Had a query from the new owner of an IVECO engined RML in Brittany.
Hasn't used it for a month, checked water and oil levels all round, started it up and it ticked over OK but oil pressure warning light stayed on and alarm sounded. Put it in gear, and took it for a short trip, bus functioning OK just alarm getting louder.

Appreciating diagnostics from afar is difficult, apart from actual low oil pressure could the switch be faulty or sticking?

Next problem came later when they tried to rev the bus up in neutral, hardly any revs at all, On the run round round in all gears the engine ran normally, but struggled to produce any revs in neutral.

First thought was stuck in gear was causing the loss of revs. Obviously letting go of the handbrake would tell if that is the problem, but is there any inhibitor connected to the oil pressure system that reduces revs on the IVECO refurbs?

My bus number (if any): RTL 960, RMC 1458 RM 1585 and several RTs

There's an inhibitor in most refurbs that prevent you getting revs in neutral once you've selected a gear. the only way to get revs again is switch off and start again. It's fun on the smoke test on MoT, not being able to rev up!

Sorry I can't answer the question about the oil switch.

My bus number (if any): RML2532

Thanks Roy, just to clarify, once engine has been started and a gear selected, putting lever back in neutral position puts the bus in neutral but does not allow revving up. Is that it?

My bus number (if any): RTL 960, RMC 1458 RM 1585 and several RTs

Not 100 % sure on this but isn't the alarm for low coolant in the reservoir ? RML2391 alarm works for low coolant level . Not sure if it works on the oil side of things tho' ?
As for reving in neutral RML2391 sometimes will rev or sometimes only gives a limited range of revs which can be a pain but I wonder if this is to prevent drivers' from revving the b*****ks off the bus when the engine's cold ?

My bus number (if any): RML2391

Yours is an ex-Leaside Cummins engined bus Mark, this one is ex LG IVECO, not all done the same when refurbed. Be interested to know if alarm is coolant as oil pressure light is on it's assumed that is the problem.

My bus number (if any): RTL 960, RMC 1458 RM 1585 and several RTs

Could be a faulty alarm / float switch . I've seen another cummins C with the wiring disconnected from the float switch which may have been done because it wasn't working correctly . But not a clever move to completely disable a warning device , its there for a reason !!!

My bus number (if any): RML2391

Brian

Just a thought, does the RML have a 551 gear control unit, if so I wonder if the problem is connected with the ' throttle dip function ' acting by way of a Parker Air Valve connected electrically with the 551 unit and cutting the throttle control whilst in neutral when gear changes are made. When the ignition is switched on the throttle lever rod is rigid or should be, it may be worth checking its function whilst the bus is standing in neutral to see if the throttle is maintaining a rigid link.

Thanks Ed, problem with is its 3rd hand diagnostics. Don't know what it has and the owner doesn't know much about Routemasters plus we are translating it all! I'll pass on your idea as I have Roy's theory about the inhibitor preventing revving in neutral.

Do you know if water level and oil pressure both have audible alarms? This is an IVECO ex AF London General bus.

My bus number (if any): RTL 960, RMC 1458 RM 1585 and several RTs

Ed and Roy are both correct. The 551 panel has an inbuilt inhibitor circuit to operate the throttle dip, thus restricting the engine to idling speed if the driver attempts to rev-up the engine when in neutral. This is to prevent damage to the gearbox should the driver select a gear at excessive engine revs. This feature is temporarily over-ridden when the air pressure falls below a set level.

There are also other features which were originally available. Any, or all of these may at some time have been by-passed or deleted from operation. The throttle-off 'coast' feature (existing gear held) is quite often not present.

The presumed oil pressure warning activation will have to be investigated and proved to be spurious.

Thanks to all that have replied, I'll pass on the information.

My bus number (if any): RTL 960, RMC 1458 RM 1585 and several RTs

If I remember Brian. The Bn ivecos had a similar system some worked some didn't. As Roy rightly says the throttle used to cut off once gears where selected and as for the low water/oil that didn't work either and was removed from problematic buses.
tony

My bus number (if any): 1083