3.9 efi vacuum system

skintnow · Dec 28, 2009

Hi folks bought a 3.9 efi partialy rebuilt have finished her off over christmas but am slightly confused by the vacuum pipe lay out any one got a picture of this or could tell me where each pipe starts and finishes i notice it has a valve on the back of the plenum chamber with 2 vacuum pipes from it does it matter which goes where
many thanks

fett · Dec 28, 2009

If I had mine on the drive I would go and have a look for you as I have done this for few peeps.

As its at the garage getting un-fooked at the moment have a look at this reply I did for someone else

http://www.landyzone.co.uk/lz/f10/vacuum-system-help-83277.html

classic kev · Dec 28, 2009

skintnow said:
Hi folks bought a 3.9 efi partialy rebuilt have finished her off over christmas but am slightly confused by the vacuum pipe lay out any one got a picture of this or could tell me where each pipe starts and finishes i notice it has a valve on the back of the plenum chamber with 2 vacuum pipes from it does it matter which goes where
many thanks

As far as I am aware the only vacuum line at the back of the plenum is to the fuel pressure regulator. Not sure what the other one is that you refer to. Post a pic, should be able to tell you from that.

fett · Dec 28, 2009

Dizzy advance and another to that ball thing I think.

skintnow · Dec 28, 2009

Have checked the ones you describe in that post fett thanks i have them all right it has a valve on the rear of the plennum chamber which has 4 wires to it and 2 vac pipes i cant take a photo as i would need to remove the plennum this is tight to the bulkhead just wondered if there was a right or wrong way to connect the two vac pipes she may now require an engine as she smokes like hell now running :doh:

nathan5346 · Dec 28, 2009

partially rebuilt? what work had been done and what work have you done?

fett · Dec 28, 2009

Was it the engine you rebuilt?

skintnow · Dec 29, 2009

bought it with the head gasket gone and the heads off checked the play in the cylinders and had the heads skimmed and rebuilt it now it smokes like a bitch on idle

classic kev · Dec 29, 2009

skintnow said:
Have checked the ones you describe in that post fett thanks i have them all right it has a valve on the rear of the plennum chamber which has 4 wires to it and 2 vac pipes i cant take a photo as i would need to remove the plennum this is tight to the bulkhead just wondered if there was a right or wrong way to connect the two vac pipes she may now require an engine as she smokes like hell now running :doh:

The valve with 4 wires is the stepper motor (idle air control valve). You said there were 2 vac lines at the back of the plenum. One is a vac line to fuel pressure regulator, the other, if I have understood what you are looking at will be a much larger pipe that goes from the throttle body area to the stepper motor, this is the idle air bypass pipe, not really possible to put in the wrong place.

Off the top of my head the other vac lines you are likely to have are vac pipe from top of air inlet to dizzy vac advance. From the left hand side of the plenum (when facing engine) there is one that goes to a small round ball (accumulator) which I think operates the vac system on the heater. There is another line that is much bigger for crank case ventilation and if you have ABS I think there is another pipe that goes to the brake switch to break vacuum on cruise control.

Really it would be easier if you get a pic or two up on here and then you can ask which pipe does what.

classic kev · Dec 29, 2009

skintnow said:
bought it with the head gasket gone and the heads off checked the play in the cylinders and had the heads skimmed and rebuilt it now it smokes like a bitch on idle

Have you done compression test? I assume if it has been skimmed the valves, seats and guides should all be good and the valve stem oil seals have been replaced. Have you checked/cleaned the flame trap and engine breather?

fett · Dec 29, 2009

Yeah its valve stem oil seals if its smoking on idle isnt it?

skintnow · Dec 29, 2009

hi kev thanks for the reply
when i stripped the heads they appear to be different and one head had no valve guide seals at all and land rover say that some heads between a certain period didnt so it looks like someone has done a bodge on this but all valves lapped in and no misfire on idle and at low revs she is fine it almost feels as though the coil is breaking down under load and it smokes on idle but not noticeable when driving

classic kev · Dec 31, 2009

skintnow said:
hi kev thanks for the reply
when i stripped the heads they appear to be different and one head had no valve guide seals at all and land rover say that some heads between a certain period didnt so it looks like someone has done a bodge on this but all valves lapped in and no misfire on idle and at low revs she is fine it almost feels as though the coil is breaking down under load and it smokes on idle but not noticeable when driving

I'm not sure that is entirely correct. I think you'll find that only the exhaust valves have stem seals (it could be the other way round though, can't rememeber off the top of my head

)

You say it feels like coil is breaking down under load - as in misfire? I assume you have or will be changing the coil to eliminate this. Part of the problem here will be in working out if you have an ignition misfire or an injection misfire - they are difficult to distinguish.

skintnow · Jan 1, 2010

have now replaced the coil but she is still very hessitant and does not want to rev smoothly above about 2500 rpm

ssmn1234 · Jan 2, 2010

fett said:
Yeah its valve stem oil seals if its smoking on idle isnt it?

If fair amount of smoke at first start up, it is good indication of worn stem seals, cause oil weeps down em when stationary and pools in the pots, when fired up clouds of smoke which diminishes after a while to nothinh noticable depending on amount of oil, could take 5 - 10 minutes at least to clear, till next time it sits for a while. Once running, the oil is still getting into pots but is being burnt immediatly before it builds up enough to cause noticable smoke.

All the valves should have stem seals, dont know how far back the LR fella is talking, but 3.9 has em on all valves.

On the smoking like a bitch on idle, it will most likely be wear in liners and rings and valve guides allowing oil to be vacuumed in, as at idle you have greatest vacuum in pots,also happens at higher revs but then its more to do with blowby pressurising sump area forcing oils up into pots . After a while this oil will foul ya sparkplugs, have you checked them.

one other area to consider for rough running is hydraulic lifters, if they're shagged can cause problems, but you should hear them if they the cause.

classic kev · Jan 4, 2010

skintnow said:
have now replaced the coil but she is still very hessitant and does not want to rev smoothly above about 2500 rpm

Check your ignition timing. Also check the operation of the mechanical and vac advance (if your engine has a distributor).

3.9 efi vacuum system

skintnow

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