water separator woes

[trondhindenes]

Hi all,
I hope I can get some pointers & opinions on the following problems:

I've been chasing an intermittent engine hesitation issue all summer, not being able to get rid of it. I know it's due to fuel starvation and while at first I was afraid of contaminants in the diesel, I'm 95% sure it's an air leak in my fuel system.
The first thing I tried was to replace the existing CAV water separator with another unit, but I quickly discovered that the internal seals in the unit were leaking from the factory, so I scrapped that and installed a higher quality racor unit instead. The problem, unfortunately persists.

A few things I'm seing:
If I bypass the water separator, hooking the hose from the tank directly into the engine's fuel pump everything works flawlessly. I don't consider this a valid fix tho, I want a water separator in my fuel system.
With the water separator in place, the faults are quite intermittend. Yesterday the engine ran for 7 hours without problems, while this morning it stopped within 20 minutes of running.

I'm also noticing that the water separator is installed so it sits slightly higher than the bleed screw on the engine - I don't know if this could cause trapped air in some situations.

I'm also starting to wonder if the fuel pump on the engine is starting to go bad, and simply is unable to handle the extra vacuum needed to pull diesel thru both the water separator and the primary filter.

So TLDR:
- engine runs perfectly fine without a water separator in place
- engine stops randomly with the separator installed.

I'd be very eager to hear your thoughts, I'm going in circles on this one

 

[PabloPicasso]

Yes, could be a fuel pump issue. Is there a filter gauze in the pump, is the diaphragm failing? Is the pump serviceable at all?

But first look again for air leaks. Check all pipes and connections. Start with anything that has been disturbed recently. Work methodically from one end of the fuel system to the other. Don't forget breathers and return pipes

Does it only happen when fuel tank levels are low?

Is there gunge in the tank that intermittently blocks the pick up pipe?

How old are your fuel hoses? An old or faulty hose could be collapsing blocking the pipe, perhaps only under certain opaque conditions.

Good luck, do let us know how you get on.

 

[chubby]

I had a similar issue and eventually it was the electric fuel pump, perfect ever since replacement.
I have a vetus M4.17 and the vetus labelled pump was expensive and not in stock locally.

I found a much cheaper immediately available near identical replacement via a company in the midlands that does commercial vehicle spares, apparently same pump used on dumper trucks!

I bought the spare, worked perfectly and solved the issue then bought the vetus one later and kept the dumper truck one as a spare.

A friend who has worked with agricultural machinery said they offer replaced the fuel pump once you have checked the obvious air leaks as you have!

Mine irritatingly worked in calm weather when perhaps it didn't work so hard then let me down at the worst moments!

 

[rogerthebodger]

You say its a CAX water Seperator. I have a CAV filter and water Seperator that I hod that my engine would cut out and I knew it was not the seals in the filter.

Evenly I replaced the fittings into the water separator banjo couplings with non-copper Dowty washers, and it solved the issue.
It does look to me like a small amount of air leaking into the fuel line feed and causing the hunting

 

[PabloPicasso]

Some peiple like Cav filters, but not me.

Didn't the op say he'd replaces with a racor copy?

Much better and easier/quicker

 

[KompetentKrew]

You say its a CAX water Seperator.

No, OP said he's already replaced that with a Racor.

 

[rogerthebodger]

No, OP said he's already replaced that with a Racor.

Yes I know that what I was referring to us a similar issue faced by refuting the fuel in and out connections/

I have used the CAV filter for a long time and never had a issue with sealing the filter bowl as I learned the correct method many years ago/

Its like sharpening a drill drilling Stainless steel learn the correct method and the job becomes easy

I used to fix and tune Austin minis earning my way through university

 

[bluerm166]

Had similar issue, revs dropping near zero and always recovering every 5 minutes. Had relied on fact that engine started instantly and would run at fast tickover for half hour and more flawlessly. Surprised that engine filter bleed produced perhaps two minutes of air and solved issue. How could fuel be getting through at all? But it was.

 

[trondhindenes]

thanks all. The CAV filter is indeede replaced by a Racor unit. I have a gut feeling that the hose between the water separator and the fuel pump is too loose, and there's a tiny bit of air seeping in there, will try replace that too.