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1979 brat 4x4

Low oil pressure at idle

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17 replies to this topic

#1 1979subiebrat

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Posted 17 February 2013 - 07:44 PM

I got this old brat on a trade, what y'all think? It's a one owner but hasn't been driven in 10 years. The motor had been taken apart and left for the rats to live in and chew one. I've got it cleaned up and put back together, but when it warms up at idle the oil pressure light begins to blink on and off. Is this common with these old motors or is the oil pump just weak?

#2 1979subiebrat

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Posted 17 February 2013 - 10:17 PM

Here's what she looks like all cleaned up

#3 1979subiebrat

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Posted 17 February 2013 - 10:18 PM

Still trying to figure out how to add pictures on here, sorry

Attached Files



#4 biffanyus

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Posted 17 February 2013 - 11:41 PM

Wow the body looks clean as hell!!! Very nice looking brat!!!! If your oil light goes on Im guessing there possibly can be an issue on either your oil level or pump but Im no expert. Wait for a more inteligent reply from someone here on the board with better know how than me. Please post more pics!!!!



#5 1979subiebrat

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Posted 17 February 2013 - 11:45 PM

I will try but it keeps telling me my pictures are all too big to attach, is there a better way to post pictures on here? I'm new at posting to forums, I usually just read them lol.

#6 maestro

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Posted 18 February 2013 - 01:20 AM

79 brat is righ. Make sure the oil level is correct. Also I am not sure if this would affect it but make sure you have a good oil filter. One that is clogged may or may not affect the oil pressure. Running too thin oil can make the pressure low. 10w30 or 40 should be fine. If the idle is too low it can cause low ppressure. Make sure its idling 800-900RPM's. If you don't have access to a tachometer just make sure its idling fast enough to not be stumbing. Also, the sending unit could be faulty. Try attaching a real oil pressure guage and see what you get. I am not sure what spec pressure is but I will hook one up to mine tomorrow and tell you what I get. If after all of that the pressure is in fact low your next place to look is the oil pump. I am not sure if our ea71's have a screen at the oil pump but if it does it may be dirty. Clean it. If the oil pump has seals they could be seeping, replace them. Or get a new oil pump. If after that you still are have low pressure issues you may be looking at worn mains.

#7 1979subiebrat

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Posted 18 February 2013 - 08:28 AM

I will try to find an external gauge to plug In today. The pickup for the pump has a screen in the oil pan, I cleaned it when I had the motor out putting new gaskets in it. It has a new filter and fresh oil as well, 10w-30. It just seems odd to me that when cold I can idle it real low around 500 or so before the oil pressure light even begins to flicker. But when warm idling at around 800 it'll just start to flicker unless you give it a little throttle. This is my first subie motor to work on and they are pretty neat, but can be frustrating like any other motor. Thanks for the replys and ill look at mine again tonight after work. Ill try to add more pictures too of before and after the pressure washer. Good pictures of these old 1st gens aren't real easy to find I've noticed.

#8 maestro

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Posted 18 February 2013 - 09:51 AM

Get a reading of that oil pressure while cold and while warm when the light is flickering. It would be interesting to know the difference.



#9 maestro

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Posted 18 February 2013 - 12:37 PM

I'm finally home. I'll be hooking up the oil pressure guage in a few but first I broke out my factory service manual. Check out these specs.

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enginelubespecs.jpg

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Edited by maestro, 18 February 2013 - 12:59 PM.


#10 1979subiebrat

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Posted 18 February 2013 - 03:18 PM

Wow, I think I need to get one of those manuals. The guy gave me his old chiltons manual with the brat when I picked it up and it doesn't have anything like that in it. Doesn't surprise me much after I read the electrical section and it said that wiring has become to complex to provide detailed diagrams in a reasonable amount of pages. Haha
Thanks for those diagrams btw ill post pressure specs when I get home this evening.

#11 maestro

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Posted 18 February 2013 - 08:28 PM

Yep the chilton and haynes will get you so far and then leave you sucking for air. What I hate is when it says, "This procedure is too complex for the home mechanic. Take it to a pro." Or something like that. BITE ME!!!

 

Sometimes you can get these factory service manuals on ebay or amazon used when they occasionally pop up. You may be able to get it from the dealer. Publication number on mine is SM76TUS. I did find this thread: http://www.ultimates...980-to-present/ and they list several manuals.

 

I am still looking for my oil pressure guage. I keep one around to test pressure on different vehicles. I almost never trust facory sending units especially when it is a light rather than a guage.

 

Do you know where to connect your oil pressure guage? If not, look under the engine bay where the oil filter is. Where the oil filter is screwed onto the housing there will be an allen head. Obviously you will need an allen head wrench to get that out. Oil will get you in the face so look out. This is where the oil guage connects if you have a factory oil guage setup. The oil light sending unit is oposite the oil filter on that same housing. I suppose you coudl remove it and put your guage in there if you dont have an allen wrench. The oil light sending unit will have the wire on it and is easy to find. Let me know if you need a pic.

 

Keep me up on what you find.



#12 1979subiebrat

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Posted 18 February 2013 - 11:48 PM

Sounds like I guessed right. I took out that Allen plug on the bottom side of the pump and put my guage in there. With the engine cold it was reading right at 50 psi. When I got the engine warmed up the pressure dropped to 10psi. When the light starts to flicker the pressure is dropping to about 8psi and bouncing between there and 10psi. I turned the idle up to 1000rpm and the pressure stays at a constant 10psi.

#13 1979subiebrat

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Posted 18 February 2013 - 11:56 PM

More pictures

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#14 maestro

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Posted 19 February 2013 - 05:20 AM

This site explains everything about oil pressure, http://www.aa1car.co...ary/us1097.htm. That being said you should start with taking the oil pump off, clean the oil bypass valve and pressure relief valve, then measure the oil pump rotor and gear and their clearances. To do that you are going to need feeler gauges and probably a digital caliper. http://www.harborfre...ings-68304.html and http://www.harborfre...auge-32214.html in case you don't have them. Pictures from the manual below show specs and steps to do this.

1600lubediagram.jpg

disassembleoilpump.jpg

measuringoilpump.jpg

If it were me, I'd clean the valves and make measurements best I could. Even if the measurements were out of spec try replacing the oil pump and see what happens. If the pressure is low and I found the measurements out of spec or not I'd replace the oil pump, http://www.autozone....omString=search, expensive unfortunately. Alternatively you may be able to find an engine locally, either from someone with one running and on the road and see if they will let you try the oil pump before you buy a new one. Or find one in a junkyard and buy it but you don't know for sure if a junkyard one is good or not. If oil pressure is still low with a known good pump you definitely got worn bearings. You can buy new bearings and replace them only or get a complete rebuild kit if you are inclined. I'd go ahead and do a complete rebuild since changing the main bearings requires splitting the case and the engine is already completely disassembled. And... since if you've gone that far why not send the cam off for a grind. Everyone on here says deltacam will do either a torque or hp grind. The torque grind is for if you think you're going to do lots of low revving off roading. he hp grind is for more highway use. Also a port and polish of the heads is advantageous. Possibly look into shaving the heads a bit for higher compression but I am not sure how much is safe for valve clearances. Okay, I'm probably way ahead of myself but I'm just saying.

Also, please take pictures or video of the oil pump disassembly and cleaning and post. This can be useful for others with similar issues in the future. Keep me posted on your progress. And that does indeed look like a nice clean gen 1 brat. I wish my bumpers looked that nice. Mine are bent and dented.

Edited by maestro, 19 February 2013 - 05:23 AM.


#15 Kevint143

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Posted 19 February 2013 - 07:27 AM

wow thanks for posting those pictures..my brat is doing the same thing..it is also leaking out of the pan so I figured it is time to pull the pan replace gasket, switch and clean the pump up!



#16 1979subiebrat

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Posted 19 February 2013 - 08:40 AM

I will take the pump off this weekend and take pictures as I go through it, thanks for the diagrams. That should make it easy to get apart and figure out. I did find a new pump on eBay for 40$, which may be worth a shot compared the autozone one. It's made by a Japanese company I've never heard of though. eBay item number 270714892427

#17 maestro

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Posted 19 February 2013 - 09:41 AM

$40 is awesome! I didn't think to check ebay. Does the new pump come with the valves and all? If so then for that price forget about going through all the trouble to clean it up. Swap it for the new one and test it out. I hope that fixes the prob because tearing the engine down will suck.



#18 1979subiebrat

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Posted 19 February 2013 - 10:16 AM

It appears to be a complete pump, ill find out when it shows up lol I went ahead and ordered one and should be here by the weekend. I'm still gonna take the old one off and apart just for curiosity sake. I got this brat as a quick turnaround project for some cash to go towards my Fj. But the more I work on it and drive it around the yard the more its growing on me. So far I've only got an old canoe invested in it and a gasket set. I keep envisioning a lift kit and new bumpers, but only if I decide to keep it lol




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