Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
 
Old 07-31-2022, 04:16 PM   #1
New Member
 
Join Date: Aug 2021
Posts: 4
Exclamation MBE 906 Losing Prime

I have a 2003 Freightliner Thomas bus lolwith a Mercedes 210hp diesel.
Motor has been flawless. Started it one day to run it and move it. Ran for 30 mins. Turned it off. 2 days later I went to start it and nothing. If I bleed the injector lines it will start and run great. When I shut it off, I can immediately start it back up no problem. If I wait 10 or more mins, it wonít start unless I crack the injector lines and bleed it again. I have replaced the inline fuel filter in the frame rail, replaced fuel pump and replaced 2 check valeís going into fuel filter housing. Still does the same thing. The other fuel filters have about 3000 miles on them. I donít see any fuel line leaks. I took plate off above tank and itís a brand new fuel tank.
Any ideas?

John

Snoopjohnny5 is offline   Reply With Quote
Old 08-01-2022, 07:34 PM   #2
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 2,303
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford 1998 e350 4x4 7.3 2 mercedes 2004
Engine: 7.3 powerstroke & MBE906
What part of the fuel pump did you replace? There are several check and bypass valves in the fuel pump assembly..
I had a similar problem and replaced the engine driven file pump with an electric pump. Problem went away.

Good luck,
Johan
joeblack5 is offline   Reply With Quote
Old 08-01-2022, 09:09 PM   #3
Bus Crazy
 
ewo1's Avatar
 
Join Date: May 2015
Location: Miami, Fl.
Posts: 1,065
Year: 1999
Chassis: Amtran / International
Engine: DT466E HT 250HP - Md3060
Quote:
Originally Posted by Snoopjohnny5 View Post
I have a 2003 Freightliner Thomas bus lolwith a Mercedes 210hp diesel.
Motor has been flawless. Started it one day to run it and move it. Ran for 30 mins. Turned it off. 2 days later I went to start it and nothing. If I bleed the injector lines it will start and run great. When I shut it off, I can immediately start it back up no problem. If I wait 10 or more mins, it won’t start unless I crack the injector lines and bleed it again. I have replaced the inline fuel filter in the frame rail, replaced fuel pump and replaced 2 check vale’s going into fuel filter housing. Still does the same thing. The other fuel filters have about 3000 miles on them. I don’t see any fuel line leaks. I took plate off above tank and it’s a brand new fuel tank.
Any ideas?

John
I know nothing about MBE engines…. But I found this interesting post on another forum where the guy had the same problems you have.

It kinda points to what Jose lack is pointing at, check and bypass valves.

Let us know if it was helpful…

Good luck!
ewo1 is offline   Reply With Quote
Old 08-02-2022, 12:31 AM   #4
Bus Crazy
 
Join Date: May 2018
Location: topeka kansas
Posts: 1,534
Year: 1954
Coachwork: wayne
Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
prime,suction and rubber hoses

Ever try to suck up a drink through a straw that had a crack in it?

tiny tiny tiny crack will dump vacuum and never get the fluid up under suction conditions...

I have seen more than once where a rubber line is porous and sucked air through the walls of the hose..... the remedy was to change all the rubber in any areas that "sucked" fuel. pump in the tank and pushing fuel was a different ball game.

william
magnakansas is online now   Reply With Quote
Old 08-02-2022, 06:49 AM   #5
New Member
 
Join Date: Aug 2021
Posts: 4
I replaced the Main fuel pump bolted to the front of the block.
Snoopjohnny5 is offline   Reply With Quote
Old 08-02-2022, 06:51 AM   #6
New Member
 
Join Date: Aug 2021
Posts: 4
I replaced the 2 check valves that screw into the filter housing on one side and has the line coming in from Fuel tank on one end and the return line that goes back to tank. I cant find any other check valves.
Snoopjohnny5 is offline   Reply With Quote
Old 08-03-2022, 06:54 AM   #7
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 2,303
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford 1998 e350 4x4 7.3 2 mercedes 2004
Engine: 7.3 powerstroke & MBE906
When mine had the same problem I took the fuel pump assembly off. If I remember correctly, probably should re-read my posts 3-4 yrs ago on this issue, the output of the gear pump goes into a fuel gallery in the engine blocks casting.

A new pump for the mbe was $180 or so, a rebuilt kit a lot cheaper...bearings..o- rings..etc.

With some studying it showed that there is a bypass valve integrated in the pump housing so that fuel can be pumped thru the system with a hand pump. See mbe manual and articles.

Anyhow ,my bypass valve was broken and was not on the rebuild kit. Without a partnumber I could not buy one and it looked to me that it was very hard to replace since it was stamped I to the casting... Very similar to the checkvalves stamped into the mechanical fuel.pump of the power stroke 7.3..

That is how I recognized that it was even a checkvalves.

Maybe you have some debrie stuck there or yours is a rebuild unit without a new bypass valve.

I do not know.. in that time I decided to replace the mechanical pump with an electric Mallory pump.. check out my earlier posts on this problem.

I can only say that last week I tried to start my mbe after 2 yrs sitting for our upcoming trip and it it is very comforting to hear the electric pump building up pressure and be rewarded with an immediate start within one crank.

Good luck johan
joeblack5 is offline   Reply With Quote
Old 08-03-2022, 03:54 PM   #8
Bus Nut
 
sportyrick's Avatar
 
Join Date: May 2006
Location: mid Mo.
Posts: 645
Year: 1976
Coachwork: bluebird
Chassis: F33695
Engine: 427 chevy converted to 466
Rated Cap: 84
Of course you could wire and plumb in an electric fuel pump now just to prime to start. Of course that is going to present a visit from Murphy down the road but would get you going now. The way the valves in most in line fuel pumps work you can pull fuel through them when not turned on.
sportyrick is offline   Reply With Quote
Old 08-03-2022, 04:34 PM   #9
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 2,303
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford 1998 e350 4x4 7.3 2 mercedes 2004
Engine: 7.3 powerstroke & MBE906
Took some while to find my old post regarding our mbe 906 fuel pump problem.

Thread: not a skoolie
Post376

This is all a long time ago.
Johan
joeblack5 is offline   Reply With Quote
Old 08-13-2022, 04:57 PM   #10
New Member
 
Join Date: Aug 2021
Posts: 4
MBE 906 Losing Prime

Can someone tell me the purpose of this and what would happen if it didnít work?
Attached Thumbnails
08CB30BA-5EDB-4F10-88F4-0AE69168B322.jpg   38F15FBA-53A2-4AFC-924C-3B0D067BEFFA.jpg  
Snoopjohnny5 is offline   Reply With Quote
Reply

Tags
fuel prime, losing fuel prime

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 10:50 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2022, vBulletin Solutions, Inc.