The real JD 4520: Compression Issues

[brendonh]

excellent rockcreek. Same as in the 40 series book almost word for word.

If I was the OP, i'd stop chasing this. I'll bet the 30psi he's looking for is in altitude of his location and / or the temp outside on the day of testing.
The book value for the 4520 compression spec is wrong.
IMO:
Deere's of this vintage start hard even when new. Have to live with this one.....
Mitigation:
Full throttle
Plug it in.
Heat the intake manifold in some manner, weed burners work, heat guns are better, THIS helps tons even if you didn't plug it in. Heat.....you don't have to burn the paint. It does take patients to do it, but it will make a huge difference.
New/good batteries
New/good starter
patients
Flammable brake and parts cleaner - much softer than ether and does the same job.
Ether - you will addict your 404 to this stuff.

 

[buickanddeere]

Just curious here, how far do you pull the throttle when starting?

For me, it was all the way. Simulates the starting fuel setting of a bosch inline pump of later machines.
In my experience, Grandpa's 5010's, both early and late 4020's and my 4230 all need that max fuel throttle setting to wake up easier.

Also agree with buickanddeere. Nobody ever checks valve recession very much on these old heads even after a regrind. Neither did I. Mostly because you could see it. The valves wouldn't have any margin left, so they would get replaced. If the seats took that much cutting to get cleaned up and sat low, those got replaced. I don't know this, but I rather doubt a usable seat and or a usable valve would recess in the head that bad to cause super low compression by itself, and across all cylinders at the same time? Ok... well... maybe...stranger things have happened..

I'm sure the cam is shot, but those are only ever changed when the oil pump won't turn anymore on these 404's. I'd bank on the pump is also out of time also.
However, none of this addresses low compression, rather ease of starting. Assuming the valves don't leak, the piston rings don't leak, there's nothing left except stroke. I doubt that anything is wrong there either.

I do know that Deere had this problem..... Starting has been an issue until the days of the 6076, when they redesigned the combustion chambers and where the top ring was on the piston. 404's were miserable when they put turbos on them. The compression was reduced on turbo engines because of the turbo. So, anything with a 404 or 466 was a miserable female dog to light off when it was 50* or less outside. Personal experience comes from 4020's, 4230, 4630 (that I grew up with) and a 4640 (also grew up with, both were my office during my school days and college). I'm wondering if the book is wrong. When we rebuilt engines in the dealership, we never, I mean no of us, even the old guys didn't ever check compression. I've never checked compression on any of them either, so I can't tell you what "actual" ever was, new or used..... They either ran good, or they didn't. Compression was checked by how much blow by we got and how much blue smoke was issued after she'd warmed up. We did things they way cause we were on the clock and the bill meter was running. Compression testing was deemed unnecessary by the elders.

My 4320 book shows the same numbers for compression as what's been listed already.
The 4640 and 4840 run in the book at 330 - 370.
Theoretical compression ratio for the 4640/4840 would be 24:1, calculated by taking atmospheric pressure on a standard day of 14.7 psi, and diving the requested psi on the compression gauge, i used 350psi. That came to : 350psi / 14.7psi = 23.8. So, the ratio, per math is 23:1. The book for the 46/4840 said the compression ratio is actually 14.9:1. Running that number, 14.7 psi * 14.9 compression ratio = 208psi. So, I'd expect a perfectly good engine in a 46 or 4840 to be at least above 208psi on the gauge. The book says 330-370psi. The difference is in all the factors the math is not considering on the given day and with the given engine along with factors of gas compression laws the simple math formula isn't looking at.

All that said, I think the compression is fine on that engine. 330 is a lot closer to measured in this instance. I understand its a 404 vs 466, but I don't put much stock in that difference since both engines basically the same in combustion chamber design, and both are Deere engines. A compression number from a 4620 or a 4430 would be usefull since both of those engines are exactly the same as the 4520 in question here.

I would give anything to set down at my old service manager computer and search the DTAC solutions for starting and/or compression related solutions on these. I'm sure there are suggestions in there. Alas, I never had reason to do that search when I was a service manager, so I don't remember any of them.

Sorry all for the rambling. Just trying to think this out a little more..

Thanks~
Brendon

some of the compression pressure is due to the air heating during the compression stroke . Universal gas law etc. A slow cranker will show less compression pressure vs a fast cranker .

 

[used red MN]

View attachment 141034

some of the compression pressure is due to the air heating during the compression stroke . Universal gas law etc. A slow cranker will show less compression pressure vs a fast cranker .

So you are saying his fresh engine should not be able to achieve the compression specification that Deere put in the repair manual?

Per the manual the compression should be between 385 – 410PSI @ 215 – 245RPM

Cranking RPM is averaging 225RPM (coolant & Hydraulic pump not hooked up) with photo tachometer

??

 

[brendonh]

Used Red,
The 4520 was Deere's first shot at a turbo built diesel engine. It was also a continuation of Deere's first more than 2 cylinder diesel engine and only 8 years from the first 6404D ever built. None of those had turbo's Turbos require a decrease of compression ratio because some of the compression is done in the turbo, this shows up the most under maximum rated load.

The 4520 used a 6404T which means, 6 cylinder, 404 CID T Turbo. This engine continued use through to the 30 series (4430, the direct replacement for the 4520) until 1977. The 6466 rolled out as an improved version of the 6404 in 78 with the introduction of the 40 series. 4440 as example. The 6076AF another improved version of the 6466 rolled with the mid serial number 50 series or start of 55 series, I don't exactly remember. That being said it was when the 6466 became the 6076 that the combustion chambers and compression rings were redesigned and compression numbers moved along with a greatly improved cold starting performance.

The manual values are incorrect for the 404T engine when referenced in the 4320/4520 books. The 4430 book, states 330-370 on a standard day at sea level, and indicates a 3.5% decrease of compression pressure for every 100 feet of altitude increase. For me a brand new 6404T would produce only 220psi compression on my gauge at 3800 feet above sea level at the same cranking speed and ambient temperature.

Does this help?

*years listed above may not be exact, going from memory figure +- 2 year tolerance

Also note: the 830 was deere's last 2 cylinder diesel engine before the 4010, which rolled with the 6404 first. The compression psi listed for the 830 was 380 - 400 psi. No mention of altitude compensation. This falls in line with the 4520 manual, I suspect but cannot confirm that a 4010 and 4020 would show the same values. Reason: no turbo.

 

[Hay maker2]

excellent rockcreek. Same as in the 40 series book almost word for word.

If I was the OP, i'd stop chasing this. I'll bet the 30psi he's looking for is in altitude of his location and / or the temp outside on the day of testing.
The book value for the 4520 compression spec is wrong.
IMO:
Deere's of this vintage start hard even when new. Have to live with this one.....
Mitigation:
Full throttle
Plug it in.
Heat the intake manifold in some manner, weed burners work, heat guns are better, THIS helps tons even if you didn't plug it in. Heat.....you don't have to burn the paint. It does take patients to do it, but it will make a huge difference.
New/good batteries
New/good starter
patients
Flammable brake and parts cleaner - much softer than ether and does the same job.
Ether - you will addict your 404 to this stuff.

I reside at between 1050-1100 above sea level.
As stated, even at a 90-degree day I have to crank the snot out of it to get a fire

 

[Hay maker2]

Valve recession spec for the 4520:
View attachment 141009

Per my 4520-tech manual, it calls out the same maximum recess valves as your screen shot as well as the valve angle face. My machinist stated that the recess is less than the maximum value.

 

[Hay maker2]

Used Red,
The 4520 was Deere's first shot at a turbo built diesel engine. It was also a continuation of Deere's first more than 2 cylinder diesel engine and only 8 years from the first 6404D ever built. None of those had turbo's Turbos require a decrease of compression ratio because some of the compression is done in the turbo, this shows up the most under maximum rated load.

The 4520 used a 6404T which means, 6 cylinder, 404 CID T Turbo. This engine continued use through to the 30 series (4430, the direct replacement for the 4520) until 1977. The 6466 rolled out as an improved version of the 6404 in 78 with the introduction of the 40 series. 4440 as example. The 6076AF another improved version of the 6466 rolled with the mid serial number 50 series or start of 55 series, I don't exactly remember. That being said it was when the 6466 became the 6076 that the combustion chambers and compression rings were redesigned and compression numbers moved along with a greatly improved cold starting performance.

The manual values are incorrect for the 404T engine when referenced in the 4320/4520 books. The 4430 book, states 330-370 on a standard day at sea level, and indicates a 3.5% decrease of compression pressure for every 100 feet of altitude increase. For me a brand new 6404T would produce only 220psi compression on my gauge at 3800 feet above sea level at the same cranking speed and ambient temperature.

Does this help?

*years listed above may not be exact, going from memory figure +- 2 year tolerance

Also note: the 830 was deere's last 2 cylinder diesel engine before the 4010, which rolled with the 6404 first. The compression psi listed for the 830 was 380 - 400 psi. No mention of altitude compensation. This falls in line with the 4520 manual, I suspect but cannot confirm that a 4010 and 4020 would show the same values. Reason: no turbo.

While both the 4520 and the 44/4630 unitizes the same 6404T engine, the do call out different piston assemblies. The 4320, 4520, and 4620 all uses the same piston kit. The 4430 / 4630 do not share the same part number. What is the difference between the two, I will probably never know.

I installed a new Reliance high compression in-frame kit in my 4020 (1965 build year) a few years ago. When I did a compression test prior to tear down the compression was at 320PSI. Per my 4020-tech manual, compression should be between 450 - 475. I did not do a compression test afterwards, but she will start on a 20-degree day with no heat and hardly a misfire / white smoke.

 

[buickanddeere]

For all the boost and fuel applied to the 404 in a 4520 . A set of 4020 reliance high compression pistons would probably provide adequate service . The 4520 did cool the pistons with an oil spray .
Odds are that a rebuilt head with valves set up to almost smack the pistons . This Would raise the compression pressure .

 

[brendonh]

Yea,

I'd expect the 4020 to start better. They always have. Higher Compression. Cause.....no turbo.
That was the very gripe everyone had about Deere engines when they put turbos on them.....they won't start anymore.

Deck the head, put the high compression pistons in it, basically make it a 4020 again, and poof.....it'll start.

Oh, Buick, you can do that, and the head gasket will blow. Every time. (well it might not today, cause the gasket is modern, but in 1975, it didn't) It is the very reason Deere lowered compression. In fact, Deere struggled for 8 years on how to make a 404 and a 466 head gasket not leak. 6 or 7 different gaskets, 5 different bolt types, washers, no washers, Special, hi grade, low grade, 5 or 6 different DTAC solutions, torque the head this way, no that don't work, do it that way, retorque after hot, no don't retorque after hot, use these bolts and this gasket, blah blah blah..... for 8 years..... cause the head gasket leaked........ cause: too much turbo....so sayeth Deere anyway....

The solution finally came in for all 466 engines with the adoption of the 6076 way of doing things. I nice rubber coated, steel fire rings and silicone water rings, along with another new torque pattern.......torque turn method eh...hummm.. and new bolts.......again.......flanged this time.

Finally, fixed!! No more blown head gaskets! Well, it took longer to leak oil around number 6 this now anyway. I remember the first time I did this, I thought for sure I was going to bust the bolt with the breaker bar and fall off the ladder doing the last 90* turn.


Oh, it didn't help that a 4630, ours included, were usually turned up from 160hp to somewhere around 185 to 210. In fact, that might be the sole reason 404's and 466's couldn't keep their heads, but...Deere saw enough of it to go through a crap ton of work to stop the head gasket leaking...

Anyway, for this issue......personally. I wouldn't chase compression anymore. I'd chase starting.

Destroker kit, make sure it works and/or it's installed.
Replace or rebuild the injectors. Make them pop at 3800psi again, and have good nozzles in them. No streamers
Advance the timing by about 3 degrees on the pump. It'll start better, just know the limit is egt under max load fuel delivery cause of the turbo.
Overhaul the pump, it's gotta be almost perfect for your best chance at starting.
Biggest CCA batteries you can fit, use 00 cable size. Ground the battery to the starter bolt.
Overhaul the starter or use a nippondenso version, it'll have the gear reduction in it.
Ideally, the starter will crank that engine at nearly 300 to 500 rpm. This will make it start.
Oh, use full throttle, every time, just back it off when it starts hitting on all six smoothly and the tach is north of 1200 rpm

Anyway, my buck fifty on the matter and some stories from an old western kansas deere mechanic......i miss those days....working on those was fun.

 

[Fritz Maurer]

What is a destroker kit?

 

[brendonh]

What is a destroker kit?

It's a solenoid package installed on the main hydraulic pump up under the fuel tank. It's purpose is to "destroke" that pump during cranking, so the starter doesn't have to fight hydraulic pressure too.
Basically, during starter engagement, cranking, this solenoid will "turn the hydraulic pump off" so it won't make pressure.
All of those pumps can be 'turned off'. Look up at the pump, see the square block with the big hex plugs in it. One of those will have a smaller allen key bolt with a jam nut around it. That's where it goes. The solenoid replaces that allen key bolt. If you loosen the jam nut and turn that allen key bolt in (feels like 100 turns when you're doing it), the pin inside pushes on a valve that opens. This will basically cause an internal leak inside the pump, preventing pressure from being built by the pump. Just remember how many turns you made, you need to reset it back where it was or your output pressure will be wrong, you might find the weak spot in the high pressure hydraulic system if you don't.

 

[Fritz Maurer]

Why is the pump not in zero stroke to begin with? Are we talking about a piston pump?

 

[brendonh]

It is, and yes, the Deere Radial piston pump is the one in question.
A good system, about 3 seconds of cranking, that pump goes to stand-by pressure and stays there. Usually 2350 to 2400 psi. This extra load causes starting issues in cold weather especially. These pumps are closed center flow compensated. First one of their kind to be installed on tractors, clear back in 1961 on the 4010.
According to a good friend of mine, sugar beet harvesters and this pump is what killed IH tractors in western Kansas. IH hydraulic systems burned to the ground running whatever it was on a sugar beet harvester. The Deere system didn't ever get hot, so most farmers changed to Deere at that point around home. It was this radial pump, and how it worked that made all the difference.

Note: This is why "turning the steering wheel on your 3020 makes it start" is a thing. You're using the pressure from that pump, reducing load on the engine and starter, allowing the engine to start running much easier. Gasser 3020's are famous for needing the steering wheel turned or it won't fire. This is why.

 

[Fritz Maurer]

I get the stand by pressure and the fact that makes it hard cranking.... Just a curiosity to me that they would set it up this way. I mean, what did they think was gonna happen in the brutally cold North, when the engine is hard enough to crank by itself, much less try to put the hydraulic system on stand by before the tractor is even running.

 

[Tx Jim]

IMHO JD closed center hyd system won't stay in zero stroke due to a small internal hyd leak that causes pump to go into stroke but leak isn't large enough to relieve hyd pressure so load on starter is lower.

There are 2 different style hyd pump destroking mechanisms manual & electronically controlled.

 

[brendonh]

Better hydraulic system performance the rest of the time. They did, the destroke kits were factory options. Deere did plan for it. However, not many worried about it, or knew about it, so if it failed, it wasn't fixed. When the pump was rebuilt, or replaced, it didn't go back on. None of the reman units have the kit installed out of the box. Most days you don't need them.

If I rebuilt, 20 years ago, 100 pumps, 3 of them had destroke kits on them. Nobody worried about it.

 

[brendonh]

IMHO JD closed center hyd system won't stay in zero stroke due to a small internal hyd leak that causes pump to go into stroke but leak isn't large enough to relieve hyd pressure so load on starter is lower.

There are 2 different style hyd pump destroking mechanisms manual & electronically controlled.

Ahh, thanks for the reminder.

The bottom sets pressure. The top was the destroke port.
Agreed, leaks will put the pump back in stroke, and all of those leaked. That just burns up more amps trying to turn it. The destroke system turned the pump off completely. No resistance on the pistons since no oil pressure in the block was ever produced. The only load that was left was the friction of turning the shaft inside the pump.

 

[Tx Jim]

My JD 4255 that I purchased used in Feb '93 has 12,000 hrs showing on the speed/hr meter. It will start fine in cold ambient temperatures without destroking the front hyd pump. No need to wiggle steering wheel from side to side. The front hyd pump & control valves are all original IE haven't been repaired.

 

[brendonh]

My JD 4255 that I purchased used in Feb '93 has 12,000 hrs showing on the speed/hr meter. It will start fine in cold ambient temperatures without destroking the front hyd pump. No need to wiggle steering wheel from side to side. The front hyd pump & control valves are all original IE haven't been repaired.

Those 55 series were about the best a man could get back then. Most of the bugs were long worked out when those came.
That would have the 7.6 in it IIRC.
Does it rattle when ya shut it off, the last few turns like a tin can full of marbles?

 

[buickanddeere]

My JD 4255 that I purchased used in Feb '93 has 12,000 hrs showing on the speed/hr meter. It will start fine in cold ambient temperatures without destroking the front hyd pump. No need to wiggle steering wheel from side to side. The front hyd pump & control valves are all original IE haven't been repaired.

Coyote Flats does not get cold . The place is however on my to do list to visit . https://www.timeanddate.com/weather/@5340338/climate