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dirt racer · 07-24-2016, 11:00 PM

Have a 1999 Newmar Dutchstar DP with a 8.3ISC engine that we bought in April. It ran fine for the 6 hour trip home after purchase and around home on some short runs, like 30 miles or so.
Left for vaca and made it about 4 hours and stopped at a rest area to check tires and tow dolly before going thru Omaha rush hour.
Took off and had some serious bucking but was able to get to speed, barely made it thru Omaha and decided to turn around a go to Cummins there.
It never had a light on in the dash nor did it have any stored codes.
They looked at it, decided to put filters on it that I had replaced a few days before and no change, they kept it over night and found a plastic chunk under positive cable on batteries, hooked up to insight and drove it for 11/2 hours with no issues and said they had it fixed.
Got down the road 20 miles a bucking came back and finally stopped and decided to head home.
Took us 10 hrs to do a 41/2 hr trip but saved us a 2K tow bill to put towards repairs.
This thing doesn't smoke, miss at idle and starts the second you hit the switch.
So after a buddy helps me with some diagnosis we decide to first eliminate the fuel lines and run a hose from back of lift pump to a 5 gallon jug of fuel,,still had no power,,even in neutral it won't go over 1600 rpm and is slow getting to that.
So he decides its got to be the pump and in a couple of days i start the removal only to find out that its been replaced before with a 9-14 date code on it and has had the suppressor replaced and new lift pump installed.
After I find this I'm having a hard time thinking its a pump problem so he comes back to help check fuel pressure this am and its got 15psi with key on and 180 at the pump when running up to the 1500 rpm mark. This was done by checking the pressure at the pump housing not lift pump housing.
I know that 15 psi is great for lift pump but is that enough pressure running above idle or when lift pump is off? Really couldn't find info on that part.
Question i have to anyone here is do you think it could still be a pump issue or am i looking for an electrical problem or both at this pointer something else?
We did not check to make sure its returning fuel ok but did check turbo, waste gate and exhaust brake and all are fine, and i also replaced the air filter before we left for vacation.
Would like some ideas before i take it to cummins.
Myfear with local shop is that even tho they are a good shop they don't do many Rvs where as cummins in DesMoines does and is also seem to know spartan chassis stuff after i called a talked to a tech there.

I just don't want to take it somewhere and have parts thrown at it with a big bill and be no better off than now.
By the way my buddy is more of a Cat guy and not fluid with cummins stuff but was big help none the less.
Thanks for any ides!

vsheetz · 07-24-2016, 11:12 PM

Sorry I can't help with engine issue, but somebody who can will likely come along. I do want to comment on the comment regarding a $2k tow bill - do you have a ERS via such as Good Sam or other? Towing should/would be covered.

MnTom · 07-25-2016, 07:46 AM

The first thing I would do is check the plugs for the injection pump. Unplug the plugs and look to make sure all the pins and connectors look the same. There is a possibility that a connector got pushed back and is not making a good connection. Keep in mind that there is a possibility of an electronic issue with the pump also. Another possibility (although slim) is the TPS. If it is giving flaky info to the ECM then it can cause run problems too.

jleamo1 · 07-25-2016, 08:17 AM

If it were mine, I would also do as recommended above check connections. Check your air charge cooler clamps and connections from the turbo to the inner cooler, put a volt meter on the batteries while running, make sure the alternator is working properly. Retrace the steps of the dealer that was working in the battery area. Check engine grounds and power to ECM, chassis etc.

mackwrench · 07-25-2016, 04:07 PM

I'm sure your Cat friend covered most everything....but sometimes the simplest stuff is the hardest to see....

I'll take a few WAG's......

I can't find lift pump supply psi either but will continue to look....Have you looked at fuel lines from primary filter to secondary filter? Or did you bypass all filters when testing... What you describe sure seems fuel related.
Does it ever completely shut off on it's own? If so, does it fire right up again or do you have to crank & crank till it states?

The fact that Cummins dicked with the batteries and somehow it ran for an hour and half may have something there? Keep in mind if the batteries are unhooked for a length of time the ECM will "reboot" and may clear any inactive codes.

Look for a fuse holder at the engine/chassis batteries, that is the main ECM fuse and sometimes corrosion there can be issue
Make sure there's no intake restriction, or exhaust restriction.....does it have a exhaust brake? Make sure it's not stuck closed.......

dirt racer · 07-25-2016, 10:04 PM

MnTom, did check all of the plugs, cleaned all and did look for pins pushed in. Nothing looked out of place and really had no dirt or fuel in them, pretty darn clean i thought!

jleamo1, did all those things with turbo and its all good and alternator is working as it should, forgot to mention that we checked it. I will start looking for grounds and start the cleaning process with them and also positive connections.

mackwrench, when we did the jug test we bypassed the primary filter and hooked into the inlet of the lift pump. Cummins mechanic told me 15 psi for lift pump but didn't say anything about running pressure but like i said its got up to 180 running at 1500 rpm.
Never shuts off on its own and never has.
I will unhook the batteries again and let it sit for awhile and see what it does after that tomorrow night.
Put new air filter on less than 400 miles ago and did take exhaust apart and looked at exhaust brake and its wide open.
i will look for fuse holder also tomorrow night and make sure nothings fishy with it.

I even talked to some older tractor mechanics today that has worked on these via case/IH and they had really no ideas for me either.

Thanks for the help and if any other ideas or know others that might would be appreciated!

jleamo1 · 07-26-2016, 06:25 AM

dirt racer, something just occurred to me. I read a post somewhere else, when the guy would rev the engine the exhaust brake wouldn't hold and drift closed. I know you posted you checked that but was it at full throttle? Maybe you can see its position with a mirror while someone revs it up? Just be careful if you have to crawl under it while its being revved up!

MnTom · 07-26-2016, 07:36 AM

I highly doubt that the exhaust brake is causing the bucking. The symptoms point to an electrical problem and there is a possibility that it is your injection pump. It is also possible that your ignition switch could be flaky, or even the ECM failing. If it was a fuel issue then you would have a lack of power when the fuel runs short of what you need.

**CountryFit** · 07-26-2016, 10:22 AM

what about the basic - how old the air filter? don't trust the air gauge too much. for a 17 year old rig, it's time to replace air filter regardless.

jleamo1 · 07-26-2016, 11:38 AM

Dirt Racer, I noticed your comment "just put filters on it" what make filter did you install? How many did you replace? what chassis make do you have?
Reason; some manufactures hide a fuel filter under the coach, I m wondering if one was missed. I have a Cummins ISL, when my primary filter has the slightest restriction it will buck violently. I replaced my Fleetguard with a Napa and it didn't last long at all, and until the bucking it felt normal. I experienced the bucking after it idled in traffic maybe 60 miles into a trip started to buck and the filter was brand new. Come to find out the Napa replacement for my primary is not the same GPH flow or micron as the Fleetguard it is supposed to replace. Switched back and no problems since.

mackwrench · 07-29-2016, 09:51 AM

dirt racer, where you go? Figure it out?.....inquiring minds want to know

dirt racer · 07-30-2016, 04:10 PM

Still working on it.
Filters are fleet guard and both the one on the motor and one on the chassis have been replaced twice in less than 300 miles.
Heres what we have done since last post:
Checked all grounds, cleaned and dielectric greased all.
Checked all connections on pump and ECM and main loom connections, cleaned and dielectric greased all then as well but wasn't anything out of ordinary with any electrical i came across.
Fuses and relays are all good and working.
Took apart exhaust and ran without muffler plus inspected exhaust brake, turbo and waste gate and all is fine.
Took apart intake system and no blockage or boots torn or rot, air filter replace 400 miles ago.
Took of return line and blew air thru it and all seems fine plus ran the motor again but no change with hose going to fuel jug instead of back to tank.
Checked ignition switch and it seems fine.
It does have a light on in the dash and have our local truck shop coming monday to hookup computer and see what it says.
Im out of ideas except i am confident I have done all i can to try to find the issue unless someone has other ideas.
Thinning it has to be the pump even tho the pressures seem good, or its the ECM but will have to wait and see what we find out monday.
Ill let you all know.
Another question i have is does anyone know of a rebuilder for these pumps besides going to Cummins? Really haven't heard good things about their pumps and don't need this to happen again.
And have read about push pumps at the tank to bypass the lift pump and would like any info or some place i can call to get that figured out.
Thanks all.

TR4 · 07-30-2016, 05:18 PM

Sounds like you've eliminated all you can. Get a good Cummins mechanic to read the ECM. The pump has a lot of different components. You said the gear pump pressure was 180 psi, that sounds about right. But from there the fuel has to go in and out of the accumulator past sensors controlled by the ECM.

May you only need a new sensor.

Here's more on the pump;
http://www.irv2.com/forums/f123/repe...lp-289659.html

Bill

mackwrench · 07-30-2016, 08:31 PM

Dirt racer, you've covered it......I'd wait till I could get the code, hopefully it'll be some that don't mean $$$$ .......

A few more WAG,

My loot says the ECM is good.....

is the coolant temp normal? There's 2 coolant sensors, one for the gauge and one for ECM.....I have seen them give a code but I can't remember how/if it affected performance.......

You've checked fuel psi with a manual gauge? The fuel psi sensor still could be defective and showing low/excessive pressure affecting timing at high rpm.....same with ECM oil psi sensor.

Hopefully the guy you got coming can check live data.....

Keep us up to date, we all need an education!

BTW.....what type of dirt racing y'all into? I was a wrench for many years on a limited Steel block and crate dirt late model program, went all over the southeast......but that's another thread