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Cummins PT pump weirdness

Truck Shop

Truck Shop

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The fact that you try to accelerate slowly the engine will slowly pick up tells me something internal in the pump or drive through the pump. I remember some tears :( ago one
that had similar symptoms and the pump shop found issues with the something in the drive system inside the pump. Now that's only been 30 years ago and I can't
remember the total details.
 
DMiller

DMiller

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Worst cases of truck intermittent foul ups was a old Pete COE with a 6V92 in it, would drive fine a LONG time then just die, owner had been to FIVE shops along his route, towed three times and none had found the issue, drained tanks, found the pop caps of seven HEET bottle and the aluminum seals laying in the tank bottoms, he had used the fill neck for a bottle opener when could not finger them off(arthritic) did not see them or the seal foils go in either. Next up a Brand New Union Electric tandem Digger Derrick Utility truck, fresh from ALTEC industries, would run a day or so then could not keep running, had it to their OWN ST. louis shop to no avail, I get stuck with it as a tow in. First to note fuel filters sucked almost dry, suspected blockage but 1987 C8000 Ford with 3208 had nylon fuel lines little chance for skive, fuel less than 1/4 full shine flashlight into Custom ALTEC fuel tank, a absolute mess of welding slag and trash, had not been cleaned prior to placed in service. Lucky with this one had a alternate fuel pump installation plate so could get hands inside and clean out.
 
funwithfuel

funwithfuel

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DMiller said:
Worst cases of truck intermittent foul ups was a old Pete COE with a 6V92 in it, would drive fine a LONG time then just die, owner had been to FIVE shops along his route, towed three times and none had found the issue, drained tanks, found the pop caps of seven HEET bottle and the aluminum seals laying in the tank bottoms, he had used the fill neck for a bottle opener when could not finger them off(arthritic) did not see them or the seal foils go in either. Next up a Brand New Union Electric tandem Digger Derrick Utility truck, fresh from ALTEC industries, would run a day or so then could not keep running, had it to their OWN ST. louis shop to no avail, I get stuck with it as a tow in. First to note fuel filters sucked almost dry, suspected blockage but 1987 C8000 Ford with 3208 had nylon fuel lines little chance for skive, fuel less than 1/4 full shine flashlight into Custom ALTEC fuel tank, a absolute mess of welding slag and trash, had not been cleaned prior to placed in service. Lucky with this one had a alternate fuel pump installation plate so could get hands inside and clean out.
Click to expand...
I've had the fuel filler cap tether chain all wadded up on the first elbow out of the standpipe. You wouldn't think chain could get pulled up.
 
Truck Shop

Truck Shop

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The next time this engine acts up and dies, before restarting blow the dirt away from top of pump. There will be a hex head 1/4" pipe plug on top of pump near the front outer edge.
remove it and see if the pump is full of fuel, you might need a mirror to see down that fill port because of the type of truck you have. My problem with a restriction in a fuel line is this
engine should not start right away or as soon as engine stops. If it had a restriction it should require some cranking to prime system each time.

Had a T800 4 years ago that would shut off intermittently. Checked fuel pressure at filter head it was reading ok after about 20 minutes of running I noticed the fuel pressure go erratic
and drop to Zero. Put a fuel hose in a 5 gal bucket of fuel reprimed and ran fine for an hour. Hooked line back up ran under 1 minute pressure dropped it died. Put air back through fuel
line you could hear it bubbling in tank. Drained tank removed from truck and found that part of a fuel tank sending unit { about 20" long 1 1/4" wide} piece that fit inside the tube type senders
was laying such a way that the suction would pull it against the pick up tube opening. It was fun to remove it {two hours later}. But every time this engine died it was a reprime. CAT
That Cummins should at least take some cranking to restart each time if pump was being starved of fuel.
 
mitch504

mitch504

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Okay, this problem finally happened often enough and consistently enough for me to be able to do some troubleshooting. It would do it two or three times, then not at all for a few days, then two or three times. Usually, it would restart immediately, but not always.

Day before yesterday, it did it 15 or 20 times, and NOT WHILE BLOCKING THE HIGHWAY!

It would die when you tapped the throttle, and not restart when you hit the starter. When I screwed in the override screw, it would restart, and run fine. Unscrew the screw, and it would die when you hit the throttle hard and not restart until you screwed the screw in. As long as the screw was in, it wouldn't cut off. As soon as you screw the screw out, it would do fine with everything except a hard tap on the throttle, then it would die and not restart until over ridden. It suddenly straightened up and has been fine since.

I did not have a way to measure voltage at the fuel solenoid, but I examined and wiggled all the wires involved and could not come up with any scenario where pressing the throttle hard would cut electrical power, and nothing else would.

My current theory is that with the pressure surge the shut off closes. That great video says that the shut off is on the discharge side. I guess I am going to go ahead and change that solenoid and see if it cures it.

Now I'm about to start another thread about a pickup I'm probably going to buy with a similar problem.o_O
 
R

RZucker

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mitch504 said:
Okay, this problem finally happened often enough and consistently enough for me to be able to do some troubleshooting. It would do it two or three times, then not at all for a few days, then two or three times. Usually, it would restart immediately, but not always.

Day before yesterday, it did it 15 or 20 times, and NOT WHILE BLOCKING THE HIGHWAY!

It would die when you tapped the throttle, and not restart when you hit the starter. When I screwed in the override screw, it would restart, and run fine. Unscrew the screw, and it would die when you hit the throttle hard and not restart until you screwed the screw in. As long as the screw was in, it wouldn't cut off. As soon as you screw the screw out, it would do fine with everything except a hard tap on the throttle, then it would die and not restart until over ridden. It suddenly straightened up and has been fine since.

I did not have a way to measure voltage at the fuel solenoid, but I examined and wiggled all the wires involved and could not come up with any scenario where pressing the throttle hard would cut electrical power, and nothing else would.

My current theory is that with the pressure surge the shut off closes. That great video says that the shut off is on the discharge side. I guess I am going to go ahead and change that solenoid and see if it cures it.

Now I'm about to start another thread about a pickup I'm probably going to buy with a similar problem.o_O
Click to expand...
It may be that you have a weak solenoid coil, I seem to remember a warning in an old 220 Cummins manual advising not to shut the key off while coasting, other wise the engine had to come to a complete stop before the shutdown valve could reopen.
 
T

thepumpguysc

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Or a cracked plate.??
Mitch, why the H didn't u call me before I went to Andrews yesterday.!! I have 1 already rebuilt I woulda brought ya..
I have to do another job up there, so hold off on buying 1 if u can.. I'll be there Saturday if my parts come in..
I'll only charge ya my NORMAL delivery fee.. 1.25/mile & 35.00hr/ drive time.. 120miles R/T & 21/2 hrs.. seems reasonable.. Lol
 
DMiller

DMiller

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On the pickup, likely a Dodge? with a 5.9 Cummins that will be a external solenoid to a lever if an older engine with a Injection Pump. Totally different scenario, other breeds also complete different animals.
 
Wytruckwrench

Wytruckwrench

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Those solenoids are interesting. Will work great for 40 years then all of the sudden cause ya fits. Do love the fuel screw to get home with.
 
mitch504

mitch504

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Truck Shop said:
The solenoids can and will quit like that especially at a intersection with fire trucks coming.:p I think the
second reply to this thread said something about the fuel shut off solenoid.
Click to expand...

Umm, you were too subtle. You should have put it in red 7 point type. I saw that, but was thinking electrical, not failure of the solenoid itself. I was thinking hitting the throttle wouldn't cause that.

Seriously though, the problem was so intermittent it was nearly impossible to diagnose, until it finally did it more than once or twice.
 
Truck Shop

Truck Shop

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No joke about the fire truck, had it happen in Moses Lake Wa at 5:30 p.m. I had everyone pissed off til I got the screw turned and the hood shut.:eek:
 
R

RZucker

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Truck Shop said:
The solenoids can and will quit like that especially at a intersection with fire trucks coming.:p I think the
second reply to this thread said something about the fuel shut off solenoid.
Click to expand...
I had my solenoid experience climbing that steep grade out of Kahlotus headed to Devil's Canyon, no momentum, and wasn't going to coast a set of doubles backward. I saw all the electric gauges dip at the same time and knew something shorted out. Tipped the hood and saw the solenoid smoke, yanked the wire and turned the screw, didn't even latch the hood 'til I got onto Devil's Canyon road.
 
mitch504

mitch504

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Just a little update. Pumpguy did bring me a new solenoid, and I put off changing it for a few days, because the pump is under the cab. I drove it by turning the screw in for a few days and it got well. I have had absolutely no trouble out of it for almost a year.
 
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