[scout4bta]

Unless there's been some major problem in the past, the cam and crank journals don't wear much. Might need a bottle of valium if the pump has major issues. Nothing from Bosch is cheap on those pumps. I check one time to find out how much the 4bt P7100 costs new. Seems like it was something over $10,000. That particular pump was made in very small quantity compared to the 6 cylinder model.

I don't expect to find any anomalies with the journal measurements.
As for the last half of the pump rebuild, I choked when the shop gave me estimate for the complete rebuild. I persuaded the shop to rebuild just the governer, which it did need thinking that the problem was with the injectors having low pop pressure. I did look for a rebuilt 4b p7100, non to be found. I did find new no name pumps that resemble the p7100 for $850, No thanks. I'll have my Valium close by.

 

[char1355]

The last rebuilt P7100 I saw for sale was $3500 and that was a couple years ago. Another issue with those pumps can be the overflow valve. The spring in those weakens over time and they bypass most of the fuel back to the tank. That is a very inexpensive part and easy to change. Some of those Chinese clones may be OK but they don't have the name Bosch on them. The original pumps are just kind of rare. There were only two 4bt's that ever used it. The road model you have and the 250 HP marine engine.

 

[scout4bta]

The last rebuilt P7100 I saw for sale was $3500 and that was a couple years ago. Another issue with those pumps can be the overflow valve. The spring in those weakens over time and they bypass most of the fuel back to the tank. That is a very inexpensive part and easy to change. Some of those Chinese clones may be OK but they don't have the name Bosch on them. The original pumps are just kind of rare. There were only two 4bt's that ever used it. The road model you have and the 250 HP marine engine.

I expect the total rebuild price for my pump to to exceed the $3500 mark.
The overflow valve was replaced long ago.
The main journals clearance plastic-gauged out to .0040 (max of .0047) and the rod clearance measured .0030 (max of .0035).

 

[scout4bta]

Pulled the head off, here's what the block looks like.
I've had the engine rotated upside down and all the oil I used on the new bearings found it's way past the rings. All the piston bowls were half full of oil.
Lots of rust? on the right (passenger side) top of the block.
Crosshatch is still there. Cylinders 2 and 4 show some very light scoring. Can't feel the lines.

 

[char1355]

In other words, it's was time for a rebuild. It may not be but I was curious whether that block had been sleeved. Pretty sure that block deck needs to be shaved to clean it up. Some of that rust looks pretty severe. Probably someone ran straight water in that thing instead of a good coolant with anti rust. Wonder how many miles that engine may have had on it when you got it? Rebuild kits aren't nearly as expensive as they used to be. Depending on how much the block is cut you may need one of the thicker head gaskets. Want to go through the head too while you're at it. Leave no stones unturned. LOL. One thing about this, although it is costly you will know exactly what you have. This is one of the examples what I always say never believe the assessment that it's a good engine unless it comes with a warranty.

 

[scout4bta]

I agree on the assessment, my version is " if you don't see it run, it's a core".

Top of #4 piston has a surprise. There is a .062 dia (1.6mm) non-ferrous ball embedded in the top of the piston. You can see that the magnet is holding the ball in pic #2. There is also what appears to be a previous crater the ball was in. Haven't cleaned up the head to see if there is more damage. The ball came out with the help of a sharp chisel.
Does anyone know what the "00" and the "F13" on top of the piston mean? I know what the others mean, STD bore and 6632-last 4 digits of PN.
The erosion on top of the #4 is evident on all the other pistons and is in the same location. I added a outline of the exhaust valve in red.

 

[scout4bta]

Measured the cylinder bores, at the top end all cylinders measured 4.017 or less. At the bottom I could only measure at 4.50" below the top and again all cylinders measured less than 4.017. Other than the scoring on no's #2 & #4 All cylinders are in good shape, good crosshatch. I'm going to take my chances with the scoring and run it till it quits.

Next I'll put it back together, attach the trans, the T case and hook up the turbo temporarily to give the IP a pressure signal from the intake manifold. It's been mentioned by 2 individuals that with out the pressure signal, this could be the cause of the misfire. This had better work because I'm out of ideas for whats causing the misfire. I'm not sending the IP back to Perkins, Talked with the owner and he said the pumps checks out for flow/pressure all the way up to 3000 (engine) rpm.

edit:
Finely thought, I haven't looked at the head yet, maybe I'll find something there.

 

[Russ McLean]

The folks at Perkins are good people, they treated me well - Good luck with the test run.

 

[char1355]

The little steel ball might have come off the side of an injector that aligns to the slot in the head but that little ball is smaller than that, That little critter is sort of a mystery, You are correct that the piston part number is 3926632. No idea about those other numbers. Pistons are normally serviced as a kit 3802562 for STD units, If the injection pump is checking AOK then the misfiring almost has to be related to the injectors. Either one is not firing properly or timing is off. Timing would likely affect all of them. Another issue that comes to mind would be a lack of compression on a cylinder.

 

[scout4bta]

Change of plans:
Pulled #4 piston. You can't get a grip on size of the piston and rod from pictures, these are massive and heavy.
Anyway did a complete (correct) measurement of the of the cylinder bore. Every thing measures within spec for reuse.
Looking at the oil ring it looks gummed up with crud. The buildup of carbon on the head, on top and side of the piston points to excessive idling time.

 

[char1355]

Yes, the pistons and rods in these engines are not feather weights. They are designed to withstand years of torture of the diesel firing. Must remember that the #4 cylinder is the hottest in these engines. Just a matter of the design of the cooling network. It is a cylinder that often gets scored and also one that locks up and breaks a rod and knocks the side out of the block.

 

[scout4bta]

Yes, the pistons and rods in these engines are not feather weights. They are designed to withstand years of torture of the diesel firing. Must remember that the #4 cylinder is the hottest in these engines. Just a matter of the design of the cooling network. It is a cylinder that often gets scored and also one that locks up and breaks a rod and knocks the side out of the block.

I was concerned when I saw the scoring on #4, started getting ready for the rebuild. Instead bought the needed micrometers and started measuring the engine. I'm amazed that this engine, despite the misfire, is in really good shape. The crankshaft journals are close to the limits, If I regrind the crankshaft, mains and rods, the cylinders, pistons, all well within limits, it's ready for another 100,000 miles.

 

[char1355]

When properly cared for, the rebuild on these engines may be in the 300,000 to 500,000 mile range. Engines in the Cummins class often have many million miles in their life. It's all a matter of proper maintenance. I remember when Ford first installed the Navistar 6.9 in their pickups around 1983, a local company bought one. They used it to transport boats they made to locations all over the country. It literally was never shut down except to change oil and filters. In 3 years it had traveled 375,000 miles when they had it rebuilt. I spoke with the mechanic who did the overhaul and he said they just installed rings and bearings but they weren't really necessary. The engine was still within tolerance with that many miles. They retired it after another year with near half million miles and who knows it may still be running. The secret to diesels is to run them. Short hop driving and letting them sit for long period is not what they are best at. They want to be driven. I've owned 3 and the least mileage I had was 130,000 on my 1986. There was nothing wrong with it but I wanted a larger cab when I bought my 1990. It's got about 335,000 miles on it.

 

[scout4bta]

#4 after soaking for 24 hrs in carb cleaner. One down, three to go.

 

[scout4bta]

#2 pistons has forced a change of plans. Check out the top ring. Frozen by carbon build up.
Have a theory why the engine misfires, blows smoke and flame. At cranking rpm #2 would have enough compression and give a good reading. At idle and slow rpm it has enough compression to run but as soon as throttle is applied it would loose sufficient compression to begin misfiring sending unburnt fuel through the exhaust to cause the flames and white smoke.
Maybe after the soaking in carb cleaner the top ring will pop out and be in good shape.
Might as well have the crank ground the while I'm at. Last I checked Cummins piston with rings was $250 each! No thanks I'll use Aftermarket.

 

[char1355]

Yeah, #2 piston don't look so good up top. Aftermarket pistons are OK and you can find them under $100 per hole. That #4 you cleaned looks fine. If you're not boring the block then a touch with a hone in the bores and new rings should be fine. As far as the misfiring issue you have to look at it logically. Firing only takes place when the injector fires the fuel into the piston. You'd think a misfire would occur if injectors are not firing at the same pop pressure, That's not controlled by the injection pump but by the injectors themselves, That is unless the pump has a defective delivery valve or bore and not building pressure equally across the injectors. That heavy carbon build up on #2 makes one think that could be the culprit cylinder.

 

[scout4bta]

The cylinder head cleaned up nicely. I outlined the 2 areas on #4 where the steel "BB" impacted the head.

Tried to remove the valve springs but my automotive (gas motor) valve spring compressor was not able to compress the valve springs. I'll let the machine shop do it's job.

 

[scout4bta]

As I mentioned in post #92 this engine is in really good shape, despite #2 being caked in carbon. Broke down and purchased the needed micrometers for measuring the journals and pistons. All the journals are in the middle of the range for wear as are the pistons. No need to grind/replace any thing except the rings, those had end clearances of .010" over the max. Did have to buy a Flex-Hone for the cylinders. The rings (Cummins) all had the end gap near the middle of the range when installed in the cylinder for checking the clearance. All the cylinders checked out OK, no more that .0013" taper and out of round and no ridge at the top. But will have to send the head out for a valve job.

 

[scout4bta]

I knew that the engine had been worked on (over) in it's previous life, the idiots had reused a torn timing gear housing gasket and just added silicone sealant and called it good.
Found out how deep they went into the engine. They had all the pistons/rods out for some reason. Found markings on the rods from a vice jaw where they had clamped the rods with pistons in a vice. They didn't just snug it up, no they tightened it with enough force to flatten the surface of the rods. Just wonderful. These are forged rods so I'm not too concerned. The two bright areas are very smooth.

 

[char1355]

If you're talking about the gasket on the front of the gear housing Cummins doesn't even recommend using that. Rebuilds get RTV between the front cover and housing. Of course you do have to replace the front crank seal anytime you remove that front cover. Otherwise it is guaranteed to leak. Just remember that the crank has to be totally clean with no oil on it when replacing that seal. No reason for them to have clamped the rods in a vice that tight. Nothing on the pistons and rods is overly tight. Those rods are super strong. No worries on those shinny spots.