CAT 3208 Low boost

[JoeBioDiesel]

A buddy of mine has a fishing boat with twin 3208s. Cat has tried several times to repair a low power complaint. They've been using the "parts dart board" method of diagnosis so far, replacing the injectors and several other components... and failing to correct the problem. On the latest visit they noticed that one engine had low boost, and adjusted the pump to supply more fuel. According to the Tech, the boost is still low. He said the turbo housings are worn out (with 1500 hours on the motors) and he needed to replace the turbo housings and the (mechanical)injection pumps. This sounds like another questionable diagnosis to me.

Here's my question:

Has anyone ever heard of a turbo housing wearing out on a 3208? The Cat tech told me it is a common problem on them, and that the pumps are ready for a rebuild at that hourage. I'm going to get a chance to work on it next week. Hopefully we'll be able to make a diagnosis after cheching the EGTs, boost and fuel pressures(or vacuums, not sure how they're plumbed).

Any help appreciated.

Joe

 

[bmoeller]

I'm calling BS on the turbo and fuel injection pump.



I'd be checking the air intake system and exhust system.



Getting enough fuel to the engines? Fuel pressure OK?



No collapsed fuel lines?



Cracked lines sucking air?



Bent valves?



Excessive blow-by or oil consumption?

 

[JoeBioDiesel]

Thanks for the feedback. I'm pretty sure I won't find a worn turbo housing... but you never know. The engine with the low boost doesn't huff black smoke when you snap the throttle. It used to. Whatever the problem is must be fuel related. Low boost would probably make it smoke worse.

I'll post it here if I figure out the problem.

Thanks again,

Joe

 

[BILLVO]

On a Cat engine it is very common for the AFC (Air Fuel Control) diaphram to blow out. It is on top of fuel injection pump and has a line from intake (post turbo) into the top of it this is a very common problem with CATS.

 

[bmoeller]

The engine with the low boost doesn't huff black smoke when you snap the throttle. It used to. Whatever the problem is must be fuel related. Low boost would probably make it smoke worse.

It won't smoke worse (or at all) with low boost, if it isn't getting enough fuel.

 

[24VChev]

Does the engine with the low power complaint reach rated RPM? If you put both throttle at WOT what's rpm are each engine getting to? The engine should have a data plate on it stating rated RPM. The engines should get to that RPM or should be able to go past it. This test should be done while in gear in open water. The engine should also reach max rpm in neutral. When where the valves last adjusted? I have seen lots of 3208 with really bad valve guides and seat.



PS I don't remember if the 3208 in the marine application has a AFR. Turbo housings do not wear out unless the wheels have hit it. Sometimes water can errode the housings and wheels on the hot side so that is a possibility. I would be more suspicous of the fuel injection pump. The old scroll are competley dependent on fuel quality for a long life.



Good luck



Malcolm

 

[JoeBioDiesel]

24VChev: The engines will both reach rated RPM in neutral, but the one with low boost is 150-200 RPMs lower in gear at top speed. Valves were adjusted last year, after the problem appeared.



BILLVO: I'll check to see if it has an AFC, and if it does, I'll checkm the diaphragm.



bmoeller: Thanks- I did realize that. I was just thinking if it didn't smoke with low boost, it must really be a lack of fuel.



Thanks everyone for your help.

I do appreciate this.



Joe

 

[JoeBioDiesel]

The engine is all set now. While doing a simple cylinder balance check it was obvious that there were 2 dead cylinders, and one weak one. The dead cylinders had no fuel pulse to them when you cracked the injection line. When you backed the line all the way off, it leaked fuel continuously at low pressure. I suspected cracked delivery valves. . but after removal of the top of the pump there were a couple of lobes worn completely off the camshaft.

Further questioning of the boat owner revealed that he had to change fuel filters on that engine several times/season, while the other engine ran fine. Now... if they're both running off the same fuel tank, and off the same primary filter, there is no reason for only one engine to need constant filter replacements... . unless more fuel was being filtered by that engine.

The diagnosis: The overflow valve on the pump for that engine failed. Because of the unequal pump pressure, this engine was filtering much more fuel than the other one. The filters were plugging, and starving the pump for fuel. The fuel starvation for long periods of time wiped out the camshaft.

We got the pump camshaft reground, and the pump rebuilt.

Thought you want to know... .



Thanks again for your feedback. The turbo housings were fine.



Joe

 

[MMiller]

I had a 3208 do that too, and amazingly enough it was hard to hear it miss, it wasn't a dead miss like one would think, but a lazy miss.



Glad to hear you found it. If your buddy needs any more Cat work done, he better not allow Mr "your turbo is worn out" back on the boat again!



Michael

 

[nickleinonen]

The diagnosis: The overflow valve on the pump for that engine failed. Because of the unequal pump pressure, this engine was filtering much more fuel than the other one. The filters were plugging, and starving the pump for fuel. The fuel starvation for long periods of time wiped out the camshaft.

We got the pump camshaft reground, and the pump rebuilt.

Thought you want to know... .

the cam box on the pump is engine oil lubed [at least i am pretty sure. . ]. . there is only fuel lube up by the plungers/bushings. . when i was at a school, i remember seeing several cat inline pumps with the cam lobes worn down flat. there was a problem with the hardening of the lobes and the cam would wear down off the hard surface then very quickly wear down flat

 

[JoeBioDiesel]

Hi Nick,

I took the pump off this engine. No oil lines on this one. (I was surprised too. I think most in-line pumps are). The camshaft is definitely lubed by fuel.

Thanks for the info on the hardening. Hopefully that's not our problem with this one... or we'll be doing it on the other engine soon.

Joe

 

[MMiller]

Hi Nick,

I took the pump off this engine. No oil lines on this one. (I was surprised too. I think most in-line pumps are). The camshaft is definitely lubed by fuel.

Thanks for the info on the hardening. Hopefully that's not our problem with this one... or we'll be doing it on the other engine soon.

Joe

These pumps are certainly lubed only with fuel. They generally have problems with the governor housing cracking the ears off and then leaking diesel down the back of the block, picking up enough junk that the operator thinks its an oil leak. I hope you had fun getting to the pump having to remove the injector lines, air piping and the intake manifold. Timing the pump on these jewels can be very difficult, as the gear kinda slops around and the pins do not keep things perfect. Its easy to get timing advanced or retarded, and a little off makes them run bad. Retarded they will pop, crack out the exhaust and be low on power. Advanced, they will be very spunky and have good power, but run hot I think. I've never had one advanced, yet, I have however had a couple retarded.



The 3208 was Caterpilliars entry into the "most expensive boat anchor" category. :-laf In their defense they make a good 190 hp engine. Its when they decided to turbo/intercool them and ask them to run at 300 hp at 3000 rpms, all day long, is when they don't live very long. Yeah, that was in some OEM applications.



Michael

 

[Nyoest]

You won't get a 3208 hot in a boat, they have almost unlimited cooling capacity. If I remeber right factory horse in a marine app. was around 400. But I do stand to be corrected.

 

[MMiller]

I *think* its more hot like, burn a hole in a piston hot, but yeah I understand the cooling capacity. A boat doesn't run a whole lot of rpms though right? In a Terra Gator they run a lot more rpms to get pump speed up, without using a pump drive with a overdrive. I *think* in a dump truck or concrete truck they keep the rpms a lot less then 2900-3000. I am shooting from the hip here, as the only 3208s I have worked on are in Ag Chem spray equipment. I try and stay away from 3208s at all cost.



Michael

 

[JoeBioDiesel]

The pump was a bit of a pain to get off, but probably because I didn't have a service manual. It was definitely a jigsaw puzzle... in order to get one thing off, you had to take three other parts off to get to it. You basically had to remove everything on top of the motor to get to the pump, and I was down in the bottom of a boat with kneeling room only. I remember two intake manifold bolts being a pain the the butt too.

Joe

 

[MMiller]

How long did it take youto realize the intake was slotted so you did not have to fully remove the bolt? What is really a pain is when you get the injection pump mounted, timed, locked down, and then realize you pulled the intake bolt out to clean the gasket, and forgot to put it back in before installing the pump. I've pulled apart several that had a super short bolt, ground off in that place, so it could be installed with the intake in place.



Michael

 

[JoeBioDiesel]

How long did it take youto realize the intake was slotted so you did not have to fully remove the bolt? What is really a pain is when you get the injection pump mounted, timed, locked down, and then realize you pulled the intake bolt out to clean the gasket, and forgot to put it back in before installing the pump.

Michael

How did you know? It's like you were there!

... apparently I'm not the first one to do that then...

Joe