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2nd Gen Non-Engine/Transmission Fuel Sender, Capacitance Type Install Notes

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Engine/Transmission (1994 - 1998) 47 re symptoms help

2nd Gen Non-Engine/Transmission Dually to single wheel conversion

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BarryG

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Well I finally got around to installing a capacitance type fuel sender to replace the stock unit. I have replaced it twice already and was unwilling to spend the money on it again.



What you need is a sender. I got mine from Centroid

CENTROID PRODUCTS - Computerized Tank Display - Electronic Senders - capacitive fuel gauges. You need a 220/20 ohm unit, which is not listed but they will do it no charge. They have different mounting styles. I used the standard 5 hole SAE mount (no charge) but they have other options. You also need to know how long it needs to be and they will cut it and calibrate it for you. However you can cut it yourself if need be. I ordered mine 14. 5 inches long. They say it needs to be 1/2 inch off the bottom mine ended up being about an 1 inch off the bottom. Had I been able to measure it accurately I would have gotten it 15 inches long. It will depend on where you place it as to the length you will need



You will also need a drill, 1 inch spade type bit or hole saw, 3 butt splice connectors 16-18g size, 3 ring connectors/ends. I also used a 3 wire GM Weather Pak Connector 1 ea male and female. Also need some type of gasket sealant good for diesel fuel. I used Permatex Form a Gasket #2, so far it is working fine. You will also need 5 bolts and nuts. I used 10/24 1. 5 inches long with a washer on top, washer underneath with a lock washer and the nut. (1/4 inch will not fit nor will 6 mm)



Remove the tank from the truck. You might be able to do this by removing the bed but you may find your wires might be a bit short to work with.



Drain remaining fuel if not already empty.



Clean top of the tank to help keep any crud from getting into the tank once opened up.



Remove cannister lock ring. A few soft hits with a hammer and chisel got mine right off.



Remove the module. I checked mine and was suprised it was very clean very little stuff inside the screen was free of dirt as well. In fact the entire tank had little crud if any in it.



Remove float assembly from module (you could leave it in but why take the chance of the float disintegrating over time like has been mentioned on this forum many times in the past).



Set cannister aside in a safe clean place for now.



Drill your 1 inch hole in your fuel tank (it drills easily). I placed a couple shop rags inside the tank underneath the area I was going to drill to catch the drill shavings. My hole was placed on the step up about 12-14 inches forward of the module. From the manual this appears to be a spot for a rollover valve on the gas vehicles. There was a nice flat recessed area even had a centerline cross on it. The circular area was the exact same size as the sae mount for the new sender. (by the way my tank is from a 4x4 long bed qc truck either 35 or 36 gallons in size). It appears that not all trucks have the same type of tank so be aware of that.



Place new sender in your new hole and drill the 5 holes for the mounting bolts.



The sender came with a gasket and I used it but I also used some gasket sealant so if using it now is the time to apply it.



Put it all together and tighten down the bolts firm but not too much. You dont want to mess up the gasket or crack the sender head.



I reinstalled the module at this time but you could do it later especially if you are combining this with a draw straw install.



From the electrical plug that plugs into the module snip of the end connector (you might want to leave enough wire so that if you wanted to put it back you could).



From one side of your 3 wire GM weather pak connector (mine came with pigtails on them) attach 3 ring connectors/ends.



From the remaining side of the GM weatherpak connector attach two wires from the bundle you previously clipped. On my truck (2001) the two wires you need are black/light blue is sensor ground and dark blue/white is fuel level sensor signal. The remaining two wires(green & black) in that harness are unused by the vehicle they are for a gas truck. Use the butt splices(I also used shrink tubing) to connect the harness to the gm connector wires. The gm connector is labeled A,B,C (on each side) take note of which wire goes to which letter as you will need to know that later.



Now you need to run a 12v ign switched power wire to the remaining wire of the GM connector. Again take note of which one a,b or c it is.



Take the gm connector side with the ring terminals and attach it to the new sender per the directions. This is where knowing the a,b,c comes in handy.



Now put the tank back in place. Once in place just push the GM connector together.



Turn on the key in your truck and check your fuel level. Well at least after you put some fuel back in it. Mine read as follows being approx 1 inch off the bottom of the tank. 9 gals 5/16 of tank, 14 gals 7/16, 19 gals 9/16, 24 gals 11/16, 29 gals 13/16, 34 gals 16/16(full), 36 gals 17/16 (just over full). I only waited a bit after each 5 gals I pumped in then checked the level except for the inital 9 gals poured that all in at home.



Not sure if the low fuel light will work or not. Have no reason to think it wont but it was not on after I poured in the 9 gallons of fuel initially.



Anyway I hope this helps someone I wanted to do a cap type sender but was afraid of the wiring and as it turns out it is nothing at all. 3 wires two of which are already there and a simple 12 v feed. No problem what so ever.



I have some pictures but cant figure out how to put them in. If someone can help with that it would be great. I could email them to you and you could post them up.
 
Thanks for the great post and pictures. You probably have answered many folks unasked questions. Geo
 
Barry,

You used your factory gauge? My gauge doesn't read accurately at all and I think pieces of the float clogged my filter in front of my walbro. Did you get the GM connector at an auto parts store? It looks like something I would like to do. Thanks Jeff
 
Jeff:

Yes I got the GM connectors at a Pep Boys Auto Parts Store. I have seen them at other places as well. They had them in single, double, triple and four wire. Pep Boys had just the connectors or ones with pigtails like I purchased. You dont need the connectors but thought it would be a cleaner way. That way if you need to drop the tank in the future for any reason you can just unplug instead of unscrewing each termination on the sender.



Yes it uses the factory gauge. I have had two stock senders go out due to the contacts not keeping contact properly. That and the float deterioration. My float was still in pretty good shape however it did look like it wouldnt be long before it started to go. As I noticed on the corners especially and along one side of the long axis that the outer coating had worn off and the interior of the float was exposed.
 
Great post. I have a complete change of my fuel system and with the tank down I could easily do this mod. Thanks, Sam.
 
Hey Barry,



I was under my truck looking at my fuel tank. It looks just like yours. With that said would you order the probe 15". Thanks for your patience with all the questions.



Jeff
 
Jeff:

In different places on Centroids website and the installation directions it mentions a couple different figures for being off the bottom of the tank. One place reads 1/4 inch several say 1/2 inch and I believe I saw one that said 3/4 inch somewhere. I dont think it matters as long as it is not touching. One thing to remember though is Dodge felt for some reason to leave a fairly large reserve. My guess is to prevent or help prevent people from running out of fuel and the huge hassle that entails. Can you imagine the customer relations nightmare that could be for them if it happened frequently with the hassle it is to fire one these bad boys up after running out of fuel.



I digress, one other thing to think about is I have read some posts about the tank ballooning some when installed compared to when not installed(some draw straw threads). Which would mean the bottom of the tank would be yet deeper than on the bench. However I think this particular location is right by the forward strap. Dont think it will balloon but might actually constrict it? Dont know. I did not measure the tank inside on the bench or after it was installed as it didnt matter to me at that point. I had what I had. After I mounted the sender in the tank I stuck my hand in there and I could stick two fingers (on top of each other, not side by side) underneath the end of the sender. Looked at my fingers and it appeared to me to be about an inch.



So to answer your question I really dont know considering the ballooning/constricting thing. I drove it to work today and from being a full needle width above full (with 36 gallons in it) it is now on full maybe a hair below but still definitely touching the full mark. 40 miles, approx 2-2. 25 gallons. I might be able to tell you better after this tank runs down low and I refill it. Until then I guess I would stick with the 14. 5 inch.



If it makes any difference when I ordered it the lady who takes orders was very helpful. She looked up several others who ordered the same ohm sensor and told me how long they ordered them. There was only one other one 14. 5 inches long. One was 14, 13, 12, 9. 5. She even said a couple ordered 14 and then reordered a shorter one and I think the one who ordered a 14. 5 also did the same thing. So I got scared and kept it at 14. 5 as I was thinking 15. I measured the outside top to outside bottom of the tank(while it was on the vehicle) and came up with 16. 5 inches. Then I guessed on the following- subtracted 3/8 inch for the thickness of the tank bottom, 1/2 inch to be off the bottom and 3/8 inches for that recess in the top. Leaving 15. 25 inches. That recess might actually be closer to 1/2 an inch deep now having seen it clearly. So 15 should work but again depends on the ballooning constricting thing. You can cut them down but you have to recalibrate which they show you how to do in the install instructions.



Hows that for a definitve answer.
 
Barry,



Thanks for the reply. I would be interested to hear how your fill-up goes. That will help me make up my mind on which length to go with. Thanks again.



Jeff
 
Jeff:

Will let you know. Hoping to go fishing this weekend. If I do I will need to fill up after I get back. If I dont go fishing it may take another week as I want to let get pretty low.
 
Well I filled up this morning just as the needle hit "E". After inital install I put in 36 gallons of fuel. This morning I think I filled it up the same as last time and I put in 31. 4 gallons so that means I had 4-5 gallons of fuel left in the tank as the needle just hit "E".



By the way the low fuel light came on right at 1/8 tank.



Jeff:

After doing this fillup I think the 14. 5 is good (at least at the mounting location I used). Again this was just as the needle hit "E". So whether 14, 14. 5 or 15 inches probably depends on how much reserve you want. I can say that when my stock gauge did work when the low fuel light came on it had approx 9-10 gallons left in the tank. This time while it came on right about 1/8 tank based on how far I drove after it came on I think I only got about 2 gallons worth of driving before it touched "E". So that would mean when it came on I had 6-7 gallons left in the tank. While it is still plenty it is approx 30+% less than the reading from stock gauge, just something to be aware of I guess.
 
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Hey Barry,



Excellent write up! Have you had the opportunity to see how the guage reacts when the truck is on uneven ground at less than half a tank? I don't know if you drive off road or on steep mountain roads very much, but do you think the guage would be swinging around a lot when the truck is not level?



Thanks,



Jeff
 
CTD:

The stock pcm/ecm whichever has the fuel sensor stuff in it seems to have a delay in it (saw that here or in the service manual). The centroid sender also has some type of delay in it that I read about on their site. So no it doesnt swing alot. My driveway is pretty steep. I can say that when I start up in the morning in my driveway the gauge reads about 1/8 of a tank low until I get going but it is slow to get up there. I mean as soon as I pull out of my driveway it does not come right up it takes a few minutes, within a few miles it seems to have gone up about as much as it is going to. The stock gauge I dont remember it doing that. However that is probably because the new sender is located much closer to one end of the tank instead of in the center. Ideally you would put the new sender in the same location as the stock one. However with the whole cannister, return fuel etc going on there I didnt want to get that involved at least at this time. I may go back and move it later but it will require reengineering that whole cannister setup.
 
Just an FYI - if you go to the trouble of drilling the SAE bolt pattern (it comes from SAE J1810), you can use a wide variety of fuel level sensors (including ISSPRO - shameless plug). If someone could verify the length, I could have an "off-the-shelf" part number created with that length.



The benefit of the ISSPRO sensor is that it is still a resistance-based unit (and therefore can tie directly into factory wiring without requiring a power wire). Unlike a factory float-arm sensor, the electrical components are all non-contact. There is a magnet on the float, which passes by sealed reed switches. These designs are used on many Class 8 OEM applications (standard equipment on some brands, premium option only on others). They have been tested to well over 1 million tank cycles without failure.



If anyone is interested, let me know and we will set up a part number.



Regards,

Michael Pliska
 
BarryG
Thank you for taking the time to write this one up. It looks like a great alternative to the stock float.
Is it still working accurately?

Andre
 
Barry,



You technical geek. Once again you amaze me with the things you do. Way to GO!



Pliska: great idea of a unit from your company with no wiring changes.
 
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