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1991 940 compression test

vcolper

vcolper

New member
Joined
May 4, 2008
Location
North Port, FL
I just purchased a 91 940 Turbo. Odometer stopped working at 140000. PO says its been many years broken, so we dont know mileage (a lot I'm sure).
When I go to start it it seems weak. Battery is good (12.75 volts). it always starts up, just not like my other Volvos...it takes a little longer.
I did a compression check (cold): results: 128 to 137. Not impressive.
Could this be my "slow start" cause?

The car is also not as responsive/quick as my 242T. Boost gauge doesnt go much in the boost side...maybe 1/8".

Comments, suggestions appreciated.

Thanks,

Vic
 
Those numbers are entirely too low. Should be *at least* in the 150's (the lowest I would "accept" to squeeze out of a HG job) and to spec in the 170's.

It could definitely be the reason for your slow start and IS definitely contributing to the responsiveness and low boost pressure.

Just crack the head off and slap a new gasket in there, it's super easy on these cars. Make sure your 14MM socket (head bolts) is an impact (black.) I broke about 3-4 normal sockets on the first head stud before I gave up and got an impact.

Other things to do while you're in there... Exhaust manifold gaskets, intake manifold gasket, new turbo drain gasket & o-ring, new water pump/gasket, (at least clean pref. new) PCV breather box and hoses, front cam seal and obviously the valve cover gasket. While you've got it torn down, inspect all parts.. Vacuum lines, intercooler hoses (specially the airbox->turbo hose), timing/accessory belts.

Of course this is not including general maintenance items that you may also want to replace.. New dizzy/rotor, new plugs/wires, new fuel filter, oil filter, fluids, etc.
 
As long as the numbers are even look elsewhere for the problem. And try another gauge and see if the numbers differ as gauges can have large variance depending in quality and calibration.

My engine is 110/cyl but it still starts fine and makes 350+who just fine.


Do the basics of getting the car back to stage 0 as they call it.

Low boost can be normal as many cars only ran 4-5psi stock while others were 8-9psi stock.... At full random on factory boost setting.
 
compressor bypass valve. The round thing on the front of the turbo with vacuum line going to it. 3 small bolts to remove the cover and check the rubber diaphragm, and inspect/replace the vacuum hose that goes to it.
 
Update:
Just checked the CBV diaphragm and it's toasted/brittle, all cracked and has a hole in it.
Any ideas where I can get one? I think it's the Mitsubischi turbo. Although it says Volvo on it.

Thanks for the help.

Vic
 
if yer not makin BOOST yer not makin POWAH...

see post # * 5 * (the bit about ESTAGE ZEEROW)
go thru the engine and controls and get it all up to NEW SPEC
(this means NEW plugs / wires / cap / rotor / filters / check for
VAC leaks / set the valves check the ignition timing / check the FUEL
PRESSURE / put an INDEPENDENT GAUGE on the inlet side to
verify your level of BOOST / check all yer TURBO PLUMBING (hoses etc)

you have to have a LOAD on the engine
for the "boost to work" free-wheelin' don't mean squat!
see post # * 3 *
 
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