Over boost switch?

[Bully]

Lately developed a problem when I get on the boost suddenly, everything cuts out hard. Like face through the windshield hard. First time it happened, I thought I'd blown the engine. Limp to side of the road, give it a minute or two and then all is well.
Car has not been running hot when this happens, and is not RPM dependent.
Any thoughts from the collective?
Many thx
DB

[Mocker]

Need more information. First, what year is your car? It might not have an overboost switch.

[Bully]

1985 Euro version car.
1 BAr spring
Larger intercooler
Rarely late exhaust
Everything else stock

[908/930]

What pressure was your boost at? Make sure you are not over boosting and the switch is ok. Take the switch off and apply pressure to see when it opens. Or you can try bypassing it, just install a small wire that is attached to ground with a spade terminal on it. Do not leave the bypass on permanently.

[gassian]

i would check your wastegate operation / lines

[mark houghton]

Really only two possibilities. You're either over-boosting and the switch is reacting as it should, or your switch is faulty. You could unplug the wire to the switch and ground it out to bypass the switch, and take a boosted run while closely watching the boost gauge. I don't remember exactly but I think a properly functioning switch will activate at 1.2 bar.
Suggestions from other folks here are right on.

[Alan L]

Yep - supposed to cut at 1.1 bar - so watch the gauge in case you do the bypass and it doesn't cut. Seconds are important - that tach gauge ain't super accurate. If it gets a shade over 1 bar and ain't cut, shut it down. Then as above , remove the switch and either bench test or replace.
Alan

[930cabman]

rear fuel pump

you can thank me later

[mark houghton]

Originally Posted by Alan L

Yep - supposed to cut at 1.1 bar - so watch the gauge in case you do the bypass and it doesn't cut. Seconds are important - that tach gauge ain't super accurate. If it gets a shade over 1 bar and ain't cut, shut it down. Then as above , remove the switch and either bench test or replace.
Alan

1.1, or 1.4? I pulled my switch the other day to test it and the inscriptions on it include the number 1.4.
Either way, I couldn't put much more than 1.0 bar to it with my crappy Chinese MightVac, and it did not open.

[gorskined]

Originally Posted by mark houghton

1.1, or 1.4? I pulled my switch the other day to test it and the inscriptions on it include the number 1.4.
Either way, I couldn't put much more than 1.0 bar to it with my crappy Chinese MightVac, and it did not open.

a small air compressor with a regulator works well or any bottled gas with a regulator argon, nitrogen, oxygen ex set reg to 10 lbs then slowly turn the reg to increase pressure.

[Bully]

Disconnected over boost and still have problem. I am thinking it is likely a fuel pump relay problem. Have a couple on order.
DB