Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

tree mechanic with a complete set of hand tools. If you're unsure of your
experience level or tool crib, have the job done professionally. Ensure that the
sub-assembly is completely cleaned and dried before disassembly as FI
systems do not react well to ingested dirt. It will require Volvo PN 1389562-8.
While you're replacing filters, don't forget the air filter -- you engine will always
run better with a new one of these! Again, a bit of basic maintenance that
should never be skipped.
5. If you lack a fuel pressure gauge capable of reading fuel pressure to at least
400 kpa and lacking the proper fittings, true troubleshooting will be difficult.
Your car's LH system is supposed to operate at a constant 300 kpa.
6. Lacking the proper diagnostic equipment, your only solution will be to replace
each component until the problem is solved. I won't list all of the possible
problem components as most situations are traced back to either the main fuel
pump or the pressure regulator. Use a long piece of hose to listen for the main
fuel pump as the car is being cranked. If you cannot hear the fuel pump turn,
check the voltage using a VOM.
7. If all is well, skip to the fuel pressure regulator. Replace the unit with Volvo PN
1389564-4, but may also be replaced by Bendix PN 4088942-0001.
8. If the car now runs, but frequently requires long periods of cranking to start,
then suspect the check valve in the fuel pump. The check valve is a threaded
in-line valve that maintains line pressure between 200-300 kpa after the engine
is shut off.
9. If the car still does not start, check the fuel pump relay. If in doubt, replace it
with Volvo PN 3523608-3.
10. If the car will not re-start while warm, check the radio suppression relay and the
rpm sensor (LH2.4) or Hall sensor (LH 2.2).
11. If the car stalls while hot, check the ignition power stage amplifier which is
cooled through body contact.
12. Regina-Equipped Cars: Check as well the coil pack and MAP sensor.
13. Conclusion. The beauty in the approach listed is that you first complete the
basic maintenance required; car's just won't run well without regular
maintenance! Second, you're using a rudimentary tool (the hose) to check for
fuel pump operation. That's important since the fuel pump is a very expensive
piece of gear that you would not really wish to replace unless it is dead. Third,
there's some merit in repair by replacement, especially if you lack the proper
fuel system diagnostic equipment. The pressure regulator is about $40 buck
and, with age, will eventually die anyway. So replacing it just saves you being
stranded at some point in time. Finally, the pump relay is the next most likely
culprit. [Editor's Note: See the notes below about rpm or Hall sensor and radio
suppression relays; these can also be frequent culprits.]
14. Hope this helps. Remember the merits of maintenance before trying to solve
any recurring problem.