Loss of Speed and Power

[Chief55m]

I thought I would share an experience in hopes others will benefit. I was returning from the Tampa Supershow and after passing through Macon on I75 I started to lose speed and power going up any grade whatsoever. Down hills no problem. As soon as I hit a grade, slowed down to a point of 45mph was all I could do.

My last service was at 15,500 miles at Spartan (full engine and chassis), current mileage is 29,000. We made it home, so the next day I went to Cummins in Atlanta and left the coach for diagnosis.

Cummins ATL is great, albeit expensive. After running diagnostics (almost $900, including labor) it turns out I have air in fuel filters and some debris. They replaced Fuel Filters FS1098 ($67.67) and FF63009 ($41.03). My total bill was $1,145.

These filters had a little over 14k miles on them – is that too much?

Anyway, I typically get all my fuel from large truck stop locations – Loves, Pilot etc.…. However, I have on occasion went to small station to save a little $$. Cummins offered no opinion as to what caused the filters to fail. So, I don’t really know if the fuel was the cause.

I had planned on an annual service at about 15k miles. I have to rethink this now.

Thoughts? TIA

[brobox]

The filters are 15,000 miles with perfect fuel, so 14,000 was pushing the limit. I carry spare filters and a strap wrench for just that reason, never know when bad fuel will be delivered. I once got a tank of watered fuel from a nice clean Pilot. Did someone leave the tank cover opened and it rained, bad fuel in the truck, who knows, but I got it. Thankfully filters on board and the next Walmart parking solved the problem, along with 10 bottle of diesel HEET from the Walmart auto section.

If loss of power is experienced, change filter before going to a shop. $900 to diagnostics a common problem, bad fuel filters is a little overboard, or the mechanic is a little slow and padding the clock. Good post for others, carry spare filters, even if you can't change them, roadside service can at a lot less money.

[Craig36]

Hi Steve,

Your post is timely. I just experienced the same symptoms on my Newmar. Loss of normal power and a drop in mileage of a little over 1 MPG.

I also have a Spartan chassis and Cummins engine. I just dropped it off at my local repair center and told them to first replace the two fuel filters and air filter. Seemed to be a good first step.

I typically replace all of them when I change oil once a year, regardless of mileage.

[buddy110]

Originally Posted by Chief55m

I thought I would share an experience in hopes others will benefit. I was returning from the Tampa Supershow and after passing through Macon on I75 I started to lose speed and power going up any grade whatsoever. Down hills no problem. As soon as I hit a grade, slowed down to a point of 45mph was all I could do.

My last service was at 15,500 miles at Spartan (full engine and chassis), current mileage is 29,000. We made it home, so the next day I went to Cummins in Atlanta and left the coach for diagnosis.

Cummins ATL is great, albeit expensive. After running diagnostics (almost $900, including labor) it turns out I have air in fuel filters and some debris. They replaced Fuel Filters FS1098 ($67.67) and FF63009 ($41.03). My total bill was $1,145.

These filters had a little over 14k miles on them – is that too much?

Anyway, I typically get all my fuel from large truck stop locations – Loves, Pilot etc.…. However, I have on occasion went to small station to save a little $$. Cummins offered no opinion as to what caused the filters to fail. So, I don’t really know if the fuel was the cause.

I had planned on an annual service at about 15k miles. I have to rethink this now.

Thoughts? TIA

I'd bet fuel filters. I had the same issue at ~9,000 miles. After changing the filters it cleared up

[znt1186]

Both of you faired a lot better than I just did. I was getting an intermittent check engine light. Happened about this time last year and shop could not find anything. Ran great all summer. Started again this year and went to a different shop. Analysis, two bad injectors. $4,000 later it is running fine. Had filters changed numerous times to no avail. You just never know sometimes.

[twinboat]

Fuel is dirty, no matter where you by it.

Change the filters at 10,000 miles and you should be fine.

Did they address the air in the filters ?

That's a sign of a slight fuel leak on the suction side of the filters. It may not leak fuel out but can suck air in.
Even with plugged filters, there is no way for air to get in the filters unless its pulled in at a leak.

Sometimes its just some loose fittings or clamps.

[Gary.Jones]

OK, I will share my experience also since Chief brought it up, and our stories are not a lot different, but maybe a different reason that is also good to get out there for other owners.

My situation was similar in some ways and different in others. For approximately the past year, or maybe even for the entire time that I have owned this coach, I have been impressed with how little power this 605 Cummins has when trying to do a fast acceleration such as climbing an upramp to an interstate starting from a dead stop at a traffic light, or simply coming out of a rest area and standing on the fuel pedal to come up to speed quickly when merging. I have previously posted that I was surprised at how "listless" this Cummins was in first and second gear. I was really surprised about how little get-up-and-go I got when I needed it (at slow speeds).

I have experienced this off and on for at least a year. In contrast to acceleration, this 605 really pulls hills and maintains speed on some surprising grades. So, its got lots of powder. On the way out here to Quartzsite, I had lunch in a reststop and stomped it on the way out to accelerate. Again, not much power and the Cummins threw a code: Cummins 559, FMI 18 (Moderate severity). So called Spartan... checked Spartan app.... the 559 code indicated that the fuel pressure at the "Fuel rail" was low. Serious but not the highest level. So decided to turn back to Cummins-Odessa to try to avoid a tow truck. Of course, Saturday. Waiting until Monday morning.

Mechanic started essentially at the fuel tank to measure pressure of fuel in line. He quickly said that I had a lot of air in the line but unsure from where. He worked himself back to the Cummins and then the primary fuel filter. He didn't have some fitting he needed to check the filter so asked if he could just change filters. I said "Sure". As soon as he put the strap wrench on the filter, we both noticed that the filter turned almost before he put any muscle into it, and we both said.... "Boy that filter was loose". When he removed it, we noticed another issue. There is a separate "O"ring on top of the filter. One side of the ring (that should be up) is flat. the other side is peaked. The peaked side should be installed down into the groove on top of the S3238 RACOR filter. Mine was installed with the peaked surface up which was wrong.

So, we tehn changed the primary fuel and the secondary fuel filters (I had spares aboard). The diagnosis was that someone at Spartan installed the O Ring upside down or Speedco installed it upside down and didn't bother to tighten the filter snug either. There was no dripping of diesel at the filter, and there was no water in the sight dish on the bottom. What was happening was that as long as there was only the normal need for vacuum (normal engine torque), the system functioned fine, but as soon as I stomped on it and produced a high demand for fuel and acceleration the engine started to suck air through the loose filter and upside-down O ring and thus no power.

Now, file this away. When starting the engine, the fuel pump kicks in to deliver fuel to the primary and secondary fuel filters. However, after about 10 seconds the fuel pump stops pumping and the Cummins-based fuel pump starts to draw fuel by vacuum from the tank. If there is a bad seal anywhere upstream, it draws air along with the fuel and there is not enough fuel to meet the demands of the Cummins. The fuel delivered through the secondary fuel filter is under pressure so the fuel is pushed through that filter. So, that little mistake on someone's part cost me $1,200 to figure it out as this problem was not under warranty.

If I had just changed the primary myself, I still would have had to go to a Cummins shop to get the blasted alarm and fault code cleared or I would have to drive the rest of the trip with the alarm dinging every couple seconds.

We live and learn.. I wish I could prove who screwed up. I'm going to have to return home to get my paperwork to see if Speedco did change the filters ..... I thought they did, but maybe they didn't !

Same symptoms but totally different reason....

Gary

[buddy110]

Since we are discussing fuel filters, where are the two located? I have done little to none of my own service to date.

[LWBAZ]

Originally Posted by Chief55m

I thought I would share an experience in hopes others will benefit. I was returning from the Tampa Supershow and after passing through Macon on I75 I started to lose speed and power going up any grade whatsoever. Down hills no problem. As soon as I hit a grade, slowed down to a point of 45mph was all I could do.

My last service was at 15,500 miles at Spartan (full engine and chassis), current mileage is 29,000. We made it home, so the next day I went to Cummins in Atlanta and left the coach for diagnosis.

Cummins ATL is great, albeit expensive. After running diagnostics (almost $900, including labor) it turns out I have air in fuel filters and some debris. They replaced Fuel Filters FS1098 ($67.67) and FF63009 ($41.03). My total bill was $1,145.

These filters had a little over 14k miles on them – is that too much?

Anyway, I typically get all my fuel from large truck stop locations – Loves, Pilot etc.…. However, I have on occasion went to small station to save a little $$. Cummins offered no opinion as to what caused the filters to fail. So, I don’t really know if the fuel was the cause.

I had planned on an annual service at about 15k miles. I have to rethink this now.

Thoughts? TIA

I'm frequently tempted to do that (go to a smaller outlet to save on diesel fuel), but several years ago I sat through a presentation where the presenter recommended buying from the major truck stops simply because their turnover of fuel is so frequent. The idea being that those busy outlets are likely to have the freshest fuel.

Of course that doesn't guarantee you won't get tainted fuel, it just makes it less likely. I considered it good advice and have chosen to follow it.

I can't remember who the presenter was or which company he represented. Pretty sure he worked for Freightliner or Spartan.

[buddy110]

Originally Posted by LWBAZ

I'm frequently tempted to do that (go to a smaller outlet to save on diesel fuel), but several years ago I sat through a presentation where the presenter recommended buying from the major truck stops simply because their turnover of fuel is so frequent. The idea being that those busy outlets are likely to have the freshest fuel.

Of course that doesn't guarantee you won't get tainted fuel, it just makes it less likely. I considered it good advice and have chosen to follow it.

I can't remember who the presenter was or which company he represented. Pretty sure he worked for Freightliner or Spartan.

You need the TSD discount card!
https://www.tsdlogistics.com/services/fuel-program/

[Finance]

I’m sticking with the manufacturers recommended 15k. I’m just coming up on 30k service on this coach now. You can get bad fuel at any time, though, I’ve had to change filters prematurely before on other vehicles and I always travel with spares.

I avoid stations with low turnover. And I use biocide in storage.

[brobox]

Originally Posted by buddy110

Since we are discussing fuel filters, where are the two located? I have done little to none of my own service to date.

Last door on the passenger side, same compartment as the chassis batteries. There are 2 filters, primary and secondary

[buddy110]

Originally Posted by brobox

Last door on the passenger side, same compartment as the chassis batteries. There are 2 filters, primary and secondary

Not sure what I thought one was a hydro filter.

Thanks!

Doing a plant tour this Thursday. Hope to garner some info on the 21's

[brobox]

Gary your post was a good heads up to change the filter(s) before heading to Cummins with any slow speed problem. Yours was one I would not have thought of, but added to my mental list. Filters are cheap compared to what Cummins charges to check out fuel filter problems. If the problem is still there after changing filters, head to a shop.