Author Topic: Engine will not start  (Read 3874 times)

Ron Johnson

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Engine will not start
« on: October 07, 2018, 09:52:08 PM »
Moho has not started for 5 months .. 40F .. Tried to start coughed once then the starter just chugged .. Tried again hitting the boost button sounded exactly the same no cough no start. I then manually connected jumper cables from house bank to chassis batts same result..Batteries were 7 years old put new ones in yesterday charged them up .. Same result .. Had roadside assistance charging etc for 45 minutes same result which was the starter turned the engine but except for some white smoke as it coughed again the result was the same.


There is a wire chewed in half lying on a tank in the waste tank bay. As we have not tried to start the engine for months we do not know when the chewing happened. My next step is to try and splice/replace this wire. If anyone has any ideas I would appreciate the input.

Mike Shumack

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Re: Engine will not start
« Reply #1 on: October 07, 2018, 10:49:54 PM »
If you got some white smoke, the engine is trying to start. I doubt that wire has anything to do with your no start problem.
You need the engine to crank around 500-600 rpm on starter. If batteries and starter is good and your getting this cranking speed, my suggestion would be to put fresh fuel filters on (with fresh fuel in the filters). I think you have some fuel gelling due to the low temps.

Ron Johnson

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Re: Engine will not start
« Reply #2 on: October 07, 2018, 11:27:30 PM »
Thanks Mike! More information .. The chewed wire is black and turns out it is a  sheathed cable with metal sheathing plus some cotton strands plus telephone size wires ... Black white and red .. The core is aluminum colored strands. This cable is 3\16 inches diameter.

David T. Richelderfer

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Re: Engine will not start
« Reply #3 on: October 08, 2018, 03:22:35 AM »
Does your coach have an engine preheater, either the electric plug-in style or the AquaHot engine preheat feature?  40F should not cause a problem starting due to being cold.  But preheating may just make the difference because you're getting white smoke.
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Dave Atherton

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Re: Engine will not start
« Reply #4 on: October 08, 2018, 08:58:37 AM »
Ron, would suggestion go to the back of engine an disconnect hose that is connected to the
return fuel pressure thn connet clear plastic hose and put one end into gallon container.
Next have someone turn over the engine like you going to start. What you are looking
for fuel coming from engine into the gallon container. If you have a good fuel flow and
make note of air bubbles In the clear line. If that is ok then check electric panel for 12 volt
power from key switch to the ECM. Dave Atherton retired Cat Mechanic

Mike Shumack

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Re: Engine will not start
« Reply #5 on: October 08, 2018, 02:45:04 PM »
Ron, would suggestion go to the back of engine an disconnect hose that is connected to the
return fuel pressure thn connect clear plastic hose and put one end into gallon container.
Next have someone turn over the engine like you going to start. What you are looking
for fuel coming from engine into the gallon container. If you have a good fuel flow and
make note of air bubbles In the clear line. If that is ok then check electric panel for 12 volt
power from key switch to the ECM. Dave Atherton retired Cat Mechanic

Dave, how much pressure will be in that return hose if/when engine starts?
I want to do this test on my C13 - (i.e. check for suction side leaks) and want to be sure to get the correct type clear hose so that it will not blow.

I saw the "Air in Fuel test" in the CAT manual (which uses a CAT sight-gauge tool), but did not see any reference to the typical pressure in the return system.

Dave Atherton

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Re: Engine will not start
« Reply #6 on: October 08, 2018, 03:09:31 PM »
Mike , yes I understand what you indicated. With the 3126 engine your fuel transfer pump is
different in volume and pressure than the Cat C-13. What we are looking for is starting point
To check to see what fuel is exiting from the engine via of fuel return pressure regulator and
is very important to see if there is spurts of fuel / air, steady stream of fuel while cranking or
no fuel. Note this return fuel pressure regulator returns fuel back to fuel tank in front. Reason
I mention starting point, everything from fuel tank to fuel transfer pump is under suction and
after fuel transfer pump is under pressure. Something as simple as fuel filter was not installed
correct or tighten enough and loosen up just enough to break the suction in fuel line. Air leak
From fitting could be loose allowing air entry. All these little details could perhaps let the fuel to
drain back with suction broken and now fuel transfer pump is cavaiting and cannot push fuel to
the secondary filter that is under pressure before the engine and yes this would affect start up
and operation of engine. Dave Atherton retired Cat mechanic
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Gerald Farris

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Re: Engine will not start
« Reply #7 on: October 08, 2018, 04:42:09 PM »
Gentlemen,
The no-start coach in this thread is a 2000 model with a C-12, so the first place to look at for suspected air in the fuel system is the primary fuel filter screen and/or it's O-rings. If the owner has not checked and/or serviced these O-rings, they could be leaking air into the system since they are now about 19 years old. The plastic screen column should be checked for cracks and/or fuel seepage at the O-rings at least yearly.

Mike,
The fuel return hose only operates under a few pounds of pressure at most. It only requires enough pressure to cause the return fuel to flow back to the tank through about a 3/8 inch opening, so there is virtually no restriction.

Gerald


Doug Allman

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Re: Engine will not start
« Reply #8 on: October 08, 2018, 06:09:10 PM »
I believe Gerald is referring to the RACOR fuel water separator that needs annual if not more service.
If you have a coach that uses the fuel water separator that is a rectangular shaped glass unit with metal backing it also has O rings on the back of it and they can also dry out and result in air into lines and a no start.
Our 1991 Contessa used this rectangular type and after 812 miles running continually we pulled in to a campground on the Interstate 80 to pay for a site. Came back out and would not start even though it rolled over superbly. Spent the night plugged into the Coke machine.
Next morning from NAPA replaced the fuel water seperator and without doing anything else it started right up! All I could see was a few small bubbles of air on top of the sight glass on the old unit - evidently it does not take much air in these diesel engines.

Dave Atherton

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Re: Engine will not start
« Reply #9 on: October 09, 2018, 12:25:47 AM »
Ron,( never assume) I answered your post thinking you had a 3126 Cat not C-12 and your
answer is located on Page two On Ask Dave heading Hard starting C-12. The fuel system
Is a manifold that maintains 90 psi and has a check valve as shown in picture on Ask Dave.
If you have been to one of the DIESEL SEMINAR at different rally’s I have a fuel filter base
For Cat C-12 secondary fuel filter with the check valve. What this check valve does maintains
Fuel pressure on fuel manifold on C-12 and excess fuel returns back to fuel tank in front.
Over time the diesel fuel fines will settle in the check valve and check valve will not seat and
Hard starting will happen. Last there is so a new upgrade that replaces this check valve, did
not look to see if Imposted the new upgrade number if not I can provide you with upgrade
Number. Dave Atherton Retired Cat Mechanic

Ron Johnson

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Re: Engine will not start
« Reply #10 on: October 11, 2018, 07:30:22 PM »
Thank you all for your suggestions. Turns out the problem was a failed starter motor .. I had replaced the starter only two years ago so did not seriously consider this could be a problem but after installing the new one the trusty Cat started right up as though I had just shut it down. The troubleshooting process involved cleaning all grounds and changing out the starting batteries (8 years old).

Thanks again for all your help !!