MBE 900 Misfiring

[are12]

I was wondering if anyone else with the MBE 900 has had any problems with your engine rapping (or like the dealer calls it - misfiring)? And if so, what was done to fix the problem?

We have had to replace, both, the #3 injector and the unit pump, twice and we are still getting the rapping.

We can't be the only one's with this problem - or maybe we can! The only thing I do know is that we have been chasing this noise since we bought the truck and I am getting tired of throwing good money after bad!

 

[Moot]

If a dealer told me my diesel was misfiring I would find a new dealer.

 

[greg334]

Piper may confirm this but I thought that there was a way to put the ECM in to a diag mode and do a cylinder balance test.

 

[are12]

If a dealer told me my diesel was misfiring I would find a new dealer.

If there was a dealer that could tell us something different, believe me, we would be there!

 

[are12]

Piper may confirm this but I thought that there was a way to put the ECM in to a diag mode and do a cylinder balance test.

They have done all types of tests on this truck and the only one that got any type of reading was Detroit Diesel in CT - that was when it showed the #3 injector was bad. The sad part was, after they replaced the injector and fired the truck, it was still making the same noise. So once again, they pulled it back into the shop and took another look at it and told us the #3 unit pump was bad and needed to be replaced. Now, 60,000 miles later, the same unit pump was replaced again!

We are just disgusted and do not even know who to take it to because we get the same results from everyone we have dealt with so far.

The dealer, we go to at home, feels it may be an internal problem and wants to rip the motor down!

 

[piper1]

Yes they can do a cylinder balance test with a computer with DDL software. Sounds like they did that to nail it down to number 3.

If the unit pump is failing in a short time (60 k is short), I'd be looking at a couple of things.

First, make sure it is a fuel noise. Fuel noises change tone with different throttle positions at a given rpm. Mis-adjusted valves that have excessive or not enough lash can cause a "misfire" or cylinder out of balance condition but the noise won't respond to throttle position as much as an injection problem. The valve lash can also come from things like a worn cam lobe or cam follower. Some C-12 cats were bad for this.

Most likely (IMO) the pump was installed poorly. These units need to be calibrated properly to work 100% right. If the tech wasn't familiar with how to do it....? Also, do you see any sealant around the pump? I might be stretching here but the pump seals with an o-ring and IF the tech decided to put some silicone or something on it it would affect the depth of the pump which would affect the effective stroke of the pump. I'm going out on a limb on that one but maybe.

It could be just a bad re-man part.

Not much help to you on this one......if you have any more info maybe I can come up with something.

 

[are12]

Piper, Thanks for the come back.

The 1st time the unit pump was replaced was at Detroit Diesel in CT, I would hope that their techs now what they are doing but that may be a stretch! The mechanic at Freightliner in Dunmore, PA thought it may be a bad part but since it started doing it again, right after we got it back, that seems like a stretch - that we would get two bad pumps. Jim didn't even make it 5 miles down the road from Freightliner when it started rapping again.

When we were at Detroit Diesel, the tech did say that if it still made the noise, after the unit pump was put in, the next thing to look at was the cam. However, it did not make the noise so they just figured the unit pump was bad.

The best way I can explain the noise is it sounds like it is rapping - like you are running it with no oil. This can happen when you have the cruise set, going up a hill or even going down a hill. When this starts, the truck looses most of it's power. Also, when it first starts, if we shut the truck off and let it sit for a minute and restart it, the rapping goes away and it may not happen again for months or it could do it 10 miles down the road. (we were told to do this, by one of the techs, when we 1st starting having the problem)

As far as Jim can see, there is no sealant around the pump.

Our main problem with this is, by the time we get to a dealer, the noise has usually stopped. Most of the time, they cannot find any fault codes, even if the check engine light is on. If the shop cannot make it duplicate the noise, Detroit Diesel tells them to "cut it loose"!
So, what do we do? Do we let them tear our motor down and hope they find something? We are about at the end of our ropes with this problem.

 

[JustUsTrucking]

Arlene:
Listen girl: time for a new truck!! Get the big fridge, the roof top air conditioner, the Onan generator, the kitchen drawer and a CAT engine!!!
Talk to you soon. Be safe.

 

[davekc]

Based on your information, I see a couple places to look if it isn't throwing any codes.
Probably done, but make sure there is no water present in the separator. Drain and change filter if this hasn't been down.
Second, you may have low voltage/grounding issue at the fuel pump and or connections to it. This usually will throw a code 32 if the ECM picks it up.
Lastly, and probable, there is a loose connection or grounding issue at one of the injectors. This can happen and never show up on a ECM code or read out. They may have replaced the injector when it could have had a fault at the injector wiring.
This would be intermittent and would show at times with relation to heat/moisture or possibly just vibration a certain way.
Still a tough call without any codes or other info present, unless it can get duplicated while hooked up to a laptop.

 

[piper1]

If shutting the truck off can make the problem go away it really sounds like it's electrical/electronic.

Davekc's advice is a great place to start.

Without codes it will try your patience as techs are taught to follow the codes and very few are taught any more how to listen and think diagnostics. It's a shame really because they should be taught and are more than capable of learning, guess it doesn't pay.

If it's been number 3 both times I'd look at all the wiring for the unit pump #3. Not an easy DIY though.

 

[arkjarhead]

I know this is off topic, but in high school I had an old Chevy pick up and it went to missing. A crazy buddy of mine said pop the hood then he licked his finger and touched the spark plugs some kind of way. They all shocked him except one. So we replaced it. Sorry fr getting off topic.

 

[nightcreacher]

I know this is off topic, but in high school I had an old Chevy pick up and it went to missing. A crazy buddy of mine said pop the hood then he licked his finger and touched the spark plugs some kind of way. They all shocked him except one. So we replaced it. Sorry fr getting off topic.

this is great info,next time my diesel has a miss,ill check my spark plugs,wet my finger,and touch,wait there are no spark plugs. Ark,was just trying to be funny.and as far as the subject,there should be a code,just had injector replaced,they also replaced the harness,said needed replaced evrytime replacing an injector.

 

[are12]

Without codes it will try your patience as techs are taught to follow the codes and very few are taught any more how to listen and think diagnostics. It's a shame really because they should be taught and are more than capable of learning, guess it doesn't pay.

Piper, I think you say it best by your statement above.

Steve, you are right, there should be a code but, most of the time, there isn't. So I guess we will just have to play the "guessing game" until someone is able to figure it out.

Thanks, everyone, for your input on this but so far, everything has been checked by one dealer or another, except for the cam. So that may be our next step but only time will tell.

 

[are12]

Arlene:
Listen girl: time for a new truck!! Get the big fridge, the roof top air conditioner, the Onan generator, the kitchen drawer and a CAT engine!!!
Talk to you soon. Be safe.

Very funny Melaine!

Craig, did you notice I left you out of this. Melanie just likes to be a smart azz!!

Be safe and have fun in Canada!!