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Discussion Starter · #1 ·
Hello,

I am new to the 12 valve Cummins, but not to the family. I have worked on two 6.7 before they were my fathers, and now finally bought a 5.9 12 valve. I have ran into the same problem, when I was driving the truck out to North Dakota, where I go to college. Running through Pennsylvania the truck started to lose power at 2,000 Rpm doing about 70. So I back down a bit and ran it at 60 or 1,800 Rpm, it still continued to lose power. So I decided to pull off the turn pike and get to a Napa for some injector cleaner. I had the same thing happen to our Mercedes E300 Turbo diesel, with the same symptoms, but as I down shifted to 3rd, double clutching, she died when she went into neutral. The pickup's a little hard to steer, and stop with no power. :shock:

I then limped to the Napa got some injector cleaner, filled it with clean diesel No 1. then let it idle for a bit. The problem ceased, and the truck made it to North Dakota with no other issues that. Now today she start doing the same thing, but this time She could not even limp to the Cummins dealer in town, I had to get a tow.

I thought that this issue was a fuel filter issue, and decided to bite the bullet and have it replaced at a shop because I really don't feel like messing with this at -18 degrees.

Am I correct with thinking this will be just a fuel filter issue?

Thanks,
-Paul
 

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Probably?:confused013:

It could also be substandard #1 fuel gelling up and waxing in the filter. In which case the new filter will do the same thing. I'm sure some northern folks will chime in here with ideas for the best fuel additives for really cold weather.
 

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The fuel filter could cause this but so could a failing lift pump, failing pressure regulator, or a pinched fuel line.

The spring in the fuel pump on one of my 97s failed at about 240K miles and the pressure dropped to about 20 PSI at idle and to near zero at moderate power settings. Fortunately I already had a fuel pressure gauge installed. I used a fluid filled gauge and a restrictor to keep the needle from ticking.

A post fuel filter pressure gauge would be a good thing to have. Since the fuel pumps are very reliable the gauge would allow you to monitor the state of the filter and to more quickly diagnose running problems.
 

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Discussion Starter · #4 ·
It seems weird to me that I could be a failing lift pump, pinched line, pressure regulator, due to the fact that I has only happened 2 times in the course of 6,500 miles in the past month. If it was a pump failing wouldn't it be a more common occurrence, and a note degrading as the time passed on? Just what I was thinking
 

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Fuel filter or prefilter screen in the fuel heater, we've had a couple of low temp swings this month did problem happen during these times. If so pour some antigel additive in the fuel tank.

no.1 fuel (kerosene) has a lower gel point than no. 2 fuel (diesel)
 

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It seems weird to me that I could be a failing lift pump, pinched line, pressure regulator, due to the fact that I has only happened 2 times in the course of 6,500 miles in the past month. If it was a pump failing wouldn't it be a more common occurrence, and a note degrading as the time passed on? Just what I was thinking
If that is the case it would have been good information for you to have put in your initial post.

Installing a pressure gauge would help diagnosis now and in the future.

I failed to mention the prefilter so it's a good thing Destroked did. It is often overlooked. I've gone aftermarket prefilter on all of mine for reliability and easier service (Larger surface area for water coalescing and a drain). Water and fuel can turn to snot on the prefilter screen and block fuel flow. Of course in cold weather water turns to ice and can plug lines and filters.
 

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Discussion Starter · #7 ·
Just an update. It was the lifter pump that had when, and the plunger was also bad causing the truck to run away. Now just to which body parts I can sell to afford a rebuild.

Anyone's opinion is valued here does $1,700 for a complete rebuild sound reasonable, as in the guy will replace every part on the pump except the injectors. I looked around on the net and saw ones that where $1,200, an when I confronted the guy he said that the ones online aren't completely rebuild they just have some rebuild parts, is this a line of horse, or is there truth in that?
Thanks, Paul
 

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I feel your pain but I don't understand what you meant to say with, "It was the lifter pump that had when, and the plunger was also bad causing the truck to run away."
 

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Discussion Starter · #9 ·
Sorry about that the mechanic said that the lifter pump had failed, or went out on me, also the plunger was warped internally and binding, was causing it to stick
 

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That might explain the intermittent behavior.

I have to wonder how it got bent.

I've never seen any of the following conditions. I am just writing hypothetically.

It can get bent during installation. If the pump piston seized the cam could bend the pin. Since the cam side loads the cam follower pin I suppose very dirty oil could be a factor.

Dismantling the pump and closely examining the parts could be instructive. Look also at the end of the pin that rides on the cam to see if it is galled. Look at the bore in the pump that the pin slides in to see if it is oblonged or scored.

I had a pump run 240K miles on one of my 97s that still looks good inside except the return spring failed.
 

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Discussion Starter · #11 ·
I wasn't able to get a look at the pump before they sent it away. When I get the truck back I plan on adding a fuel pressure gauge, and a boost gauge.
 

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We have two pumps, the lift pump and the injection pump. You use the term lifter pump which by your narrative points to being the injector pump. With that said, $1700 to refurbish the IP is way too much.

In the future it would help if you give some pertinate information since all 12 valves are not the same. In addition, using the correct terms will avoid confusion.

http://www.cumminsforum.com/forum/94-98-powertrain/287781-beginners-thread-read-first.html
 

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I missed the $1700 dollar part. All my posts were about the lift pump only. Part of the confusion to which GAmes referred.

When I P-pumped my 98.5 I bought a new P7100 for $1600.
 
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