mx71 Posted August 21, 2017 Report Share Posted August 21, 2017 Ok, so my truck I bought has 173,000 miles on it. It seems pretty well maintained, but it's also likely the rings aren't great, and the valves could be out of spec. Other than those two things, anybody have any idea why a '85 4x4 z24 with properly aired 235/75r15s and well working brakes would get around 5-6 mpg? I haven't found any fuel leaks. 1 Quote Link to comment
Tinman Posted August 22, 2017 Report Share Posted August 22, 2017 Does your truck have the electronic feedback carb? Because the mileage tends to suck on the 4X4 with out it, or if it's not working. I never got over 14-17 mpg out of my 4X4 WITH the feedback carb. That system HAS to work right to get decent mileage. 1 Quote Link to comment
racerx Posted August 22, 2017 Report Share Posted August 22, 2017 Fuel leaks? 1 Quote Link to comment
Lockleaf Posted August 22, 2017 Report Share Posted August 22, 2017 I average 14-17 in mine. Usually on the lower end of that. I'm rolling on 31x10.5. 1 Quote Link to comment
Roadster-ka Posted August 22, 2017 Report Share Posted August 22, 2017 Does the choke open? 1 Quote Link to comment
captain720 Posted August 22, 2017 Report Share Posted August 22, 2017 I got 17 going over the pass in my 4wd and 14ish in town. But something is wrong, maybe Weber time? :-) 1 Quote Link to comment
datzenmike Posted August 22, 2017 Report Share Posted August 22, 2017 Look at the electrical connector at the right rear of the carb. If round and six wires you have the ECC carb and you will have an O2 sensor in the exhaust manifold. If you ahve the regular carb it will be a three wire connector no O2 sensor. Let me know which. Either carb could have a stick choke that doesn't shut off, or the electric choke heater not working. With engine warmed up just remove the top of the air filter and look. The choke flap should be vertical. Is it? For a properly working choke heater the alternator must be working and charging. If choke is open, start the engine and take another look. Is there gas dripping or wetness down inside? Carb could be flooding from float stuck or set wrong or needle valve stuck open with dirt. 1 Quote Link to comment
MaxChlan Posted August 22, 2017 Report Share Posted August 22, 2017 I get about 21 to 22 overall in my '86 4x4, dead stock, with air conditioning 1 Quote Link to comment
MaxChlan Posted August 22, 2017 Report Share Posted August 22, 2017 Nope, just the good old Hitachi. I typically get about 20 point something if I do a lot of local driving, about 21 to 22 if I spend most of the time hanging out around 55-60. Most of the freeways around the Twin Cities are 55 and 60, with a few exceptions. The book says I should be getting 21 on the highway and 19 in town, so I am not sure why my mileage is on the high side. Mine is also a California emissions version, and I almost always shift around 4000 when accelerating in 2nd and 3rd. :confused: 1 Quote Link to comment
datzenmike Posted August 22, 2017 Report Share Posted August 22, 2017 Then O2 sensor and he ECC (electronically controlled carb) with the round 6 pin connector on the back. 1 Quote Link to comment
captain720 Posted August 22, 2017 Report Share Posted August 22, 2017 Wow Max, those numbers are almost unheard off! Good for you! 2 Quote Link to comment
bottomwatcher Posted August 22, 2017 Report Share Posted August 22, 2017 In flat florida I got 18-20 with 31s with a weber. Definitely sounds like a stuck choke as mentioned. Just about any other cause would have additional symptoms. 1 Quote Link to comment
datzenmike Posted August 22, 2017 Report Share Posted August 22, 2017 .... or a locking gas cap. 3 Quote Link to comment
mx71 Posted August 22, 2017 Author Report Share Posted August 22, 2017 It has a motorcraft carb, which was identified as a Holley 5200 variant, which apparently is a licensed version of the Weber 32/36. So in a way, I have a really old shitty version of the Weber. There's only one wire coming out of it and it wasn't hooked up until recently. I assumed it was the choke so I hooked it up to the choke circuit on the 6 pin round plug (it does have an o2 sensor in the exhaust manifold). No idea if the choke works or not, but it seems to start easier since I hooked it up. Quote Link to comment
mx71 Posted August 22, 2017 Author Report Share Posted August 22, 2017 I had it hooked up to the blue wire on the six pin connector, but tested it with the ignition on and it wasn't getting any power. I hooked it up to the red/yellow wire next to it which was getting 12 volts. Is that the fuel cutoff wire? Quote Link to comment
datzenmike Posted August 22, 2017 Report Share Posted August 22, 2017 Red is usually the idle cut solenoid. Connecting the wire to the choke heater only turns it off after 5-10 min. It won't help you start as its cold and should be on anyway. Having a properly shutting off choke would clean the plugs and maybne make starting easier. Quote Link to comment
captain720 Posted August 22, 2017 Report Share Posted August 22, 2017 Just wire the choke to the ignition coil. Works every time and let's you figure out if that is the problem quickly. Quote Link to comment
mx71 Posted August 22, 2017 Author Report Share Posted August 22, 2017 Got it. Does anyone have a diagram of what the wires are on the 6 pin round plug? I have access to the service manual, but I can't seem to find it in there. Quote Link to comment
datzenmike Posted August 23, 2017 Report Share Posted August 23, 2017 Blue............................. auto choke heater Yellow/Black (stripe) & White............................ air ratio solenoid. White/Green (stripe)..... Throttle switch... tells ECU if above idle. Red & Black.............................. idle cut solenoid You only need the Blue for the electric choke heater. I doubt the Holly has an idle cut solenoid but if so then you just connect the Red wire. The solenoid will grounded return through the carb. Quote Link to comment
mx71 Posted August 23, 2017 Author Report Share Posted August 23, 2017 Any idea why the blue wouldn't have any power with the key on? All my fuses are good. 1 Quote Link to comment
datzenmike Posted August 23, 2017 Report Share Posted August 23, 2017 Auto choke heater is run from a relay right on side of glove box on the upper part of the kick pad just out of sight. It needs a charging alternator to work or it may have been removed as not needed. It's a little blue or brown plastic cube about 1" square. The black fuel pump relay is also there but it's the size of a pack of Camels. Any ignition switched supply will work for the choke heater.. 1 Quote Link to comment
mx71 Posted August 23, 2017 Author Report Share Posted August 23, 2017 Ok, well I've got it hooked up to the idle cut off at the moment. Also, since this is a Holley 5200, it doesn't seem to be the type of operation that heats. It seems more like a magnet/plunger type deal. 1 Quote Link to comment
datzenmike Posted August 23, 2017 Report Share Posted August 23, 2017 Idle cut is what I used. 1 Quote Link to comment
mx71 Posted August 23, 2017 Author Report Share Posted August 23, 2017 Ok. I didn't know if it was a problem to not be hooked up to the correct circuit. You had mentioned something about when it's connected to the choke circuit it keeps the plugs clean. 1 Quote Link to comment
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