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Old 06-26-2018, 11:24 AM
v8volvo v8volvo is offline
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Join Date: Jun 2009
Location: Montana, USA
Vehicle: '86 745, '83 764
Posts: 1,618
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Leakage from the turbo outlet to downpipe gasket shouldn't be related to the symptoms you described. Leaks there will not affect boost or performance unless the root cause for the leak is a plugged muffler or other exhaust restriction downstream of the turbo creating excess pressure at the turbo outlet, which is extremely unlikely. There are much more common explanations that would be worth looking at before going after this.

These are textbook symptoms for a plugged fuel filter, 99% of the time this is the cause. I would start by replacing it, even if it was done fairly recently. One tank of dirty fuel is more than enough to plug a new filter and can happen anytime.

If it doesn't give you an improvement, check for other fuel restrictions. Plugged pickup in the tank? On your car, the original low pressure lift pump should run with the key on, so there should be positive pressure at the filter whenever it runs. If that pump fails it might create a restriction at the tank too. Confirm it runs and pumps fuel to the filter. One other trick that can help for diagnosing restriction upstream of the fuel filter is to install a hand primer bulb in the filter supply line and see if it collapses when the engine is running. Seeing it pull in a little bit if the car is pointed uphill or the tank is low is no big deal but if it sucks down flat then you have a problem.

If it ran properly before and now it's different, then there is a new issue and you want to find it before making changes to injectors, IP, etc. Loss of response or power at high RPM almost always means something is restricted somewhere. Fuel restriction is the usual cause, but if everything checks out perfectly there, look for intake air or exhaust blockage too.

Good news is it's probably something simple.
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86 745 D24T/ZF 345k lifted 2.5"
83 764 D24T/M46 155k
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