Technical Ducato II - Engine starvation when tank is below half full

[Communicator]

It's 2024 and I'm back.

No need to read the whole thread I guess, I'll tell you about the last trip which will give you a more precise idea of the problem.

1996 Fiat Hymer C Swing 544, Iveco 2,5 TDI engine, 180000 km.

So I went on a small trip in southern Sweden days after the last post. After a couple of days and 400 km we parked by a bay, close to the water, fantastic spot. The engine had worked perfectly.

When leaving the next day I had to go up this tiny, steep road, and I had 1/4 tank. It's obvious that the fuel line didn't get fuel the whole way uphill. The engine started struggling again after that, badly. It stopped several times per minute, and even pushing down the clutch barely helped.

I was able to buy 10 l diesel from a guy nearby, and it started to go a bit better, but it was still a struggle. 12 km later I filled the tank to 3/4 just to se how it behaved. Much better, but still not good. I got full tank 20 km after that, and finally it was working well and continued to do so the whole 350 km return trip.

View attachment 446087 View attachment 446088 View attachment 446091

I think it acts like it doesn't have a working check valve for the fuel, and the only remedy is to get a full tank. In the last post I said it could run on fumes, but if I would have lifted the fuel line above the fuel surface in the tank and put it back, I would probably have induced the problem.

Where is the fuel check valve located?

I cannot help with the location of a check, or non return valve in the fuel supply line. From reading other threads, it appears that the Bosch VE injection pump was commonly fitted without a separate lift pump. (It has aninternal transfer pump.) Given that the symptoms only occur with a half full tank, I would advise considering the possibility of a small leak in the fuel delivery line which allows air to be sucked in at the higher vacuum when the tank is only half full. Alternatively a small hole in the fuel dip tube? Another possibility is that an ageing transfer pump cannot create sufficient vacuum to suck the fuel from the tank.

 

[SL2]

Going back a bit, did you locate a lift pump that feeds the injector pump?
I know on the older Sofim engines like yours, when fitted to Iveco Daily's they had a mechanical lift mounted on the large unit bolted to the engine block that has the injector pump, oil filter, brake vacuum pump and sometimes the power steering pump all driven from it.
The item I mean is in this photo just below the dipstick and with a red plastic pipe attached to it.
If yours uses that system and the mechanical lift pump's, diaphragm or valves are getting lazy , then as fuel gets lower and if pulling hard up a hill creating more demand for fuel..... , it could just be something like that.

I cannot help with the location of a check, or non return valve in the fuel supply line. From reading other threads, it appears that the Bosch VE injection pump was commonly fitted without a separate lift pump. (It has aninternal transfer pump.) Given that the symptoms only occur with a half full tank, I would advise considering the possibility of a small leak in the fuel delivery line which allows air to be sucked in at the higher vacuum when the tank is only half full. Alternatively a small hole in the fuel dip tube? Another possibility is that an ageing transfer pump cannot create sufficient vacuum to suck the fuel from the tank.

Thanks for the replies. Unfortunately, I'm currently far away from it, and not able to check it right now.

It's more complex than just having problems than going uphill, or low fuel (like I said last year) I'm afraid.

- I can run it on near empty tank, no problems there (unless the problem already stated).

- Forgot to mention, changing the fuel filter alone causes no problems.

- It's only when the line of fuel gets interrupted with air (dunno how to say it) the engine starts struggling, and the only cure is a full tank. The introduction of air that makes all the difference, and leaving the engine running idle makes no difference.

This makes me believe that there's something wrong between the fuel filter and the tank. Still searching for info about the check valve.

 

[bugsymike]

I am not to convinced about a check valve on your system, as to me the only advantage of one would be when stationary so as not to have fuel drain back to the tank, so once running it wouldn't make a lot of difference, although in fairness most of my information is Iveco related rather than Ducato though similar engine.
It may be that the fuel tank is much nearer to the engine on a Ducato so Bosch VE injector pump has less of a problem priming it's self.

 

[SL2]

I am not to convinced about a check valve on your system, as to me the only advantage of one would be when stationary so as not to have fuel drain back to the tank, so once running it wouldn't make a lot of difference, although in fairness most of my information is Iveco related rather than Ducato though similar engine.

You're right, if you're running out of diesel and then fill the tank, a check valve wouldn't help since the fuel would be gone from the lines anyway.

Now I realise the inconsequence of having a faulty check valve, while still being able to change filter easily..

I admit, I've been so eager to find a solution off and on for two years now, it's easy to jump to conclusions. I guess this is a job for a mechanic.

 

[bugsymike]

You're right, if you're running out of diesel and then fill the tank, a check valve wouldn't help since the fuel would be gone from the lines anyway.

Now I realise the inconsequence of having a faulty check valve, while still being able to change filter easily..

I admit, I've been so eager to find a solution off and on for two years now, it's easy to jump to conclusions. I guess this is a job for a mechanic.

The dying out whilst pulling up a hill does point to fuel starvation, so my thoughts may be relevant, but see what your mechanic feels, if you feel you have gone as far as able.

 

[SL2]

The dying out whilst pulling up a hill does point to fuel starvation, so my thoughts may be relevant, but see what your mechanic feels, if you feel you have gone as far as able.

Yeah, that one was in first gear, and with a steep enough angle to get air in the fuel line. The problem is that it never recovers after that even though it's 20 l left in the tank, that's not normal.

Thank you both for your support, I'll try to give an update when we get it fixed. Skål!

 

[sliderr]

Isn't this a classic leaking vacuum hose?

 

[bugsymike]

Isn't this a classic leaking vacuum hose?

OP mentions fuel level affects the issue?

 

[SL2]

Isn't this a classic leaking vacuum hose?

I'm no expert, but I'd expect to have a more permanent problem if that were the case.

 

[bugsymike]

Going back to last year when you had the fuel tank cleaned and subsequently changed fuel filter etc. was there any sign of water in the old fuel?
You mention a red light coming on, was that a water sensor light on fuel filter housing possibly or just the generator light due to the engine struggling and barely running?
Unless fuel tank was removed to clean it is hard to get every drop of water out.
Some years ago I was driving over the moors in a Peugeot 504 diesel Pick up and it was "stumbling" at first I thought it was the strong winds, but as it persisted I checked the drain on the fuel filter and a lot of water came out, I then checked the fuel tank and fortunately on that model there was a drain plug , so I was able to drain the water out and the flush through the system with new clean diesel which solved the problem.

 

[SL2]

At least you found water, I don't remember seeing any. I don't really know where else to check for water. No water warning light.
I remember the tank having its lowest point right under the fuel line (image) and I got everything i saw out of there. I've changed filter three times.

 

[SL2]

It's the light without a symbol.

 

[Communicator]

Is the low pressure electric fuel pump in Ducato on chassis if like Iveco working?
Older Ivecos with Sofim 2.5 engine had a low pressure mechanical pump on engine with a primer, diaphragm could be weak
Bacteria in diesel if left standing, any signs in tank?
Fuel pick up in tank faulty / damaged?
If electric pump working can you put pipe after filter into clear container and see if air is coming through from tank?
Can you jury rig a temporary tank to eliminate any other issue, remember it will run out quickly due to no return feed?

I noticed that there's pressure in the tank when I open it.

No misfire, just strangled, no power to run, the engine stops when there's very little diesel left in the tank. The red light goes on, I'd guess newer models have an engine symbol there.

Yup, more fuel is needed. I've had a really bad situation last year when I thought our week long trip was coming to an end after just a few hours.

I realized it might have something to do with the amount of diesel, and there was nothing else I could do at that point as I wasn't at home anymore, so I added the extra 10 l of diesel I had with me. After that it worked much better, but not perfect.

With a full tank the next day it worked great for more than 300 km, until it got close to half tank and it started struggling again. Repeated and continued.

It does reoccur. Both last year and now,

It's the light without a symbol.
View attachment 446193

Grasping at straws. I have a further suggestion, amd a question.

I previously owned a 1990 2.5TD Talbot Expess from new. When it was about 12 years old, I had an intercooler fitted by a specialst company, who were located over 100km from home. On my return journey the engine stalled twise, but restarted immediately. Bothe events occured when climbing hills, so fuel demand would be increased. This was a new expreience to me. On seeking advice from the diesel specialist. I was advised that the CAV push button priming pump diapragm could harden with age, develop cracks, and let air into the system. After changing the filter mounting/pump, the fault did not reappear.

Question. What is the warning light indicating on a mechanical injection engine?

 

[SL2]

Grasping at straws. I have a further suggestion, amd a question.

I previously owned a 1990 2.5TD Talbot Expess from new. When it was about 12 years old, I had an intercooler fitted by a specialst company, who were located over 100km from home. On my return journey the engine stalled twise, but restarted immediately. Bothe events occured when climbing hills, so fuel demand would be increased. This was a new expreience to me. On seeking advice from the diesel specialist. I was advised that the CAV push button priming pump diapragm could harden with age, develop cracks, and let air into the system. After changing the filter mounting/pump, the fault did not reappear.

Question. What is the warning light indicating on a mechanical injection engine?

I don't know, and I don't have the manual here. Like I said, I drowe up that particular hill in first gear. I've travelled loads of hills in 80 km/h. There's no priming pump.

I won't be doing any more with this. A mechanic will start working on it before I will have a chance to do anything myself.