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Discussion Starter #1
I have a 1989 bronco Eddie bauer with the 5.8 351 w everything is still stock. I am having a issue where the truck looses oil presure. It happens mainly when I am running the a/c. The a/c works great but I don't know why the oil pressure drops when I run it while stoped with the truck in gear. If I put it in neutral or park the oil presure goes up and it runs fine. It has 5w20 oil in it that's just what my mechanic put in it. I am not sure if that was right for its age and size. The truck has no oil leaks that I can find. I feel like it does it mainly when it is hot out side I tried it when it was nighttime and cold and it took longer to happen. Sorry for the bad grammar typing from my phone will update when I get to my comp
 

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Do you have the (normal) oil gauge. Meaning does it just have a normal range and not actually show pressure?
 

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Sounds more like you are getting a voltage drop when the ac puts a load on the electrical system, which in turn is causing erratic behavior from the 26 year old gauge/sender/wiring.
The factory gauge is designed to just display pressure if there is only a few psi or more. Like a switch, it is either on or off, and does not actually respond to variance in pressure.

You would need an actual pressure gauge to get a true pressure reading, which is not a bad idea. I would suggest verifying proper function of the oil gauge and circuit, as well as the charging system.
 

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My 2 cents. If you are in an area where you are already running the A/C, then in my opinion you need to change the oil to 10-30, 10-40 or anything other than 5-20.
 

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Discussion Starter #6
The truck will also stall if i stay still to long.
 

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Yeah I definitely think that's not an oil pressure issue, the ac compressor turning on would not affect oil pressure. Maybe fluctuate it a bit due to an rpm drop but nothing that dramatic
 

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Also looks like your voltage guage is dropping a bit too much when you turn on the ac
 

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Discussion Starter #10
Stalled with ac on. it has dropped oil presure without the ac on before but it's not as common. Would you recomened new battery and alternator?
 

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Stalled with ac on. it has dropped oil presure without the ac on before but it's not as common. Would you recomened checking the battery and alternator?
Sounds more like you are getting a voltage drop when the ac puts a load on the electrical system, which in turn is causing erratic behavior from the 26 year old gauge/sender/wiring.
I would suggest verifying proper function of the oil gauge and circuit, as well as the charging system.
Yep....
 

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I wouldn't go replacing things in hope the issues will go away, however I can tell you that my voltage would drop with the ac on, needle would go almost to the N or O of normal at night with the lights on and stopped, I replaced the alt. and when I switch lights and ac on the needle moves about 1/16 of an inch then goes right back to dead center of normal.

As for oil pressure, have you checked your connection at the oil press sending unit? It may be loose or corroded
 

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Discussion Starter #13
No not yet still doing my research on it. I had the altenator checked and they said it was good. but the person who did it I don't think did it right I had just taken it to orileys I'll get a differnt shop or mechanic to look at it and check back in. Also even if the sending unit is loose or bad that wouldn't explain the stalling would it? They both seem to happen together.
 

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Discussion Starter #14
The whole reason I'm worried is because the drop in oil presure causes it to stall when in idle. If the gauge just jumped I would be less worried.

Also what do you mean by charging the system? Are you referring to oil, electrical or a/c?
 

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Do the lights dim when this happens?
The oil pressure is not killing the engine, seems more likely that a lack of 12 volts going to the coil is killing the engine.
Your volt gauge shows less than 10 volts, much lower than that and the coil will drop spark killing the engine.
 

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I have a 1989 bronco Eddie bauer with the 5.8 351 w everything is still stock. I am having a issue where the truck looses oil presure. It happens mainly when I am running the a/c. The a/c works great but I don't know why the oil pressure drops when I run it while stoped with the truck in gear. If I put it in neutral or park the oil presure goes up and it runs fine. It has 5w20 oil in it that's just what my mechanic put in it. I am not sure if that was right for its age and size. The truck has no oil leaks that I can find. I feel like it does it mainly when it is hot out side I tried it when it was nighttime and cold and it took longer to happen. Sorry for the bad grammar typing from my phone will update when I get to my comp
You should be running 5w-30 or 10w-30. 5w-20 is spec'd for most newer trucks not 20+ year old 5.8s.
Do the lights dim when this happens?
The oil pressure is not killing the engine, seems more likely that a lack of 12 volts going to the coil is killing the engine.
Your volt gauge shows less than 10 volts, much lower than that and the coil will drop spark killing the engine.
IIRC the computer won't function with less than 11 or so.
 

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Discussion Starter #18
How many miles on that engine ? 5/20 is really thin oil.
I pulled car fax it says 110,000 and it only shows one roll over. I still doubt it has that low but i wouldn't guess more then 210,000
 

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Discussion Starter #19
The engine stalls because the oil pressure is actually dropping, and the lifters aren't staying pumped up enough to open the valves. The pressure drops because the idle is going too low. The idle is too low because the EEC is having trouble controlling idle speed. That's probably because of neglected maintenance, but it could also be wear. We need to know ALL the truck's details & history, and "all stock" tells us NOTHING. There are a few dozen "stock" configurations - research your truck's, and then add it all to your signature & profile so it shows automatically. Don't post it where we'll have to dig back through the thread to find it. Click this & read the caption:
http://www.supermotors.net/registry/media/72354
The reason why I say all stock is because there has been no changes to it, aside from keeping it running. The previous owner used it to tote around a tractor for a landscaping business. I just bought the truck three weeks ago.

thelittlehoe.com (you can see my truck in the background)

I am reading that site you gave me now.
 

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Discussion Starter #20
MADE IN USA FORD MULTIPURPOSE CLASS E HYDRAULIC 6-7 KIP
WAGON BODAY FULLSIZE LIGHT TRUCK 1/2 TON LIGHT TRUCK 4WD
(88-98 ) 5.8L (351ciW EFI) V8 1989 Wayne, MI

adding to sig in a few when I get to my computer.
 
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