Detroit 12.7 Hard Start, High Fuel Consumption


Few weeks ago my 2003 Freightliner Century with a Detroit 12.7 has developed a hard starting problem. It is become so hard to start that I have to use the start up fluid or else I will drain the batteries. Apart from that it has lost power and is consuming quiet a lot of fuel. I got someone to check the codes but unfortunately there seems to be no problem. I have also noted that the fuel in the filter and tank is quiet dark.

A friend suggested I clean and check all the electrical sockets and connections from the batteries right up-to the ECM and all other sensors. He thinks there could be some rust and or loose connections that is limiting the current.

Any suggestions and advice will beappreciated....... Thanks


curmudgeon extraordinare
When was the last time you changed your fuel filter? Your Air filter?

Here's a video of a time I was dealing with a fuel issue. You can see how black the fuel was after I filtered the tank. I was using a fuel filter every day for this crap.

At best, I was getting 7000-9000 miles to a filter. I use a Davco (has the clear dome) filter. You should be able to get 40,000 miles to a filter.

To clean my tank up, I put in EACH tank:
one 32 oz bottle of Diesel 911.
one 32 Oz Bottle of Clear Diesel
1/2 bottle of Kill'em.

After I put that chemical mix in, I filled the tank full of fuel, driving it about 20 miles to make sure that the entire system had mixed fuel in it to clean the system.

I then let it sit over the weekend with full tanks and drove it.

The key part I have found since then, run your tanks down as far as you can get them to on a regular basis. The heat generated in todays fuel system has a tendency to create what is called asphaltene. It's a product in fuel. It starts to reform as you recirculate your fuel and coat your system.

How do you keep from it forming? replace your fuel with new as often as possible. How do you do that? Run your tanks as low as you dare often enough to keep clean fuel in your system.
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Driver just brought in the truck. As I was testing it I noticed the clutch is slipping a little.

By any chances, would that affect the power and Fuel consumption?
I also found a cracked exhaust manifold. Would that cause any harm?

The dash is showing it has 4 active faults, I was trying to check what the codes are by pressing the diagnostic request switch and got the following codes:-

Red/Stop Engine - 46
Orange/Check Engine - 53, 77, 45, 46,16, 42, 56, and 43

The code 46 has been there for sometime and I was told it a low ECM Battery. Dont have any idea about the rest, and they are orange/check engine which means there are inactive. So why does it say there are 4 active faults?


curmudgeon extraordinare
The cracked manifold is just as bad as a bad charge air cooler. So yes, it has to be dealt with.


curmudgeon extraordinare
Hard start is going to be either a compression issue or fuel. Compression either from not having good compression or just not turning over fast enough. Most likely from the later.

How old is the starter? The batteries? The bat+ cables? Are they all in top shape?

If it's a fuel issue, which I doubt, you'd be noticing it dramatically in performance.

You've got a ton of issues on that engine and its going to kill you cost wise to correct it all. I was at close to $4000 before it stopped.

Exh Manifolds are going to push $1100 with parts and labor. Your turbo boots will be a must too. Along with new clamps. Get the red boots too. The blue are for the intake side. Different material to help seal with the heat. I've tried the blue and went back to the red boots. It matters.

I chased issues on my 14L series 60 from the exhaust manifold through the boots to the cac to the intake back to the turbo. That system needs to be completely tight the entire way or you'll loose mileage and power.

And before anyone goes and tells you to get a Pitts urg power ceramic manifold, don't. This is a forced induction(turbo) engine. Ask them for the actual dyno results showing real improvements. They don't exist. Why? Because it doesn't make any difference over a stock manifold.

Even the guys who sold me my turbo when I told them I wanted a blanket told me to not waste my money. They'd have gladly sold one to me, but their testing showed no significant improvement to justify the cost.

If your charge air cooler is leaking, that will Rob you of power and mileage just as bad as a leaking manifold. Often, if one component is leaking, it can hide another issue until you fix it. I fought mine for about 4 months chasing it through the system. When it was finally completed, big difference.

Don't overlook your fan clutch either. That sucker takes big power from you as well. There is a test procedure for it as well. You'll have to talk to Detroit or Freightliner to get it as it is dependent on which clutch you have.
I removed the exhaust manifold and started it (with starting fluid). The cylinders were all heating the same and very little smoke which i think is normal for a diesel engine. I feel the injectors are fine, apart from the seals which are letting oil in to the fuel line. Could the fuel pump cause hard starting and heavy consumption?
I borrowed a fuel pump from a friend and tried it on my truck. There was no change at all. I have now removed the injectors and found that the lower seals (3rd from the top) especially on 3 injectors are dry, very brittle and breaking.

I have ordered a set of seals which I expect over the weekend. I'm just keeping my fingers crossed thatreplacing the seals will resolve my problems. Although few friends stillsuggest I must replace the injectors... Any thoughts??
I changed the injector seals and it was still the same. I got 2 used injectors from a friend and fitted them in cylinder 1 and 3. And guess what??? It fired up without starting fluid.... So guess it was it's the injectors. Unfortunately I can't get the injectors immediately, the friend only had 2. After driving it I still felt it's lacking power, it doesn't have that boost pressure as it had before. Might have to keep it off theroad until I get anew set of injectors.


** Commie Express **
You can't just throw injectors in. You must know the flow rate of each one and program it into the computer. Every injector is bench tested at a certain rate then given a number. That number goes into the computer so they all inject the same amount of fuel.


** Commie Express **

About half the board will recognize that number immediately.
I heard that number has been auctioned off many times around the U.S. Most have a message recorder and it's women calling asking for their lost husband or lover to come back and stuff.