C7 Cat is Hard to Start

[suibielski]

I have noticed recently that my C7 is very hard to start in both warm and cold weather. When it does start, blue smoke comes out for about 30 seconds. Also, my fuel mileage has dropped from 8 to 7.5. Otherwise, it runs fine. Any suggestions?

Jim Suibielski

2007 Tiffin Phaeton

[wolfe10]

Jim,

Welcome to the FMCA Forum.

Very difficult for us to "arm chair" diagnose your issue.

My first question is how many miles on it. If 30k plus, have you had the initial valve adjustment?

Has a Caterpillar dealer put it on their computer to check for codes?

As far as starting, is the intake manifold heater working as it should?

When were the fuel filter(s) changed last? Clogged filters can give several different symptoms.

[dave111451]

Does this happen after 8 - 10 hours of not running or every time you start it? If it does it after sitting a few hours it most likely has a small leak where air is getting into fuel system. Usually causing long crank times, smoke for awhile after starting, sometimes will run rough till air bleeds out. Can be hard to find leak because they mostly are internal. Good luck Dave

When this happened on our buses usually never set any codes.

[wolfe10]

To expand on Dave's post, the air leak into the fuel system is on the suction side of the system. So, between fuel tank and lift pump. A loose hose fitting, crack in fuel line between tank and primary filter or primary filter and lift pump, leak at primary fuel filter, etc.

Were the leak on the pressure side (after lift pump) instead of allowing air to be sucked into the fuel, you would have a fuel leak.

ALL diesels are cranky when their normal fuel supply is "supplemented" with air in the fuel line.

[jamador]

Couple things to check. FIrst, in relation to MPG, when was air filter last replaced? Have the precharge (air to air) hoses and clamps all been pressure tested? Tire inflation and tire wear all also play a huge part in MPG. Overhead ran as previously stated should be done every 300 to 500,000 miles.

In regards to hard starting, first, filters as previously described and did o ring get put on and replaced upon installation, this engine is famous for injector leak off, from o rings inside-injectors. This will need to be pressure tested also.

Lastly, age of fuel, with today's low sulfur fuel it don't take long for fuel to get bacterial if fuel looks black in filter you will Need to treat tanks and replace filters several times before solving this issue.

While this sounds like a lot, routine preventative maintenance is always priority, on any engine, overall in my opinion cat makes an exceptional motor and you should have years of trouble free issues...

[jamador]

I should have added one last thing, there may be a hand pump on top of primary fuel filter, if there is replace this first, not just gasket before pressure testing it is inexpensive and easy to change. Again you must change both hand pump and gasket.

[bfpruuitt]

Hi Jim,

I have the same problem-- 2007 Phaeton Cat C7 hard to crank.

I noticed when I fill up and park in storage building, I have fuel on floor under the tank. I have a bad fuel gauge also. I have appt. to replace fuel gauge and will get the line checked then.

This thing has been hard to start since new. 32000 miles. Filters have been changed. Fuel probably leaking back?

bp

[Garyr]

Had a problem on an older coach and found the vent tube on fuel tank was closed shut from the factory.

When I opened the fuel fill cap there was the sound of suction. Hose from top of fuel tank had a tie wrap to close this vent.

Solution-- cut the hose no more problem.

[suibielski]

It turned out to be dirty fuel injector(s). I put some diesel fuel conditioner in and my MPG went from 7.4 to 8.2. Starting problem is gone. Thanks for the responses.

[wildebill308]

Welcom to the forum. Glad you found the problem.

Bill