2001 XC70 Cranks but won't start

[abscate]

You need to go back to basic no start troubleshooting, which coincidentally we are in the middle of developing a master thread on the P80 forum

Compression, fuel, spark, timing

There are several posts on other fora where people report DICE clones giving spurious error codes especially the COM errors on otherwise well running cars.

[altalake]

Possibly solved. After countless hours, diagnostics & clearing codes (not necessarily reliable with DICE clone), checking and cleaning connections (everything looking good), $300 worth of unnecessary parts and at least one tow truck, this showed up: loose ground screw inside the Upper Electronics Module (UEM) - the computer which is behind the lights next to the rear view mirror. Loose ground = intermittent problem, but is this something which would keep the car from firing up (about 10% of the time) and yet let it run when it does catch?

[abscate]

Yes, exactly that.

Pretty soon Im going to start a tally of 'fancy problems' vs bad wires/grounds.

Right now, its about 999-1 for grounds

[altalake]

Misguided optimism. Ground @ UEM disconnected and car started fine. Ground reconnected and car started a few times and now won't start - usual crank but no fire. Back to the drawing board.

[altalake]

Looking for more ground connections. Checked battery, 6 points on either side of the engine, main lead to engine and UEM lead (this one doesn't actually ground the UEM itself but feeds off to 2 other locations). Locations of others ground points not so obvious? (this car is a 2001 V70)

[regent]

I say you look for some help with your electrical here: http://www.volvowiringdiagrams.com/?dir=

[altalake]

Problem still unsolved but changed somewhat. This is either an additional problem or a variation of the 'cranks but does not start'. That issue, when it occurs during about 5% of starting attempts, will persist for 5 minutes to 48 hours, typically about 6 to 12 hours. No sequence of keys, locking/unlocking, battery disconnecting/reconnecting, tapping fuel pump, wiggling wiring, swapping relays has ever got it started - but it still eventually starts and runs fine when it does. No unburnt fuel smell so it seems fuel is not getting to the cylinders.
Now the car stalls periodically - 3 to 4 times in 15 minutes of driving. In one case an immobilizer message came up on the dash but on all subsequent events there have been no warning lights, all gauges appear normal until the car stops or I press the clutch so the engine can stop. After this the car will crank but not start but, if left alone for about 2 minutes, will start.
If there were no electronics it would seem like a simple fuel problem but the engine revs up over 5,000rpm easily on a hill climb and never misses - it's either all good or nothing at all. Fuel pressure about 50psi which is within specs.
Ideas?

[altalake]

Anybody know where the Fuel Pump Electronic Module (controller) aka PEM might be located on a 2001 V70? Supposed to be under the car in the cavity between the fuel filter and gas tank but is not there. Retrofit is supposed to be in spare tire well but it's not there. Some XC's have it in the RF corner where the alarm siren is located but I'm hoping for something more accessible. This car is a FWD V70 T5 (not XC), manual transmission. Maybe it doesn't actually have a separate PEM? (although VIDA shows a part number for it - but also shows it next to the fuel filter)

[abscate]

I have the same car, but 1999. I think the 1999-2001 are the same. I'll look mine over and see if I can find it this weekend, on travel

On edit...got that wrong, I think you are P2 chassis right??

[altalake]

Just got word back from a dealer. Apparently I can't find the PEM because it doesn't have one. Circuit now controlled by the CEM.
Yes, it's a P2.