Intermittent fuel starvation

[Acoals]

Cat 305c, HWJ01191

After sitting for a week, the machine would crank but not start. Took lines off and blew through, pressurized tank, ect, no good. I used a temporary fuel line to bypass the filter assembly, pressurized with air, machine started. Ran it onto the trailer and brought it back to the shop. I replaced the fuel filter and replaced all the o rings in the filter housing. Machine started but had a miss. Shut it down, started it 15 minutes later, ran fine.
Ran the machine for a couple hours, and then it starts bogging and stumbling. I replaced the fuel lines from the tank to the lift pump, ran good, finished the job I was on, about 2 hours. Next job machine runs a couple hours and the problem returns. I had a lift pump for it, so I replaced that. The new lift pump sounded louder and stronger, and the machine ran well . . . for a couple hours.
At this point the fuel tank has been drained and inspected, the pickup tube inspected, all the rubber fuel lines replaced, the filter assembly re sealed and the lift pump replaced. The machine will run like a top for a couple of hours, and then start stumbling and bogging out, at times it can be restarted, give it some throttle and it will be ok for a while. The problem does seem to be worse when the machine is hot and ambient temps are high.

I don't know much about injection pumps, and I sure don't like throwing big money parts at something without being sure that is the problem, but I am not sure what else it could be at this point. Am I missing something? Could an IP failure be intermittent like this?

 

[Nige]

One thing you that didn't mention is the fuel filter head assembly. They have a nasty habit of trapping particles in the passages.
Remove the filter assembly complete, take off the element, then remove all the pipe fittings/connectors & plugs that are in the head. Blow through all the passages with compressed air. Reassemble and try again.

Question: When the engine starts to stumble after running for a couple of hours, have you tried cracking the fuel tank cap loose to check for a vacuum in the tank.?

 

[Acoals]

I actually did clean out the filter head. I had the whole assembly torn down completely, sorry to leave that out. I have been kind of banging my head on this for two weeks now and I was trying to avoid writing a volume that nobody wants to read . . .

Edit: I started the machine cold just now to take it off the trailer, started fine, idled for a little and then started stumbling. I took the fuel cap off, didn't notice any vacuum, and the machine continued missing a bit with the cap off. I think that should eliminate the vacuum possibility.

 

[Nige]

Well that ticks those two boxes at least.......

 

[Acoals]

Any possibility of getting a copy of the procedure to R+R the IP? I know there are timing marks and such to be tended to . . .

 

[Nige]

Here you go. This should be everything.

 

[Delmer]

The fuel starvation can come from the fuel system blocking, that will cause a vacuum somewhere in the system, and usually leak air in and cause stumbling. Or air can be introduced from a damaged injector, would have to be pretty catastrophically damaged, and I don't think it would come and go.

Still most likely to be a blockage, sounds more like a suction leak. But since you tried that already, have you checked the inlet to the transfer pump on the side of the injection pump? see if there's a screen inside that banjo bolt, the bolt pointing straight down under the transfer pump, visible on Nige's pdf's, usually hidden from view on the machine. The other possibility is still something floating around the tank, like a piece of plastic is all it would take.

You could tee into the fuel system before the injection pump with a fuel pressure/vacuum gauge to see what that does when running normally, and when it stumbles. There is probably also a port on the injection pump to test internal pressure, that will be something like 20-30 PSI, again, when running normally, and then when stumbling. I'd want to try those before removing the injection pump, just not easy for an injection pump to fail intermittently like that as far as I know.

 

[Acoals]

I drained and checked the tank yesterday, there were a few bits of trash, cleaned them out, still having the problem.

There is a screen in the pump inlet, I just pulled it out and found it to be clean.

 

[Acoals]

I tee'd in a gauge between the lift pump and the IP. Not sure how accurate the gauge is; some random vacuum/pressure fuel gauge I found in the bottom of my box.
Warmed up and idling it is reading about 2psi, it drops down a little at full throttle, to about 1-1.5.
Right now the machine is running fine at full power, but idling it will intermittently miss. The gauge doesn't really do anything when it misses, except that it seems like the needle will start fluttering more at idle and when the engine stumbles. Again, this is some auto parts store gauge of unknown quality . . .

Does Cat publish a spec for the lift pump pressure?

 

[Delmer]

The lift pump absolute pressure doesn't mean anything to me, just that it stays consistent. Just keep working until it stumbles and see what the pressure does then. Putting it on the suction side might show more dramatic results, very little vacuum when running, I'd expect 5-10 in hg (2-5PSI) vacuum if the fuel plugs up.

 

[Nige]

Does Cat publish a spec for the lift pump pressure?

Not exactly, although 1-3psi is quoted as being the "normal" pressure range. See M0121431.
It appears as though the symptoms of low fuel pressure and/or the presence of air in the fuel system are not unknown on this product line.
The original 240-8381 fuel pump was updated to 370-4008.
See attached for troubleshooting low fuel pressure.
I reckon you need a known accurate gauge probably no more than 10psi full scale reading to accurately measure fuel pressure.

 

[heymccall]

You insist that the filter head was thoroughly cleaned...but, I have seen the inlet elbow plugged, and, more importantly, the outer concentric pipe that the filter pushes onto. I know I have pictures on here somewhere.
I'm arguing a $3k bill on a takeuchi for the exact same intermittent restriction, as I have replaced all of my Takeuchi screen filters with that filter assembly. It had a straw and dirt blockage that moved around to the inlet side. Ran like a top and then would randomly shutdown.

So, what I would do...remove filter, remove filter head, remove inlet fitting, and daylight all the way through the inlet fitting. Then, daylight all the way through the inlet port thru to the outer concentric tube that the filter seals upon.

I would follow this up with a Napa 3972 inline screen between the tank and said filter head.

The blockage on mine have been in the inlet fitting AND where highlighted below.

 

[Acoals]

You insist that the filter head was thoroughly cleaned...but, I have seen the inlet elbow plugged, and, more importantly, the outer concentric pipe that the filter pushes onto. I know I have pictures on here somewhere.
I'm arguing a $3k bill on a takeuchi for the exact same intermittent restriction, as I have replaced all of my Takeuchi screen filters with that filter assembly. It had a straw and dirt blockage that moved around to the inlet side. Ran like a top and then would randomly shutdown.

So, what I would do...remove filter, remove filter head, remove inlet fitting, and daylight all the way through the inlet fitting. Then, daylight all the way through the inlet port thru to the outer concentric tube that the filter seals upon.

I would follow this up with a Napa 3972 inline screen between the tank and said filter head.

The blockage on mine have been in the inlet fitting AND where highlighted below.
View attachment 291712

Completely tearing down the filter housing and thoroughly cleaning it as you described was the first thing I did. I actually had problems with nearly identical symptoms with this machine 4 years and 1300 hours ago when I first bought it. Back then I found the filter housing to be all plugged up with dirt as you described, as well as the hose from the tank was failing internally.

This machine was the first I have bought sight unseen from another part of the country, and will likely be the last. It was a bit of a mess when I got it, and I had to sort through a number of issues early on. It's been a good machine since though.

 

[Acoals]

Thanks all for the input, I really appreciate it . . .

I was talking to a buddy of mine today, going over the symptoms, and he pointed something out which may be pertinent. Currently the machine seems to be running fine at high rpm, although I have not really had the chance to work it much since the last things I did, but at an idle it will intermittently stumble. The stumble at idle seems to be a miss, which does not equal fuel starvation. Other times it will bog down and die from full power, but today it has only been intermittently missing at an idle, increasing engine speed smooths things out.

 

[Nige]

Thanks all for the input, I really appreciate it . . .

I was talking to a buddy of mine today, going over the symptoms, and he pointed something out which may be pertinent. Currently the machine seems to be running fine at high rpm, although I have not really had the chance to work it much since the last things I did, but at an idle it will intermittently stumble. The stumble at idle seems to be a miss, which does not equal fuel starvation. Other times it will bog down and die from full power, but today it has only been intermittently missing at an idle, increasing engine speed smooths things out.

As others have pointed out, the way you describe the symptoms doesn't sound like fuel starvation, or even injector pump related.

To tick another box, have you checked the valve adjustment recently.? I'm just wondering if on these engines the valves tend to hammer into the seats and as a result close up the clearances.

 

[Acoals]

As others have pointed out, the way you describe the symptoms doesn't sound like fuel starvation, or even injector pump related.

To tick another box, have you checked the valve adjustment recently.? I'm just wondering if on these engines the valves tend to hammer into the seats and as a result close up the clearances.

I have never touched the valve train, actually. Judging from the condition of the machine when I got it neither has anybody else. The machine has 5400 hours on it.
Wouldn't a valve lash issue cause a constant problem?

 

[Nige]

I have never touched the valve train, actually. Judging from the condition of the machine when I got it neither has anybody else. The machine has 5400 hours on it.
Wouldn't a valve lash issue cause a constant problem?

@5400 hours it's well overdue for valve lash. Why not whip the valve cover off and do it.? You have nothing to lose. In my experience valve lash issues are usually more pronounced at low idle than they are at higher RPM.

Does it burn any oil at all.?

 

[Acoals]

@5400 hours it's well overdue for valve lash. Why not whip the valve cover off and do it.? You have nothing to lose.

Does it burn any oil at all.?

It doesn't burn oil. I will do it though, should be done anyway. I do need the procedure for the TDC and lash specs.

 

[Nige]

Valve clearances are 0.010" cold for both inlet & exhaust.

On a 4-hole engine such as that one I would simply get the inlet and exhaust valves rocking (one closing, the other opening. i.e. TDC on the exhaust stroke) on one cylinder then set the valve adjustment on the corresponding cylinder. So for example if #4 is on exhaust stroke TDC you set the valves on #1. If #3 valves are rocking you set #2, etc, etc.

EDIT: There should also be a "0" mark corresponding to TDC on the crankshaft pully

 

[Acoals]

Just by way of update, I got a good fuel pressure gauge set up and ran it for a while. Aside from having a rough time staying running on cold startup, and intermittently missing or stumbling at idle, the machine ran fine. No issues working at high rpm. The lift pressure stays between 2 and 3 psi while running. Even when it missed and stumbled pressure stayed in that range.

I thought to adjust valve lash late Saturday, but there is no good way to bar the engine over from the crank. It's pretty well stuffed in there. The only way to service anything on the front of that engine is to pull the coolers.
It might work to bump the engine over with the starter while holding the fuel shutoff down, but I didn't go any further with it at that point.