Loss of power, low rail fuel pressure. Acted like clogged fuel filter, turned out to be crud clogging the lift pump in fuel tank.

caeppinger

Joined 2010
2008, 3500 Itasca motorhome, 52,000 miles. I'm 59 and a shade tree mechanic. I have gotten bad fuel before and know the symptoms of a clogged fuel filter (low power, trouble going up hills and won't go above 50 or 60 MPH). This is my 5th diesel and have learned to pick my fueling stations (mostly wisely) over the last 18 years.

We did not travel last year or this year , but still wanted to take a day trip (200 - 300 miles) to use the old fuel and exercise the van/RV. It would be great doing 71 or 72 MPH for 150 or so miles, then suddenly lose power and barely crawl along at all, and then just shut down. I would get it pulled over and quickly change the fuel filter on the side of the road or off ramp. Van would then start back up and be good for another hour, then it would lose power again, and I changed the fuel filter again and go another 45 mins or so. This happened in June, and I restocked my filter supply, I also cut open the old filters and they did not look very dirty, the one with only 50 miles looked very clean! I suspected that I had crud of some type in the tank and it was causing us problems. Also have had a vibration in the fuel return line coils (at rear of tank) for the last 4 years. They would start out quiet and then after a hour of driving they begin to buzz. I added a quart of Power Service (white bottle) and filled up (after 100 mile test loop with no problems running up to 65 MPH). So now we are ready to try another interstate day trip. We did this past Wednesday and it was an almost exact repeat of the June trip (same destinations and same problems), but after having to change the fuel filter twice again, and after the second time it did not want to start (after priming). It did finally start and we limped along till it lost power and died again. This time I would just try to get it to start (3 or 4 tries) and take the surface streets home at 30 or 40 MPH, repeated this 3 times for the last 15 miles to home.

I did the removal, cleaning and reassembly by myself over 2 days, total about 12 hours. I was very reluctant to start this project, but really glad that I did.

At this point I'm convinced that the problem is in the tank and the pre filters for the lift pump, The nearest dealer is 80 miles away and I'm not sure it will make it without a tow. So I drive the front wheels on to my ramps and drop the tank, since we do not drive this in the winter the bolts and tank straps are in very good shape and come off fairly easily in the drive way, (except for the 4 bundles of RV wiring that are on the wrong side of the filler neck) (filler neck on 2008 is part of the fuel tank and so 1 big piece). Used a strap wrench to remove the lift pump nut/lock ring. I disassembled the lift pump assembly and cleaned it the best I could with gas, tooth brush rags and compressed air. The pre filter (round removeable screen) on the bottom of the actual pump motor was caked solid with 1 or 2 mm of crud (biomass or just crap from a fuel storage tank)?
There is a 2 ft. long pickup tube that seems to be part of the fuel return lines that had some crud on its plasticly strainer end ( before and after pic is included).

Cleaned the tank with water (probably could have skipped this step), then drilled a 3/16 hole in the very highest part of the tank (part that is most forward) to drain the water, wiped out the inside as best I could reach. The tank mostly air dried over night. This morning I finished drying out the tank, used compressed air with the tank standing on its nose (front end), then added 1/2 gallon of gas to tank and sloshed it around for 5 minutes as best I could. Drain the gas out using my new drain hole, clean with more paper towels. filled the new drain hole with a rubber faucet washer and a rivet, then completely cover with a 2 part Permatex black plastic weld.

Reinstalled tank (used some very colorful words), connected all 3 fuel lines (supply, return and heater lines) all electrical added 8 gallons diesel (check for leaks) drove up small hill and added 10 more gallons at fuel station (check for leaks) drive 15 miles on controlled access road at 68 MPH (this includes a decent incline on a 3 mile hill) no problems (check for leaks) top off tank (check for leaks) drive the same 15 mile route again (like I stole it!!) and returned home to check for leaks again, no leaks found.

I will update after we take another day trip next week, when the wind is not blowing 20 mph.

This is an after cleaning picture (did not get before), and it did get cleaned more before I reassembled.
bottom of lift pump pre filter.jpg
Clean what ever it is .jpgWhat is this part.jpgCrud .jpgCrud smashed between thumb and fore finger.jpg
 
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caeppinger

Joined 2010
Also, for the past 8 years the fuel gauge has not read full (the last 2 segments would never appear), it worked right the first couple of years. I noticed that one of the lines near the sender unit could possibly be causing this, so I used a bare copper #12 solid wire to gently hold the 2 hoses together and out of the way of the sending unit movement. Either tis was the problem are I accidently did something else in my cleaning and reassembly that fixed the fuel gauge on the dash, It is great that that little annoyance is gone.

Removed about a 1/2 cup of crud from the tank and pump.

If you start to suspect that you are having this problem, try not to let your fuel level get below 1/2 full, until you are ready to drop the tank. The lift pump sits in a 1qt. sized cup and below 1/2 tank there is less movement of fuel in an out of that cup/ enclosure, There is a small rubber flapper (dime size) in the bottom of the cup that would allow some fuel movement, but it is a small 1 or 2 mm size hole.

I forgot to listen for the fuel return line buzzing today, will check on it during the trip next week and report.
 
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caeppinger

Joined 2010
Tools used

E14 socket for fuel tank straps (mark the straps to make it easier to reassemble).
Torx T30 for bolts inside the fuel door.
Phillips #2 for 1 filler neck bolt (at top inside fuel door).
A small straight screwdriver (pencil size) aids in removing fuel line clips and tabs on wiring plugs.

Took 300 mile day trip, and the results were great, power is restored (at 11,000 lbs) every little bit is needed, I had it up to 80mph 4 or 5 times with no problems, no buzzing from coiled fuel return lines by tank, Fuel gauge displaying all 10 segments after fill up.
 

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