Intermittent Misfire/Stalling 19TXD

[TheOtter]

Apologies if you've already tried this, but did you see my photo above? If you haven't eliminated this as a possibility, try pumping the priming bulb while looking for leaks around the white thermostat valve. This allows diesel to flow through the heat exchanger passageways between the thermostat housing and filter during cold weather.

If it's leaking there when pumping, chances are the O ring behind needs replacing. I have an overhaul kit but rather would like to keep it on the shelf - I can give you the part no. or measure the relevant O ring for you if you need though?

EDIT - you mention plastic to plastic mating surfaces on the filter housing - there should be a rubber seal which fits around the rim of the filter, to seal between the lid and rim of the housing. If this is missing then that's likely to be the problem. Either way, you've successfully isolated it to the filter housing so that's a good start.

Sorry Mat, I did see your photo and had a look, but I couldn't see any diesel coming out. That doesn't mean air isn't getting in though I guess (I'd like to be pessimistically hopeful here!), so maybe that should be my next port of call. I was going to ask what that funny white cross thing was for!

I'll have a look at that (hopefully on the weekend) and I might get back to you for a measurement of the O-ring, but unless mine is completely gone somehow then I should be able to match a new one to the old in there already.

Yes the rubber ring is there on the filter itself. I was talking about where the filter lid actually butts up to the rest of the housing - it's just two plastic surfaces. Maybe I'm imagining it wrong, but I thought the plastic of the lid seals to the plastic of the housing to stop air getting in/clean fuel getting out, and that the rubber ring seal is there more to stop dirty fuel mixing with clean fuel?

EDIT: Just wanted to say thanks to everyone for their suggestions! I wouldn't have got this far without all your advice for the fault finding! Boy I hope this is just an o-ring that needs changing

[mat_fenwick]

The rubber seal on the filter should sit in a slight recess, and seal between the housing and the lid so that there is no direct contact between the fuel and the plastic/plastic mating surfaces. So it's effectively sealing the filtered fuel from the dirty, but also keeping both from the air. (Or should be!) I've heard it mentioned as a source of air leaks, but never experienced it personally. I guess if the filter hasn't been changed recently the seal may have compressed beyond the point at which it seals.

The only other thing I can think of is the bleed screw on the front of the housing. Worth nipping it up, and I don't recall whether there is an O ring on that too. A blob of grease might be useful as a temporary seal to see whether it stops or reduces the amount of bubbles.

[TheOtter]

The rubber seal on the filter should sit in a slight recess, and seal between the housing and the lid so that there is no direct contact between the fuel and the plastic/plastic mating surfaces. So it's effectively sealing the filtered fuel from the dirty, but also keeping both from the air. (Or should be!) I've heard it mentioned as a source of air leaks, but never experienced it personally. I guess if the filter hasn't been changed recently the seal may have compressed beyond the point at which it seals.

The only other thing I can think of is the bleed screw on the front of the housing. Worth nipping it up, and I don't recall whether there is an O ring on that too. A blob of grease might be useful as a temporary seal to see whether it stops or reduces the amount of bubbles.

The filter is brand new (obviously with brand new seal), so I'm ruling that out for now.

That bleed screw, is it right in the middle and quite low down? Does it usually have a piece of rubber tubing going down the engine and out towards the floor? If so, I was also wondering what that was earlier! Will give it a check tomorrow, cheers!

[mat_fenwick]

Yep, that's the one! Although the tubing often is missing. Should have said drain screw really, as the main purpose is to drain off any water in the filter housing.

[Defender110]

Another possibility that I have seen before is the primer bulb getting weak and they suck themselves in when under load restricting fuel flow then pop back out again when the demand has stopped.

[TheOtter]

I changed the o-ring on the thermostat valve thing (thanks muchly for the suggestion Mat, it was very cracked), and I added a small o-ring in behind the rubber disc that sits on the inside end of the bleed screw, just to pack out the seal for that.

The problem still exists... EURGHFLAJIBBLEWIBBLEAAAAHHHHHHHHHHH

Is it possible that the entire plastic filter housing is not seating properly on the alloy part below? If that would even cause an air leak anyway? I see it's held on with a single bolt inside? If that couldn't cause a leak then I must've diagnosed this wrong and I'll need another session with the clear tubing!

[themildbunch]

This can be frustrating but you'll feel great when you fix it!! - had a similar fault on mine that uses the earlier filter housing but with a lucas pump... It was the filter housing and In the end I permanently plumbed in some clear line between the filter and pump like VW use on some of their diesels. Gives you an early warning of problems. You can buy diesel resistant clear line and metal ferrules so the clear line can be clamped to rubber hose.

The Lucas and Bosch pumps work in different ways so IIRC a leak on the return side of a Bosch pumped diesel will cause problems which wouldn't happen on a Lucas equipped car... Maybe not your problem here if the bubbles are only between filter and pump but worth knowing..

[sdelasal]

Just to resurrect this thread for the record. I just changed the o-ring around the white thermostat valve in order to cure a dribble from it and what I assume/hope is a source of air leak. Here's how I did it.
- Remove the plastic intake manifold to get access to various hose clips. Make sure you stuff clean rags/tissue into the alloy intake runner, now open, to ensure nothing drops in them by mistake!
- Remove the four bolts securing the filter housing lid. Remove the filter element and its large o-ring. Remove the 13mm bolt in the centre which locates the plastic filter housing to the alloy mount underneath. Retrieve the large o-ring.
- You should now have the black filter housing in your hand and next step is to remove the metal 'star' washer which keeps the white plastic thermostatic element in place. What I did was used a pair of long nosed pliers to rotate the star washer at the same time as applying pressure so as to pull it out of the housing. I think if you simply try levering on the star tabs, then it'll break.
With star washer removed, next step is to remove the white plastic element. It's important to first get it moving as it will likely be gummed in place. I used the same trick and gripped it with long nosed pliers to get it ROTATING. When it's moving i applied some pull pressure and out it popped.
- Remove the o-ring - I measure 17mm ID and 2mm width. I found a replacement.
- Clean everything up - removing crud, debris. Also clean up the outer edge of where the star washer will sit - to remove any torn plastic which will act so as to catch on the new o-ring.
- After replacing the 17mm ID O-Ring, oil the o-ring and where it will sit in the housing & pop the white plastic thing back into place in the housing. Rest it on a large cloth so as to steady it. I used a 10mm socket and gave it a sharp tap to knock it into place - the o-ring will tend to resist movement. I then used the same socket to pop back the star washer.
- You are now ready to start re-assembly. I reused the o-ring between plastic housing and alloy base as it was fine. Make sure you clip it in place on the housing. Clean out the tapped hole where the 13mm bolt will locate. Remove any diesel fluid in there, otherwise there is a risk of hydro-locking damage as you tighten the bolt into a hole full of diesel with no-where to go!. Tighten back the 13mm bolt securing everything together.
- after that, its a case of making sure all fuel lines are secure, remove the rags protecting intake runners & fit the intake manifold. Prime the fuel system and fire her up. Cross fingers and check there is no diesel leaking from areas you have disturbed.
Steve