200FT Hard cold start. Pulls like a train when warm.

[Laird Scooby]

Originally Posted by Dirty Rooster

What about that temperature sensor in the block under the inlet manifold?
If it's telling the ECU the engine is WARM when really its COLD ...

Generally speaking, if the CTS fails, it fails so the ECU thinks the engine is cold, like in Siberia type cold! It's designed that way so that if it failed and told the ECU the engine was hotter than it was, the ECU wouldn't supply as much fuel as the engine needed, resulting in overheated pistons and imminent engine failure.

[Danders]

Hello all. Apologies about my tardy response. I dropped in some Methylated spirits on Friday before heading off abroad for a wedding.

....I'm back now and greeted with the same old problem. I appreciate this may be the case as it would take some time to clear any water through the system.

However I did some other checks - I further checked the resistance of the temp sensor at the ignition ECU. All looks good. I wondered if spark may be sent off if it thought things were warmer-colder than they are.

I also this morning I only got the thing started after disconnecting the temp sensor. Prior to that I got extended crank, then evantually it caught on 1 or 2 cylinders and sat there jumping around for some minutes until it finally died. No response to throttle. I repeated this a few times before eventually disconnecting the sensor and it fired almost straight up...


In answer to some of the notes above;

- Would love to check the rail pressure, but my fuel pressure gauge wont attach to the bike-size schrader valve. Its on the cards, though. I'll work something out.

- Carbon brush inside the cap? Ive swapped the cap twice over for a new Bosch part (now just got a spare I suppose). I'm happy with the rotor arm in there.

- Im happy with vac pipes/intake leaks. I've spent some time with damp start, tryign to listen for rev drops/pick ups whilst squirting.

- Yes been a long and stressful process - its my only daily car. Changed lots and checked lots, but yes -I also feel like there's not much structure now to the diagnosis.

- PLugs all checked at .7 -.8mm

- throttle stop fine 'mode 2' and '3' on the diagnostics run through without issue.

My hunch really is that spark is fine - no dips in the tacho, timing is good, and spark on all plugs (when pressed against the head) in the non-start condition.

My hunch is that there is far too much fuel going in - putting the spark out and fouling the plugs in the first few revolutions.

--> Does anything else enrichen the mix during cranking? Apart from the temp sensor is there some logic to 'wet the walls' below a certain cranking speed? Could it be failing in 'wall-wet-mode'? I'm not too close with the LH 2.4 unit.

Thanks for your time.

[Danders]

Also - I'm trying to find a compression tester. I'm pretty confident in the comps but would be good to know.

[Laird Scooby]

Originally Posted by Danders

Hello all. Apologies about my tardy response. I dropped in some Methylated spirits on Friday before heading off abroad for a wedding.

....I'm back now and greeted with the same old problem. I appreciate this may be the case as it would take some time to clear any water through the system.


Thanks for your time.

Which car did you travel in to this "offshore" wedding? You need to add the 2L of meths into no more than 1/4 of a tank (the concentration is important) and then drive it. The returning fuel from the system helps to stir the fuel in the tank up and shift the water around so the meths has a chance to emulsify with the water.

There's a good chance that (if i've understood correctly) now you've got it started for the first time since adding the meths, it will start to do its stuff.

By disconnecting the CTS, you told the ECU the car is in Siberia so it made the mixture much richer. That further implies fuel quality is the problem, out of the extra fuel getting into the engine, a similar percentage of good fuel will be present in the extra quantity injected resulting in more "active" fuel getting into the pots. As such it fired.

You mention spraying "Damp Start" around the inlet manifold etc. Damp Start or Easy Start? They are two very different products and usually Damp Start isn't particularly volatile so won't alter the state of play.
On the other hand, Easy Start is ether which is volatile so will cause a change in engine note and could, as a test be sprayed directly into the air cleaner prior to trying to start the car first thing. If it then starts easier, that really does point to fuel quality.

I'm sure this has been mentioned before and whether you have one or not is open to conjecture, but you may have a cold start injector. This only operates for a few seconds during starter motor operation. Some versions of the LH2.4 had it, others not.

[Danders]

Put the meths in then jumped on the tram to the airport. This morning was the first try since adding it. Yep - concentration as you said.

Fingers crossed.


Damp start - pretty sure it was. None left now to check the bottle. Also used brake cleaner without any form of stumble or pickup.

Near positive on the lack of a cold start injector.

[Laird Scooby]

Originally Posted by Danders

Put the meths in then jumped on the tram to the airport. This morning was the first try since adding it. Yep - concentration as you said.

Fingers crossed.


Damp start - pretty sure it was. None left now to check the bottle. Also used brake cleaner without any form of stumble or pickup.

Near positive on the lack of a cold start injector.

Brake cleaner, surprisingly, doesn't burn very well in an engine either. Even WD40 (a petroleum distillate) isn't great these days but Easy Start will certainly find the leak if you have one. It could also relieve the starter and battery until you find the exact cause of the problem. If all the ignition side is ok as it seems to be that only leaves fuel. If there's a lot of condensation in the tank you will get an improvement but have to re-treat with meths in a month or two.

As you say, fingers crossed!

[AndyV7o]

It does sound to me like its too lean not rich... An engine will usually fire easier if a bit rich vs lean, if the sensor you disconnected does enrichen the mixture if not functioning (or disconnected) and it fired immediately then thats a very good indication of it being too lean.
Tomorrow morning, disconnect it again before trying, if it fires straight up you have a very good reference from which to work from.

[TonyS9]

+1 on the lean. I'd also suspect fuel pressure or injector(s).

You need a weak spark normally to get drowned sparks, the engine pretty much lives in rich land, except idle, which once in closed loop mode can compensate for low pressure or maybe 1 blocked injector. During warm up it won't be compensating for faulty items, and if its summery weather the management won't use much additional fueling (just like a carb car starts cold without the choke).

Can you use a tyre pressure gauge on the fuel rail? I'd nearly bet on the FPR at this point.

[Laird Scooby]

Originally Posted by TonyS9

+1 on the lean. I'd also suspect fuel pressure or injector(s).

You need a weak spark normally to get drowned sparks, the engine pretty much lives in rich land, except idle, which once in closed loop mode can compensate for low pressure or maybe 1 blocked injector. During warm up it won't be compensating for faulty items, and if its summery weather the management won't use much additional fueling (just like a carb car starts cold without the choke).

Can you use a tyre pressure gauge on the fuel rail? I'd nearly bet on the FPR at this point.

I still have mixed feelings Tony, either FPR or condensation in the fuel. Can see where you're going though!

[Danders]

I cobbled my fuel pressure gaugeonto the rail yesterday.

Sits happily at exactly 42PSI without manifold vac on the regulator. With the manifold vac on, its sits just under. A bit of boost and it goes over. All looks good.

I also checked the pressure this morning during the poor start event - all looks good.





Same as before though today - only started almost immediately when I disconnected the coolant temp sensor. I reconnected it straight after the start.

Whats really interesting is that after the start, with a code present and the sensor all reconnected, I turned off the ignition as I was driving along (still cold). Just to see. I then turned the ignition back on (effectively bump starting at ~2000rpm) and the engine did not re-fire immediately. It coughed and stumbled and I almost came to a stop before it sorted itself out again.

Its like during 'start' whether that's bumping or cranking on the starter, the fuel is totally wrong.

If it is that wrong and its only the lambda sensor thats trimming off the excess or adding a bit more when it goes closed loop, then surely I'd have a rich/lean fault.

Anyone know if you can read the current fuel trims from the LH jetronic?

...anyone know a good diagnostic specialist for Volvos in the North West? I'm starting to give up.




Andy