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Mechanical Troubleshooting

Brand: Caterpillar - Model: DP35K

Number of messages: 8

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Prentice
Ontario, Canada

Hello all,
My customer complains that the truck will stop and be hard to start. He will pump the primer on top of the fuel filter and that sometimes works. I have changed the fuel filter and bled the system all is good. every time i go to the truck it is running and test o.k. It's hard to troubleshoot when it's not broken..
Has anyone had a similar problem????? I may be overlooking something. It might be the driver running out of fuel, but he swears he does not.
Any advice would be great.
Thanks

Posted 4 Jul 2008 03:47 AM

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justinm
New York, United States

did you find air in the lines?
be careful though those primers can be funny
ive had a few su ck ( i have to edit this or else the site blocks the word lol) air in because the valve got stuck open

do you have an inline injection pump or a rotary pump?

you might even want to run clear fuel line to the lift pump to make sure youre not suc king air out of the tank

make sure there isnt a blocked return
take the return off the tank and make sure fuel comes out

make sure the shut off solenoid is working and the connections and wiring is all good

im gonna tell you 2 diesel stories now that are important to check yet easily overlooked

1- vented fuel cap
i had a guy call me in for his offroad Liftking (a candian product lol)
he tells me it will shut off and he wont be able to start it for a few days
at this point some other shop had replaced the injectors, lines, injection pump,and lift pump to the tune of about 2000 US$ with no success
it was dead when i got to see it so that helped
after crankin it a few times and it had a solid head of fuel
i open the gas cap and i hear a huge rush of air
im say to the guy "holy sht i found the problem"
i tell the cutomer to start it now
after 2 cranks it starts right up
turns out he had lost the original gas cap and replaced it with a non-vented cap
as the truck draws fuel air has to replace the volume or the vacuum in the tank will build to the point that it will over come the lift pumps ability to draw fuel
20$ cap and 1 hour service call - fixed never had another issue

2 - fuel line blockage
i had a linde diesel that was hard to start and had little or no power in manhattan
luckily that has clear low pressure lines oem
so i noticed bubbles in the line from the tank
after checking and tightening the hose connections and still had the air i just took a walk around the truck
i noticed there was no fuel cap
so i ask the operator what happened to it
he said after they refueled it they ran it over by accident (lol)
so i ask "how do you keep the rain out"?
he says that "we put a plastic bag over it but it must have fallen off"
i say "i dont think it fell off i think its in the tank"
i take the whole tank apart and get the pickup assy out
and sure as sht   i can see it has a plastic bag stuck about a foot up an 8mm ID metal tube
3 hours and 1 sacrificed metal coat hanger later  that truck ran great
and still does he just traded it in for a new linde diesel

check those things out
try to get there when its acting up
and ask him to notice if he gets a noticable rush of air when he refuels the machine or if it has an after market cap on it

the tank cap part# should be 9136410600 but have that double checked by serial number
sometimes the vents go bad or get clogged so clean or replace it
its pretty cheap (25$ list) and you can UPS it to the customer lol

if all else fails you can pull the pump and have it bench tested at a diesel fuel shop and have the injectors pop tested

but make sure you line up all those timing marks b4 you pull it

also you may want to take samples of his fuel and send them out

-------------------------
New York, New York its a heluva town ..you know that The Bronx is up ..and im Brooklyn down

Modified 4 Jul 2008 09:31 AM
by poster.

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roadrat
North Carolina, United States

Found the cap problems before also.
justin, have you ever seen the primer move down with cap vent plugged while running?

-------------------------
"ARE WE HAVING FUN YET?"

Posted 4 Jul 2008 12:19 AM

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justinm
New York, United States

lol no but i could imagine

during a pm i couldnt get any primer pressure on an S4S
took apart the base and found a rubber band stuck in the little flapper valve
the guy had rubber bands in his gastank lol

-------------------------
New York, New York its a heluva town ..you know that The Bronx is up ..and im Brooklyn down

Modified 4 Jul 2008 03:25 PM
by poster.

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Prentice
Ontario, Canada

Thanks for the info Justin, its a small world, I have had the exact same problems over the years with venting tank caps and plastic bags. I also had the driver turn off the fuel shut off( above the tank) and it sucked the rubber right out of it.
Back to my S4S, it is a rotary pump and i think the problem may be in the primary pump assembly. There was air in the lines when i bled the system. the customer has not complained yet, but it is still Monday morning and anything can happen. I appreciate your advice
Thanks

Posted 7 Jul 2008 10:30 PM

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justinm
New York, United States

lol
a wise man once told me when looking at any problem
SSS- "start simple stupid" lol
the rotary pump i believe will be a Lucas CAV pump (tractor pump)
the injector lines off the pump will be in a circular pattern off the inj pump head

inline the outlets would be "inline" across the top of the pump and i believe will be a "diesel kiki"

either way if you got air b4 the inj pump its not the problem

look for anything
you might even want to pull the pickup assembly and inspect the pickup tube for rot or a broken weld (water in the tank at some point?)

you may want to see if the lift pump is pumping air in too
see if its weephole looks wet

do you get air before or after the filter?
change the gaskets or base altogether
ive had a base or 2 in the s4s go bad b4

good luck

-------------------------
New York, New York its a heluva town ..you know that The Bronx is up ..and im Brooklyn down

Modified 8 Jul 2008 00:23 AM
by poster.

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Prentice
Ontario, Canada

LMAO,
We call it the K.I.S.S method ( Keep it simple stupid) Too funny.
Still no word from my customer. So i assume all is well. Thanks allot for the tech advice, it gave us peace of mind to have a second opinion.

Posted 8 Jul 2008 10:56 PM

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justinm
New York, United States

yeah its sometimes its good to beable to pick some1 elses brain and this site is def perfect for that

but if you want better and quicker answers you can post in the technical arena since in this section (mechanical troubleshooting) its tough for some1 to tell what posts are new and even harder to tell when some1 posts in an older one unless youre subscribed to the thread
i use the sitemap to tell when new threads are started

-------------------------
New York, New York its a heluva town ..you know that The Bronx is up ..and im Brooklyn down

Posted 9 Jul 2008 02:23 AM

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