Community Forums

BobJones · 08-04-2020, 01:41 PM

Hi guys!

As I recall, the motorhome used to make a loud buzzing noise when you turned the key on but did not start it. It seems to me there was an auxiliary fuel pump or something of that sort. I'm going on memory but I'm pretty sure that when I used to change the fuel filters that I used to just cycle the key to get them to fill up.

The other day I changed what I think was the primary filter. I found it located behind the condenser in the side panel. Because it was empty after changing I cycled the key. I went back and looked and it had filled up....

But I didn't notice any noise, and thinking about it, it seemed it was some time since I heard that pump noise.....

Anyway, since the filter filled up, I was not worried about it. Today, I ran the unit for a little while to get some air to fill up my motorcycle tires. After running for a few minutes....the engine died!

I tried to start it a couple of times but no dice. This has me wondering if there is a transfer pump and because I haven't heard it for a long time....is the thing even working?

Any ideas? As I said, the fuel filter did fill even though there was no pump noise. This caused me to think it was working. Now, I'm not so sure...

Skip426 · 08-04-2020, 01:55 PM

Cummins , ISB and ISC , use the lift/transfer pump, mounted in similar location , although with different duty cycle ( run time ).

Filter may have gravity filled if fuel tank was full.

The pump may require the starter be bumped to start running , then continue running for 25>40 secs.
ICS. The CAPS fuel injector pump has a mechanical lift pump that takes over while engine is running.
ISB. The VP-44 injection pump requires the lift pump run continually while the engine runs as the VP-44 has no mechanical section. Fuel starvation can kill the VP-44.
For more details , please add engine type to your post .

ISB. is the 5.9l ; ISC, is 8.3L

Ivylog · 08-04-2020, 02:02 PM

When you turn the key on you should hear the lift pump run for aprox 30 seconds and then shut off automatically on a ISC. If it’s not running you need to find the fuse (at the back) that powers it. Cycle the key 4-5 times so the lift pump runs for 2+ minutes to fill the filters and get air out of the system.

kenwyatt · 08-04-2020, 02:06 PM

Little info on the engine would help, mine is a Cat. Ran it out of fuel in WV. ( please don’t ask) was a real bear to start. Know how mines set up but not sure what you have

jacwjames · 08-04-2020, 02:37 PM

When I first got our rig in 2008 I would change the fuel filters, put an empty one on and then cycle the key 4-5 times to fill it up. In 2014 I did this and could not get the rig started, I even put compressed air on the tank but NO GO. Finally pulled the fuel filter and prefilled it with clean fuel and I got the rig started.

Now I just go ahead and prefill the filter.

You should be able to hear the pump running if you turn the key and walk to the back of the rig, passenger side.

BobJones · 08-04-2020, 05:47 PM

Quote:

Originally Posted by Skip426

Cummins , ISB and ISC , use the lift/transfer pump, mounted in similar location , although with different duty cycle ( run time ).

Filter may have gravity filled if fuel tank was full.

The pump may require the starter be bumped to start running , then continue running for 25>40 secs.
ICS. The CAPS fuel injector pump has a mechanical lift pump that takes over while engine is running.
ISB. The VP-44 injection pump requires the lift pump run continually while the engine runs as the VP-44 has no mechanical section. Fuel starvation can kill the VP-44.
For more details , please add engine type to your post .

ISB. is the 5.9l ; ISC, is 8.3L

Wow - great stuff! Thank you for posting it. The engine is an ISC315
Gravity filling the filter makes sense because the tank is full. I just tried to start it again (now that it's sat for 3 or 4 hours) and it cranked for ~5 seconds (longer than normal but not excessive) and then fired right up.

In any event, as I recall, the pump made a real racket when turning the key and waiting for the glow plugs before starting. It does not do that anymore

I did drive it for about 3 hours the other day (prior to changing that one filter) and I found it to be pretty gutless. I don't know if that's normal but I floored it several times and it seemed I would have to wait.......

The primary filter (if that is what it was) had been in there since early 2010.....It's now new as is the oil & filter and the cummins fuel filter (the one on the side of the engine) and also the antifreeze filter.

Is it important to fix that lift pump? (assuming it's gone)

kenwyatt · 08-04-2020, 07:07 PM

Believe Skip is more familiar with your engine but dirty fuel and or filters will kill any diesel quick. Sounds like you are on track for getting caught up. Any filter in service sense 2010 is cause for concern

BobJones · 08-04-2020, 07:09 PM

That one has been replaced. I think what happened is that we were replacing the secondary filter. Either way, it seems the lift pump does not work. Does that only operate for a few seconds when the key is on or should it be repaired or?

Alpine36 · 08-04-2020, 07:24 PM

Yes, the ISC uses a lift "priming" pump that runs about 40 seconds when the key is switched to the run, or wait to start position. Ours used to make lots of racket prior to failing. It eventually quit all together and set a check engine light fault code.
Yes, you absolutely need that lift pump to work.
Without it, serious damage can occur with fuel starvation to the injector pump. Big bucks, you don't want to go there.
We scrapped the flawed/problematic OEM lift pump and upgraded to a FASS fuel system.
Go to the irv2 Cummins engine forum and search FASS. You'll learn why you need to upgrade from the original failing lift pump. AirDog is another good choice for an upgrade also.

Ivylog · 08-04-2020, 07:34 PM

The engine starting implies the lift pump is running for the normal 30 seconds... should be able to hear it before starting the engine. Once running the injection pump has a gear pump that supplies all the fuel you need, without the lift pump.

jacwjames · 08-04-2020, 07:36 PM

It should run for about 30 seconds and you should be able to hear it.

Suggest you go to the Cummins quickserve site and register, use you engine SN and get the information on your lift pump.

Alpine36 · 08-04-2020, 07:48 PM

Quote:

Originally Posted by Ivylog

The engine starting implies the lift pump is running for the normal 30 seconds... should be able to hear it before starting the engine. Once running the injection pump has a gear pump that supplies all the fuel you need, without the lift pump.

FWIW ours ran ok without the lift/priming pump working.
HOWEVER....bad things can happen to the injection pump in short order with a failed lift pump. The CAPS engines really like positive fuel pressure, something the OEM setup can't provide.
In fact, in stock form, the fuel delivery system operates in a negative pressure. (Vacuum) This is why CAPS engines are very prone to plugged fuel filter issues, when in fact with only a slight fuel filter restriction you can encounter performance issues or, worse yet, leave you stranded as a pedestrian with a lunched $5,000 injection pump.

BobJones · 08-04-2020, 08:26 PM

Quote:

Originally Posted by jacwjames

It should run for about 30 seconds and you should be able to hear it.

Suggest you go to the Cummins quickserve site and register, use you engine SN and get the information on your lift pump.

Done. From what I can see the lift pump is a little bracket with some kind of little filter under it. I don't see anything that looks like an electric pump.

Quote:

Originally Posted by Alpine36

FWIW ours ran ok without the lift/priming pump working.
HOWEVER....bad things can happen to the injection pump in short order with a failed lift pump. The CAPS engines really like positive fuel pressure, something the OEM setup can't provide.
In fact, in stock form, the fuel delivery system operates in a negative pressure. (Vacuum) This is why CAPS engines are very prone to plugged fuel filter issues, when in fact with only a slight fuel filter restriction you can encounter performance issues or, worse yet, leave you stranded as a pedestrian with a lunched $5,000 injection pump.

$5,000 !! Five thousand dollars !! I guess I'm going to look into that lift pump and fix it!! Thanks for the scare - it's just what I needed!

BobJones · 08-04-2020, 08:41 PM

According to the Cummins Quick Serve this is what my transfer pump should look like. I'm guessing the round part at the bottom that looks like a fuel filter is actually an electric pump?

Where would this thing be located?