out of hope mp7 fuel issue

[refuse guy]

Hey guys i have a 08 mack mp7 that is losing fuel pressure while under load. we have replaced the fuel supply line and all fuel lines on the motor, also injector cups and injectors have been done 3 times in the last 50,000 mi by the dealer. then we did the fuel filter housing and main fuel pump any ideas will be greatly appreiciated. We are sick of the dealer guessing and throwing parts at it and would like to get the truck fixed.

[staxx]

How do you know you are loosing fuel pressure is it just running rough hard to start are you driving and watching fuel psi with computer or manual gage . First thing I would check for is oil in wire harness at engine ecu if the truck is running rough this can be caused by more than just fuel pressure.

[refuse guy]

using the mack software to watch fuel pressure. at first we thought it was regen related since it would die when it tried fueling the aftertreatment, It now seems to do it all the time it will idle fine and rev in neutral but when underload it will bog sputter and die then it will start and idle but if you touch the go pedal it stalls and dies and you can watch the fuel supply pressure go from 45 to 0 psi. the harness was changed last year, twice because the dealer did it under warrenty and ripped two of the wires pulling it thru the hole the first time. then it ran good for 6 months, and now its back to this.

Edited October 31, 2012 by refuse guy

[Mackpro]

Have you replaced the fuel pressure regulator on the left side front of head? The new style should have 2 knoches on it. Check the fuel lines and blow out the ECM cooler plate fuel galley and check the fuel line coming out of the ECM cooler plate as it goes into the back of the filter stand , it seems to plug at the filter stand banjo fitting. If black rubbery snot looking stuff is found , add asphaltteen ( spelling???) fuel treatment made by Fleetguard, its the only thing that will clean this stuff out. If still no luck I would pull the injectors and checked for cracked cups or injectors. If its been changed to stainless cup already check for hairline cracks in injector body. The stainless cups dont give like the copper ones and cracks the injector.

[staxx]

Dont forget to check fuel tank for debris if you have duel draw fuel tanks this shouldnt be a issue but singal tank could have cracked pickup tube sucking air ....just a few weeks ago I found a entire fuel nozzel from a fill pump at truck stop in bottom of tank.

[refuse guy]

thanks for the response we did the regulator with the lines i belive its just the banjo bolt. The injectors seem interesting but why no fuel in the oil and why does it sometimes run ok for a few hours. I will defintantly check the injector but it doesnt make a lot of sense. yeah we just pulled the tank to check the stand pipe we pressurized it no air loss resoldered it and rechecked it and ran it again still the same thing goes ok for a few hours after the fuel sstm is apart then it falls on its face again

Edited October 31, 2012 by refuse guy

[staxx]

There are several banjo fittings that need to be checked .

[Mackpro]

I take it that in injectors have never been out? I know of only 1 2008-2009 MP engine in our area that still has the orignal copper cups/injector holders in it, most were replaced once with the original style copper the again with the new conical stainless cups and injectors. Some would be hard to start after setting and some would set low fuel pressure codes only after getting warmed up. We say many weird things caused by compression in the fuel system from a leaking injector cup.

[refuse guy]

injectors and cups have been replaced 3 times with updated cups all three times.

[Mackpro]

Make sure your primary fuel filter is a Mack brand filter. Many other filters may say they fit but the Micron rating might be to small and since the primary filter is on the suction side its hard to suck through 5, 7 or 10 micron when it should be and 25 or 30. But its easy on the secondary side where you are pushing fuel through a 5 micron filter. We had problem with a customer who liked to use balwin filters on his truck and it would have low power/ fuel pressure only with a loaded trailer.

[DCR]

Make sure your primary fuel filter is a Mack brand filter. Many other filters may say they fit but the Micron rating might be to small and since the primary filter is on the suction side its hard to suck through 5, 7 or 10 micron when it should be and 25 or 30. But its easy on the secondary side where you are pushing fuel through a 5 micron filter. We had problem with a customer who liked to use balwin filters on his truck and it would have low power/ fuel pressure only with a loaded trailer.

That is interesting about using Mack fuel filters. I have a 2000 Vision with an E7 460. Does the Mack fuel filter apply to this engine also?

Thanks

[refuse guy]

It appears the fuel pump is internally regulated and when we removed it the gear housing was full of fuel? it looks like it has a weep hole like a water pump is this lubricated by fuel? we replaced it again maybe a defective unit. It seems to have improved. its on route today will let you guys know thanks for all the tips.

[Mackpro]

That is interesting about using Mack fuel filters. I have a 2000 Vision with an E7 460. Does the Mack fuel filter apply to this engine also?

Thanks

Not so much on the older engines it seems. Our boss has been experimenting with fuel filters brands and part# s on the MP engines and has found out some intresting stuff! On the older trucks with the Davco fuel filter/ plastic upside down bowl style fuel filter system, there is alot of different micron rating filter that we didnt know about.

[Mackpro]

Heres some info on the pump. We always replace them as a set or they will leak fuel.

PV729 -FSB233-004_M.pdf

[DCR]

Thanks Mackpro. I have the primary and secondary spin on filters.

[staxx]

Found this the other day banjo fitting inlet side of ecu cooling plate completly clogged with debris another shop had replaced cups and fuel pump but this is the real problem.

[Keffer inc]

Did that new fuel pump fix your problem? How does one check the fuel pressure on a mp8? I have a 2011 mp8 455hp and at higher (1400 rpm and up or 60 mph +) I get a mid fire, if I'm empty, I can go about 30 miles and the misfire goes away, almost like something turned on or got powered up, but if Im loaded, it normally won't go away. 

I have changed the fuel filters with Mack filters, cleaned the plugs that go into the ecm. Thats all I've done so far. When I get home next weekend, I think ill look at the banjo bolt at the ecm fuel cooler and see if there is debris. Would checking preasure confirm clogging?

 

Another theory is the injector plugs have oil contamination? I haven't pulled the valve cover off yet to know, but what you ya'll check?

[bts-4120]

On 11/2/2012 at 8:17 AM, DCR said:

That is interesting about using Mack fuel filters. I have a 2000 Vision with an E7 460. Does the Mack fuel filter apply to this engine also?

Thanks

I run baldwins on my 01 427  with no issues  it makes 95 or 100psi of fuel pressure.   I wonder who makes  Mack Filters anyway