Bleeding BMC 1.8

[Slim]

At the moment take the title any way you will.

OK, had the boat 20 years + so think I know what I'm doing but ?....

In the process of replacing stern tube, shaft, flywheel casing, driveplate, engine mounts& flexibles and variouus other non fuel erelated bits I disturbed the fuel pipe from the ĺift pump to fuel filter. Thought I'nipped it up but when I started the engine it cut out after about a minute with classic air in the system symptoms. Couldn't stop the fuel weep soo replaced the pipe. Took the opportunity to replace the filter element (and seals). Now I just can't get the fuel system to bleed properly. What am I doing wrong? I've done the job any number of times in the past but not today. 

Got plenty of fuel and fuel valves on.

Lift pump works and off cam when hand pumping 

Aggro?...../ water trap clean and bled

Fuel filter CAV 296 bled

Ignition system on (electric fuel cut out)

Injector pump bled (via bleed valve between the throttle spindle and maker plate on pump body) 

Throttle half open with engine out of gear

All the above bleeding both by hand and with engine turning over Battery started off fully charged.

All 4 injector pipes cracked 

Fuel everywhere apart from the injector pipes

 

If anyone can come up with what I'm doing wrong or missing I'd be most grateful

Should add that the engine normally starts on the first turn with very little heaters. 

 

Many thanks

 

Frank

[Stilllearning]

12 minutes ago, Slim said:

At the moment take the title any way you will.

OK, had the boat 20 years + so think I know what I'm doing but ?....

In the process of replacing stern tube, shaft, flywheel casing, driveplate, engine mounts& flexibles and variouus other non fuel erelated bits I disturbed the fuel pipe from the ĺift pump to fuel filter. Thought I'nipped it up but when I started the engine it cut out after about a minute with classic air in the system symptoms. Couldn't stop the fuel weep soo replaced the pipe. Took the opportunity to replace the filter element (and seals). Now I just can't get the fuel system to bleed properly. What am I doing wrong? I've done the job any number of times in the past but not today. 

Got plenty of fuel and fuel valves on.

Lift pump works and off cam when hand pumping 

Aggro?...../ water trap clean and bled

Fuel filter CAV 296 bled

Ignition system on (electric fuel cut out)

Injector pump bled (via bleed valve between the throttle spindle and maker plate on pump body) 

Throttle half open with engine out of gear

All the above bleeding both by hand and with engine turning over Battery started off fully charged.

All 4 injector pipes cracked 

Fuel everywhere apart from the injector pipes

 

If anyone can come up with what I'm doing wrong or missing I'd be most grateful

Should add that the engine normally starts on the first turn with very little heaters. 

 

Many thanks

 

Frank

This might help

 

 

[Tony Brooks]

First thought - are the seals in the 296 filter correctly seated and not twisted, a very common cause of bleeding problems.

 

Next, although I don't normally advise doing it after bleeding the cylindrical body (which is what I think you mean) try bleeding from the bleed screw in the idle damper (top of turret) but put a spanner on the damper to stop it twisting.

 

Note - some 1.8s have a low pressure type bled screw in one of the high pressure injection pipe banjos on the pump, if loosening the injectors you should not have to touch this one.

 

Final desperation - leave the injector pipes loose but tighten the other bleed point. Remove the   injector pump return pipe from the filer end and direct it into a can. Spin in starter.

Edited December 29, 2019 by Tony Brooks

[Boater Sam]

Are you certain that the stop valve (electric cut out ) has power to it? Not moved a wire?Check with ignition on and a bulb or multimeter to ground.

Open bleed screw on the injector union to the injector pipe on the pump, it sometimes lets air out of the high pressure side better than just through the cracked pipe at the injector.

 

"Injector pump bled (via bleed valve between the throttle spindle and maker plate on pump body) "  Is this the one on the round body of the pump? It should be. Don't try bleeding the slow running screw with the lock nut, it won't!

 

If there is no fuel at the injector pipes, the pump is air  locked.

[Slim]

Had to give up in the end , flattened battery. It's now re-charging. As the combi  only charges at a nominal 5 amps i'll give it 48 hours and go back in a couple of days. 

To answer various questions:-

Reasonably confident the filter seals are correctly fitted but will bear in mind

Yes, i bled the pump from the valve on the cylindrical body. Will bear in mind  bleeding from the turret and removing the return pipe

The stop valve has power. Caught by that one before. Disconnected and flashed to supply to it, felt it opening and closing.

Bleed screw on injector union to injector pipe. Is this the same as the bleed screw screw on high pressure injection pipe banjo. If so I don't think my pump has one.

Anyway, thanks for all the advice. I'll get there in the end after all it's only air!

Never had this much trouble before

[Tony Brooks]

1 hour ago, Slim said:

Had to give up in the end , flattened battery. It's now re-charging. As the combi  only charges at a nominal 5 amps i'll give it 48 hours and go back in a couple of days. 

To answer various questions:-

Reasonably confident the filter seals are correctly fitted but will bear in mind

Yes, i bled the pump from the valve on the cylindrical body. Will bear in mind  bleeding from the turret and removing the return pipe

The stop valve has power. Caught by that one before. Disconnected and flashed to supply to it, felt it opening and closing.

Bleed screw on injector union to injector pipe. Is this the same as the bleed screw screw on high pressure injection pipe banjo. If so I don't think my pump has one.

Anyway, thanks for all the advice. I'll get there in the end after all it's only air!

Never had this much trouble before

Yes, that's the one. I mentioned it just in case you mistook it for a low pressure bleed point.

[Boater Sam]

Tank Vent clear?  

Daft but, enough fuel?

Work from lift pump up to filter, will the filter bleed on the pipes?

Tank return clear?

 

Not much else is there!

[Slim]

5 hours ago, Boater Sam said:

Tank Vent clear?  

Daft but, enough fuel?

Work from lift pump up to filter, will the filter bleed on the pipes?

Tank return clear?

Plenty of fuel and the vent is clear ,generator feeds from same tank. 

Haven't checked return pipe ,willdo so next visit.

There's pplenty of fuel up to the pump but none coming out of the injector pipes. Whether it's air free is another matter. When i turned the engine over with the cylindrical vent open a steady air free stream of fuel came out. Did this several times for 20-30 seconds at a time.

Where, exactly, does the cut off stop the fuel?  Whilst I could feel it operating I've never had great faith in it. Got a spare somewhere on the boat but finding it would be a task. 

Thanks 

 

Frank

 

Just had a thought. The place I've had the pump overhauled by in the past is only a couple of miles away. It's an old style one man band and he's really helpful. I'll pop over and see if he's open today He might have an idea.

 

 

Quote

Not much else is there!

1

Edited December 30, 2019 by Slim

[Albion]

20 hours ago, Tony Brooks said:

First thought - are the seals in the 296 filter correctly seated and not twisted, a very common cause of bleeding problems.

 

Next, although I don't normally advise doing it after bleeding the cylindrical body (which is what I think you mean) try bleeding from the bleed screw in the idle damper (top of turret) but put a spanner on the damper to stop it twisting.

 

Note - some 1.8s have a low pressure type bled screw in one of the high pressure injection pipe banjos on the pump, if loosening the injectors you should not have to touch this one.

 

Final desperation - leave the injector pipes loose but tighten the other bleed point. Remove the   injector pump return pipe from the filer end and direct it into a can. Spin in starter.

I agree with the idea about the filter as a friend of ours once used a replica CAV 296 style filter and had the same problems. We bought him a genuine 296 locally and took it along to him (as he was miles from the nearest shop local to where he got stuck) and, when fitted, it solved the problem so presumably there was some issue with the seals on the look-alike filter. Can't remember all the details now as it was years ago but it is worth checking as Tony says.

Roger

[bizzard]

Its a bit of a knack assembling the 296 filters. Make sure the 0 rings are properly in their grooves, if the upside down one under the top casting keeps falling down, grease it so it sticks up there, don't forget the wee one under the bolt head. Assemble, screw down the bolt, but not tight, just enough so the 0 rings just touch. Grasp hold of centre filter and turn it back and forth a bit, also the bottom bowl, while screwing the bolt down bit by bit. You will feel the seals rubbing on the filter. If you feel metal to metal scraping, stop and undo it again to check the 0 rings arn't dislodged. Gradually tighten the bolt whilst moving the the filter and bottom bowl until they won't move anymore, finally tighten down the bolt, not too tight but just so.   Its all about feel.

[Boater Sam]

2 minutes ago, bizzard said:

Its a bit of a knack assembling the 296 filters. Make sure the 0 rings are properly in their grooves, if the upside down one under the top casting keeps falling down, grease it so it sticks up there, don't forget the wee one under the bolt head. Assemble, screw down the bolt, but not tight, just enough so the 0 rings just touch. Grasp hold of centre filter and turn it back and forth a bit, also the bottom bowl, while screwing the bolt down bit by bit. You will feel the seals rubbing on the filter. If you feel metal to metal scraping, stop and undo it again to check the 0 rings arn't dislodged. Gradually tighten the bolt whilst moving the the filter and bottom bowl until they won't move anymore, finally tighten down the bolt, not too tight but just so.   Its all about feel.

Said with feeling. Note that the 2 large o rings are different sizes too.

Well described, don't forget the o ring on the inside spindle that seals to the inside of the filter, else you may as well not have a filter at all.

[bizzard]

2 minutes ago, Boater Sam said:

Said with feeling. Note that the 2 large o rings are different sizes too.

Well described, don't forget the o ring on the inside spindle that seals to the inside of the filter, else you may as well not have a filter at all.

Indeed.

[Slim]

As I said earlier I'm reasonably confident the seals were inserted/used correctly. The filter itself is Unipart 296 and came with a full seal kit. If I get to the point of removing the filter I'll replace all the components. I've got a couple of Delphi / CAV (at least that what the cartons say). filters on board. The thing is I've got a steady air free flow out of the pump bleed screw but not even a splutter at the injectors. I keep wondering if it's the cut out even though I can feel it triggering.That's whyI'm wondering where in the 'circuit' it stops the fuel flow

[Slim]

5 hours ago, Slim said:

Plenty of fuel and the vent is clear ,generator feeds from same tank. 

Haven't checked return pipe ,willdo so next visit.

There's pplenty of fuel up to the pump but none coming out of the injector pipes. Whether it's air free is another matter. When i turned the engine over with the cylindrical vent open a steady air free stream of fuel came out. Did this several times for 20-30 seconds at a time.

Where, exactly, does the cut off stop the fuel?  Whilst I could feel it operating I've never had great faith in it. Got a spare somewhere on the boat but finding it would be a task. 

Thanks 

 

Frank

 

Just had a thought. The place I've had the pump overhauled by in the past is only a couple of miles away. It's an old style one man band and he's really helpful. I'll pop over and see if he's open today He might have an idea.

 

 

1

 

He was closed.

[WotEver]

1 hour ago, Slim said:

 

He was closed.

You might have to wait until next Monday.  

[Ex Brummie]

Helped a friend once with a similar problem, and we could bleed with the lift pump through to the injector pump, but when turning the engine on the starter, it cut out. The fault was found as a leak before the lift pump which was not apparent under manual operation, but sucked air like mad when under greater suction. We heard a faint whistle after the engine cut out.

I once had a leak on the flexi hose into the lift pump on a Perkins which was not noticeable as fuel did not leak out, but air got in. I only found it when I got to the pipework immediately it cut out, and there was the slightest trace of damp on the rubber.

[Slim]

On 30/12/2019 at 21:58, Ex Brummie said:

Helped a friend once with a similar problem, and we could bleed with the lift pump through to the injector pump, but when turning the engine on the starter, it cut out. The fault was found as a leak before the lift pump which was not apparent under manual operation, but sucked air like mad when under greater suction. We heard a faint whistle after the engine cut out.

I once had a leak on the flexi hose into the lift pump on a Perkins which was not noticeable as fuel did not leak out, but air got in. I only found it when I got to the pipework immediately it cut out, and there was the slightest trace of damp on the rubber.

Not sure how to highlight sentences but the pipe into the lift pump was the answer. After heaven knows how many attempts to bleed system (flattened agood 110ah battery 4 times in total)  someone 35 years my  junior and far more supple got really close to the pump, felt all around it, gave the inlet pipe a tug and thought he felt movement. When the nut was undone there was no evidence of the olive having been compressed.  A few sseconds with a spanner and problem was resolved. The amazing thing is that that joint had held faultlessly for at lèast 10 years without a hint of a leak.  

Thanks to everyone for their advice and comments. 

 

 

 

 

[Boater Sam]

Thanks for coming back, most don't.

Glad you solved the problem, that does seem strange. Gremlin at work.

[Slim]

21 hours ago, Boater Sam said:

Thanks for coming back, most don't.

Glad you solved the problem, that does seem strange. Gremlin at work.

What I missed out was the fact that the thread was very short. When i did an initial spanner check uf all the connections the nut was tight. That and the fact that there was no sign of a leak fooled me into thinking the joint was sound. In fact it was the shoulder against the pump body not the olive compressing. 

As an aside 1/2" unf union nuts are a rare item an outfit on a Scottish island can supply 6 or 8 mm with olives but the thread part is very long wwhilst the only other ones i could find were £8 EACH

 

Frank

 

 

[Boater Sam]

3 hours ago, Slim said:

What I missed out was the fact that the thread was very short. When i did an initial spanner check uf all the connections the nut was tight. That and the fact that there was no sign of a leak fooled me into thinking the joint was sound. In fact it was the shoulder against the pump body not the olive compressing. 

As an aside 1/2" unf union nuts are a rare item an outfit on a Scottish island can supply 6 or 8 mm with olives but the thread part is very long wwhilst the only other ones i could find were £8 EACH

 

Frank

 

 

I think some of the pipes were assembled with longer olives and short reach nuts, don't know why but BMC were a weird company, they made a lot of their own nuts and bolts unlike most engineering companies.

[blackrose]

Glad you got it sorted. One thing's for sure though, swearing at your engine as per your title rarely helps.