Number 6 cylinder knock

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Number 6 cylinder knock

Postby Luther Grimace » Sun Nov 13, 2011 3:11 am

I pulled my engine out tonight because it has been knocking. I could loosen off the #6 injector and it would silence the knock. When I get it out I checked the oil pan and the thrust bearing was laying in it. Is this a common problem and could this have been causing the knock? I'm hoping its not the piston.
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Re: Number 6 cylinder knock

Postby Richie O » Sun Nov 13, 2011 10:34 am

If the injector was frigged ( popping early ) that could make that cyl knock. One thing for sure, check that cyl while its out. I have heard of thrust bearings breaking off before.
1989 W250 727, 3.07 L/S, S300, P/S Intercooler, Stans exaust, Pump adjustments, 127k miles,297 hp
1993 W250 extended cab, rag, 4.10 l/s, 6x16's, HTT 62/71/14 piston l/p, Isspro EV series tach, fuel pressure, boost, oil pres, water temp, volt, pryo, 132k/ 301 hp
1992 W250 with NV4500, 3.54's, 16cm 60mm GDS H1C, ground stock cone, Isspro tach, pryo, boost, fuel pressure, slow, rusty, dented,180k
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Re: Number 6 cylinder knock

Postby Luther Grimace » Mon Nov 14, 2011 2:09 pm

How can you tell if the injector is frigged? Would that be a pump problem or injector problem? I should have moved the injector before I removed the engine to see if the knock followed the injector or stayed with the #6 cylinder.

I pulled the #6 main cap off and removed the thrust bearing which was already missing the thrust washer. I'm gonna try to buy the upgraded. I prolly should go ahead and put all new mains and rod bearings in while the pan is removed.

What should I be looking for cylinder wise? Should I be looking for a galled piston or bad wrist pin on #6? I wanted to not have to take the head off but maybe I should.
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Re: Number 6 cylinder knock

Postby Hansen01 » Mon Nov 14, 2011 3:10 pm

how many miles on the motor? might not be a bad idea to take it off and replace the headgasket while its out of the truck, only take another 2,3 hours
1990 dodge W250 cummins 6 speed. 4in diamond eye, a turbo,and a pump :D
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Re: Number 6 cylinder knock

Postby Richie O » Mon Nov 14, 2011 5:05 pm

If the cyl was firing early due to a bad injector it may have burnt the piston. I would have a look.
1989 W250 727, 3.07 L/S, S300, P/S Intercooler, Stans exaust, Pump adjustments, 127k miles,297 hp
1993 W250 extended cab, rag, 4.10 l/s, 6x16's, HTT 62/71/14 piston l/p, Isspro EV series tach, fuel pressure, boost, oil pres, water temp, volt, pryo, 132k/ 301 hp
1992 W250 with NV4500, 3.54's, 16cm 60mm GDS H1C, ground stock cone, Isspro tach, pryo, boost, fuel pressure, slow, rusty, dented,180k
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Re: Number 6 cylinder knock

Postby dazedandconfused » Mon Nov 14, 2011 5:41 pm

You already have it out you might as well break it down and freshen it up.
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Re: Number 6 cylinder knock

Postby Luther Grimace » Tue Nov 15, 2011 8:19 am

It has 275K on it. What brand bearings do you guys recommend? I was gonna try sealed power.
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Re: Number 6 cylinder knock

Postby Mark Nixon » Thu Nov 17, 2011 6:44 pm

This is just MY experience, but ALL of the Intercooled '91 engines I have had, or taken apart, had bad thrust mains.
Not saying this is a dead nuts true "for sure" deal, but for every one of the '91 Intercooled's I've taken apart, it has been true.

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Re: Number 6 cylinder knock

Postby ahale2772 » Fri Nov 18, 2011 5:17 am

^ what do you think causes that?
84 CCLB W350 project
94' W350 Dually, Diesel, Auto 1080HP/1980FTlbs
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Re: Number 6 cylinder knock

Postby Mark Nixon » Fri Nov 18, 2011 8:20 am

I didn't mention the fact that these were ALL 5 speeds, but they also all had stock Sachs clutches.
I've yet to check an automatic, though my old '91.5 flatbed 1 ton is an auto.

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Re: Number 6 cylinder knock

Postby Luther Grimace » Fri Nov 18, 2011 1:19 pm

See Mark I don't think that the bad thrust bearing would cause it to knock. Did it cause yours to knock? This one is a 5 speed. I believe the reason they failed was because they were built as a 3 piece bearing with the thrust washers pressed onto the main instead of one solid piece like bearings on other engines.
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Re: Number 6 cylinder knock

Postby Luther Grimace » Fri Dec 02, 2011 8:48 am

Put it back together last night and it still knocked. I pulled the number 6 injector out last night and took it to the local diesel shop. They tested it and said it was bad. It was just pouring fuel out. I'm hoping this would cause some sort of detonation which would be giving me my knock. They are gonna rebuild it and i'm gonna try it out.

I had a couple question for you guys though. What upgraded injector would be good to put into this truck? I haven't messed with the pump because i've been rebuilding the Getrag. I know the pump is advanced but i'm not sure about the fuel pin. It was bad when I bought it. I've seen all these 30hp, 40hp, and 60hp injectors. I don't want it to smoke alot and i want good mpgs. The guy at the diesel shop tried to sell me "Power Wagon" 40hp injectors.

My other question was what clutch i should install in it? The one i have now is close to the rivets. I didn't realize how expensive clutches are for this truck.
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Re: Number 6 cylinder knock

Postby Luther Grimace » Fri Dec 02, 2011 8:49 am

Forgot to say i put in new mains and rod bearings. An upgraded one piece thrust bearing came with it.
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Re: Number 6 cylinder knock

Postby ahale2772 » Fri Dec 02, 2011 10:48 am

Valair would be the best cheep, upgraded option for a clutch
84 CCLB W350 project
94' W350 Dually, Diesel, Auto 1080HP/1980FTlbs
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Re: Number 6 cylinder knock

Postby Luther Grimace » Fri Dec 02, 2011 12:33 pm

What would be the advantage to getting the high perfomance clutch over the stocker? Would it be alot "grabbier". Also the diesel shop called me back and said that injector is broken pretty bad and it will cost $105 to fix. I almost feel like I should just buy 6 new injectors.
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