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Discussion Starter · #1 ·
In trying to determine the overall health of my newly acquired 4HE1, I decided to check the oil pressure with an actual gauge rather than depend on the idiot light. With the old oil, at room temp, I get 80 psi at 840 RPM. After it warms up a bit, I get 40 psi at 840 RPM. When I rev it up, warm or cold I max out the gauge at around 120 psi. This seemed high to me.

I changed the oil (Rotella T 15W40) and filter and got about the same readings as with the old oil. The FSM specifies a minimum pressure of 14 psi at idle but doesn't tell maximum. The oil diagram in the FSM shows two pressure relief valves, one at the oil pump (114 psi) and one on the main oil galley (64 psi). The pressure gauge is connected to the main galley so I'm assuming that the pressure relief valve on the main galley is stuck closed.

Is this a problem that I should be adressing or am I worrying about nothing? I have little experience with diesel engines and what would be considered normal oil pressure. Any thought, suggestions, etc?
 

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Discussion Starter · #3 · (Edited)
To access the relief valve means pulling the transmission, flywheel, and some of the timing gears. The timing gear train is on the back of the 4HE1, between the engine block and the flywheel rather than the front of the engine like in a 4BD1/2. :( I was hoping to avoid the task! Kinda wished that I had run some sea foam through the system before changing the oil and filter.

I haven't cut the oil filter open yet. I just got back my "filter cutter opener" tool from a friend that borrowed it a month ago, I'll do it tomorrow.

I'm beginning to think that the truck's prior life as a Chem Lawn truck may be partially responsible for some of the anomalies: the truck had less than 90,000 miles yet an hour meter that I found under the dash showed close to 9000 hours. That would indicate an average speed of 10 mph - a little slow. The truck had a pto on the transmission and I'm beginning to think that the standard mode of operation was to drive a few miles to a customer and then run the truck for an extended period at idle, using the pto to drive the pumps to apply the lawn chemicals. This might also explain the great compression of 500# on each cylinder, higher than usual. This high compression reading may be from the carbon buildup in the cylinders from hours of idling. Excessive idling might also have contributed to sludge build up which could be responsible for the stuck oil relief valve.

Maybe the next step is to pull the valve cover and get a peek inside.
 

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Yeah, I'd check under the valve cover for sure (but I'm a nosey sort :D ).

Bummer on the involved access to the relief.

FWIW the only oil pump relief that I have had stuck closed was in an engine that had a head gasket go just before I shut it off. The oil was just 'wet' enough with water that the relief piston swelled up with corrosion just enough to stick it closed.

Every other relief I have had problems with (ie trash in the galleys) it has stuck open or partially open (low or no pressure).:(

I would expect they had the 'throttle advance' wound up if they had a pump engaged (not quite idle, but not full load either). Are you sure that's the original hour meter?:eek:
 

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Discussion Starter · #5 ·
...FWIW the only oil pump relief that I have had stuck closed was in an engine that had a head gasket go just before I shut it off. The oil was just 'wet' enough with water that the relief piston swelled up with corrosion just enough to stick it closed.

Every other relief I have had problems with (ie trash in the galleys) it has stuck open or partially open (low or no pressure)
You are right - whenever I've had problems with a pressure relief valve, it was the result of some kind of crud holding it open resulting in low or no oil pressure. But there is always a first time. :(


...I would expect they had the 'throttle advance' wound up if they had a pump engaged (not quite idle, but not full load either). Are you sure that's the original hour meter?:eek:
I'm not sure about the meter but would expect it to be original. The add-ons were done quite professionally so I can't imagine they would have installed a used hour meter that already had time on it. Also, I couldn't find any indication that there was a hand throttle that would allow them to rev the engine. I didn't look very hard so I could have missed it. The pto gearing is 150% of engine rpm so they could drive a small pump easily at idle.
 

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Yep, always a first time for anything.:D

I meant maybe that was a replacement hour meter and the old one had worn itself out.:eek:

I dunno, on the 4BD vintage NPR trucks the throttle advance comes stock with the truck (on all I have seen, it's even in the owners manual on the '94 I've got). Maybe the newer vintage (as evidenced by the newer engine) doesn't have one??:confused:
 

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Discussion Starter · #8 · (Edited)
So ASTR, how's it coming with your 4HE1 and AW450? Tearing that thing apart yet? :)
I'm still trying to get the truck driveable so I can use it as a test bed. Turned out that accident destroyed the steering gear box, bent the steering linkage, busted a wheel bearing and bent the front axle in addition to shearing he u-bolts that held the axle in place. I took the whole front axle assembly with the steering box of the '86 NPR that I have and have it mounted on the truck. Amazingly, I only had to redrill two of the mounting holes in the frame. However, it turns out that the old wheels were 5-lug whereas the newer one are 6-lug so I had to move the hubs and brake assemblies from the 2003 to the axle that came from the '86. The spindles were the same except that I need to enlarge the bolt holes on the spindle that are used to mount the caliper mounting bracket to 14 mm. Needless to say, I don't have the right size drill bit handy so I'm trying to get my hands on one.

This weekend I'm taking off to go camping and wheeling in northern Michigan so I don't expect much progress until next week :grinpimp:

NEXXUSSIAN: I did finally cut the oil filter open and found no sign of any metal what so every. Other than the regular diesel crud, the filter media was quite clean. It was rather an interesting filter arrangement - two separate filters in one can. Unlike the 4BD1's that have a main oil filter and a separate bypass oil filter, this engine puts both of them in one can.

Also, I couldn't find any indication that a manual throttle ever existed on this truck. On both of the older NPR trucks that I looked at, the dash-mounted throttle knob is connected by a cable to the throttle pedal assembly. Although I can't tell for sure as most of the dash is missing, I can't see any indication that a manual cable was ever attached to the throttle pedal assembly.

Also, just for the hell of it, I disconnected the engine ecu. The engine started and ran fine without it. I couldn't tell that the ecu was disconnected. However, based on the FSM, I wouldn't expect a lack of ecu to effect the engine except during cold starting and high power output. IIRC, it also controls the exhaust brake, send codes to the OBDII connector, and turns on some indicator lights in the instrument panel. To find out the true functions of the ecu, I'll have to run some time trials once I get the truck off the jack stands!
 

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I was at a local truck breakers recently and they had a 4HE1, are they 3.9 litre? what power and torque? It looked all mechanical, are they?

Gaza
All 4HE1- are 4.751 litre. There are 4HE1-T, 4HE1-TC and 4HE1-XS (that I know of).

I only have power and torque for the -XS.

107 kW (143 hp) @ 2300rpm
451 Nm (333 lbf ft) @ 2000 to 2200 rpm
 

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In trying to determine the overall health of my newly acquired 4HE1, I decided to check the oil pressure with an actual gauge rather than depend on the idiot light. With the old oil, at room temp, I get 80 psi at 840 RPM. After it warms up a bit, I get 40 psi at 840 RPM. When I rev it up, warm or cold I max out the gauge at around 120 psi. This seemed high to me.

I changed the oil (Rotella T 15W40) and filter and got about the same readings as with the old oil. The FSM specifies a minimum pressure of 14 psi at idle but doesn't tell maximum. The oil diagram in the FSM shows two pressure relief valves, one at the oil pump (114 psi) and one on the main oil galley (64 psi). The pressure gauge is connected to the main galley so I'm assuming that the pressure relief valve on the main galley is stuck closed.

Is this a problem that I should be adressing or am I worrying about nothing? I have little experience with diesel engines and what would be considered normal oil pressure. Any thought, suggestions, etc?
I would be a little concerned with such high pressure. From working with GM diesels, they would start spinning bearings at 70-80 psi. I dont know anything really about this little rice oil burner, but that is pretty high...
 

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Discussion Starter · #13 ·
I'm not comfortable with this excessively high oil pressure so I will fix it. I'm assuming that the relief valve connected to the main oil galley is the one sticking. Its difficult to get at but eventually I'll be pulling the transmission and, if by then its hasn't freed its self up, I'll pull the relief valve.
 

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bobpr

Hi, I have only just logged on and I noticed that astr's question on the oil pressure of his 4HE1 engine has attracted some coment. Let me say firstly I am a mechanic and work on these engines. He said that his oil filter has 2 filters in the filter can.This is the old type of filter the newer type is full flow only and will overcome the high pressure and bearing problem.Secondly if the bearings turn then the block may have to be scraped, however I have had made for me, oversize bearings to repair the damaged tunnel.The bearings are available from me at a cost of $200.00 AU plus postage each journal.I hope this may help .
 

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Discussion Starter · #16 · (Edited)
Hi, I have only just logged on and I noticed that astr's question on the oil pressure of his 4HE1 engine has attracted some coment. Let me say firstly I am a mechanic and work on these engines. He said that his oil filter has 2 filters in the filter can.This is the old type of filter the newer type is full flow only and will overcome the high pressure and bearing problem.Secondly if the bearings turn then the block may have to be scraped, however I have had made for me, oversize bearings to repair the damaged tunnel.The bearings are available from me at a cost of $200.00 AU plus postage each journal.I hope this may help .
Thanks for the response. So you are saying that I should switch to the newer filter which is much smaller than the one that I have. Do you have a part number?

Is there a way that I can tell if a bearing has been damaged without pulling the whole bottom end? Do you know what the upper oil pressure limit is? The fsm only specifies a minimum pressure at idle. When I start mine, at cold idle the pressure is around 100 lbs and drops to 50 after it warms up.
 

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astr,
I am about to remove the crankshaft on my 4HE1. My engine has a bad #3 journal. All other journals are like new. The engine has only 110K on it. My plan is to remove the crankshaft and see if a local crankshaft company can fix it. The thing that is bothering me is "what made this happen in the first place?".
I want to install two oil pressure gauges on the engine when I put it back together. If you could tell me where the sending units should be placed, that would be helpful. I am concerned that maybe the turbo is robbing oil pressure. It takes it's oil from the block, very close to the #3 cylinder.
 

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Discussion Starter · #18 ·
astr,
I am about to remove the crankshaft on my 4HE1. My engine has a bad #3 journal. All other journals are like new. The engine has only 110K on it. My plan is to remove the crankshaft and see if a local crankshaft company can fix it. The thing that is bothering me is "what made this happen in the first place?".
I want to install two oil pressure gauges on the engine when I put it back together. If you could tell me where the sending units should be placed, that would be helpful. I am concerned that maybe the turbo is robbing oil pressure. It takes it's oil from the block, very close to the #3 cylinder.
I just tapped into the regular oil pressure port using a T. IIRC, the oil pressure switch is mounted just above the oil filter. I'll try to get a photo of it this weekend.

Also, check out Post #15 of this thread by bobpr regarding repair of bad bearings in these engines.
 

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Discussion Starter · #19 · (Edited)
Oil Pressure Tap

Isuzu 4HE1: Here is the photo of my oil gauge tap. I just removed the switch that controls the "OIL" idiot light, replaced it with a "T" with one leg of the T going to the gauge, the other to the original switch. Be aware thet the threads are not 1/8" NPT but rather 1/8" BSPT - close but not the same.

Another thing, I'm beginning to question the oil diagram in the FSM. It shows the oil switch plumbed into the main oil galley past the oil filter but it acts as if it is connected to the passage between the pump and the oil filter. I may change my oil filter per bobpr's suggestion and, at the same time, verify where the switch really connects.
 

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bobpr

astra, Check the oilfilter housing to block face, there are normally 'o' rings that seal the passageways. If a gasket is used to replace the 'o' rings the small hole that is the bypass passage for the filter may be blocked. This will definitely make the pressure go through the roof.The Isuzu filter kit part No 92955808 has the latest type filter.I dont thimk that the turbo oil feed will cause a problem provided nobody has interfied with the turbo oil circuit.Is the turbo wheel and shaft within spec and does not have excessive clearance
 
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