Cat 426 Engine Will Not Run

[Rocket Man]

Ok, back again. Got the hydraulics problem solved and now the motor keeps dying. It will start up and run maybe 2 minutes sometimes and 15 minutes at the most and then it will scale back like it is going to idle and then just quit.
When it is running it runs good, but does not last long.
Here is what i have done so far:
1) Changed primary and cleaned lines, blew out lines to tank.
2) Changed secondary and blew lines to tank.
3) Operated it on mechanical pump, no change
4) operated it on an electric pump, no change
5) Blew lines out to tank, no change
6) Cleaned filter in the injection pump, no change
7) Looked for and can not find the return line check valve, (do they even have one?)
8) Installed a rubber hose directly into tank thru the filler port to bypass hard line, no change.
9) Put rubber line in 5 gallon can directly and no change.
10) Exhausted all my patience, got mad and kicked tires, no change.
So, if anybody out there has any ideas please let me know so i can try whatever it is i am missing.

 

[funwithfuel]

Not familiar with CAT products, could you post a pic of your injection pump. A pic of the serial tag would help the CAT knowledgeable to help you better. Is this a pump-line-nozzle engine or common rail?

 

[Vetech63]

Are you positive its a fuel problem? I have had electrical shutoff solenoids act similar.

 

[heymccall]

Is there a screen on top of the mechanical pump?
Did you clean that?

 

[Rocket Man]

Not familiar with CAT products, could you post a pic of your injection pump. A pic of the serial tag would help the CAT knowledgeable to help you better. Is this a pump-line-nozzle engine or common rail?

Here are the pics of the pump and rail. Pump was rebuilt 6 months ago. I can not get the plate because it is mounted on the underside of pump but here is the number of it :"
Rebuilt Injection Pump 4.236 Perkins and Caterpillar 3343F742".

 

[Rocket Man]

Is there a screen on top of the mechanical pump?
Did you clean that?

Yes, screen is clean. I can get a flow of fuel to the pump by taking the INPUT line loose. Has a good flow BUT there are bubbles in the flow. I let it run a long time and bubbles did NOT clear up. Now i have to find the air leak on the input line somewhere. Must be a hole in the line somewhere? OR is it normal for electric pumps to produce bubbles? Seems unlikely to me.

 

[Rocket Man]

Are you positive its a fuel problem? I have had electrical shutoff solenoids act similar.

No, am not sure of it. Never thought of the solenoid being the source. Is it possible for the solenoid to act that way? How can i eliminate the electric one and go to a manual one?

 

[jimg984]

you don't say anything about fuel flowing from inj. pump to fuel storage tank,, must have flow back to tank to work right, reliefs pressure and get rid of air

 

[funwithfuel]

The bubbles are a concern. Seeing what you're dealing with, the first issue I see is the fuel lines. Those damn rubber olives. They suck air, leak fuel. Wherever you can replace a length with hose barbs and rubber line, that's what i would do. That water separator/filter housing is another nightmare. The top and bottom seal/gaskets get dry and suck air as well as the central screws seal ring on top. Since it's a Perkins , do you have a fuel line that runs across to the intake manifold? Most are equipped with a flame start which will sometimes cause aeration problems as well.

 

[Rocket Man]

you don't say anything about fuel flowing from inj. pump to fuel storage tank,, must have flow back to tank to work right, reliefs pressure and get rid of air

Oh yes, you are correct. I did check to see if fuel was going back to the tank and it has a free flow back. I can hear it flowing back into the tank, engine off and key on with the electric fuel pump on. Stoll don't know why the fuel has bubbles in it.

 

[Rocket Man]

The bubbles are a concern. Seeing what you're dealing with, the first issue I see is the fuel lines. Those damn rubber olives. They suck air, leak fuel. Wherever you can replace a length with hose barbs and rubber line, that's what i would do. That water separator/filter housing is another nightmare. The top and bottom seal/gaskets get dry and suck air as well as the central screws seal ring on top. Since it's a Perkins , do you have a fuel line that runs across to the intake manifold? Most are equipped with a flame start which will sometimes cause aeration problems as well.

No flame start on this one. Fuel lines are direct to the filters and fuel pump. I bypassed the separator and ran line direct from tank source to the electric pump. Was checking just what you are talking about and it did not solve the problem. I took the mechanical pump out of the equation and that did not help. I just replaced all rubber lines with new rubber hoses and that did not help. I am now suspecting the injector pump itself. No matter what i have done so far, the max running time is about 15 minutes before it starts shutting down. Slow shutdown, not immediate like turning key off.

 

[funwithfuel]

This is a job for thepumpguysc.

 

[edgephoto]

Was the pump "rebuilt" for this concern? Or did this appear after?

From your description it sounds like it is running out of fuel. When it starts to die try a squirt of ether and see if it makes a difference. I mean a squirt not 1/2 the can.

 

[funwithfuel]

Does your muffler rattle a lot? I'm wondering if a broken baffle could be choking the exhaust.

 

[Rocket Man]

Was the pump "rebuilt" for this concern? Or did this appear after?

From your description it sounds like it is running out of fuel. When it starts to die try a squirt of ether and see if it makes a difference. I mean a squirt not 1/2 the can.

Actually it dies too quickly for that action. However i do try to start it back up with the ether and it does try to start but wont stay running. Let it sit for a few minutes and then start it with ether and it will run for max of approx 15 minutes.

 

[Rocket Man]

Does your muffler rattle a lot? I'm wondering if a broken baffle could be choking the exhaust.

No, the muffler is ok. But you do stir up some doubts about the intake system. Will check the intake filter today to see if MAYBE it is clogged up. That would be embarrassing.

 

[Rocket Man]

Well, i changed the intake filter that was not very dirty anyway, but changed it anyway. NO CHANGE, ran about 10 minutes, scaled back to idle then died.
So began another approach. This time i took a closer look at the pump. I discovered there is a chckvalve in the return line that comes off the pump. The attached photo shows where it is located.
First off i loosened and removed the line that attaches to the checkvalve and turned key on. There was very little fuel coming out of the hole.
I then pulled the checkvalve and turned the key on and the fuel ran freely. It did NOT squirt out, just kind of FLOWED out,,, is that the way it is supposed to be??
In contrast i took the supply line loose on the back of the pump and fuel Squirted out hard.
I then looked at checkvalve which seems to have a steel ball held in by a spring. Pic attahced. The ball is tight in the tube and does not rattle when i shake it. Is that the way it is supposed to be?? It is hard to depress with my finger. Not sur why. Also not sure how that spring and ball are held in the tube.

 

[Rocket Man]

OK, another question while i am on this subject of fuel return. I can not figure out the sequence or logic on the fuel return line.
For instance i know that when i turn the key on i can hear fuel coming back into the tank from, i assume, the return line.
So in my prior post i took out the line to the "check valve" and discovered there was no flow from the line or the pump. However when i took out the check valve itself the fuel flowed out when i turn on the key.
So question is, at what point does the fuel decide to enter the return line and from where? Is it returning from the secondary, pic attached, or does the fuel go thru the pump and exit thru the checkvalve? Note that there is a "T" on top of the secondary filter. So what keeps the fuel from flowing back into the pump check valve.

 

[funwithfuel]

The pump check valve. The spring loaded ball does 2 jobs, it maintains pressure in the pump, once the pressure need is satisfied, the ball unseats and allows fuel to get by to return. The pressure is always pump first, so flow will carry away . Does this make sense?

 

[Rocket Man]

The pump check valve. The spring loaded ball does 2 jobs, it maintains pressure in the pump, once the pressure need is satisfied, the ball unseats and allows fuel to get by to return. The pressure is always pump first, so flow will carry away . Does this make sense?

Yes. I do understand that logic. After i took out the check valve i set up to clean it and as i was looking at it i can see a tiny pinhole right next to the ball in the body of the seat. I tried to take a pic of it but it would not come out right.
Is that the way it supposed to be? It appears to me that the pinhole would allow the fuel to go straight thru the valve thereby reducing the pressure needed for the pump?
So, if that check valve is defective would that be the cause for the way the engine is acting? ie run for a few minutes and then just taper off to an idle and then just die? Wish i knew more about these things.