Stranded in New Mexico - opinions and ideas certainly welcome

[Greg Roberts]

Hi folks, Having an issue and would like your opinions. I am 100 miles from home and in Roswell New Mexico (Aliens may be at work here??).
Anyway, here is what happened. Drove first 100 miles of my trip and stopped at Walmart in Roswell. Bus ran great and climbed the pass in the Capitan area with no problems. After coming out of Walmart I pressed the start button and she fired right up and went up on fast idle just fine and idled smoothly. I proceeded to exit the the parking lot and, upon pressing more throttle, the engine started stumbling.

The engine runs smoothly at lower idle but stumbles out if I press the throttle too far. If I press too far then it stumbles and I let up a little and it smooths out, however, this throttle position is hardly enough to allow acceleration.

The bus is a 1989 Eagle Model 20.
The engine was a fresh rebuild from New Jersey Transit and now has about 10,000 miles. I actually received the engine is a crate and it had a new turbo and blower with fresh internals.
The engine is a Detroit 6V92 DDEC II with an Allison HTB 748
There is no black smoke at any time when this happens.
Changed both primary and secondary filters and this made no difference.
Air filter is fresh.
Standing at the rear and when hitting the kill switch I hear the turbo spin down.
All fittings appear tight and does not appear to be sucking air.
DDEC II is not indicating any codes or stop commands.
All oil and coolant levels and temps are within normal ranges.

Thinking it could be the mechanical fuel pump because it seems fine until the fuel demand gets to a certain level.

By the way, I can only push the throttle to a point where the bus will just barely accelerate and shift to second gear. In fact it takes a couple of blocks to coax it up to where it will shift.....if I push too far then it starts stumbling and looses power.

I coaxed it along to a local RV park in Roswell NM and will let the engine cool overnight and will start wrenching for a closer look in the morning.

What do you guys think? - Greg

[JohnEd]

Would a fuel pressure gauge in the output side of the fuel filter eliminate isolate the failure cause to a plugged filter?  Or catch air being pulled into the fuel line when demand goes up?

My experience with clogged filters is that they act like a governor.  No sputtering....just power rolls off.  True for the DDEC?

John

[JackConrad]

Greg,
      Something similar happened to our MC-8 8V71 several years ago. It turned out to be a fuel line between the bulkhead fitting in the engine compartment and the primary fuel filter. The fuel line had delaminated and the inside layer was sucking shut restricting fuel flow.  The problem became much worse when the fuel warmed up.
     We found it by disconneting this line at the primary fuel filter and connecting a piece of hose feeding into a 5 gallon can of diesel fuel. WQhen this solved the problem, we then cut the end off a water hose, clamped that over the primary fuel fliter inlet fitting, taped the hose to the side of the bus with duct tape, and stuck the other end into the filler spout on the fuel tank. We drove about 200 miles that way. When I got home, we replaced the fuel line and I cut split the old fuel line on my bandsaw. That is how we found the delamination. The hose felt solid from the outside.  Jack

[Dreamscape]

Hi Greg,

I'm really feeling for you, especially this time of the year. I can relate as I broke down in Palm Springs Dec of 06 and made it to my new home on Christmas day.

I don't know what to say of your problem, but it sounds like no fuel or sucking air, like Jack said. At first I thought of emergency shut down until I read you have a DDEC II, especially with no codes appearing, and no black smoke.

I'm sure others will post that know your engine better than I.

Good Luck and hope you are able to get it fixed soon, hope you have a Merry Christmas anyway!

Paul

[Sojourner]

As what Jack mention is good indication...an internal wall collapse but outside appearance is normal. Not common but I have seen a very few of my customer cars to have the same condition as Jack's case but with regular fuel inlet hose. I am not talking about common collapse hose you can see under power...that is common due to poor design hose material.

Are you using reinforce fuel line material...such as Aeroquip line?

Or a plugged pick-up inlet line in main fuel tank...it can happen still after replace fillers.

If no code from DDEC, suggest to by-pass main intake line from tank with a remote line to filler opening into about 8 inch of leveled fuel to road test. If you don't mind using Jack's system...disconnect return fuel line to add a hose to a five gallon container along with fuel intake hose...then road test.

If it runs OK...then you know it one of those inlet line restricted before the fuel gear pump.
1)   A pick-up line in main tank plugged
2)   A hose between bulk-head and primary filter
3)   A hose between primary filter and fuel gear pump
4)   Or a fuel gear pump is low pressure

Remember there is a special restrictor fitting that the return line attach to on cylinder head...that be in the circuit at all time. Otherwise it can run very poorly or no running.

FWIW

Sojourn for Christ, Gerald

Merry Christmas

[Kwajdiver]

Greg,

Glad your safe and off the road.  Can't help much with your problem, sounds like the experts have given you a full days work already.

Just wanted to ask if you had lunch at the " Cover Up Cafe"

Good Luck, and Merry Christmas

Bill

[jjrbus]

Greg what did you do that Santa was so baaaad to you on Xmas??? I'd be happier with a sock full of coal.
I don't post much on start and run problems, there are people far more qualified here than me. However I did have a similar problem, so will chip in my nickle.
Mine turned out to be an alge problem (alge is the wrong term, can't remember right one)  When primary fuel filter was removed there was some black stuff suspended in fuel in filter, it was far less than I would have thought would cause a problem.
The fuel line was plugged with alge??  The remedy was to remove the fuel line  at the filters and at the tank and blow air throught the fuel line. You cannot just unhook line at filter and blow into tank as there is a check valve in tank. You do not want to use lots of pressure either, I would say 10 lbs psi max, so as not to ruin lines.  Use a gallon jug on the filter end to catch content ( 1 quart +-fuel) from the lines. This just saves big spill in compartment and on ground.
After blowing out lines, reconnect line at filter end. Look at fittings on tank end, off to NAPAhardware store and buy some fittings to be able to cap off and pressureize the fuel line also will need some type of air gauge. You will have to be inventive on the parts and use what is available! Pressureize line to 10 lbs and watch for 10 min for air leaks. If line holds pressure you are good to go, if it leaks down, well you have a leak!!  If there is black junk in fuel you might skip pressure test, but as long as you have it apart and can get the parts, I would check it.
If it is an alge problem you need to add a biocide to the fuel and watch filters.  You want something that is desiged specifically for growth in fuel, not the magic elixairs at truck stop's. The only place I know to get it is at marine supple places, there may be others.

       http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/21560/377%20710/0/fuel/Primary%20Search/mode%20matchallpartial/0/0?N=377%20710&Ne=0&Ntt=fuel&Ntk=Primary%20Search&Ntx=mode%20matchallpartial&Nao=0&Ns=0&keyword=fuel&isLTokenURL=true&storeNum=6&subdeptNum=169&classNum=764
  Try to be a better boy this year!!!      Jim

[Sammy]

Check the harness connection to your accelerator pedal (TPS). Make sure it's clean and tight, even though you say there are no codes from DDEC.Check both 30 pin connectors at the DDEC ECM to make sure they are clean and secure too.Check battery and ground connections for DDEC.
I'd pull air intake hose off turbo to make sure it's not seized,or broken. I realize you said there is no black smoke but I would check it anyway.
I'd try to isolate engine fuel system from fuel tank - run temporary fuel pickup line (primary-suction)from fuel pump to a 5 gal fuel can as mentioned already.
Good luck.

[Greg Roberts]

Update: This morning I installed the pressure gauge on the top of the secondary filter (which is after the fuel pump but before the second filter) and the gauge read 15-20 PSI at idle. I then had someone press the throttle and the engine increased and did the same thing as before but the pressure indication did not budge. The needle stayed exactly in the same position. I have verified that the gauge is working (shut off the valve and bled it off and then opened the valve and it returned to the 15-20 PSI range.

If the pressure is supposed to go up to 50 lbs. on an electronic DDEC II engine at full speed no load then it looks like the issue is likely in the fuel delivery system. Could be the fuel pump or collapsing fuel lines as has been mentioned.

Let me describe the engine symptoms while standing next to it with someone else working the throttle. The engine is smooth as always at idle and up to a certain RPM that I believe is probably 1900 or so and then it starts rattling very loud. (Would a gear issue act this way?) It was suggested to check all connections and I did do that again including on the electronic throttle. Sounds like the fuel pressure my be the culprit??

[Sojourner]

Greg...if fuel reading goes down while accelerating in drive with full brake on...you have fuel inlet restriction.

FWIW

Sojourn for Christ, Gerald

Merry Christmas!

[jjrbus]

Fuel inlet restriction???  Gerald, could you elaborate a bit on that. What inlet??  Spinning Jim

[Gary '79 5C]

A method I have gotten home with a plugged fuel tank filter ( internal) on a Mercedes, was to disconnect the supply & return lines at the engine.
Depends upon how much fuel you have on board, and the height of the return line within the tank.
No sure of your setup, but this got me home twice.

Best of luck on Christmas Day

[Busted Knuckle]

Greg,
I'm sorry to here that you are having problems! OK now I am late to the show as I have been busy with other things so far today.
Well I see that some of the best of the few we have left(sure wish Cole was still around!), are already on the case. Now from what you are describing after testing with the pressure gauge, it does sound to me that you either have a weak/bad pump or line restriction. Which some of the others can probably be of better assistance on as I have been fortunate not to have experienced this yet.
Now I have had 1 similar experience that made my DDEC 8V92 act the exact same way as yours is. Now I was again fortunate to have been on the phone with a very smart mechanic at the time I was on the side of the HWY trying to find the problem, which like yours was not showing ANY codes! I had not dug out lots of tools, gauges, and such yet when Jim told me to find the DDEC (12V) fuses (on a Setra they came off the center of the batteries for the 12V connection & were right there in the battery box!). When I found them I grabbed hold of the fuse holder and the engine made a slight "blip". So I yelled to dad who was in the bus making phone calls trying to find a replacement bus. "To hit the throttle!" When he did it was like magic and it roared as normal! I told dad to keep it reved up while I played with the fuse holder and sure enough the holder was old and corroded and when I'd twist, or push just right it'd stall back like it had been before! So I cut the fuse holder out of the wire and used a "butt connector" to wire it straight for the day. I did this to both wires and sent dad on his way on the charter. When he got in that night I replaced the fuse holders with new ones I'd picked up at NAPA that day and we never had a problem out of that on that bus again!
Now I never Had a chance to try a gauge or anything on it so it may not be where you problem is. But it is worth a try.

Now if that's not it, and I'm afraid it won't be. There is an easy way to see if it is a pump or line problem. When the parts stores open in the AM go and get an in-line electric 12 Volt fuel pump, a 5 gallon jug of fuel, enough 3/8" or 1/2" fuel line to make it from the filter housing to a safe place to put the fuel can (and a little to spare), the proper size barb fitting to hook it to the filter housing, and a piece of metal fuel line or brake tubing about 7 or 8" long, and some hose clamps.
Hook the line up, with the pump in-line and one end hooked to the filter housing, and the other to the metal line. drop the fuel line into the tank with enough so that the metal line lays on the bottom (the weight of the metal will help it stay on the bottom). Then duct tape the hose around the top of the can to keep it from coming of of the can. Hook the pump to 12V and give it a whirl! If the problem is between the tank and filter you have just temporarily bypassed it!
Hope this helps.    BK  

[Greg Roberts]

Bryce, Sounds like just exactly the method I will be using to divide and conquer. I kind gentleman called me this morning and left a message with the electric fuel pump suggestion and I certainly appreciate the advice and suggestions from the brain power of all of you. Appears that my cell phone service is not the best here because I missed the call and it came to my cell phone as a message some 3 hours after the call was made. Anyway, waiting for the autozone to open tomorrow. Looks like we are probably going to rent a car continue our short trip tomorrow and then I will get back on it in a few days to keep the family smiling. Any other ideas you guys have will be much appreciated! - Greg

Greg,
I'm sorry to here that you are having problems! OK now I am late to the show as I have been busy with other things so far today.
Well I see that some of the best of the few we have left(sure wish Cole was still around!), are already on the case. Now from what you are describing after testing with the pressure gauge, it does sound to me that you either have a weak/bad pump or line restriction. Which some of the others can probably be of better assistance on as I have been fortunate not to have experienced this yet.
Now I have had 1 similar experience that made my DDEC 8V92 act the exact same way as yours is. Now I was again fortunate to have been on the phone with a very smart mechanic at the time I was on the side of the HWY trying to find the problem, which like yours was not showing ANY codes! I had not dug out lots of tools, gauges, and such yet when Jim told me to find the DDEC (12V) fuses (on a Setra they came off the center of the batteries for the 12V connection & were right there in the battery box!). When I found them I grabbed hold of the fuse holder and the engine made a slight "blip". So I yelled to dad who was in the bus making phone calls trying to find a replacement bus. "To hit the throttle!" When he did it was like magic and it roared as normal! I told dad to keep it reved up while I played with the fuse holder and sure enough the holder was old and corroded and when I'd twist, or push just right it'd stall back like it had been before! So I cut the fuse holder out of the wire and used a "butt connector" to wire it straight for the day. I did this to both wires and sent dad on his way on the charter. When he got in that night I replaced the fuse holders with new ones I'd picked up at NAPA that day and we never had a problem out of that on that bus again!
Now I never Had a chance to try a gauge or anything on it so it may not be where you problem is. But it is worth a try.

Now if that's not it, and I'm afraid it won't be. There is an easy way to see if it is a pump or line problem. When the parts stores open in the AM go and get an in-line electric 12 Volt fuel pump, a 5 gallon jug of fuel, enough 3/8" or 1/2" fuel line to make it from the filter housing to a safe place to put the fuel can (and a little to spare), the proper size barb fitting to hook it to the filter housing, and a piece of metal fuel line or brake tubing about 7 or 8" long, and some hose clamps.
Hook the line up, with the pump in-line and one end hooked to the filter housing, and the other to the metal line. drop the fuel line into the tank with enough so that the metal line lays on the bottom (the weight of the metal will help it stay on the bottom). Then duct tape the hose around the top of the can to keep it from coming of of the can. Hook the pump to 12V and give it a whirl! If the problem is between the tank and filter you have just temporarily bypassed it!
Hope this helps.    BK  

[Lin]

I have not yet had the experience on my DD, but clogged fuel filters have produced those symptoms on other vehicles I have had.  Has that already been disqualified?