble on our clear hose ..?