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zakthor zakthor is offline
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Join Date: Jun 2010
Location: beaux arts, wa
Posts: 426
Garage
muddled boost (and 2 cranks to start)

Hoping the collective wisdom will point to a definitive cause, or at least streamline the debugging. Car going to mechanic next week but it has never hurt to ask here.

Car is 1979 930, stock except for later exhaust.

Two symptoms started occuring at the same time:

1) When car has sat for more than 10-15 minutes it takes 2 cranks to start. First attempt the car will crank but not catch, second attempt it starts instantly.

2) Full throttle boost causes engine to sort of cut out. Happens at 0.3 bar in 1st, happens in 0.7 bar in 3rd. Engine seems to muddle, power drops down but not to zero. Can drive car at 0.6 bar in 3rd, no problem, but giving more gas seems to cause the muddle.

If given gentle throttle car will rev high. Except for boost and taking two cranks to start car otherwise drives normally.

More info:

- I can hear both fuel pumps are working.
- Fuel filter was dirty but cleaned.
- Tried grounding the pressure gauge on the back of the intercooler, made no difference.
- Tried bypassing the fuel pump relay in the engine bay and that made no difference (the one that makes the fuel pumps run for a little while after engine has been shut off).

Any ideas? I'd no idea how often I used the boost, its been almost 2 weeks and I really miss it!

Thanks!
Old 07-20-2011, 08:47 AM
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