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Wayne
Wayne, Journeyman
Category: Heavy Equipment
Satisfied Customers: 9345
Experience:  34 years experiance as engine rebuild and problems.Thermo-King repair and trouble shooting.
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A 3406E cat engine in a 9400 int.that is..Camshaft sensor..fire right

Customer Question

We have a 3406E cat engine in a 9400 int.that is hard to start after setting for 8 hrs or so. Camshaft sensor has been replaced and didn't help.If we use either it will fire right up and run great.Any ideas?
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  Wayne replied 7 years ago.
Hi I'm Wayne,
I will help you with this,
Sounds to me like your losing your prime pressure
On the back of the filter inlet side is a check valve ,this is letting fuel leak back down, causing a no pressure when you try to start, and will start on Either
Just go to the dealer, and ask for fuel line check valve.

If this helped you, please hit Accept,if not get back to me...Cool
Wayne, Journeyman
Category: Heavy Equipment
Satisfied Customers: 9345
Experience: 34 years experiance as engine rebuild and problems.Thermo-King repair and trouble shooting.
Wayne and other Heavy Equipment Specialists are ready to help you
Customer: replied 7 years ago.
I changed to fuel line check valve on the 3406E cat and it still dont start. it will start after cranking for ever! do you have any other suggestions?
Expert:  Wayne replied 7 years ago.
HI 2cgr6j16,

No I do not, I am going to opt out, we have several veryy good Cat experts on line hang tight,I will try to get one of them .

Thanks, Wayne
Expert:  Cat Man replied 7 years ago.

Hi. Thanks for using JA! I will try and help you out.

I would like to ask you a few questions if that is OK. This will help me give you accurate information.

First, When your engine eventually runs, does it smoke and run rough like the fuel has air in it? Then does it run good all day until it is shutdown? Then the next day it is hard to start again?

 

Thanks.

Customer: replied 7 years ago.
right as it starts up it might smoke a little but i cant say it runs rough like it has air in the line! When it is started it will run fine you can shut it off and 30 min. later it will fire right back up, it is when it sits over night it will not start.
Expert:  Cat Man replied 7 years ago.

Thanks for the information.

It sounds to me like the fuel is leaking out of your engine. Wayne recommended the same thing I would have. The fuel pressure regulator is always the most likely cause. It will fix this problem 9 times out of ten.

Since the regulator did not fix it, there are only 2 other reason the fuel can leak out or your 3406E. You either have a plugged or restriction fuel tank vent tube or a bad fuel transfer pump. It easy to check the vent tube. Just blow air threw it. If it is restricted, the supply line will pull a vacuum on the fuel system and suck the fuel out of it.

If your vent line is OK. The problem is your fuel transfer pump. When the engine is shutdown both the regulator and the transfer pump are suppose to hold fuel in the engine.

Basically, the relief valve in your transfer pump is not closing. Slowly over night the fuel is leaking out. The only way to test this is to cap off the fuel inlet port of the transfer pump. If the next morning you reconnect the line and the engine cranks and runs fine, it is the transfer pump.

Most of the time I check the vent, then check the regulator, if they are OK, I replace the transfer pump.

 

Please let me know if you have any more questions.

Expert:  Cat Man replied 7 years ago.

Hey. I just wanted to see how things were going.

 

Please let me know if you have any more questions.

Customer: replied 7 years ago.
insted of caping the line i went and put a ball valve right before the transfer pump and i just got done running it and parked it for the night shut the valve off and we will see what it will do in the morning. I checked the vent tubes they where fine. Do you think the valve idea will work?
Expert:  Cat Man replied 7 years ago.

Yes. It should. Basically what happens is when the check valve fails, fuel will return to the tank via the fuel inlet line. In order to do this, air will be sucked either from the weep hole of the transfer pump. Or it will be sucked passed the shaft seal of the transfer pump. If we stop the flow of fuel to the tank, the fuel should stay in the engine.

 

Let me know how it works out.

Customer: replied 7 years ago.
ok will do!
Customer: replied 7 years ago.
I went out and tried to start the truck this morning and it did the same thing it just cranked and cranked the valve that i put in was cosed all night! got any other suggestions. I was thinking that it might be leaking back before the valve but the valve is lower than some of the other parts of the fuel line.
Expert:  Cat Man replied 7 years ago.

Thanks for the information.

If you have a new regulator and you have closed off the inlet fuel line it sounds like your engine is not losing prime.

I have 2 other things that could cause this.

One is that your ECM is not receiving adequate voltage "During Cranking". This means that when the starter is engaged and pulling amps, the voltage to the ECM falls to low for it to operate. Of course, when you use either to fire the engine and release the starter at the same time, the ECM then gets enough voltage to operate. I know this sounds crazy but I have seen this several times. The only way to verify this is happening is to supply the ECM with a separate 12 volt supply. If this is the problem, the engine will start.

The second thing is that you have severly worn injectors. I have only seen this problem a few times in my career on a Cat. The EUI injectors at a cranking speed cannot induce enough pressure to unseat the needle in the injector at a cranking speed of around 250 RPM's. The problem is that the pressure is escaping the injector and going passed what is called "Worn poppet seats". The only way to verify this is to replace at least 1 of the injectors. If you crank the engine over and hear it trying to fire on one cylinder, you'll know worn injectors are the problem.

 

Please let me know if you have nay more questions.

Customer: replied 7 years ago.
ok one thing i did not tell you is that this morning it cranked for awhile and then it started with out ether. would this narrow it down to one or the other
Expert:  Cat Man replied 7 years ago.

Yes. If it cranked for a while and eventually started, it may be the injectors. If it was a low voltage condition, I would think it would have never started.

 

Do you know how many miles are on your injectors?

Customer: replied 7 years ago.
ok got some more stuff on it. I talked to the two guys that owened it before me and they have not done any thing to the engine besides put bearings in the bottom. and he took it to a shop and they thought it was the injectors to and they took them out and checked them and they where ok. Could it be that my fuel pump is week enough that it takes awhile for it to build up enough pressure to activate the injectores. The macanic that checked the injectores thought that might be a posibility. But they never checked it out. what do you think. the truck has 900,000 miles on it. as far as they know nothing else has been done to the engine.
Expert:  Cat Man replied 7 years ago.

Thanks for the information.

It's possible that your fuel pump could be weak. You could test it by installing a gauge to the outlet of the pump. Crank the engine and see how much pressure the pump builds. It should hold steady around 905 psi during cranking.

However, 900,000 miles is alot for injectors.

Customer: replied 7 years ago.
but it has benn doing it since about 750,000 miles and they just lived with it
Expert:  Cat Man replied 7 years ago.

Thanks for the information.

That makes sense if the problem has been happening since 750,000. To be honest, Injectors rarely last that long.

I am thinking your injectors are worn and causing your problem.

Customer: replied 7 years ago.
Hey Scott! We finally fixes our problem. There was an Oring bad on one of the injectors about half of the Oring was gone and it was letting air in. and now it cranks over one or two times and fires right up. I thank you for you help.
Expert:  Cat Man replied 7 years ago.

That is Great! I'm glad you found an o ring problem and you didn't have to replace any injectors.

Please let me know if you have any more questions.