No boost

[TonyS9]

Originally Posted by vickyg

Driving the boost gauge won't go past say 11 o'clock. We have some steep hills nearby (17%) and it barely crawled up, didn't think I'd make it home at one point. On the flat someone who didn't know better would probably think it was just a really old slow banger. It does accelerate but v.v.slowly (no turbo engaging) and no more than 50-60mph. Can be hard to judge as the speedo often doesn't fire up until you've been on the road a bit!

Ah ok thats different, 12 oclock onwards on the guage is boost or positive pressure above atmostpheric, before that its just a vacuum gauge (negative pressure). Idle has the most vaccum as the throttle is closed, when you open the throttle the pressure rises closer to atmostpheric.

Your original assertion that there was no boost was correct, you just misread the boost guage which I tended to trust more. It was telling you there was no boost. afterall.
Have you have the front pipe off the turbo and checked if it can be spun?

[Laird Scooby]

Originally Posted by TonyS9

Ah ok thats different, 12 oclock onwards on the guage is boost or positive pressure above atmostpheric, before that its just a vacuum gauge (negative pressure). Idle has the most vaccum as the throttle is closed, when you open the throttle the pressure rises closer to atmostpheric.

Your original assertion that there was no boost was correct, you just misread the boost guage which I tended to trust more. It was telling you there was no boost. afterall.
Have you have the front pipe off the turbo and checked if it can be spun?

Another thought crosses my mind - an obstruction in the air intake. Even if the turbo has siezed, it should be possible to achieve zero vacuum (the 12 o'clock position i believe?) which suggests there is an obstruction somewhere in the intake. Perhaps a collapsed air filter?

[TheLeeds]

Originally Posted by B10B

................ you may well have a partial blockage in the exhaust............

My 2.3 lpt has similar symptoms, although it still revs fine. I've known these 940s having blocked silencers before. On my last 2.0 Wentworth, it suddenly lost power on a motorway slip road. I thought the turbo had died. This coincided with the centre silencer starting to leak, and when I looked, it appeared to have blown apart at the side. I did away with the silencer and replaced it with a straight bit of pipe which I had lying around. Before running the car again, I fitted a known good 2nd hand replacement turbo, and the car went very well afterwards, so I don't know whether the exhaust was the problem all along, or if the old turbo had failed.

[tofufi]

Originally Posted by Laird Scooby

Another thought crosses my mind - an obstruction in the air intake. Even if the turbo has siezed, it should be possible to achieve zero vacuum (the 12 o'clock position i believe?) which suggests there is an obstruction somewhere in the intake. Perhaps a collapsed air filter?

When my turbo seized, it was pretty tough to get the gauge to 12 o clock, iirc

[stephend]

Originally Posted by Laird Scooby

Another thought crosses my mind - an obstruction in the air intake. Even if the turbo has siezed, it should be possible to achieve zero vacuum (the 12 o'clock position i believe?) which suggests there is an obstruction somewhere in the intake. Perhaps a collapsed air filter?

+1 to this, at least as an easy thing to check. Happened recently to a friend's Peugeot. You could see the hose from the turbo to the intercooler visibly imploding when she revved the engine. It turned out the air filter had ripped itself apart, and the remains had blocked the hose leading to the turbo!

[vickyg]

No blockages just the stuck wastegate arm, which if stuck in the open (?) I believe will mean no boost. Hopefully will have the turbo off today to see if it can be freed up.

[vickyg]

It hadn't seized as such, the cotter pin holding the arm on was gone and it was partially off. Vacuum end very stiff with oil in lots of places where it shouldn't be lol, all cleaned up and put back, we renewed a hose. Boosting perfectly. I also sealed the diaphragm hole while I wait for new one. No more overboost, no lag (which I sort of miss) just smooth acceleration! We're back on the road!

[Laird Scooby]

Glad you got it sorted and it's running as it should. Hopefully plain sailing for you now but there's always something to do on older cars, it's why we love 'em!

[volvo always]

Originally Posted by Laird Scooby

Glad you got it sorted and it's running as it should. Hopefully plain sailing for you now but there's always something to do on older cars, it's why we love 'em!

Glad you got the turbo boosting issue sorted.

I'll be under my 96 940 LPT changing the oil cooler hoses Saturday as last weekend too busy.

Hope it's a dry few hours.

James

[vickyg]

Originally Posted by Laird Scooby

Glad you got it sorted and it's running as it should. Hopefully plain sailing for you now but there's always something to do on older cars, it's why we love 'em!

Yes I'm waiting on some starlock washers to arrive from Amazon to push on the shaft to keep the arm on as the hole for cotter pin option is not viable. Then it's the sunroof seal, heater valve, some welding required under the jacking points....thanks for remind me