Rough on startup 945 B230FT

[jlawler]

The Beastie started running a bit rough on startup a couple of weeks ago.
Only lasted about 30 seconds before running normally but not quite as smoothly as I'm used to. There was also a smell of petrol at start up so I assumed it was an ignition issue. It started to get worse so I started looking for the culprit.

I found that cylinder No2 plug was wet with petrol just after startup and was carboned up (the others looked fine (new only about 6 months ago).

I got another plug and have systematically gone back through the system seeing if anything fixes it over a number of days as it's only really noticeable on a cold engine. I have swapped (and not fixed the problem).
1. Spark Plug
2. Plug cable.
3. Coil
4. Ignition Amp
5. Radio Suppression Relay.
There is a brand new Crank Case position sensor in the engine so I know it's not that. I have also checked the induction system for leaks (had that before) so the hoses are secure.

So I was coming around to the fact that it might be the injector.
Either not spraying properly or not closing properly and dripping into the cylinder when the engine is sitting there so flooding and not firing properly at startup from cold.

What are your thoughts?

Thanks

Justin

[TonyS9]

Test your compression, slight compression leaks can manifest in a misfiring as they warm up. It may take less than a minute to clear, but you will just have low power after that.

Run the engine with 4 plug lights and compare.

Squirt WD40 around the injector seals and manifold gasket.

Measure fuel pressure

Remove the fuel manifold with injectors and prime the pump (ignition on) check for leaks.

Test rather than use the part canon (except for parts that should be replaced anyway under normal servicing)

[Laird Scooby]

Try pulling #2 plug before you start it from cold. It might already be wet but not necessarily with petrol.

The RSR won't let any petrol in and on later engines (96 on) won't give any sparks at all so the fact the rest of the engine runs rules that out and the ignition amp module, Crank Position Sensor, coil and several other things.

It is as Tony suggested, likely to be a faulty injector leaking overnight, a bad plug lead (it is possible to have two faulty in a row), faulty dizzy cap or something causing loss of compression on that pot.

Does it misfire when hot on #2? Might be worth swapping injectors #1 & #2 to see if the cold start fault moves with it.

[jlawler]

Thanks for the guidance.

I'm picking up a set of plug spark leads tomorrow. They are somewhere in storage
To rule it out I'll test with anther plug lead.
I tried the WD40 test around the injector and inlet manifold but no change. The manifold gasket is only about 3 years since it was replaced so I would think that's Ok. The engine had a different kind of rough running when it was leaking. This has a feel of mis-firing on one cylinder and I'm just used to that usually being an electrical issue rather than an injector (first time for me).

I'll check if it's wet from cold in the morning.
I have a spare set of injectors I'm going to get cleaned and I have new seals for them somewhere. I'll try swapping No 2 first to see if it fixes it.

[jlawler]

I think I've found the problem.
Took out the plug and while it was damp it didn't smell of petrol
I disconnected the crankcase position sensor and HT lead to the coil and put a tissue down at the plug entry.
When I turned it over the tissue was damp but still didn't smell of petrol.
Replaced the plug and reconnected and turned it over. It started and running less roughly and then this damp patch appeared on the exhaust manifold and started to evaporate.

I think I have a leaky head gasket leaking into No 2 cylinder and therfor not firing properly until the water is cleared out. (sigh)
Coolant is a bit below the max mark but not something I'd be concerned about.

[Laird Scooby]

Originally Posted by jlawler

I think I've found the problem.
Took out the plug and while it was damp it didn't smell of petrol
I disconnected the crankcase position sensor and HT lead to the coil and put a tissue down at the plug entry.
When I turned it over the tissue was damp but still didn't smell of petrol.
Replaced the plug and reconnected and turned it over. It started and running less roughly and then this damp patch appeared on the exhaust manifold and started to evaporate.

I think I have a leaky head gasket leaking into No 2 cylinder and therfor not firing properly until the water is cleared out. (sigh)
Coolant is a bit below the max mark but not something I'd be concerned about.

Looks like HGF then

It seems you've probably caught it before it gets too bad so you'll probably get away without having it skimmed, will still pay to check or have it checked though. Renew the timing belt while you're at it and don't forget to retension after 600 miles!

[jlawler]

Yes absolute PITA.
The timing belt was only done last year and with the milage I'm not doing in the pandemic it doesn't need changing.

I'd need to totally disassemble if I was going to get it skimmed. I'd have to think about that. Is there anything special for removing the valves? If I get it off during the week I can reassemble next weekend.
In the mean time as i'ts my run around I'll loosen the expansion tank cap after I've driven it to reduce the pressure forcing more water into it.

Just thinking of what else I might do at the same time. The Skandix full gasket kit seems to come with everything (see photo)
Distributor oil seals?
I'll probably do the injector seals as well while I'm at it.
Is it worth doing the exhaust manifold studs?

It's an opportunity to change out the turbo drain sump seal as that's been dripping for while.

[Laird Scooby]

Originally Posted by jlawler

Yes absolute PITA.
The timing belt was only done last year and with the milage I'm not doing in the pandemic it doesn't need changing.

I'd need to totally disassemble if I was going to get it skimmed. I'd have to think about that. Is there anything special for removing the valves? If I get it off during the week I can reassemble next weekend.
In the mean time as i'ts my run around I'll loosen the expansion tank cap after I've driven it to reduce the pressure forcing more water into it.

Just thinking of what else I might do at the same time. The Skandix full gasket kit seems to come with everything (see photo)
Distributor oil seals?
I'll probably do the injector seals as well while I'm at it.
Is it worth doing the exhaust manifold studs?

It's an opportunity to change out the turbo drain sump seal as that's been dripping for while.

As far as i'm aware, just a normal valve spring compressor is needed to remove the valves. Obviously keep the shims with the valves and tappets in order, doing the cam seals front and rear will prevent oil leaking out into the dizzy or onto the timing belt.

While the valves are out and the head is being checked and/or skimmed, get a rotary wire brush wheel in your bench grinder or drill and use it to clean the valves one at a time (so they don't get mixed up) then when you get the head back, lap them in then reassemble enough to check the valve clearances and re-shim as needed.

In addition to the turbo oil drain seal into the sump, it might pay to fit new cooling hoses on the turo as well. Exhaust manifold studs on the head should probably be replaced too, might be easier to get the machine shop doing the skimming to do the exhaust studs too. Use new nuts and some copper grease on reassembly in case they ever need to be removed in the future.
Also renew the seal between the head and water pump, apply some silicone grease to it when you fit it in the pump and the head should fit tightly on top, the silicone grease helping it to stay supple and also to slip into the correct place.

The timing belt tensioner is designed to tension a new belt then retension it correctly after 600 miles, not for a used belt. For the cost of a new timing belt and continued peace of mind, it's not worth messing about, just fit a new one.

Think that covers most of the things you can do at the same time, obviously renew the engine oil and coolant (ethylene glycol), might pay to renew the thermostat if it hasn't been done in the past 2 years and budget for potentially a new Lambda sensor as they don't like antifreeze vapour which would have gone onto it as a result of the HGF. They don't always fail, just most of the time.

If i think of anything else, i'll add to it

[360beast]

You will only need to remove the valves if you are planning on doing a full rebuild, ie stem seals, valve hushers, decoke the valves and lap them in. If you're just wanting a quick job then take the cam out and you can get it skimmed like that as the valves are nowhere near the mating face.

I used a big G clamp and a lambda socket to remove my valves!

The distributor O-rings are about £4 for the pair from Volvo.

Only use genuine seals otherwise you will be changing them again shortly.

The exhaust manifold gaskets are NLA from Volvo but parts for Volvo sell the professional parts Sweden gasket which is the same as the originals, ie they are two metal mating faces with a gasket material in the middle that squashes down.

[Laird Scooby]

Originally Posted by 360beast

You will only need to remove the valves if you are planning on doing a full rebuild, ie stem seals, valve hushers, decoke the valves and lap them in. If you're just wanting a quick job then take the cam out and you can get it skimmed like that as the valves are nowhere near the mating face.

Many machine shops still insist on removing the valves though Luke, even though what you say is right. I think a lot depends on their skimming machine..........