| Author | Message | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 231 Registered: 4-2002 Posted From: 75.211.254.209 Rating: N/A |
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 (Message edited by gregeagle20 on December 25, 2008) | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 731 Registered: 7-2006 Posted From: 68.18.41.165  Rating: N/A |
Hmmmm.... Re: " -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. -I can only push the throttle to a point where the bus will just barely accelerate and shift to second gear. " Sometimes, reading what you've posted, will tell you what you've missed? It sure appears that your fast idle isn't disconnecting. If it's on, you won't be able to accellerate properly, and the attempts to do so will only result in the engine "stumbling", and a seemingly loss of power. You can try disconnecting the fast idle, either at the voltage supply, or the air supply, and see if that clears things up. | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 232 Registered: 4-2002 Posted From: 75.211.254.209 Rating: N/A |
It does idle to the low setting as soon as I flip the switch to the fast idle off position but it is worth a shot. The switch is merely an input to the ECM so it will be easy to verify. | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 515 Registered: 1-2005 Posted From: 97.104.18.54 Rating: N/A |
Does your bus have a CATALYTIC converter If so - can you just disconnect the exhaust pipe going to it and push it aside & try the engine Just this year alone - I know of 2 RTS's that this has happened to - happens fairly suddenly Pete RTS/Daytona | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 516 Registered: 1-2005 Posted From: 97.104.18.54 Rating: N/A |
The primary fuel filter is before the fuel pump - and pulls a vacuum to draw the fuel from the tank. the secondary fuel filter is after the fuel pump - just unscrew the plugged port on the filter and put in a "pressure" gauge to check your pump Fuel pressure AFTER the secondary fuel filter is to be approx. 15 psi at idle. And N/L speed fuel pressure should be greater than 50 | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 233 Registered: 4-2002 Posted From: 75.211.254.209 Rating: N/A |
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?? | ||
| ED Hackenbruch (Shadowman)
Registered Member Username: Shadowman Post Number: 84 Registered: 11-2003 Posted From: 68.26.44.66 Rating: N/A |
Don't i remember that a couple of years ago somebody had sort of the same problem and it turned out that they had a small crack in the fuel line and the more throttle they gave it the more it sucked in air? | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 517 Registered: 1-2005 Posted From: 97.104.18.54 Rating: N/A |
Greg This time I looked thru "DA BOOK" - not just search via google Fuel Pressure --> 50-70 psi at 1200 -2100 RPMs Minimum fuel pressure is 30 psi The relief valve is set at approx 65 psi Here's the fuel pump inlet side valves -- Pump inlet side suction (clean filters)-> 06 in. hg. vacuum pump inlet side suction (dirty filters)--> 12 in. hg. vacuum Hope this helps Pete RTS/Daytona MINIMUM ---> (Message edited by pete rts/daytona on December 25, 2008) | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 234 Registered: 4-2002 Posted From: 75.193.111.85 Rating: N/A |
Pete, Thanks so much for looking this up for me. Looks like this is certainly the problem since the pressure is running so low. Was that for a DDEC style engine for those pressures? Just confirming because it could be different for the mechanical engines than a DDEC engine such as mine. I am also wondering about the relief valve. Any idea where it is located? Will also be something I need to check out to make sure the relief is still set correctly and operating properly. All of you guys....thanks so much for your input and help!! | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 518 Registered: 1-2005 Posted From: 97.104.18.54 Rating: N/A |
DDEC / MUI - no difference the relief valve assembly is mounted on the side of the fuel pump There is also a .080 restricter located somewhere in your fuel return line The fuel spill rate back to the tank at (NO LOAD - Idle) should be .9 gallons/minute (this is how much fuel should be going back to the tank on a no load idle condition) (Message edited by pete rts/daytona on December 25, 2008) | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 519 Registered: 1-2005 Posted From: 97.104.18.54 Rating: N/A |
If you do get to check the return flow - There should be no bubbles after 1 minute | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 235 Registered: 4-2002 Posted From: 75.193.111.85 Rating: N/A |
Thanks so much for taking the time and effort Pete and all. Obviously I need to get a copy of "dat book" as well but it sure is good to have you guys as a resource! I will see if I can locate a pump assembly tomorrow. I am guessing there might be a coupling involved too that I should consider. Thanks! | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 108 Registered: 11-2008 Posted From: 70.52.104.178  Rating: N/A |
I'm just a rank beginner but my bus did the same thing... the one time it broke down, A fuel line was sucking air.. the more throttle the worse it ran. I have a post about it somewhere. but after DAYS in this 'shop' a real bus guy fixed it in about one hour. Best I recall, He disconnected a fuel line, extended it (with a coupling and some tubing) and hooked it to a vacuum pump. The fuel was frothy with air bubbles. That's how he knew what the problem was. How he found WHERE it was, I don't know. Sorry. But it didn't take him long once he knew what he was looking for. HTH and best of luck to you. Nellie Wilson | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 619 Registered: 10-2006 Posted From: 66.82.9.75 Rating: N/A |
Folks that prefer to trouble shoot BEFORE the hassle of being stuck roadside , should check the archives for installing an armored refrigeration Sight Glass in the fuel lines. FF | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1442 Registered: 12-2000 Posted From: 76.66.18.193  Rating: N/A |
Will the sight glass off the discarded coach AC tank in the condenser room do the trick? Lots of busnuts have one of those kicking around! happy coaching! buswarrior | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 620 Registered: 10-2006 Posted From: 69.19.14.19 Rating: N/A |
It might , I dont remember what mile looked like. The JOY of purchasing a new unit is you can select the in and out ,male & female fittings , so the install is one min or so. FF | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 236 Registered: 4-2002 Posted From: 71.14.157.178 Rating: N/A |
Yes, this is a good idea and is something I had on one of my motor yachts a few years back. You know right away if you have a leak on the inlet side of things. Of course you usually can also see the fuel pressure jumping around as long as you are not using a dampened gauge. I will probably add a site gauge to my bus too along with about a dozen other ideas as time and money permit. Thanks for the reminder Fred! | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 237 Registered: 4-2002 Posted From: 74.211.85.238 Rating: N/A |
The verdict is in: I replaced the fuel pump and improved the pressure a good deal, however, not as good as the book numbers and the pressure was falling back at the highest RPM. I had a new fuel line made up and replaced the line from the tank all the way to the primary filter and pressure went to the book number and stabilized with no fall off at all. The original installation had 8 connections and went from hose to tubing and then back to hose again and also had one bulkhead fitting. My new installation has one connection at each and that is all so removing a lot of potential leak points. I now carry a spare fuel pump and drive fork by the way. Thanks to all of you for your suggestions and help! Question for all of you: What spare parts do you carry and what is your philosophy regarding your choices? | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 412 Registered: 7-2006 Posted From: 75.211.89.173 Rating: N/A |
"Question for all of you: What spare parts do you carry and what is your philosophy regarding your choices?" Big discussion on this subject a few years ago...might check the archives. Happy New year all!  RCB | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 238 Registered: 4-2002 Posted From: 74.211.85.238 Rating: N/A |
RC, I did a search and came up with one thread with one list and a lot of scattered threads and this is why I brought the subject up. I may be searching wrong but I would sure like to find the big discussion you mention. About when do you think it was so I can narrow my search a little? | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 239 Registered: 4-2002 Posted From: 74.211.85.238 Rating: N/A |
I was able to actually find a lot of spares chatter over at the MAK board. - Greg | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 413 Registered: 7-2006 Posted From: 75.211.89.173 Rating: N/A |
Greg...could have been on both boards...it was some time ago. As I recall some guy was even talking about hauling around a spare engine, transmission or whatever. From my point of view it depends on one's ability, desire, and lifestyle. For me it is a few belts, filters, antifreeze, extra 6 gallon can of diesel and very little more. I do have an extra water pump, steering knuckles, some bearings and who knows what( came with the coach when I purchased it. I do not carry them. I don't carry a spare or any major parts, do carry good tow insurance and lotsa' prayers. Pretty much take it as it comes. Redundancy is fine, but when it encroaches on my attitude, finances, storage space and weight I defer to the Lord. Over the years (8 coming up) I have had to replace a starter, 2 tires and a clutch. All readily available and at reasonable prices on the road. FWIW...and as BW says Happy Coaching. | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 244 Registered: 10-2003 Posted From: 74.244.14.221  Rating: N/A |
I'm probably the wrong person to ask because of my lack of experience but I carry spare filters, belts, 6 gallons of diesel a couple cases of delo 100, antifreeze and a couple spare injectors. |