Rough Running CAT 3208TA

Hello,

This winter I had all my injectors replaced and when back in the water, it took some effort to get the port engine started. I primed and re-primed before she finally fired up.

During the priming process with the manual plunger, I noticed a small amount of fuel leaking in and around the plunger. I made a note to "self", I needed to spend more time with this unit and research the possibility of having to repair/replace/overhaul this primer pump.

Well, yesterday was the first day cruising since my return to the water and at the onset, both engines started right up and ran great.

Then about an hour of cruising, I noticed what seemed to be a degradation of power along with some minor vibration. After some trouble shooting, I determined the culprit was the port engine. Hmmmm..

I ran at a slower RPM with no vibration for about an hour then throttled back up to normal RPM. All seemed good but whether it was my mind playing tricks or there was actually some vibration, but either way, it seemed to be working okay.

We spent a lovely night on the hook here on the Gulf Coast but this morning when I went to start the "girls" up, the port engine balked. I am NOT one to spend time turning and turning over these engines, so a trip to the engine room was in order.

I once again focused on the manual primer plunger and it was soft with no resistance. Another "aha moment".

After several pumps, she firmed up and another attempt to start was made. She started without hesitation.


Okay... after all this information,.. the question is...

Is this situation connected? Did I somehow introduce air into the fuel system with a less than perfectly airtight primer pump? Could this be the culprit of my engine running rough?

Or could this be an issue with contaminated fuel?

Thanks for taking the time to read this. I will hang up and listen.

Everyone stay safe. Wash those hands

Rusty Bliss
M/V Kristine
DeFever 53 POC
Sheltering in Place.. on the Gulf Coast!

All things point to the lift pump. When you discovered the small leak at the plunger, what did you do about it? If you just left it for a later day, guess what? It's now that day.

It isn't the leak of fuel causing you trouble, it's the air getting into the system from that location.

Replace the pump, re-prime the lines and injectors.

If it was contaminated fuel, both engines would be acting up.

pete

pete meisinger said:

all things point to the lift pump. When you discovered the small leak at the plunger, what did you do about it? If you just left it for a later day, guess what? It's now that day.

It isn't the leak of fuel causing you trouble, it's the air getting into the system from that location.

Replace the pump, re-prime the lines and injectors.

If it was contaminated fuel, both engines would be acting up.

Pete

Click to expand...

^^^^^^^^i think he's got you there^^^^^^^^

Primer pump is on suction side of filter. If it leaks fuel when pumping, air can get in when not pumping. Replace or re-seal pump. Easy to replace, two screws and a gasket.

Are you closing the priming pump after use by pushing in and turning clockwise till it seats? With it closed it should not leak air into the system even if the plunger seal is bad. Anyhow, these pumps are available aftermarket and I got one on ebay for about $30 a while back. There are two places on the injection pump where air can get in if seals fail - The main drive seal and the fuel rack lever shaft seal (throttle lever shaft). If the throttle shaft seal is bad you should be able to detect at least trace leakage there. Bad main shaft seal will also leak when stopped, and this is directed through a tube to the front lower right of the block, when facing the engine. By pinching off the return line and keeping constant pressure on the priming pump for a couple minutes you should be able to confirm either of these. The throttle shaft housing should come off with the injection pump in place. The main seal means remove and tear down. I have worked around a bad main seal by installing an electric lift pump and placing a can under the tube. It collected about 1oz or so per hr running. This got me by for quite a while before I got the pump overhauled.

^this

Ski in NC said:

Primer pump is on suction side of filter. If it leaks fuel when pumping, air can get in when not pumping. Replace or re-seal pump. Easy to replace, two screws and a gasket.

Click to expand...

Yes, it appears to be an easy R&R and I have one on order which should be at the marina on the 8th.



Thanks for your help.


Rusty

EngNate said:

Are you closing the priming pump after use by pushing in and turning clockwise till it seats? With it closed it should not leak air into the system even if the plunger seal is bad. Anyhow, these pumps are available aftermarket and I got one on ebay for about $30 a while back. There are two places on the injection pump where air can get in if seals fail - The main drive seal and the fuel rack lever shaft seal (throttle lever shaft). If the throttle shaft seal is bad you should be able to detect at least trace leakage there. Bad main shaft seal will also leak when stopped, and this is directed through a tube to the front lower right of the block, when facing the engine. By pinching off the return line and keeping constant pressure on the priming pump for a couple minutes you should be able to confirm either of these. The throttle shaft housing should come off with the injection pump in place. The main seal means remove and tear down. I have worked around a bad main seal by installing an electric lift pump and placing a can under the tube. It collected about 1oz or so per hr running. This got me by for quite a while before I got the pump overhauled.

Click to expand...

Yes, I am turning and closing the knob fully.


This is going to take more knowledge and expertise than I have in my wheelhouse to make this remove and repair injection pump.



A couple of years ago, I had my starboard engine's injection pump overhauled and there seemed to be some "local" knowledge on replacing back.


I will follow you troubleshooting advice and try to nail this issue down.


Also, I do have a new primer pump on the way to our marina.


Truly, thank you for everyone's help.


"learning has occurred"


Rusty

When you see a problem fix that before you go searching for other causes.

"A couple of years ago, I had my starboard engine's injection pump overhauled and there seemed to be some "local" knowledge on replacing back." post 8

You need to get a copy of Da Book, the big $125+ dollar maint handbook.

THe 3208 is the simplest engine on the planet to time. The pump is loosened in its mount and a drill bit is slid into the timing hole in the pump and where it mounts.

Remove the drill bit and tighten the mount bolts. GET DA BOOK!!!

For us newbies, the title of Da Book please.

Njlarry said:

For us newbies, the title of Da Book please.

Click to expand...

Factor service manual. Gotta find it used, they are out of print last time I checked.

Thank you. I shoulda quessed.

"YYes, it appears to be an easy R&R and I have one on order which should be at the marina on the 8th. es, it appears to be an easy R&R and I have one on order which should be at the marina on the 8th."


Your boat probably has engines built at the same tine. Only one pump ordered?

FF said:

Your boat probably has engines built at the same tine. Only one pump ordered?

Click to expand...

That's a good thought and I probably should have ordered two vice just the one replacement.



My initial thought was to replace the leaking one and thence find a way to replace the O rings and seals on the failed one to have as a spare.


We have been traveling on the river systems and to date.. all is well!!


Stay healthy,


Rusty