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Patient is a '88 760 turbo, with the newer '960' style electrical system.
Background: Main pump has been unusually noisy recently, and will vapor lock (my current theory) in hot ambient temps if allowed to idle for a while after driving. Basically fuel pump moans and groans louder and louder until the car stalls out, will restart if you give it gas but wont idle or run until it cools off. Once you get it going again it'll run fine even with the pedal floored. The amperage draw at fuse 31 was low, about 5.5 - 6 amps. So, I knew everything wasn't kosher down there.
Last tuesday I was trying to investigate the pump mystery closer. As the car was running and starting to die down, I unplugged the prepump connector in the trunk and stuck my multimeter in there to check the amps on the fly. 2.15, and the car sputtered to a halt as it had already sucked a few too many air bubbles. I removed that round metal tube thing under the drive side kick panel trying to see the wiring better. No obvious signs of damage, so I decided to call it a night and try to fire it up one more time. And that brings us to todays situation.
Problem:
No start, cranks away just fine, but won't even offer to start.
Fuel;
- Jumpered main pump relay, both pumps run.
- Fuel pressure unknown, fuel present at rail.
- Main pump is an unknown aftermarket one, I took amperage readings under the car and it was drawing between 1.0 - 1.5 with the relay jumpered.
- The RSR insulation crumbled as I pulled it out so I jumpered that too
Spark;
- Pulled #2 wire, popped in an old plug and cranked, weak orange spark was present.
- Coil resistance was 11280 ohms, both sides were identical.
- Distributor cap is a year old Bosch unit, shows little carbon tracing.
Timing;
- Belt intact, did not check for skipping
Now I've read countless postings about weak pumps pulling in too many amps, but what does that low current draw mean then? Could it be a bad battery that provides enough juice to run the starter but can't provide enough for the accessories at the same time?
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