3116 White Smoke - Hard Starting

Posts: 11
Joined: Apr 2010

Friday April 23, 2010 14:10

I'm assuming by the year that yours is a mechanical engine...if so....Several things to check.....first check fuel pressure cranking on the outbound side of the secondary filter. Cranking and at low idle should be a mimimum of 20 lbs. Remove the return line at the tank and check for bubbles. Typically the things that go bad on the GMC are the plastic line from the tank to the primary filter and the plastic line from the primary filter to the inlet line for the pump. The pump has two of the same check valves easy to replace, and the piston in the pump has a built in check valve which is the most common problem for low pressure on the 3116. High idle pressure varies from 40 to 60 lbs. There is an orface on the return line, with a check valve that controls pressure, different from the others, but it seldom gives a problem. A 3116 in good tune will start easily and barely smoke unless it is cold out.

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One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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golfgolf39

Friday April 23, 2010 16:11
Thanks for your quick response. I will give it a try.

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Saturday July 10, 2010 14:54
Hey Joe, Any chance at talking to you in depth about our 3116. We have the same thing going on. I would like to see if it is something we can check, or if you know where is a good place with a quality diesel mechanic. We have tried some dealers for some other issues and ended up doing it ourselves. Thanks, Bobby

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Sunday July 11, 2010 00:26
Describe your problem and add in year, make and model of vehicle. Also, what have you done so far? ------------------------- One of the last 2 Stroke mechanics left. 44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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Sunday July 11, 2010 04:55
One other thing to check on a 3116 with white smoke and hard starting is the timing. These engines need to be slightly advanced from the factory spec in order to run real good in colder weather. As you mentioned air in the fuel is also common due to leaking injector seats in the head. When the seats leak the fuel system looses its prime and starts hard along with lots of smoke.

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Sunday July 11, 2010 14:57

Our Truck is a 1991 GMC Top Kick. 3116 Motor
It has always been a little tough to start when cold but when warm it was no problem. Now it is even a little tough to start when warm. The first start I mean. If it has been running for more than a few minutes it will start no problem.
It spins over and tries to start right away and if you do not pump it real fast it will not start, than you have to spin it over for about 30 seconds, and maybe again. When it is trying to start it has white smoke coming out of the exhaust.
We had all new injectors put in it by CAT, we thought maybe the cups were leaking but they were not. It seems to be getting a little worse starting. Like I said once it starts and runs for about 5-10 min. it does not smoke and it starts no problem.
We just have had a tough time finding a mechanic who talks with knowledge and experience like you guys do on here.
Is changing those two check valves and the one in the pump something we can do. We work on regular cars all the time and have a lot of tools. Also what is the best way to check the low idle cranking fuel pressure, with what kind of guage and where on the motor?
Thanks for the reply, this is an awesome site.
Bobby

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Sunday July 11, 2010 16:00

Assuming you have changed both filters, we can go from there. There is a plug on the secondary filter toward the rear of the filter housing that takes an "O" ring fitting just like the plug you can remove. That's where to check the fuel pressure. Follow the other instructions for checking for air. As far as the check valves, I can't say if you can change them, but it isn't too difficult. Start with the simple things.....fuel pressure and air in the system.

By the way, when you say pump it real fast.....I'm assuming you have a hand primer on it....otherwise, pumping the accelerator pedal shouldn't make any difference.....(no carburetor on this one)....

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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Monday July 12, 2010 05:32

I have seen some 3116's that the fuel rack was sticking and pushing the accelerator helped put more pressure on the governor springs to open it up more.
The rack should open 3 to 4 mm when you turn the key on. If it doesn't it will crank longer to start.
If it fires right away and then needs to be cranked a lot to start sounds more like fuel bleed back or air in the system.
Did they ream the injector sleeves when they replaced the injectors? They have a brass sleeve under the injector that needs to be cut for proper injector seating.

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Monday July 12, 2010 12:17

Yes we change filters regularly. They are less than 1000 miles fresh.
We took the plug off the side of the secondary pump and we attached a manual guage. It is very warm today, so the cold is not an issue. When we started cranking the motor the guage did not move, and the truck was very difficult to start. After 4 - 30 second attempts the truck started very tough, it idled rough and the guage after about 20 seconds of running the guage went up to 20 lbs. when my brother gave it a little throttle to about 800 - 1000 rpms the guage went to about 35 lbs.
As for pumping the gas I think all the years of working with our Dad in the backyard and starting our 1969 Ford Ramp Truck the pump9ing is by habbit.
Also yes when we had the injectors changed they changed and reamed the new seats. At least thats what they said.
Thanks so much for the responses, this is pretty neat that we tried something you guys said and it told us something.
What do you guys think now?
Thanks again.
Bobby

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Monday July 12, 2010 12:57

Assuming you have checked for air in the return like I suggested......and found none.....Go to your local CAT dealer and start ordering parts. Get a new plunger and spring for the supply pump. There is a check valve in the plunger. That's most likely the culprit. Then go down the line and replace all the check valves. They are very inexpensive, so do it once.

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One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

Edited: Monday July 12, 2010 at 13:00 by JoeZ

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Monday July 12, 2010 13:10
I have yet to check for air, was wondering what the best method for doing this. You say check air bubbles, do you mean take the return line off the tank and put it in a clear jar with fuel to see if it pumpos bubbles? Was just wondering the best method for us? Thanks a ton. Bobby

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Posts: 163
Joined: Sep 2007

Monday July 12, 2010 13:33

Take the return line off at the tank, put it in a container, start the engine and watch as the fuel is going into the container. Keep the return line submerged in fuel. You may see a few slight bubbles, but not a mass of them.

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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TDcrash63

Monday July 12, 2010 21:29

Like Joe Z said. also raise engine speed to 2000 or so and hold it should be very little if any air. If there is air connect a line to the govener fuel in port to a another bucket of clean fuel if air goes away it is in the lines or external fuel system. If does it does not it is in the engine. From there I usually look at the amount of air. If it is in the engine and there is a lot it, is usually an injector towards the front of the cylinder head. A small amount usually a injector towards the rear but this is far from foolproof. Just start pulling them and look for carbon tracking at the tip where it seats in the carbon.

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Tuesday July 13, 2010 11:32

We took the returnline off and put it in a gallon container with some fuel in it. When we ran the truck at high idle there was a very small amount of very small air bubbles that came up around the line where it was submerged in the fuel. They were very small bubbles and the amount of them was about the size of a dime around the return line. I have ordered the two check valves for the lines.
I guess our pump is an electronic one so there is no plunger and spring?
We just had our injectors done last year, but I guess that doesn't really mean anything, the mechanic was very uninterested, and was upset because our pump is turned up? At least that is what he said, we bought the truck with 125,000 miles on it and have doubled that. We never touched anything on the motor. I will say the one good thing about this website and trying to fix this is we are learning some small amounts of diesel motor info.
Thanks a bunch, I will change the checks and let you know.
Bobby

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Tuesday July 13, 2010 15:18

So we got these two checks from cat, they are real small and have a star shape on one end and a circle shape on the other with a spring in the middle. The length of the whole piece is about 3/4 inch, and it is about 3/8 to 1/2 in diameter. Trying to understand where they might go.
I took the return line off and it had a small housing type piece that also unscrewed seperate. Inside was a spring and a plastic piece with an o-ring. Did not want to go any further and make a problem for myself. I have it bolted back, till I can figure out what is what.
Any suggestions?
Thanks,
Bobby

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Tuesday July 13, 2010 16:04
A 1991 3116 with an electronic pump? Are you sure? As far as the valves...best thing is to get a parts print out from Cat. That should show you where they are. ------------------------- One of the last 2 Stroke mechanics left. 44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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Tuesday July 13, 2010 19:32

One check valve goes in the inlet of the transfer pump . Remove the inlet line at the top front of the governor next to the throttle linkage. Take out the JIC elbow and then remove the larger fitting it threads into. Inside you will find the star check valve. The star end goes in first.
The second star check valve goes in the outlet line of the transfer pump which comes straight up out of the front of the governor and connects to the fuel filter. Remove the line, remove the fitting below the line. The check valve will go in with the flat piece down and the star up.
There is a third check valve in the transfer pump piston. Remove the three allen screws in the top of the governor to get at it. The piece will come off with the inlet fitting attached. There is a spring and seal under this cover also. Pull the spring out then remove the piston. The check valve is inside.

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Posts: 163
Joined: Sep 2007

Thursday July 15, 2010 20:38
Changed the two little star shape valves. Did not seem to really change anything. I am going to investigate into getting the plunger type one. I do not think this is an electronic injection style pump as the cat guy said. But I guess I would not really know the difference. I am also going to look real hard at where air might be getting into the system. Thanks for all the advice. Bobby

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TDcrash63

Thursday July 15, 2010 21:05
They did make a 3116 HUIE engine. WHere the govener/ fuel pump would go you will see something similar except it looks like ther is an upside down filter and a sticker that says do not remove. I serial number would be helpful

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