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CAT 3116 in GMC Topkick extremely low on power

L

LN Pipeline

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Feb 21, 2019
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Location
Montana, USA
Trying to get some information for an uncle. His truck, and it’s been weak since he bought it.

CAT 3116 is extremely low on power, runs rough and doesn’t want to start when cold. Don’t have a serial number yet.

He’s replaced everything to the injection pump. Says he has good boost.

Where does a person start with these things? It looks like they have an odd fuel system. Are there any simple things that a person can check first that could be the issue?

He specifically wanted to ask if it could be a throttle position sensor?

He’s a fabricator and has worked on gas engines his whole life, so if I can pass on some information to him, he might have a chance of getting it running right.
 
D

Delmer

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Any truck with a 3116 is getting a little long in the tooth by now. What's the history that he knows? has he been able to run it for at least an hour with load? has he replaced the fuel and/or fuel tank?

I'm afraid the only simple thing I can think of to check on a 3116 is to put the fuel return line into a glass jar and check for air bubbles. That fuel pump is mounted up high on the engine so it doesn't prime as well as it could, and if the tank or anything else is still original, it could be leaking air which will make it run like that.

Heymcall and I are assuming you have a mechanical injection system with only one wire going to the governor in the picture. I've been informed there were HEUI 3116, but I've never seen them in trucks in the USA.
 
N140MM

N140MM

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IIRC some of those TopKicks had inline fuel filters located on the frame rail between the tank and engine. Just a little silver can thing.
I've seen one 3116 HEUI. It had a really goofy HEUI pump, like a round can with a nut on the top.
 
T

Tenwheeler

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Dec 15, 2016
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Georgia
Do the return line in a jug as mentioned. If if has a lot of air bubbles put a clear line in line to the to the cylinder head supply. If it has a lot of bubbles fix that first.
 
Coaldust

Coaldust

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Was is Freightliner or the GM truck 3116 installs, or both? That used the thermoplastic fuel hoses ( air brake hose) and DOT style quick connect fittings. What a terrible idea.

Caterpillar issued a Truck Engine News bulletin about the fittings leaking air on the suction side.

The early 3116 had issues with injector cups/injector seal blowing combustion gas into the fuel galley. And injector cups blowing combustion gas into the cooling system.

Oh’ my gosh. Trying to get access to cylinders 5&6. Holy cow.
 
heymccall

heymccall

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$4200 with new cups, new fuel return check, running overhead, setting rack, oil sample, oil change, and 4 times coolant flush.

That was Cleveland Brothers. 4 days total. Was scheduled a week in advance.

Progressive was 9 weeks out and insisted that they pull the head to do so.

Could not find ANYONE else willing to cup a 3116, or even had the tooling.
 
Coaldust

Coaldust

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It’s a brutal job. The regular injector cup reaming tooling doesn’t even fit between the head and firewall, with the head on. Cat made a special kit for the GM. It’s discontinued.

So much can go wrong doing cups in a 3116 and often there is a come-back or three, after working on them. Nobody wants to touch them.
 
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Jonas302

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Jan 4, 2015
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mn
Gosh its been a while since we had a 96 kodiak mixing fuel and antifreeze Cat came out and did the cups and ran the rack for $1500 doghouse was off for the back ones it was an easy day project
 
L

LN Pipeline

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Feb 21, 2019
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Location
Montana, USA
So I stopped and talked to him today. I didn’t have the full story.

The truck was running a little rough when he bought it, so he took it to a local CAT dealer. They told him it needed injectors. They charged him an insane amount of money to put new injectors in, now it runs way worse, and the CAT dealer won’t talk to him any more.

He wants a procedure for the following:

1) Fuel rack synchronization
2) Injector timing
3) Adjusting valve lash

Don’t have serial number yet. There is a massive bracket that covers the valve cover and goes behind water pump.

If it’s needed, I’ll post it when he gives it to me.

I’ll print the rest of the thread and give him also. Thanks for the ideas.

I wish he hadn’t bought this thing.
 
Coaldust

Coaldust

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There are a couple different ways to do it.
The Cat procedure, which was updated a few times. The Carpenter way. Which, some guys like. Thirdly, some guys free-hand the injector sync.

Here is a link to the Carpenter procedure.
https://meyermrc.com/mrcManual.pdf
 
Cmark

Cmark

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Synchronisation can't be done without special tooling.

Timing can be done with a digital caliper but it's fiddly. Easier with the tooling. The dimension to check is from the top of the injector spring to a machined flat on the injector body. The dimension should be printed on the label on the valve cover. If the label is gone, we MAY be able to get the information via the serial number, but getting it off the engine is way more reliable.

Valve lash is standard procedure for any in line 6. Firing order is 153624.

More discussion on these engines here https://www.heavyequipmentforums.com/threads/cat-3116-engine-injectors-syncing.81979/
 
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