Engine/Transmission (1998.5 - 2002) 2001 24V ISB Starting/running problems.

[Lumpy]

Hey all,



I have a bus that came into my shop a few days ago. It has a 2001 ISB 5. 9L in it. Origionally, it came in for lack of power, so we did a full service on it, and found the #5 injector line had been worn through and was spraying fuel all over the place. Replaced the injector line, and that's where things got weird.



After the fuel line, it didn't want to start, found that the lift pump had also failed. Replaced that, got the thing started, and now when you start it, it idles rough, or lopes almost, like an old big block with a nasty cam. It will run like this for about 15 seconds and then shut down, every time. Also, I have no throttle control after start up.



Pulled codes, and all I found was a code for boost pressure sensor voltage above normal, or shorted high. Replaced the bad sensor, and no change. Ran a data stream with Cummins Insite. Everything checks out. This thing had the VP44 replaced last summer, along with the crank and cam posistion sensors. Ran alright, except for lack of power, when it came in. Almost acts as if there is air getting into the fuel system, but I've checked, double checked, and triple checked all of the fuel lines, connections, filter housings and every where else I can think of.



Any input would be greatly appreciated! I'm about to light this thing on fire and push it off a cliff.



Thanks!

Kevin

 

[Sticks]

Pressurize the fuel tank with compressed air (10-12psi) for 15 minuets. You may have one of those fun hard to find leaks. Make sure you are parked on a dry surface so you can spot any new drops or puddles.

Is this a pusher or puller bus?

Blue Chip Diesel has a page on their website for manually testing the VP, kind of like the Cummins hi-lo box. You can isolate the engine from the ECM that way.

Double check the wiring connections around the #5 fuel line and transfer pump (if any) since that's were it last ran fine. Might have bumped something that is also rubbed through. Also double check your fuel pressure, just because it's a new pump does not mean it's good. I've had 3 bad out of the box.

 

[Lumpy]

I've already pressurized the fuel tank, no leaks that I can see at all.

What do you mean by puller or pusher? It's a front mounted engine, if thats what you mean by puller. I read about unplugging the harness from the VP, then grounding pin 6 and jumping 12 volts to pin 7 and trying to start it. If it fires up and runs, the pump is good, so I've been told.

 

[Sticks]

I'm not sure what the exact procedure is. I've alway's had access to the Cummins Hi/Lo box.

Read this VP44 Diagnostic

 

[mwilson]

I am betting the VP44 is toast where the lift pump was not working.



In non pick-up truck service a bad lift pump will kill a VP44 fast.



There is an update from Cummins that will kick the check engine light on if the lift pump quits, if this bus does not have it then it needs it.

We did a pile of buses and medium duty trucks with that update about 10 years back.

It has least gives the driver a heads up and increases the chances the vehicle will be brought to be checked out before the VP44 gets trashed.



Remember the bus uses twice the fuel of a pick-up and it doesn't take long for the VP-44 to get hot and commit suicide without a lift pump providing cool fuel.



Mike.

 

[cerberusiam]

it doesn't take long for the VP-44 to get hot and commit suicide without a lift pump providing fuel.

So THAT has been the problem all along!! The VP-44 comes with a built-in self destruct sequence. :-laf:-laf

 

[mwilson]

It must be built in, "I'm hot and I wanna' die!!" . :-laf





Cummins told me repeatedly that there was no problem with the VP44 fuel delivery system but then turned around and made us do the check engine light update on every customers truck or bus.



So it is not a problem but here is something that will help in the rare event of a lift pump failure... ... ... ... ... ... ... .



I still laugh when I think about it... .....



I think it was to help make sure the VP44 was out of warranty before it baked, was costing Cummins too much money... ...



Mike.