T4 possible fueling issue.

[clarkey1984]

Hi all, driving back yesterday afternoon from Norwich heliport after my trip to the north sea this week and the t4 started having the odd little hiccup under acceleration, sometimes it did it and sometimes it didn't, this then developed into an absolutely huge flat spot on boost whereby it just will not rev above just over 3000 rpm, like there's some kind of rev limiter, it's not really misfiring as such, it just won't rev any higher under full throttle, but it will get there off boost or in neutral.

This also caused quite a jerky drive regardless of throttle position, resorting in me having to come to a stop using the handbrake and keeping the revs up, as it wouldn't reach anywhere near idle without simply cutting out, and was quite a pig to restart as well, trying to hold a fast idle of say 2000 rpm resulted in dipping inconsistent revs that would drop down to nearly 1000, then rise again as if I were revving it yet the throttle position remained the same.

On the odd occasion I let it drop too low I had to carefully blip it several times before it would finally climb again, the only thing I can liken it to is older cars equipped with a choke which you've pushed in too soon after a cold start, very light throttle will raise the revs slightly but any more will either have no effect or the engine just bogs and the revs die even more, there is also an accompanying fuel related smell, which is a hard smell to explain, I simply call it that lean smell, so my first suspect is either the fuel filter under the car or the one (is there more than one?) In the tank.

I stupidly took a good 6 gallons of unleaded out of the orange one and put it in this the other day using one of those pump up fuel suckers, and despite filtering it through one of those 20 micron paint filters (they look like a coffee filter) I suspect some gunk from the orange ones tank has got through, it's a major coincidence if it's unrelated as it's the last thing I did, around 100 miles ago.

I have already been and bought a new filter for under the car, and figure I can clean the in tank one(s), although incidentally on the journey there and back to buy a new filter the darned thing ran fine, which to me points to the in tank filters more, we have big suction pumps with gauze filters on at work and if they start to block switching them off and then back on causes any debris that's been sucked onto the gauze to fall away, so maybe there's something similar at play here.

So first job this morning is to pop the rear seat out and spin the retaining ring off to have a look, although if this proves to be clean and debris free I'll be at a bit of a quandary, as I'd expect these filters to block before the under the car cylindrical one as they are actually submerged, although I'll change the under car one anyway.

I may be back later if this doesn't fix it.

[aldred309uk]

I don't know much about possible reasons for your problem but the dirt in the fuel tank has merit. When running any dirt which goes on the in tank filter will get stuck on the outside due to suction and when the car is turned off, and the suction removed, the debris will fall away again.

I've also had a similar issue when driving a saxo a few years ago in the wet. The issue I had there was I went through a large puddle on the M6 and water flooded the engine bay. I suspect water got in with the plugs and coil pack and the car ran pretty similarly to what you have said. I parked the car up and after I returned to try and diagnose the problem about 20 minutes later the car ran perfectly fine again and never had an issue again. I presume and water that got where it shouldn't evaporated away. I gave all electrical connections a liberal spray of WD-40 and never had the issue again. If your car has been sat for a reasonable time whilst you've been offshore and the weather has been quite wet then maybe some condensation has got to where it shouldn't be?

[clarkey1984]

Found the problem, well, pretty sure I have, my question is how the hell it even ran like this?

Now my only issue is I have a yellow plastic washer, a black rubber o ring, and a spring, anyone know what order they go back in, as it all sort of flew apart and I don't know.

EDIT: found a post from someone called recognized in this thread which shows a picture of it disassembled, and the order of the bits i mean, what a legend https://www.volvoforums.org.uk/showthread.php?t=205207

[clarkey1984]

All done, normal service has been resumed, plus more besides, i dont think its ever tried to torque steer in third gear before.

A good scrubbing with a toothbrush and a container of fresh petrol got the filter pretty much white again, and i also scrubbed and washed out the bottom part of the housing too, then on refitting a little fairy liquid on the threads of the black retaining ring that holds the pump and sender assembly saw it tighten quite easily, and with no way of checking how tight it was i settled on light to moderate pressure with a piece of wood and a small rubber mallet until it wouldn't turn anymore, perfectly adequate id say.

Aside from a slight issue pulling the collar back on one of the hoses going to it, changing the one under the car also went without a hitch, as you can see that looked pretty ancient, nearly rusted through in places in fact, and i also found a large jubilee clip to secure the new filter into its plastic slot type thing, as the original fixing has obviously long since departed, the old filter was haphazardly cable tied around the handbrake cable, but all good again, she pulls like a train