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Factory gages.

Discussion in 'Chevy Trucks' started by KK, Feb 21, 2001.

  1. KK

    KK Member
    Messages: 45

    I have factory gages on my '83 C20 and want to hook them up properly to the new Goodwrench engine that I'm working on. The water temp wasn't working right and I found that the wire going to the block sensor was disconnected. The oil pressure wasn't working either because it always registered 40psi even when the engine wasn't running! The questions I have are as follows: What do I need to get these fixed? Arent they electric and at the most need new sending units? or, are they kinda junky as they get old? Will sending units on the engine do it or do I need to look at the gages themselves in the dash? Thanks.
     
  2. Power mad

    Power mad Member
    from Oregon
    Messages: 75

    Hey KK
    The gages in the dash are electronic, and if every thing is working properly are pretty acurate.
    The sending unit for the oil is at the back of the block on top behind the intake manifold, drivers side.
    On a fresh engine I always replace the oil and water sending units.
    To see if the gage is woking properly, {with key on} ground the lead for the oil unit to the block. The gage should max out. If not then there is a problem with the gage or a circuit problem.
    It's also a good idea to have the gages in view so you can moniter the engine.
    If you decide to get mechanicle gages get a good set. Auto meter makes nice gages, kinda spendy but they're nice gages.
    See ya
     
  3. 9521

    9521 Junior Member
    Messages: 8

    Don't be surprised if the in dash gauges are bad. I've had this problem on two separate vehicles.

    Get some autometer mechanical gauges via ebay. The stock ones aren't accurate worth a hoot anyway.
     
  4. plowjockey

    plowjockey PlowSite.com Sponsor
    Messages: 622

    Power Mad

    I have an '80 C-70 dump and my oil pressure gauge is maxxed out all the time. It moves some times but it does not respond. Could, do you think, the problem be that the sending unit has shorted out?

    Bruce
     
  5. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Plow jockry-unplug the sender-if it drops back to zero-the sender is bad-they go bad often,i wouldnt be surprised if it was bad.
     
  6. plowjockey

    plowjockey PlowSite.com Sponsor
    Messages: 622

    Thanks John

    When I shut it off the gauge goes down some but not to zero. When I turn it back on it maxxes out again. I'll try unplugging it tomorrow...I just took it back to its parking space.

    Thanks again.

    Bruce
     
  7. RTallday

    RTallday Member
    Messages: 79

    Since we are all on the subject of oil gauges, does anyone know the color of the wire that is supposed to go from the gauge in the cluster to the sending unit? I have an aftermarket gauge, and i want to hook up the origional one. THEY ARE ACCURATE!!! They wouldn't have been put in the trucks to begin with if they werent accurate.

    -Rich
     
  8. 9521

    9521 Junior Member
    Messages: 8

    I guess we'd need to agree to disagree. My own experience has been different and I tend to place a stock gauge just one step above an idiot light. If yours is accurate, it's probably the exception to the rule.

    GM Fuel and Temp gauges are particularly known for only giving you a vague idea of what is happening - especially the small ones used with 40 gallon tanks which seem only accurate to within about 20%. The Oil gauges are a little better but tend to peg at above 50 PSI. In comparing the temp gauges in my K30, the stock gauge in the 11 o'clock position just short of 210 degress correllates with about 230 on the Autometer under the dash. Go figure. These problems are compounded when the gauges are calibrated with either L&H (low and high), C&H (cold and hot), etc. Again, not to say yours isn't on the money - maybe yours was made on a Wednesday and all mine have been made on Mondays and Fridays.... :eek:) but you probably wouldn't see so many aftermarket gauges in vehicles if the stock ones were accurate and reliable.
    9521
     
  9. plowjockey

    plowjockey PlowSite.com Sponsor
    Messages: 622

    My experience with GM gauges has been that they have been pretty accurate to other aftermarket gauges that I have tested over the last 30 or so years.

    By the way I work in a GM automotive plant and I do the best quality work of my ability EVERY day. I have more personal pride than that in what I do for a living and the customer deserves the best that I can put out. I think you are selling some very good people more than a little bit short.

    Sorry but that comment just struck a nerve.

    Bruce
     
  10. mike reeh

    mike reeh Senior Member
    Messages: 114

    about aftermarket guages reading diff than stock, are the sending units in different spots in the engine?? that would give a diff reading, also, if they're hooked to the same sending unit than its probably the wrong unit for at least one (if not both!) of the guages...

    ive had stock guages read pretty decently, but its always in untouched trucks.. ive seen a few suburbans, blazers and trucks that over the years have had literally everything broken, replaced, bypassed, etc, and who KNOWS what they've got in em and the guages are always funky... junkyard guage clusters, any old sending unit, etc.. its just a mess.. those are the guages that seem to give problems..


    mike
     
  11. RTallday

    RTallday Member
    Messages: 79

    Good for you Bruce. Im sure you do do the best work you can. I am a mechenic, well, im learning, im only 19, and i do the best work i can EVERY DAY! Things arent always perfect, but oh well. Lifes too short to dwell on the little things. Also, the factory oil gauges are as accurate as aftermarket gauges, because they are using the same sending unit holes in the block. One is electric, and one is mechenical. You just swap for one or the other. I have faith in my gages.

    -Rich
     
  12. plowjockey

    plowjockey PlowSite.com Sponsor
    Messages: 622

    My apologies for the caustic reply.

    I've worked factory for going on 29 years and sometimes get tired of that old Monday / Friday mind set. I shouldn't have responded that way. Didn't mean to come off that way 9521.

    Bruce
     
  13. KK

    KK Member
    Messages: 45

    Plowjockey, don't fret it. Your opinion is valueable to us. For the most part, I have had good luck with factory gages. Its mostly when someone starts messing with the gages that problems arise. I think that is the case with my current engine, and I would like to correct it. I want to go the factory route because I like integrated gages on the dash. So any help is appreciated.......thanks.
     
  14. evldsl

    evldsl Junior Member
    Messages: 15

    Speaking of oil gauges, what oil pressure readings are considered optimal and the minimum acceptable for cold, warm running and warm idle? I have looked in 3 stinking manuals (including the factory Helm book) and could not find it listed anywhere! Mine is a 6.2 NA diesel, if that makes a difference. It has 117,000 miles, uses very little oil, and runs strong. It reads around 40-50 psi stone cold (at 60 degrees F), around 40 psi on the highway and around 20 psi warm idle. I am also going to try the tests for accuracy above. Thanks!
     
  15. 75

    75 PlowSite.com Addict
    Messages: 1,382

    Hope this isn't too far off topic, but KK's comment about integrated gauges in the dash got me thinking. My dash had the "idiot lights" and I like the gauges up in the dash as designed. Rather than changing the instrument cluster, I figured it would be possible to mount aftermarket gauges in the dash locations.

    Well, it's possible, just very difficult! One of those jobs where I got about halfway through and wished I hadn't bothered. But by this time, the dash was apart so I kept going. Turned out fine in the end, but I'm not sure I would do it that way again. Oh, and a few years later I put an onboard air compressor under my hood, wanted a psi gauge and since all the dash holes were filled, I wound up with one gauge under the dash anyway!
     
  16. RTallday

    RTallday Member
    Messages: 79

    Im not sure of the optimal oil pressure, but i know my 79 k-20, with the 350 runs at about 50 psi when its warm and im crusing. It idles at 25 pounds. I also have a Hi volume oil pump, but i dont know if that matters. It also depends on the kind of oil you use. 20/50 will give you thicker and more pressure than 10/30 will. I use 15/50 synthetic, and those are the readings i get on my mechenical gauge. Good luck!!

    -Rich
     
  17. 9521

    9521 Junior Member
    Messages: 8

    evldsl-If I recall an older Chiltons I have lists "normal" as 35-50 PSI for the 6.2, but 20 PSI at idle seems low to me and may indicate your bearings and/or oil pump are getting tired. Considering the cost to rebuild a 6.2 and the fact it runs OK, my suggestion is to use what it is called for (I believe the books call for non-detergent 30 wt.) and run it until other symptoms develop.
     
  18. mike reeh

    mike reeh Senior Member
    Messages: 114

    20psi at idle is fine, ill bet your diesel idles fairly slowly too, no? dont worry about it.. especially with a high mileage motor. a general rule of thumb is about 10psi for every thousand RPMs.. anything less and you might start to wonder.
     
  19. MTCK

    MTCK Senior Member
    Messages: 346

    I had the same idea as Rob earlier this year. Putting aftermarket gauges in the factory holes on the left side of the dash seemed like the way to go. I had swapped a small block into a diesel truck, and the wiring for the gauges went to hell during the process, so a set of autometer ultra lights went in. Oil pressure, volt meter, trans temp, water temp, a tach on the steering column and the spedo and fuel level in the stock spots. WHAT A HEADACHE. After quite a bit of cutting and swearing, it all worked out, and I've been very happy.

    Since we're all talking about oil pressure.... My 83 305 with about 110,000 miles on it has started to leak. A lot. Best guess is front main seal, but it's hard to pin point with the accumulated mess. It doesn't burn much oil, (at least not out the pipes) and has good compression, last checked about 15,000 miles ago. The problem is this. Going up hills, or pulling a load, the truck smokes a fair amount, but not out the pipes, from under the engine compartment. What I've figured is it's oil leaking onto the headers, and going up in smoke from there. Possible? Another not so attractive thought, is it's blow by going out the open element breather on the valve cover. Also, oil pressure stops climbing with engine RPM around 3500 rpm at about 40 psi. I've been going with the 10 psi for 1,000 rpm rule. On cold start up, I get about 50 psi. Then about 30 cruising and 20 at warm idle. My question is this. Could a bad oil leak be causing these presure problems, and would it be worth trying to fix, or should I just bite the bullet and go pick up that new GM goodwrench 350. Whew, sorry about the essay, thanks guys.

    MT
     
  20. 75

    75 PlowSite.com Addict
    Messages: 1,382

    MTCK - Glad you posted this, makes me feel me better knowing I wasn't the only one cursing & swearing during the gauge ordeal.

    Regarding the oil questions, first you should probably try to track down the leak(s). Give the engine a good degreasing and power washing to get the accumulated mess off, then see where it starts getting "oily" again. I don't know how much of a factor rust :mad: is in your location, but a friend of mine had a bad oil leak on his 350 which turned out to be a rusted valve cover. It was at the back on the passenger side, and the same thing you have been noticing would happen - oil smoke from drips getting on the exhaust. Depending on where the leak is, it may be possible to repair it on board. Check the compression again too, to get a better idea of overall engine condition. The psi readings may be the result of the oil pump itself getting "tired" too.

    Depending on what it will take to fix the leak and what shape the engine is in will help you determine whether the Goodwrench 350 is the way to go. Obviously, how much longer you plan to keep the truck will also be an important thing to consider - I'm guessing you intend to keep it going for a while yet so an engine may be a good investment.