sTanTruck Posted May 17 Author Report Share Posted May 17 Hey everyone, My coolant temp gauge seems to work but the fuel level gauge never gets over 1/4(it does move from 0 to 1/4 when the truck is running). I have played with the sending unit wires and found a loose wire (fixed it). I have also shorted the sensor wires and verified that the gauge reads FULL. This pins it down to the sending unit in my mind. Has anyone changed the sending unit before? How do the wires disconnect from the unit? Its too close to the bed for me to see and I don't want to twist off any wires Also, I couldn't find the gauge cluster that would fit into the center console originally for the volt and oil press gauge. So I decided to make my own and I have 3D printed a few in case anyone is interested in them. They use OEM style snap hooks to hold it into the factory location and fit two 2 1/16" gauges. It is SLS printed out of Nylon 12 and can be painted to color match. If you want a custom gauge cluster message me and we can play around with some designs. Below are some pics 2 Quote Link to comment
ElliotV Posted May 18 Report Share Posted May 18 23 hours ago, sTanTruck said: Hey everyone, My coolant temp gauge seems to work but the fuel level gauge never gets over 1/4(it does move from 0 to 1/4 when the truck is running). I have played with the sending unit wires and found a loose wire (fixed it). I have also shorted the sensor wires and verified that the gauge reads FULL. This pins it down to the sending unit in my mind. Has anyone changed the sending unit before? How do the wires disconnect from the unit? Its too close to the bed for me to see and I don't want to twist off any wires Also, I couldn't find the gauge cluster that would fit into the center console originally for the volt and oil press gauge. So I decided to make my own and I have 3D printed a few in case anyone is interested in them. They use OEM style snap hooks to hold it into the factory location and fit two 2 1/16" gauges. It is SLS printed out of Nylon 12 and can be painted to color match. If you want a custom gauge cluster message me and we can play around with some designs. Below are some pics that gauge cluster is pretty cool I always find it interesting when people will just 3d print new interior pieces to adapt stuff If I had time and was still 3d printing I would probably mess around with a few things. 2 Quote Link to comment
sTanTruck Posted May 28 Author Report Share Posted May 28 Can anyone explain what the VVT valve does? How do I test it? Where is it in the engine bay? Quote Link to comment
Sephakrid Posted May 29 Report Share Posted May 29 The VVT valve should be attached with two bolts near the rear engine hoist point. I haven't gotten around to testing mine yet and I'm not too sure how it even works. Quote Link to comment
sTanTruck Posted May 29 Author Report Share Posted May 29 My truck has an EGR delete, is there any point in having a VVT valve on it anymore? Quote Link to comment
sTanTruck Posted May 29 Author Report Share Posted May 29 I messed around with the truck some more tonight trying to figure out why the idle is so rough. I installed new spark plug wires (NGK), and went to install a new distributor cap and rotor but the rotor did not fit. Here is the old rotor (red) compared to the new one. Im sure I could modify the new one to fit but I would rather source the correct one. The tabs hit the ICM wires and the plastic shielding is too tall. I ordered this as a set for a 1984 720 so Im confused why it doesn't fit. Also, notice that the timing adjustment seems to be all the way to the max on one side. Does that seem like it's been messed with? I have tried switching coils, and it seems that one side (exhaust or intake) is never working fully. I can unplug one coil and it will run, switch to the other coil, and the truck wont start and backfires. Im starting to think the ICM is messed up?? Im so lost on this issue. Does anyone have an idea of how to troubleshoot this rough idle ?? I wouldn't care but I have to pass emissions to drive it. Unfortunately, I am starting to contemplate selling this truck 😞 Thank you, Dylan Quote Link to comment
datzenmike Posted May 29 Report Share Posted May 29 On 5/17/2024 at 1:23 PM, sTanTruck said: Hey everyone, My coolant temp gauge seems to work but the fuel level gauge never gets over 1/4(it does move from 0 to 1/4 when the truck is running). I have played with the sending unit wires and found a loose wire (fixed it). I have also shorted the sensor wires and verified that the gauge reads FULL. This pins it down to the sending unit in my mind. Has anyone changed the sending unit before? How do the wires disconnect from the unit? Its too close to the bed for me to see and I don't want to twist off any wires Drop tank, after lowering the fuel level. Remove the sender. It's obviously sticking at the 1/4 point but moves freely below that. See if you can free it up and get it moving. 11 hours ago, sTanTruck said: My truck has an EGR delete, is there any point in having a VVT valve on it anymore? No point what ever, having it. 10 hours ago, sTanTruck said: The tabs hit the ICM wires and the plastic shielding is too tall. I ordered this as a set for a 1984 720 so Im confused why it doesn't fit. Also, notice that the timing adjustment seems to be all the way to the max on one side. Does that seem like it's been messed with? I have tried switching coils, and it seems that one side (exhaust or intake) is never working fully. I can unplug one coil and it will run, switch to the other coil, and the truck wont start and backfires. Im starting to think the ICM is messed up?? Im so lost on this issue. Does anyone have an idea of how to troubleshoot this rough idle ?? I wouldn't care but I have to pass emissions to drive it. Unfortunately, I am starting to contemplate selling this truck 😞 Thank you, Dylan Replace with the correct cap and rotor. It will start and run on only one or the other coil. If back firing on one coil then wires may be mixed up. Do not assume they are correct, it's easy to mix them up. It's probably the rotor or cap but check wires anyway. Now set the ignition timing correctly. This may move the timing adjustment and correct it being all the way over. Checking wires, replacing the cap/rotor and setting the timing may fix the idle problem, so try it. 1 Quote Link to comment
sTanTruck Posted May 29 Author Report Share Posted May 29 Thanks @datzenmike! Ill give that a try later today. I did notice that right before I drove the truck last night both banks of spark plugs seemed to be working. I could pull an intake one and notice a difference and vice versa. Have you ever heard that beeping noise? Seems like something changed in the electrical system Quote Link to comment
datzenmike Posted May 29 Report Share Posted May 29 There's a warning chime for when key is in ignition and driver's door is opened. Quote Link to comment
sTanTruck Posted May 30 Author Report Share Posted May 30 Do you have the wiring schematic for that sensor? it seems to me that when I was hearing that beep the truck was running correctly. i want to trace those wires all the way back to see if I can find an issue. What are these and do I need to have vaccumm lines running to them? There are two on the passenger side and one on the driver side. None of which have vac lines currently. (Ignore the arrows I grabbed this pic from an article I am reading) Quote Link to comment
datzenmike Posted May 30 Report Share Posted May 30 It's a connection made when the ignition key is inserted into the ignition switch, but not the ignition switch itself, then through a chime and to the driver's door switch to ground. It has no other connection to anything related to the engine. The chime sound comes from a piezoelectric unit located up under the left side of the dash, on the top of the kick panel above the fuse box. Quote Link to comment
sTanTruck Posted May 30 Author Report Share Posted May 30 It seems that the truck is running on both sets of coils now. Both sides seem to have an effect on idle when I pull the spark plugs. Does this truck have a limp mode that would cut ignition or fuel? It seems to only start hitting what seems like a rev limiter when it goes above a certain rpm. Quote Link to comment
datzenmike Posted May 30 Report Share Posted May 30 Both plugs fire together and as the burn time is shorter with two ignition points the timing is around 3-5 degrees. If you unplug one wire that cylinder now requires more time to burn completely and would need an advance of around 10-12 degrees and in effect act like it was retarded. I don't doubt that the idle was affected. Quote Link to comment
sTanTruck Posted May 30 Author Report Share Posted May 30 The truck would not run when I tried to adjust the distributor timing. It sounded best where it was (completely maxed out in one direction). Also all of the plug wires are in the correct spots. Quote Link to comment
datzenmike Posted May 30 Report Share Posted May 30 Yeah someone had the oil pump/distributor drive spindle out and it's probably one tooth (18 degrees) out forcing the owner to max out the adjustment. Check the ignition timing... if it's 30 plus or minus 20 (for differences in altitude and fuel) then it's fine. But if you can't get the 30 it might be worth resetting the spindle. Set to an accurate TDC compression stroke on #1 piston. Unbolt the distributor base and lift distributor out. If you look down into the hole you should see this... Note there is a small and large half moon. If yours is off a tooth then it may read 11:30 or 11:20. To adjust the spindle have a helper. Loosen and remove the four 12mm bolts on the oil pump and carefully lower it. Have rags ready as oil will drip. The pump gasket should be ok and can be reused. The spindle will usually drop out with the pump. Lift it out if not and seat into the oil pump. Install pump and spindle and hold in place by hand and have helper let you know which way to adjust to get like in the picture above. May take several tries of trial and error. Tighten bolts 8-11 ft. lbs. Now set the timing properly to 3 degrees 1 Quote Link to comment
sTanTruck Posted July 25 Author Report Share Posted July 25 Interesting finding I thought I would share. I noticed that my voltage was spiking randomly while driving the truck and assumed that I would need to replace the alternator to fix this. I researched online and learned that OEM alt is the best way to go so I looked into having mine rebuilt. I was quoted $160-200 for a rebuild on my alternator which seemed high. I thought I would take it apart to see how it worked and learn something. I got it apart and noticed that one of the solder connections for the voltage regulator was broken. Look at the pics below You can see the second terminal on the left has broken. I grabbed my soldering iron and fixed it. Also noticed the bearings were dry and popped the dust shields off so I could repack them. Overall, it was a successful evening just messing around and taking things apart. I haven't reinstalled it to check if it solved the voltage spiking issue but I figure it couldn't have made it worse haha. 2 Quote Link to comment
sTanTruck Posted July 31 Author Report Share Posted July 31 I dropped my fuel tank to replace the sending unit. I found a ton of rust and debris in the bottom of the tank and my sending unit was so corroded it was frozen at 1/4 tank. The sending unit I ordered seems to be quite different than the one that came out of the tank. Below is a picture comparing the two . I looked for a while online trying to find this other style of sending unit. I only found one on ebay that looked similar to OEM for 4x the price of the one I bought. Anyone have some insight on this situation? Im sure the new style will work but I have to solder new leads onto it and it probably wont accurately display the entire fuel level of the tank. Ordered a new tank and now I feel compelled to change all my fuel filters. Thank you, Dylan Quote Link to comment
Stoffregen Motorsports Posted August 1 Report Share Posted August 1 If the depth of the new unit is the same, it's possible that it will read just fine, even though it looks different. I suggest connecting the sender to the wiring harness and attach a ground from the mounting ring to the frame of the truck, then, with the key on, run the sender through its arc and see what happens on the gauge. If it's not right, you can affect the reading by use of resistors. How do you know what resistor to use? Get a guitar amp volume knob and wire it inline and tweak the reading by adjusting the volume knob. Once you get it exactly where you want it, take a reading across the poles of the volume knob and get a resistor with that same resistance. 1 Quote Link to comment
sTanTruck Posted August 2 Author Report Share Posted August 2 Thanks for the reply @Stoffregen Motorsports! The sending units don't have the same range of movement so I doubt it will be accurate even if I use resistors. I am cleaning the old sending unit up and installing it into my new tank since I cannot find one similar anywhere on the internet. 1 Quote Link to comment
Stoffregen Motorsports Posted August 2 Report Share Posted August 2 (edited) What, are they reverse? Change the polarity of the wiring. 18 hours ago, sTanTruck said: Thanks for the reply @Stoffregen Motorsports! The sending units don't have the same range of movement so I doubt it will be accurate even if I use resistors. I am cleaning the old sending unit up and installing it into my new tank since I cannot find one similar anywhere on the internet. Edited August 3 by Stoffregen Motorsports Quote Link to comment
datzenmike Posted August 3 Report Share Posted August 3 For the 720 gauge to read correctly the sender in the tank should read.... FULL is 10 ohms or less 3/4 is about 25 ohms 1/2 is about 37 ohms 1/4 is about 56 ohms Empty is 80 ohms or less 1 Quote Link to comment
sTanTruck Posted August 6 Author Report Share Posted August 6 @datzenmike you are THE man once again!!! Thanks for the specs on the sending unit. Mine was pretty close to what you said so I installed it. It seems to be reading fine. Also the broken solder joint on the volt regulator seemed to have fixed the spiking issue! So that is a combined savings of $200+ in my book b/w the sending unit and the alt rebuild. In other news, I used some cleaning compound to fix the oxidized paint and bought a cheap little topper to build a camping set up! Pics below I even got some good help fixing up the paint! Thank you all for the continued guidance and support with this project! Dylan 1 Quote Link to comment
sTanTruck Posted August 22 Author Report Share Posted August 22 What is a fair price to pay for a brush guard? I have one guy willing to sell me one for 200 shipped but its in fair condition. Do you guys think this is a fair price? Pic Below Quote Link to comment
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