Help me AEU86, you're my only hope

[Nakilad]

(03-14-2021 09:32 PM)The Doctor Wrote:  Just something what came to my mind...

Similar problems on a mates volvo. Gradually got worse and worse untill it wasn't driveable anymore.
Looked like fuel pressure issues. Replaced everything, but no solution.

In the end the little hose which came off the fuel pump to the hard line outside the tank had a little split in it. So it would leak fuel back in the tank whenever the pump was making pressure. If the o2 sensor is reading leab, it must be something fuel related.

We measured fuel pressure multiple times and it all seemed OK (untill the end when the hose finally totally failed). But when the engine needed more fuel on the road, it just couldn't deliver it due to the split in the hose. When we took it out, it wasn't clear, but after further investigation we found the split in the hose.

I replaced the tank at the same time as the engine was rebuilt, replaced the internal line from pump to the housing like you described. Also, put an OEM pump in last year, just to make sure that wasn't an issue either. No change that I could tell.

I agree that it has to be fuel, somehow, but where? Fuel pressure jumps when blipping the throttle as per the Service Manual, also disconnecting vacuum line from the fuel regulator causes the pressure to rise, but funnily enough doesn't change to O2 readings. Its very odd.

Appreciate the idea though, keep em coming!

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(03-14-2021 11:36 PM)jondee86 Wrote:  Something to check... when the engine is idling, if you pull the vacuum hose off
the MAP sensor the mixture should go very rich. If nothing changes you need to
check the MAP sensor by applying a vacuum to the sensor and seeing how the
output voltage changes. The testing procedure is outlined in the FSM.

Cheers... jondee86

I've tried 3 different MAP sensors, no noticeable change. Disconnecting the MAP sensors causes the engine to stall, but I'm not sure what just dropping the vacuum line off will do, I'll try that tonight or tomorrow. Thanks for the idea.