Workhorse 8.1 and Stalling...dealing with a real problem

[Full.Monte]

In 2011, my wife and I bought a 2004 Tiffin Allegro built on a 2002 Workhorse P32 chassis. We are the third owners of this motor home. One of the problems with the vehicle is its tendency to vapor- lock under various conditions, including hot days, towing, grades and idling at long stop-lights. We have been stuck at the side of the road, in the middle of intersections, even in the middle of mountain roads. It's dangerous and possibly life-threatening to stall in some of these situations. This article is about how I re-designed the fuel system on the motor home to minimize the possibility of this happening again. Before getting into the details, I'd like to tell you that this is only what I did and is not a recommendation that you or anyone else do the same. You should have any work done by a competent mechanic. You should make any modifications to your own vehicle under the guidance of your own mechanic, or other competent professionals in the motor home industry, such as Redlands Truck and RV Performance Center or Brazel's RV Performance Center (neither were consulted on this repair). There are several models of Workhorse chassis that may require variations to this approach. This article applies only to my 2002 P32 with the gasoline filler neck on the driver's side of the vehicle, but the approach should be easy to adapt to W series chassis as well. Note also that this is a work-in-process for me. We are approaching the cool part of the year and in order to fully test the repair, I need to run it in the hot part of the summer next year, duplicating the conditions where stalling occurred. The ideas expressed in this article are not new. Others on IRV2 have had similar experiences and sometimes paid very expensive on-the-road repair bills to fix this and related problems. They have helped me through this. I will give credit to my consulting helpers later.

What is vapor lock? It is a condition where a bubble of gasoline vaporizes (or turns into a gas) somewhere in the fuel system. When the injection pump tries to pump it into the cylinders, it cannot because it can only pump a liquid and is not designed to pump a vapor (or gas, like air). So, your vehicle acts like it has run out of fuel. Even though you have a lot of gasoline in the tank, it is not getting to the injection pump in liquid form. The reason this happens is HEAT. There are two sources of heat for the gasoline. One is the ambient temperature. The other is the heat of the engine. Under the right conditions, the temperature of your gasoline can rise and increase the possibility of vapor lock. One of the reasons some Workhorse models (not all) like mine increase the fuel temperature is that not all the fuel is used by the engine and a portion is returned to the gas tank. Because it has traveled to the engine, it is warmer when it gets returned to the tank. But here is the critical point: the gasoline is not returned directly to the tank itself, but to a canister inside the tank containing the in-tank fuel pump. (This pump delivers the gasoline to the engine and the injector pump). So the fuel pump re-circulates gasoline that is hotter than the gasoline in the tank because the returned gasoline doesn't get cooled much by the rest of the gasoline in the tank. So, the idea is to somehow mix the returned gasoline with the cooler gasoline in the tank, thus avoiding the higher temperatures causing vapor lock. Again, not all Workhorse chassis were designed with the same fuel system, so yours may not have this problem.

An examination of my fuel system revealed a couple of characteristics. First, the fuel system is comprised mostly of steel fuel line with some rubber connection components used where appropriate. There is a fuel filter on the inside of the frame rail just in front of the rear wheels on the passenger side. There are some other lines and some connections in this area that I thought would serve my purposes. Second, the 75 gallon fuel tank (which was full when I did this) has two gasoline filler necks and two vent ports...one set on each side of the tank.

On my MH, the filler neck and port on the passenger side were both capped with a metal plug, a short piece of fuel hose and two hose clamps.




The fuel line is obviously the line with the fuel filter. This is a 3/8 inch line. The return line is a 5/16 line on my motor home. Note also there are a couple of additional lines 1/4 inch in size that deal with the braking system. I made sure that I had the correct lines before making the repair.




I disconnected and removed the union on the 5/16 return line. I assumed that it was a standard compression fitting. It was not. I wanted to connect this line to a new steel line and route it back to the tank where I could connect it to the unused gas tank vent on the same side of the motor home. I went to three knowledgeable vendors looking for parts. No one knew what this part type was. I think it's metric.

So, I was forced to use a standard compression fitting. Since it was a relatively tight area, I used a small tubing cutter from Home Depot to make the cut. This was made several inches forward of the union junction. I needed about 8 feet of 5/16 steel tube (yours will likely be different). Pre-measuring was necessary. I left the steel tube unconnected, but "in position" so that I could mark the correct length of the tube at the other end with a marker.






The other side of the union is a steel tube that connects to the gas tank. I had to cap this tube because the gas tank is kept at a vacuum for the emission system to work. If uncapped, it would allow air into the tank continuously. I used a 3/8 inch cap and tie-wrap to accomplish this.



I had to remove the cap and tube from the tank vent tube. This was not easy because of access problems. The hose clamp screws were assembled at the factory from the top. Removing the clamp requires a 5/16 inch closed-end wrench and loosening the screw about 1/16 turn per try. It took quite a while. I then had to cut the rubber hose off as it had bonded to the vent neck.





I considered re-using this factory plug piece for the tubing connection, but the wall thickness seemed too thin to tap for threads.


Then, I bought some copper and brass parts to make an angle fitting that I could re-attach to the vent tube neck. Here is what it looked like:



There are four parts to this. First is a copper 1/2 inch by 3/8 inch female to female adapter....slip to thread. Second is a 1/2 inch copper pipe slipped into the female adapter. When soldered in, this stiffens the fitting under pressure of the hose clamp, hopefully keeping it from collapsing. I had to cut this as short as the female adapter socket later to make it fit correctly in the installation.

Third is a 3/8 inch brass threaded plug. I drilled a 5/32 hole through the center of this plug and tapped it to fit a 1/8 inch pipe thread. Fourth is a 1/8 inch pipe-threaded brass L with 5/16 inch hose barbs on the other end.



The threaded plug was assembled to the copper adapter using yellow Teflon tape, not the white type. Yellow is compatible with fuels; the white is not. The angled barb adapter was assembled to the threaded plug in the same way, and everything was tightened.


Note that I had to cut off the 1/2 inch copper pipe even with the adapter fitting.

Next, I bought a 5/16 inch rubber fuel line...fuel injection type. (Theoretically, the fuel injection rubber line is better than the standard rubber fuel line). I needed about a foot to fifteen inches. The purpose of this line is to connect the angled hose-barb fitting to the new steel fuel return line using the 5/16 rubber hose and hose clamps. Note that all hose clamps were assembled so that the tightening screw was accessible from the BOTTOM, not the top. I assembled the angled fitting to the copper adapter using 5/8 inch fuel injection line...about two inches long, using a hose clamp. On the other end, the 5/16 rubber fuel injection line was assembled to the barb and hose-clamped on. Then the mini-assembly was loosely installed on the tank vent with the angle-barb pointing forward, just clear of the unused (and capped) tank filler neck. Then the 5/16 inch rubber tube was routed through the available hole in the frame and pointed forward toward the open end of the steel tubing. Using the natural curvature of the hose and a long enough piece, it was possible to connect the angle-adapter to the steel return line without kinking it. I couldn't take a photo of this because of the tight quarters. I marked the steel tube for length with a marker, and cut it with the small tubing cutter. Having not connected the other end of the tube to the return line made it easier to cut it to length. I attached the rubber 5/16 line to the steel tube with a hose clamp after sliding the rubber tube as far up the length of the steel line as I could. Next, the steel line was routed inside the frame, past the shock absorber and forward up to the joining compression fitting. The final connection was made to the compression fitting up near the fuel filter using a little pipe dope underneath the ferrules on each end. This helps the fitting ferrules to seal on the tubing without leaking or weeping. A few tie-wraps kept the steel line from moving.


In-line compression fitting and unmounted vacuum cap for de-activated fuel return line to tank

This project was not the easiest auto mechanical work I have ever done. I'd give it a 5 out of 10 on the difficulty scale, mostly due to the frustrations of tight quarters, thinking time under the vehicle, and chasing parts. Not having to lower a full gas tank was a plus.
There are other ways of accomplishing this repair. There are mods that can be done to the pump canister such as drilling holes in it that would get cooler gasoline into the fuel pump canister. This would require removal of the tank and the in-tank fuel canister. I chose to avoid that additional work in favor of re-routing the return line. I'll be testing this repair on the next hot period next summer.

Thanks to garyspang, M&EM (Marty), dieselclacker , Skip426 and Aldev of this forum and Bob Fogg, my lifetime friend. They all provided valuable advice that enabled me to tackle this project. Thanks also to Janet H of IRV2 who helped me through the hocus-pocus of photo placement.

[Firebug5]

WOW, what a thorough, well written report! As I mentioned previously, I am interested in following you thru the entire process. Living in Colorado at higher elevations, I too have experienced "vapor lock" with the W22 chassis several times, and am curious to see what you find. Thank you for the valuable contribution to our community.

Bruce

[Full.Monte]

Originally Posted by Firebug5

WOW, what a thorough, well written report! As I mentioned previously, I am interested in following you thru the entire process. Living in Colorado at higher elevations, I too have experienced "vapor lock" with the W22 chassis several times, and am curious to see what you find. Thank you for the valuable contribution to our community.

Bruce

Thanks, Bruce. I hadn't really thought of it before, but I guess high altitude could play a role in vapor lock. A few of my vapor lock experiences were at 5,000 to 7,000 ft. altitude. Not all, though. Temperature due to hot days, engine load and idling seem to me to be important drivers of this phenomenon.

[Firebug5]

Originally Posted by Full.Monte

Thanks, Bruce. I hadn't really thought of it before, but I guess high altitude could play a role in vapor lock. A few of my vapor lock experiences were at 5,000 to 7,000 ft. altitude. Not all, though. Temperature due to hot days, engine load and idling seem to me to be important drivers of this phenomenon.

A local mechanic here also told me to look up the weather on the days of my recent vapor lock episodes, specifically looking at the barometric pressure readings. Sure enough, the most recent episode occurring in July had a record high barometric pressure reading, and the stall happened at about 9,000' elevation. Who knows, those are things I cannot change, unless I drive the higher elevations earlier in the day. But, you my friend may just have an answer that I can do something about! My only drawback is that I have only experienced several of these episodes over the 9-year period we have owned our Dolphin, all of which occurred with high summer temperatures, higher elevations than normal, and on days with higher than normal barometric pressures. So, to get me off of my butt and do something about it, I need it to happen more often, or I need to become your neighbor .

[Full.Monte]

All it takes is one really dangerous stall to get you off your butt. How about going up hill on a freeway overpass with no shoulder? How about going down a long steep grade at altitude on a hot day, when all of a sudden, you have no brakes and no power steering? I'm sure you can think of more. Remember...it's not just you that is in danger.

If altitude is a factor, low barometric pressure readings would be more likely to cause it than high pressure readings. But 9,000 ft is pretty high. I have found that driving in the cool part of the day minimizes these occurrences, but who wants to plan a trip that way?

[Firebug5]

Originally Posted by Full.Monte

All it takes is one really dangerous stall to get you off your butt. How about going up hill on a freeway overpass with no shoulder? How about going down a long steep grade at altitude on a hot day, when all of a sudden, you have no brakes and no power steering? I'm sure you can think of more. Remember...it's not just you that is in danger.

OK, OK, how do I become your neighbor? I was very fortunate both times, having places to pull off safely while going uphill. But you have a very valid point, I was just lucky to have been able to get off the road. I will continue to follow your thread, let's see how your testing goes. Again, thanks so much for sharing with us.

Bruce

[RVThere]

Great explanation! I traded in my Workhorse back in 2008 but still interested in all the fixes that can be done to them.

[Full.Monte]

Originally Posted by Firebug5

OK, OK, how do I become your neighbor? I was very fortunate both times, having places to pull off safely while going uphill. But you have a very valid point, I was just lucky to have been able to get off the road. I will continue to follow your thread, let's see how your testing goes. Again, thanks so much for sharing with us.

Bruce

Bruce, you wouldn't want to be my neighbor. I just looked at Salida, CO and it looks much nicer than Silicon Valley, CA. Are you by any chance going to Quartzsite in Jan. for the RV event and Rock show?

[Firebug5]

Originally Posted by Full.Monte

Bruce, you wouldn't want to be my neighbor. I just looked at Salida, CO and it looks much nicer than Silicon Valley, CA. Are you by any chance going to Quartzsite in Jan. for the RV event and Rock show?

We have never been to Quartzsite, typically spend 2 months near the Tucson Gem and Mineral show around Jan-Feb. I retired over 5 years ago, been waiting on her to become vested in her pension, which finally happened last year. Our Dolphin is OOS currently, having to repair the 50-amp receptacle that our adult son ripped out with his jeep mirror. Relocating it to the electrical compartment, adding a Progressive Industries hardwired EMS, too. After that, on to your project! I am not mechanically inclined, unless calling my local shop for an appointment counts. . .

BTW, Salida is every bit as bea-U-tiful as you think! Have never been to your neck of the woods, unless Disneyland counts.

Bruce

[benge1]

Just had similar problems. Happened to me several years ago and replaced fuel filter and problem cleared up. Now I am running again and all of a sudden maybe 15/20 miles down the road it starts losing power again, no acceleration. Got back home at a crawl
Did I get bad gas and foul the new filter or after reading the post do I have another problem?
Where do I start trouble shooting this problem
Thanks for the help

[Full.Monte]

Start with the easiest and cheapest possibilities first. Change the filter and blow through the old one to see if it's plugged up. Then put a pressure gauge on the fuel rail port. See if it tests to spec. I haven't seen the specs on an official spec sheet, but I've read here that it is 55-62 psi.
Let us know what you find.

[M&EM]

F.M, Excellent write-up, photos, and details!

I checked mine for similar modifications. My chassis is an 03 and slightly different as to the fuel line couplings but doable.

Maybe we can cross paths at Qzte

[Basegasket]

I had this problem on my 98 P30 with the 454cid

After pumping 60 gals of fuel out of the tank It was relatively easy to drop the tank, even though it was the size of a Mini Cooper.

Remove the fuel pump and note the 3 lines going to it on the top of pump. One of the lines is the return from the engine. This one pumps heated fuel from the engine back to the fuel pump and dumps it directly on top of the pump. When to tank gets below 1/2, or to the top of the canister, it causes vapor-lock, making it impossible for the pump to move fuel.

I connected the black hose in the picture to the return tube on the pump housing. It's actually connected to one of the silver tubes that goes into the canister, the ones with the springs on them.

With the hose attached, the return fuel is pumped across the tank and mixes with the rest of the fuel, leaving cool fuel in the canister.

I also drilled a few holes in the bottom of the canister for good measure.

I hope this makes sense.

[Full.Monte]

Basegasket,

Thanks for the informative photos. It's pretty clear what you did and the photos help a lot. How many miles have you put on the MH since you did this modification? Have you solved the vapor lock problem, or do you still have to keep the tank more than 1/2 full?

Thanks again!