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Mech. gauges and ECMs

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BadDog, Dec 29, 2001.

  1. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I knew someone had posted some good info before on gauges and, sure enough, I found Jeff's post <a target="_blank" href=http://coloradok5.com/forums/showflat.php?Cat=&amp;Board=blazer4x4&amp;Number=230920&amp;page=&amp;view=&amp;sb=&amp;o=&amp;part=1&amp;vc=1>here</a>

    Looks like most everyone went with (suggested) AutoMeter Sport Comp mechanical gauges. However, Jeff went with VDO and seems happy with them. Normally I agree with the mechanical too. I ran mechanicals in my 66 GTO and in my 72 L82 (damn capillary busted and oiled down my new carpet in the Vet).

    My question is about using mechanical gauges with ECM/EFI. Looks like the ECM needs to know about oil pressure and engine temp so, unless I miss my guess, I'm stuck with electrical OR dual electrical/mechanical sending units (and trying to find a place for the mechanical sending units). Unless someone corrects my thinking, I guess I'll just go with electrical...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  2. 95 Silverado

    95 Silverado 1/2 ton status

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    yes, you would have to run separate senders for the gauges and ECM, but you probably can't use the efi sensors to control a gauge either, unless you use the original factory gauges. aftermarket gauges require their own sender that is calibrated for that type of gauge. one thing I have done for mounting more than one oil sender is too put a tee fitting on the fenderwell or firewall, run a flexible line from it to the engine to allow for vibration, run a hard line to the gauge inside the car, it's less likely to break, and use the extra port for the additional sender, you usually have to ground the fitting, as it grounds in the engine block when mounted normally. the temperature sender has to be in the block to get an accurate reading. I used VDO white face gauges and am happy with them.

    '95 Chevy Silverado 1500
    5.7 V8-NV4500- 3.73 rears
    See My Toys: <a target="_blank" href=http://community.webshots.com/user/wdb172454>http://community.webshots.com/user/wdb172454</a>
     
  3. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Bummer on the electrical gauges needing specific sending units. I didn't know that. I just thought they would use the same as the factory. [​IMG] Now that I think of it, I believe the gauges I put in my GTO and my old Blazer did come with their own sending units. Didn't think much about it at the time since I was replacing idiot lights and needed the sending units. Obviously that means to replace bad units, I would need to go back and order from VDO or whoever rather than getting them locally.

    &lt;rant&gt;
    I'm starting to remember why I avoided computer crapt for all those years. I'm doing my best to simplify every part of this rig to eliminate any un-necessary failure points. Heck, that is why I chose the '89 style (forget the exact year range) TBI, because it is the simplest and most reliable (I'm told) of the EFI setups. Now every time I turn around I'm fighting that blasted ECM and it's tentacles into every freeking thing. So, more lines, double the sending units, lets add in a few more things to get in the way of maintenance, and look how much better off I am. I also wanted to make sure that, as much as possible, all potential failures could be fixed with parts that could be bought at any common auto parts store. If I hadn't tried for EFI this time, I would have been way money ahead and driving this thing long ago. Hmmm, where are my wire cutters and that old Q-Jet I had laying around...
    &lt;/rant&gt;

    &lt;deep breath... in... out…&gt;

    Ok, all better now. I'm sure I'll feel better when I get near vertical and the thing keeps purring instead of sputtering and trying to die. I hope so.

    Thanks for the info, I'll just shoot the ECM rather than the bearer of bad news. [​IMG] Maybe I'll just go find some factory gauges and say @#$#% it...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  4. pcorssmit

    pcorssmit 1/2 ton status

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    The factory setup has dedicated sendors for the gauges. The computer's temp sendor is in the intake manifold, near the water neck, there is a ground for the sendor next to it. The Temp gauge sendor is in the head on the driver's side. The Oil pressure gauge sender is in the driver's side of the block, on the side, kind of above the oil filter. The oil pressure switch (hooked to the ECM harness, it is essentially a failsafe incase the fuel pump relay fails, it does NOT cut the fuel pump when there is no oil pressure as many will have you believe) is in the top of the block in the rear, where many older cars have the gauge sender (under the distibutor), and is mounted on a 90° fitting. It has a funky looking 2 connector plug, the gauge sender has a single 1/4" spade on it.

    Basically, you have to run seperate senders regardless of whether you are using OE electrical, aftermaket electrical, or aftermarket mechanical gauges.

    My brother just picked up a harness, TBI, and pluter out of an '89 Sub today, gonna start putting it on his '70 K5 pretty soon. Mine is apart at the moment so I can clean up a few things in the harnesses. Been putting it off for way too long.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  5. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Ahh, bless you yet again Pete. I really must get a component locator book on this thing. I thought the same units were used for gauges and ECM. When I was looking at the Computer/Engine harness schematic it only shows the sending units for the ECM. I just went back and, sure enough, the other units you mention are on the Instrument cluster sheet. I now realize that those couldn't be the only ones since there is no trace to the instrument cluster from the ECM schematic. It is already duplicating all those things I was trying to avoid. Here I am b@#$ing about double jeopardy and now I find out that is what I bought into (and GM gave us) anyway. LOL! Life is ironic eh? I went out and looked at it too. Hehe I actually remember noticing each one of those at various times and I never put it together in my mind. [​IMG]

    I guess I am just getting frustrated with learning the "new" (to me) computer controlled engines. Frame, body, chassis, even electrical I know my way around pretty well. Older non-computer, carb'ed engines and drive trains I can deal with pretty well too, including rebuilding. But this computerized stuff is a pain. I never know if the problem is where it appears to be or related to some distant and apparently unrelated sensor confusing the ECM into doing bad things. Oh well, the old stuff used to be frustrating and confusing, and then eventually became second nature. I guess this will too...

    So, thanks MUCH to the both of you for your help. I'm off to browse Sumit and figure out what to order.

    BTW, Pete, what are you doing to your harness? Removing unused leads? I was thinking of doing that too once I know what I'm actually going to use. I'm also thinking of getting rid of the "bundle" wrap too so that I can trace/check wires easier at the same time. Painless just uses ties every 10" or so and I may do the same.


    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  6. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    BTW, I was also under the impression (as I was told) that the oil pressure switch WOULD cut off the pump. Thanks for that clarification too.

    I would hate to be distracted with an obstacle and not notice an oil pressure drop in time. The previous engine (6.2) in this truck was toasted when the previous owner rolled it and being shook up, didn't think to turn it off in time (his girl friend was riding with him and got pretty rattled from what he told). Maybe the existing switch could be hooked up with an LED or buzzer that would go off when oil pressure is lost?

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  7. solowookie

    solowookie 1/2 ton status

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    OK Bad Dog let me give you the sender situation (most was right, but let me give you a couple clarifications)

    the gauges have differenent censors (from the factory) then the ECM. the temp ecm sender is in the intake, and the one for the gauges is in the side of the block by the manifold / headers. the one for the oil pressure is already on a T with the ECM. All you have to do is replace the senders on the T &amp; side of the block and you are ready to go.

    if you go with VDO gauges you can get a fuel gauge that is GM compatible so you don't have to replace the sender... (I'm assuming autometer has the same thing, but I'm not sure cuz that isn't what I bought)

    and just for the record, and upon further inspection I don't think I'd ever go autometer. I like the way the VDO's mount to the back of the dash much better. KISS keep it simple stupid, and I think VDO has done a better job with that.

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Mine actually has two separate mounting locations for the oil sending units. ECM switch on the top at the back of the intake and the big fat gauge unit down by the oil filter.

    Thanks for the info on the fuel gauge too. I'm leaning to VDO myself but I'm keeping an open mind.

    BTW, you mention a place that has cheaper prices than Summit on your thread. What was that place?

    As always, thanks for any and all info and suggestions...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  9. solowookie

    solowookie 1/2 ton status

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    I got a big fat one down by the oil filter (by the oil filter, or on the other side of the block?) I have a big fat one on the other side of the block too, but that goes to the computer too.

    on both my 89's I had a T at the back with a round fat sender that was for the factory gauge.

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  10. solowookie

    solowookie 1/2 ton status

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    p.s. barnette performance... I don't remember how to spell it, but it is barnetteperformance.com (you have to call, no prices on the web). once ya figure out the spelling for barnette let me know would ya?

    oh yea, and VDO's are much cheaper too (extra +), but if you decide to do autometers you better give kpanza a PM (I have a parts list for the autometers too if you are looking for it)

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  11. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Found it, <a target="_blank" href=http://www.barnettperformance.com/>http://www.barnettperformance.com/</a>

    And, yeah, parts list would be great. There was one on your other post (link at the top of this one). Is it the same or is there more to add?

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  12. solowookie

    solowookie 1/2 ton status

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    that is a complete list for VDO's... however, if you aren't going to use the stock bezels then if you change from 4" tach and speedo &amp; go down to 3 3/8" you can save over 30 bucks...

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     

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