No fire in #4 after rebuild

[wb1895]

Hey guys, I need some advice on an issue I'm having after rebuilding my LDT. I was having A LOT of blowby so I decided it was time for a rebuild.

Here's what I did, I tore the motor all the way down to the block and heads, and replaced the pistons, rings, liners, rod bearings, main bearings, lapped the valves, and installed all new gaskets. While it was apart I checked the OD of the crank and found everything to be well within spec.

After the motor was put back together, I cranked it and she fired right up.....except the #4 cylinder. So, I pulled the injector took it apart and cleaned it. Re-installed it in the truck and still nothing. So, the next step was to switch two injectors and see if the problem would move to another cylinder.....nope. I switched #4 and #5 injector, and the #4 injector worked just fine in Cylinder #5. Still, no fire in #4 cylinder. So, I pulled the valve covers and checked the gap on the valves. The intake valve on #4 was gauged at .040, when it should have been .010. So, I checked all the valves and found the rest of them to just fine. I adjusted #4 intake valve back to .010, and tried it again. Still......no fire. Okay, so I thought maybe the cylinder was loaded with fuel, I pulled #4 injector again, and ran the truck for about 1 minute with the injector out. I did have a very small amount of fuel come out, but nothing worth noting. I put the injector back in and still....no fire. I do know that there is fuel up to the injector and through it as well. While the truck is running there are small puffs of blue smoke coming out of the exhaust, but when the injector was out, there was no blue smoke. I am at a loss on what to do next. All the piston kits were new in the box.....what am I missing?? Your input is much appreciated

 

[dmetalmiki]

This has me puzzled..I would check the compression on that cylinder. And then or also what about the Actual injector line fuel pressure at #4?..If it's not firing with these up to spec..it has to be internal compression? loss. (or) sealing between cylinders..I'm still puzzling over it..keep posting on checks and results..someone else may offer up a comment..

 

[frank8003]

With injector out of the engine does it squirt?
The line from HH to that injector can be plugged.
The feed hole is only .06250".

 

[cattlerepairman]

I am rebuilding an LDS and feel your pain! Logically, you need fuel, air and compression for the cylinder to fire. I agree - I would check compression (seeing the injector needs to come out again anyway). Then check that the injector squirts fuel (or wrap a shop towel around the end of the injection tube and see if it gets soaked in fuel).
One of these things has to be amiss for the hole to be dead! Then go from there.

 

[wb1895]

I have run the motor with the injector out, and I am getting fuel out of the injector line. When I crack the other injector lines to the other cylinders, the engine bogs down more, when I close them the motor runs better. BUT, when I crack the line on #4, I get fuel out of it at good pressure, but the motor runs the same. When the motor is running, I can see a puff of blue smoke coming out of the exhaust, but when I had the #4 injector out there was nothing but "good" black smoke and no puff of blue smoke.

 

[bigbird1]

Better do a compression test. Did you have any trouble with that piston going in hard?

 

[frank8003]

post #4 do compression check.
When valves were adjusted the #4 intake went down open just like the others?
Use of a dial indicator on valves would indicate a cam problem.
This has me puzzled.

 

[bigbird1]

It ran fine before, just blowby. cam is not likely the problem. The compression check will tell him where to go from here. Maybe broken rings, or no fuel passing the injector, or even wrong valves in prospective holes. Anything could happen, but we hope not in this case.

 

[wb1895]

The only reason I do not suspect a compression problem, is the truck got all new piston/ liner kits. All 6 cylinders were replaced and all went in with no problem. I am wondering if there is a problem with the #4 injector line...BUT when I removed it from the truck I was able to blow through it from both directions with no resistance.

Is it possible to get low pressure from just one line off of the injector pump? I wonder if the HH is not putting out enough pressure on that line causing the injector to not put enough fuel into the #4 cylinder.

 

[bigbird1]

Try pointing the injector straight up and hooking pressure line up and watch it ( have done it with tractors and it works), be very careful stay far away , fuel can shoot right through your shin and a hospital visit will then be in order. Then that will tell you if the injector and pump are working. I once had a engine a 40 yr tech. overhauled and wouldn't run right and some parts guy had put lpg pistons in a gas kit and raised the compression where it would spark knock when above idle. Where all the pistons the same part number?

 

[wb1895]

All the piston kits were exactly the same, new in the box, with the sealed plastic over them

 

[WillWagner]

Any popping in the intake or chuffing in the exhaust pipe? A diesel only needs 4 things to lite, rpm, air fuel and compression. Look at those things

 

[wb1895]

I did take it for a short test drive hoping that it was just a piece of gunk that would clear out. During that drive there were a few "pops" that came from the exhaust, but other than that, just some puffs of blue smoke from the exhaust

 

[red]

Remove all the injector lines from the hydraulic head and crank the engine over. The fuel should be shooting up about 12" from each port. If the port for injector #4 is shorter than the others the problem is in the hydraulic head.

If that is good then your issue is in that cylinder or the injector line for #4.

 

[rustystud]

There could be a problem with the valves sealing. You said you had the heads done, but there still could be problems if the valves got bent or the valve guides where not changed out and now the valve face is out of round. There are a lot of reasons to suspect the valves. Of course if the rings where not properly installed on the piston you could get low compression. So the first thing to do is check the compression.

 

[rosco]

I learned to adjust/set valves, hot & running. You can tell a lot that way. Its pretty simple, if you just pull that valve cover. Is that valve spring, "spec" length? At least get a look at them.

Good Luck

 

[Welder1]

He said that he found the intake valve at .040 when he initially set it at .010. That indicates to me that the intake valve is not fully seating there for low compression. A compression check is the next thing then probably pull the head back off.



Eddie

 

[frank8003]

Brand new but cracked valve spring/s or retainer.
Comparison check, dial indicator on the valves before pull the head, quickest way. Just with the one cover off.
Befuddled here too.

 

[Wildchild467]

Be sure to adjust the valves a couple times after the rebuild. I rebuilt mine this year with new pistons, liners and new heads. After I re-torqued my heads, I found the valves were tighter. I would adjust them after you re-torque the heads and again maybe a couple hundred miles later as well. you would be surprised how much they move in the beginning.

How much blowby are you getting? After I rebuilt mine, I still get puffs of blowby out of my slobber tube and dont understand it. With new pistons, liners and heads... I don't know where it could come from unless its a compressor going bag. Did your pistons have 2 compression rings only?

 

[wb1895]

My pistons have 4 rings total. 3 compression, 1 oil. And yes I am still getting some blowby, but from what I understand these engines will always have noticeable blowby