Cummins PT pump weirdness

[mitch504]

LTA10 Cummins from about 1990 in an '87 International has developed an intermittent problem. Engine starts and runs very well, cold or hot. Occasionally it will cut off if you depress the accelerator too far too fast. If you veeery slowly press the pedal, it will go all the way to the floor and engine will perform fine. If it cuts off, it is just like you turned the switch off, no stumble no hesitation, dead. The thing that makes me think it is a pump problem is that it will not restart until the crankshaft stops turning completely. 9 times out of ten, as soon as the engine stops turning, hit the starter button and it starts immediately. No spinning, no hesitation, running in half a revolution. Sometimes, it will not restart, and the fuel filter will be only half full, but that has only happened twice. Both times, I filled it up and it started very quickly. When this problem starts. it will cut off anywhere from 3-15 times if you hit it too hard, then it will straighten up and be fine for ten days, or a week, or 2 days. I will get and post the engine numbers when I get back, I thought I had a pic of the tag.

This is a fertilizer truck, so it gets abused severely compared to most trucks.

 

[DMiller]

Will be something other than pump, sounds as two or MORE issues, sucking air with filter not full and the rapid shut down something to do with fuel shut down solenoid atop the pump. First off fix the sucking air, these trucks tended to use standpipe feed fuel tanks, if a bottom draw replace the lines as the one feeding the pump has a inleakage issue. As to the solenoid, simple check, screw the Manual Override screw full in and start the engine, without unscrewing this it will Not electrically shut off, perform the hard throttle test again.

 

[Truck Shop]

Fuel shut off solenoid

 

[kshansen]

As to the solenoid, simple check, screw the Manual Override screw full in and start the engine, without unscrewing this it will Not electrically shut off, perform the hard throttle test again.

Very nice thing about the Cummins PT pump with the manual over ride screw on the solenoid quick twist of the screw and you eliminate an electrical problem, or more correctly over ride the problem.

Just remember you can't shut off the engine until you back that screw back out!

 

[RZucker]

Being a fertilizer truck, I wouldn't discount the possibility of corroded grounds between the starter, block, frame and the cab. Seen a lot of weird stuff like that on those trucks.

 

[DMiller]

Had forgot that life lesson or that cell burnt away, used to work on Hwy 79 Farm Center Lime and fertilizer trucks, is where I learned to weld rust and how to fish thru bird nest wiring nightmares. When in doubt they would just run a new wire, while leaving the old one in place.

 

[RZucker]

Had forgot that life lesson or that cell burnt away, used to work on Hwy 79 Farm Center Lime and fertilizer trucks, is where I learned to weld rust and how to fish thru bird nest wiring nightmares. When in doubt they would just run a new wire, while leaving the old one in place.

Yep, years back had a Terragator with a triple nickle doing the same kind of stuff. Screwed in the knob and no problems, then the air conditioning started acting up, that was when they finally let me find the real problem. With the battery cables connected to the starter it would crank easy, but the rest of the grounds were a mess.

 

[crane operator]

When in doubt they would just run a new wire, while leaving the old one in place.

That's the best way to wire. Eliminate all the potential problems.

 

[DMiller]

Now that's funny!!

 

[td25c]

Being a fertilizer truck, I wouldn't discount the possibility of corroded grounds between the starter, block, frame and the cab. Seen a lot of weird stuff like that on those trucks.

Had a similar issue with my Jeep Grand Cherokee last year .

Ran fine in forward gears but put it in reverse and engine would die .

Turned out to be a loose ground strap on the engine block .

 

[td25c]

Dang Mitch ! You could lay field tile behind the spreader truck & get paid for drainage as well .


Very wet in my neck of the woods . Ground is saturated & looks to be a slow start for planting .

 

[RZucker]

Had a similar issue with my Jeep Grand Cherokee last year .

Ran fine in forward gears but put it in reverse and engine would die .

Turned out to be a loose ground strap on the engine block .

Had an N14 come in 2 weeks ago doing all sorts of weird stuff, had one bad ECM feed fuseholder. Both were hidden down below the starter in the grease and grime, not quite as bad as some Kenworths that hide them on top of the trans where you can't reach them from the front or back.

 

[Truck Shop]

The fuel filter won't be clear full on a Cummins with a PT pump. If it is electrical it should be getting worse as time goes by, but those models of International had a very poor fuse box and
wire terminals. When I worked for a Ag outfit before this job I had eleven of that series with rotted fuse boxes and electrical issues. If the windshield leaks water it will run down and soak
the fuse box and connections.

 

[funwithfuel]

Don't forget about the pulse damper. A weak or cracked disc will cause all kinds of shenanigans.

 

[crane operator]

Its been wet by us too. That stuck picture looks like it wasn't getting any better the whole way coming out. Just sunk down and stayed down.

 

[mitch504]

OF COURSE, I left out vital info in my first post. I screwed in the override screw the second time it messed up, because my first thought was electrical also. It makes no difference, and, unless I am really missing something, totally eliminates all electrical causes.

The really strange thing about all this to me is that when it occurs at highway speed, it will not restart while the crankshaft is turning, but will restart immediately if you mash the clutch and let the engine stop for a fraction of a second before hitting the starter button.
This problem only occurs with sudden hard acceleration, and I wonder if it could be an AFC problem?

The stuck truck photos were actually last year, and the truck drove to where you see it, making those canals by itself. Those trucks will keep moving through some amazingly bad terrain, and then refuse to climb out. Those pics were taken as I was extending the backhoe boom, before we hooked it up.

This year it's only been pulled once, because from the hurricanes of September until March, it simply stayed too wet to think about doing anything, then dried up.

 

[mitch504]

What about the pulse damper? can it be replaced on the engine?

If I can't find this problem soon, I am going to pull this pump off of this L10-300 and replace it with one off of an L10-270 that I have and see if the problem goes away.

I hate to do that without finding the problem, because I could fix an air leak while changing pumps and never know.

I know that when the fuel level gets low, just before it runs out, these truck will do strange things as they begin to pick up air.

 

[funwithfuel]

What about the pulse damper? can it be replaced on the engine?

If I can't find this problem soon, I am going to pull this pump off of this L10-300 and replace it with one off of an L10-270 that I have and see if the problem goes away.

I hate to do that without finding the problem, because I could fix an air leak while changing pumps and never know.

I know that when the fuel level gets low, just before it runs out, these truck will do strange things as they begin to pick up air.

Its serviceable in chassis. I lifted this image off the internet so you can see what I'm describing. 2 screws hold it together, 2 longer screws secure to pump.
So, it will start every time, as long as you allow the crank to come to a stop. Correct?
You also mentioned the filter getting drawn down. This makes me believe you have a supply issue. As DMiller already pointed out, you've got to verify supply beginning to end. Do you have plastic fuel lines or aeroquip? Aeroquip are known to break down with age and allow either flappers in the line or air intrusion through the hose itself. Many mfrs got away from braided hose and went with plastic air brake hose to eliminate this.
Hope this helps, good luck

 

[thepumpguysc]

It certainly sounds as if its a supply problem.. cuz just as soon as the crank stops turning, creating a vacuum on the inlet line, it'll start..
It sounds as if the inlet line has collapsed internally.?? 1 way to verify is to put a vacuum gauge on the inlet .
I don't work on PT pumps but I've seen THAT happen to 100's of'm that came into the shop.
It happened so often that the PT guy rigged up a hose w/ a vac. gauge that he just unscrewed the inlet hose on the engine & put "his rig" between the pump inlet fitting & inlet hose..
A 10 minute diagnosis & 100.00 worth of hose & the customer was ridin' down the road..
btw> anything over 4" of vac & u gotta a restriction.

 

[Truck Shop]

International started using nylon air brake tubing in the late 70's, so there is a possibility a short braided hose from frame to pump and return. Or it's all nylon right to pump.