Cummins Start up fault - Now doing my head in !

[superheat6k]

Again good prompts. Today I am going to check the fuel systems are primed and this will include a check of the lift pumps.

I also will use a temporary connection direct to the fuel solenoid from the opposing battery during start up.

If this does not get them started then I will remove the solenoid plungers.

I also noted the comment that energise to run solenoids are less than ideal. I am going to look at a mechanical solenoid that could pull the stop leaver. The existing ignition switches already have a disused stop position, so connecting these would be simple.

Separately I am ordering two new batteries so I can double the port / house to 220AH with 1600cca, and for the stbd a truck battery with 1000cca.

 

[superheat6k]

OK much better progress today.

Both engines had obviously not liked being run or attempted to run with the fuel supply shut off valves closed as both had air entrained at the injection pump, and this required a purge of the injection pipes loosened at the injectors too.

After this the Port engine started just fine and with the normal connection of the solenoid feed.

I then removed the Stbd solenoid valve (photo 1 shows the valve beneath the pump head) to try and run it with the valve pintle removed. I first checked the valve and then discovered that the pintle was not always pulling home properly. Closer examination showed the return spring just laying in the body of the solenoid to one side, but not located in the deep recess it should reside in. I also noticed a distinct wear patch to one side of the pintle (photo 3).

So it seems likely the valve had not been properly assembled when it was rebuilt last year, with the majority of operations not pulling back sufficiently for the valve to actually open.

So after a run with no pintle I then polished and reinstalled the pintle and with its return spring in its correct position (photo 4).

However, as the spring only sits loosely in the deep recess I cannot be absolutely sure this was the root cause, but after I re-assembled it the engine repeatedly started without an issue, in fact I didn't even have to re-bleed the engine despite the considerable amount if air it would have taken in when the solenoid body was removed the second time.

However, I am going to see if it would be feasible to install a separate energise to stop solenoid acting on the external stop lever on top of the pump governor assembly. Does anyone know if Lucas CAV offer such a device. Photo 2 shows the mechanical stop lever.

Thanks to all who have offered advice. I did suspect the solenoid from the outset, but had assumed it was correctly assembled from the pump rebuild, and the red herring of getting air drawn in has not helped. As this has now recurred several times over two years I think it is time for a new stop solenoid valve, or perhaps just an external stop solenoid instead. Ebay have several solenoid actuators listed, but not a massive amount of space in which to place it.

 

[Higgo]

Glad you're making progress and getting things worked out. Can you confirm the model/version of the 6bta5.9 engine and horsepower? I have the M3/370 HP version with the Bosch P7100 injection pump, sea water cooled aftercoolers and was under the impression you had the same. It seems you have a Lucas pump. Is it the 250 HP JWAC? Other than the fuel solenoid, linkages and lift plunger, the Bosch pump seems "plug and play".

Happy new year.... cheers

 

[superheat6k]

Glad you're making progress and getting things worked out. Can you confirm the model/version of the 6bta5.9 engine and horsepower? I have the M3/370 HP version with the Bosch P7100 injection pump, sea water cooled aftercoolers and was under the impression you had the same. It seems you have a Lucas pump. Is it the 250 HP JWAC? Other than the fuel solenoid, linkages and lift plunger, the Bosch pump seems "plug and play".

Happy new year.... cheers

Mine are the smaller output 210 HP with Lucas CAV DPA distributor pump, without the after coolers.

They both started today with an issue, however I have ordered replacement solenoid valves for both engines which were ~ £12 each. I am still going to up the battery capacity.

 

[Surfacesub]

However, I am going to see if it would be feasible to install a separate energise to stop solenoid acting on the external stop lever on top of the pump governor assembly

Whilst I'm not overly familier with your engines I think the engineering norm is to de-energise to stop. Obviously a continuously rated solenoid and to calculate a compatible lbf rating will be required. So by way of a suggestion and using a spring return off feature you then have a fail safe scenario! A spring being more reliable than an electrical source in a salt water atmosphere.

Also which may be of interest a majority of solenoids used on engines either start or control use switchable contacts (contained within) to energise a hold in lesser voltage coil to overcome spikes and an under voltage occurrence. Not unlike the early H T coils on petrol engines, and from memory a 6v coil and ballast resistor from a 12 volt source to overcome the same senario!

Don't be offended I'm far from perfect but a Diesel that is sound which yours obviously were (ie good on load) only need air and fuel, which is a good place to start. eg. if ain't broke don't fix it! I just feel for you having spent a fortune by adopting a process off elimination! I appreciate with some complex things this can sometimes seem the only solution!

Pleased to hear you finally cracked it.