Cummins 8.3 won't start

[targaracer]

So we bought a 2000 Monaco Diplomat with the 315 Cummins 8.3 yesterday. 2 hours down the road from the sale I was cruising down the highway when it quit. I had just turned off the cruise control and pressed the brakes (lightly for some traffic ahead). When I got back on the loud pedal there was nothing. I coasted to a stop and tried starting. It would crank but not fire. Fuel gauge showed just below half a tank

So. I got it towed to a cummins / frieghtliner dealer ( although I have a Roadmaster chassis). They scanned it and found no codes. All the fuses and connections were good too. Anyway, we finally tapped the fuel tank and it sounded empty so we addes about 11 gallons. It will now crank and catch for a little bit ( maybe 1-2 seconds) but won't run.

I've been turning the key and listening for the lift pump. We can hear it run and then shut off after about 30 seconds.

Any thoughts would be appreciated. I'd like to get home (still 6 hours away...)

Gord

[Steve Ownby]

Gordon,

I would add about 20 more gal to the tank. That big relatively flat bottomed tank can do things like that. If the 11 gal add just got the pick up tube wet it might still be catching air & not filling the filters completely. You may have a fuel gauge problem. Those gauges are electronic and subject to strange fluctuations. Just a thought. It's easy to try and if if it works you will feel like a master mechanic. Also remember once those fuel filters are empty it may take several tries to get them full so it may die several times.
If yours is an ISC and electronic , the act of turning the key to on for about 15 sec then off then back on again and repeat several times. This runs the fuel pump.

[H. Miller]

Next thing to try is the fuel filter (s)

[targaracer]

Its an ISB. I can hear the lift pump cycling with the key. When we drain the water separator its foamy and the tech cracked open the fuel filter it was full. I'll try adding more fuel and see what we get.

[Smitty77]

Congrats on the new RV!

And what a wonderful opportunity to learn more about the mechanical's of your rig.... Yeppers, that cup is half full - and hope the tank getting a bit more volume will prime this into full roar....

Get this one behind you, then go have a blast!!
Best,
Smitty

[Steve Ownby]

Gordon,

Your original post called out a Cummins 8.3. In 2000 the ISB is 5.9 liter. I never pay much attention to the hp rating because there is so much over lap and variation from year to year.

At any rate an ISB would behave the same way. Also make sure the chassis batteries are not marginal. The amp draw from the starter could be large enough that the fuel solenoid loses power and closes before the alternator can catch it up.

[Steve Ownby]

Hey Gord,

Sorry about screwing up you name. My spell check keeps collecting me and I didn't correct it.

Here is your brochure:

http://http://www.monacocoach.com/St...00Diplomat.pdf

The brochure calls out the ISB 275 hp as the standard engine and the ISC 315 hp as the option. Both are backed by the same Allison and both use an exhaust brake. You can't see the front of the engine easily with the rear radiator package but if you can get in there the ISB or ISC is embossed on the gear cover. If you can't a call to Monaco tech support with you coach number will get an answer. If you call Monaco ask them to email you a data card. That will give you much useful info.

[targaracer]

Thanks all. All in all I've added 25 gallons so there should be enough fuel. I've been using the house battery boost to make sure there is enough voltage. It cranks nice and strong. It will catch but not stay running for more than a second or two. It is an ISB 8.3. It was offered as an option in 2000

[freebirdbus]

Congrats on the new coach. If it ran out of fuel, there may be air in the high pressure lines. Are you sure you have a 8.3? The 5.9 has a "push pump" on the side of the injection pump that can be used to purge the lines of air. You should be able to hear the fuel push thru the lines after you pump it a while. Even with fuel on the low pressure side, the engine may not start until this is done. You may want to confirm which engine you have, and let us know that if it still won't start.

[freebirdbus]

You may need to 'crack' the hard fuel lines loose at the injectors to get the air out. Place rags around the fittings and have an extinguisher handy. Clean up and spills on the engine before driving.

[targaracer]

My mistake. Its an ISC but there was an isb manual included. Build sheet for the coach shows isc

[freebirdbus]

Have you checked the shut off solenoid? It should hold the pump rack slightly open when you go to start the engine.

[freebirdbus]

Four possible problems come to mind. 1) Lift pump screen or pump blocked by crud from the bottom of the tank. 2) Fuel filer(s) clogged. 3) Air in lines. 4) Shut off solenoid not retracting. Let us know what you find, please.

[targaracer]

Fuel pressure checks out ok and the filter is full