Bleeding fuel line

[onenyala]

Yesterday I changed the CAV 296 filter on my Beta BZ482.
After it was fitted I re-opened the main fuel valve from the tank to the filter. Fuel would not refill the filter but bubbled out through the bleed screw on the top of the filter fitting.
I spoke to Scott at TS Marine who had fitted the engine. He said that was good as it meant that the re-fitted filter and glass bowl were air and fuel tight and the fuel was just taking the line of least resistance. He told me to screw the breather down and then bleed the fuel line at the fine filter assembly where there was a breather or at the injector.
When Scott fitted the engine he did a great job but unfortunately he had to fit the fine fuel filter in an inaccessble place so I had to bleed the air out at the injector.
I seemed to have to bleed loads of fuel out before I got all of the air out.
Am I right in thinking that to get the air out of the CAV filter all of the fuel in the fuel line from the primary filter plus the fuel in the fine filter plus the fuel in the HP pump had to be hand pumped out with the fuel lift pump.
It was really difficult trying to collect all this fuel at the injector. I used loads of rags and still some managed to escape.
Any advice would be appreciated. If any one has an idiots guide to changing a CAV Filter. that would also be appreciated.
PS There is no chance of me changing the filter to a Racor as I know there has been discussion about the merits/demerits between Racor and CAV

 

[CaptainBob]

Sounds like you're not having the problem I had bleeding my Beta 22. After literally hours of pumping the lift pump by hand I called Beta to be told that unless the engine is in just the right position, the manual lift lever is likely doing nothing at all, and I was better off pre-filling the filter with fuel before screwing on and turning the engine over for no more than 10 seconds at a time, with a long wait between times, until it self-bled. This worked fine.

But.

Afterwards I installed one of those squeezy priming bulbs in the fuel line between the fuel tank and the first (CAV) type fuel filter so that it would never be a problem in the future as I could then use that to push fuel up and through the system to the bleed point.

Beta tech support are very helpful on the phone. Used them a few times.

 

[ksutton]

Do you not have a bleed screw on the fuel injection pump? maybe your engineer meant the injector pump bleed screw and not the actual injector. Can imagine your frustration trying to bleed the whole system out of an injector!! Your primary filter bleed screw should also be made more accessible, you may need to get at that this in a hurry when at sea if you need to bleed air.

 

[ianj99]

I fitted an electric lift pump next to the tank - it makes bleeding the air out a doddle.

 

[onenyala]

Do you not have a bleed screw on the fuel injection pump? maybe your engineer meant the injector pump bleed screw and not the actual injector. Can imagine your frustration trying to bleed the whole system out of an injector!! Your primary filter bleed screw should also be made more accessible, you may need to get at that this in a hurry when at sea if you need to bleed air.

It was made even more frustrating as the last time after I changed the primary filter I just opened main fuel cock with the bleed screw on the filter open and when it overflowed closed it. When I gunned the engine it fired up after a couple of coughs.
I cannot understand why this time fuel wasnt going into the filter but by passing it straight to the bleed screw and spewing out.

 

[Prospect and Sunray]

Can imagine your frustration trying to bleed the whole system out of an injector!!

Personally I find bleeding the fuel system on all the diesel engines here, via the injectors, far easier than anything else. Prime the filter, do everything up, crack off the fuel line on one injector, turn engine over on the key, once engine starts, tighten injector.
Doing it this way ensures there is no air left in the system as the injector is the highest part of the fuel line, saves cramp in hand/arm as the manual lift pump is almost always hard to get to and needs loads of pumping!

 

[jrudge]

I dont know your engine but I have Volvo D6s.

One needed bleeding ( ok well it was my fault as I ran it out of fuel - just as well I have 2). No problem thinks I. Open valve, pump, air out, job done.

Would not start.

Got out the instructions. In essence do the above AND then pump 10 more times. Result, turn key and all is well.

Just an idea! As my dad says "if all else fails read the instructions"

 

[ksutton]

It was made even more frustrating as the last time after I changed the primary filter I just opened main fuel cock with the bleed screw on the filter open and when it overflowed closed it. When I gunned the engine it fired up after a couple of coughs.
I cannot understand why this time fuel wasnt going into the filter but by passing it straight to the bleed screw and spewing out.

Before attempting to change your CAV 296 filter next time when its due, turn off the main fuel tap first. This holds the line from the fuel tank stack pipe full of fuel. Then after renewing the filter open the CAV filter bleed screw before turning the fuel tap back on. You should see the filter fill quite quickly, assisted by siphon action from the pre filled fuel line.
This was probably not possible for you after getting the CAV filter fitted from new and you could have had an air lock after having a completely emptied full line back to tank. But you will have to locate and open the bleed screw on your primary filter or injection pump as well, otherwise there will be nowhere for the air to go from your empty CAV bowl.
The bleed screw on the top of the CAV filter will vent air from the tank to the filter. The bleed screw on your primary filter will need to be open to vent air from the CAV bowl.

 

[lw395]

Surely crnking a diesel on the starter for long enough to fill a CAV filter is going to flatten the battery and overheat the starter motor?

The priming bulb is the best way.
Another good way is to fill the CAV via the bleed screw using a syringe or squeezy bottle.
If you have shut off taps either side of the CAV, the final filter and lines should not have much air in.
The cheat's way is to pressurise the fuel tank either by filling it above the level of the CAV or pumping air into the vent hose.

If the lines are empty, pulling some fuel through with a pela or big syringe works well.

The manual lift pump lever worked OK on my Yanmar 3GM.

 

[lw395]

Before attempting to change your CAV 296 filter next time when its due, turn off the main fuel tap first. This holds the line from the fuel tank stack pipe full of fuel. Then after renewing the filter open the CAV filter bleed screw before turning the fuel tap back on. You should see the filter fill quite quickly, assisted by siphon action from the pre filled fuel line.
This was probably not possible for you after getting the CAV filter fitted from new and you could have had an air lock after having a completely emptied full line back to tank.

That only works if the fuel level in the tank is above the CAV bleed screw.
On my impala, it was a simple job to detach the CAV from the bulkhead and get it low enough to bleed as you say. A bit nasty as it involves all the pipes being flexed a lot.

 

[pappaecho]

I have a Pela Oil extractor, which operates by vacuum. I fit a nipple which fits the bleed point on the injector pump filter bank. It takes about 30 seconds to get all the air out. The diesel in the Pela is returned to the fuel tank.
A couple of cranks to prime the injector pump and then crack no 1 cylinder injector nut, to get any air out, and then away she goes.
I have 2x 4 litre engines with four CAV 296 filters (each) so there is quite a bit or air to suck through, using a lift pump manual tickler system, hence the use of the Pela

 

[grazbo]

I described a similar situation in a thread I posted (.... not interesting to anyone - 'cos I had no replies )

My primary filter filled ok ..... but the lift pump did nothing and my 2nd filter remain fuel-less.

True to the short-cutting amateur that I am, I thought I'd fill the filter, turn the engine over to pump it through a little and it just started after a few cranks........and it seems fine (famous last words)

In case it helps: http://www.ybw.com/forums/showthread.php?t=318187

 

[pvb]

It was made even more frustrating as the last time after I changed the primary filter I just opened main fuel cock with the bleed screw on the filter open and when it overflowed closed it. When I gunned the engine it fired up after a couple of coughs.
I cannot understand why this time fuel wasnt going into the filter but by passing it straight to the bleed screw and spewing out.

Are you saying that the engine has been changed since the last time you changed the primary filter? If so, might your engine fitter have plumbed your CAV filter the other way round?

 

[Graham_Wright]

I fitted an electric lift pump next to the tank - it makes bleeding the air out a doddle.

I did the same. Pump came from eBay, made in India, appears to be the same as sold by ASAP Marine (except for the price!). Pressuring the fuel line seems to be the way to go.

 

[Graham_Wright]

Surely crnking a diesel on the starter for long enough to fill a CAV filter is going to flatten the battery and overheat the starter motor?

………and fill the engine exhaust with water from the Jabsco and we know what happens then.

 

[burgundyben]

I have the 296 type filters too, I find it helps once you've swapped the element and er-assembled to fire up the engine and let it idle, the lift pump will pull through the fuel.

Sometimes it pulls through the fuel quick enough and self bleeds, other times it konks out, in those cases you've got less manual priming to do as its already doen some of it itself.

 

[bendyone]

Long story but I have had problems with air getting into the fuel line, in the end I replaced the lot and fitted a filter with a primer pump built in. Primes the system without any problems. The manual lift pump was hard to reach and very slow, also the engine had to be in a certain position for the pump to work.
From here http://www.ssldieselparts.co.uk/primer-with-filter-deep-bowl-p-705.html £24

 

[Prospect and Sunray]

………and fill the engine exhaust with water from the Jabsco and we know what happens then.

IF your battery can't turn the engine over for about 30 seconds, then I would have said the battery is duff! I have never managed to flatten a battery while priming up the fuel system, and neither should the starter overheat. I am not talking about constant cranking for 5 mins, a couple of 20 second cranks and the engine will be running. But everyone has different methods of doing the same thing.

I am puzzled as to why your toilet is connected to your exhaust Graham???

 

[onenyala]

Are you saying that the engine has been changed since the last time you changed the primary filter? If so, might your engine fitter have plumbed your CAV filter the other way round?

No the engine hasn't been changed between filter changes. Last time as I said the fuel slowly filled the filter and then I turned off the breather on the top of the filter housing. This time as I said the fuel refused to flow into the filter despite the breather being open.
It has since been suggested to me that I should 'crack' centre holding bolt off a bit to allow the air to be displaced.

 

[earlybird]

... This time as I said the fuel refused to flow into the filter despite the breather being open.
It has since been suggested to me that I should 'crack' centre holding bolt off a bit to allow the air to be displaced.

If your filter is anything like mine, I can't see how fuel emerges from the breather without first filling the filter, since the breather is at the uppermost point of the housing.
Seems very strange, and I would question how the filter has been re-assembled. Can't see how loosening the holding bolt would help.