good information to have! I've been down this road with my 2001 as well. Wish I'd known about the Lingenfelter instructions two years ago..o well!

 

Ok, well, I'm not 100% sure I have a fuel pump problem. My new float sensor appears to be working. When the arm goes up, the level goes up, etc. No problems there. However, when I turn the key forward, I get absolutely nothing. I haven't bolted it in and filled the tank, but I'm hesitant since I can't hear it running. I'm about to pull it back out, but I was wondering if this is somehow normal. I have only done it a couple of times in succession as I didn't want to run it dry. But I'm getting nothing. So, I'm wondering if this is the pump, ground, or somehow the plugs on the sending unit.

Should I be getting a sound or vibration with the tank empty and the flange just loose? I assumed so only because of how loud it is with the pump running. I jumpered across the relay again, and I get voltage on the first and third pins of the plug (12 and 5 volts). I measured voltage from the plug to the connector on the ground stud in the fender. When I check the ground, I'm not sure if my meter is funky (Craftsman) or I have a ground problem. When I first make contact, I get 0 ohms, but after a few seconds, it starts to fluctuate a few volts.

So, if this is the ground, should I start my taking the ground lead off and cleaning the connection? That's about all I can think of this second, as I'm used to seeing grounds as broken wires that read open circuits. So, I'm wondering if my next step is to pull the whole thing out, dismantle the pump, and then start checking all the way across the sending unit to the pump connector itself. I may even need to run some jumper wires to the pump straight off the battery on a bench I guess.

So, is it normal to hear absolutely nothing when there is no fuel in the tank, and just button it up? That just seems wrong to me, so please let me know what you think. I'm not touching it for now.

 

So, I went ahead and disconnected the ground from the stud. I checked continuity in the wire, and it is dead zero across both grounds for power and level. I cleaned them up the connections with steel wool and wiped it all clean with WD40. I made sure the surfaces where smooth and everything tighten down well. Everything checked zero again after everything was bolted up.

I think this problem is in the sending unit or pump, but I'm hesitant to pull it back out just yet. If I do pull it, I'll need to dismantle the housing again to get down to all the connectors and the pump. Is sound a good gage for system failure at this point? I'm just used to the high pitch whine of GM pumps, that I'm not getting at this point. I mean I'm getting nothing (sound or vibration from the pump with the key on, relay jumped out, and 12V at the pump).

 

The pump ground is on G401 (drivers wheel well on the side of the frame) The picture you see is my connection.. My STUD broke upon removal and I replaced it with a self tapping screw from the hardware store.

You should read ZERO OHMS from the pump ground terminal to any good bare metal frame part. Any reading much above zero ohms means that the ground is compromised.. The more frame that you have between the pump terminal and the bare metal point, the more resistance you will see. So, you will not normally see perfect ZERO Ohms.

If you clean the top of the stud off and read from that point to the wire terminals under the nut, you can see how good the ground connection really is. That should read zero ohms.

Bill

 

Do you have full power at the connections directly on the connector/s at the pump with the key on and when you jumper?

 

Yes, I have ~12.2V on the end pin of the connector with the key on and the jumper in place. I also have a solid zero between the two ground terminals on the same plug and the tip of the ground stud on the frame. It's actually 0.0 ohms without fluctuation.

Just for information, I just made up a jumper wire to my old pump, and the one that I assumed was failed, did nothing. I felt no vibration of it turning in the old white plastic housing. I put power leads straight to the flat blades of the old pump. It did nothing. I pulled it after a few seconds because I didn't want to torch it, but the two wires warmed up a little. I truly think the old pump has failed, but I'm not sure if I have a bad sending unit or maybe a bad new pump. Or, really odd, is all this normal and I may have a good pump. If so, I'll put a couple gallons in the tank and try to crank. I just don't want to be wrong and have to gor through all gas draining again.

Edit: I'm also wondering if I'm expecting something that's not going to happen. If the pump has no liquid in it, does it make much sound or vibration?

 

Bill, were you talking about the connector down in the can that pump is in? If so, I haven't checked that yet. That would be one of next steps, but I haven't pulled the pump back out and dismantled it to get to it. I have 12V at the connector going to the sending unit. At this point, I would say everything is good all the way to the sending unit, and the only thing I know is I get no noise when the pump should be seeing 12V.

On a different note, the sending unit had some brown corrosion on the blade terminals that mount to the back of the sending unit base flange. I'll go take a look at those again in a second. I believe those are spade connectors that ground the plug. Could be a problem.

Edit: So, I tried to check continuity across the two spade connectors, and it's saying it's an open circuit. Looking more and more like a ground on the sender. The pump needs to come back out and I need to make sure I have a CLEAN ground all the way to the pump.

 

Well, I pulled and cleaned both connectors. Now, I read 0 ohms from the backside of each connector and from each connector back to the base plate. So, I think the ground block and connectors are good. Here is the new problem. I have exactly 72 ohms resistance across the yellow sending unit plug, base posts, and 4-block black plastic connector on the inside of the tank. For less than 20A, 12V, that is entirely too much resistance; I'm losing too much voltage across that connection. So, I think I'm pulling the black plug and trying to clean it, but I'm not sure the best way to clean that. My guess is it is the male posts on the back side of the sending unit that I clean easiest.

This is all a little baffling at this point.

 

Anyone know the part numbers for the wires going to the pump (orange and black in common plug), as well as the black jumper ground wire that goes from the 4 socket black plug to the 2 spade post ground block on the back side of the unit? I'm thinking that is the last piece I can rule out. I'm going to pull the pump back out to check if I'm getting 12V and solid ground actually at the pump.

 

I would call Gene Culley and see what parts are available. He will know.

If you apply power to the pump motor and it doesn't run,,, its bad regardless if its new or not. It either has a bad connection or a bad pump.


Man,, That spade terminal looks rough!!! YUCK!
Bill

 

Are there any concerns with making a set of jumper wires straight from 2 of the 4 connections on the plug on the sending unit harness to the spade connectors on the pump? I would like to bypass the entire circuit just in the unit. Then, I can tell if it is the sending unit or the pump.

 

Power to the pump is power to the pump. As long as you don't run it dry too long.

You know you can use a DC Volt meter to see where the break in the circuit is. If you put the POS & NEG meter leads in series on the extreme ends of the pump 12 VDC circuit and read voltage BETWEEN the meter leads, that indicates an open. Just keep moving the meter leads toward each other until you find that open.

If the break is on the ground circuit, the same principal applies.

 

Thanks for the advice, Bill. The pump is now changed. It was a combination of a bad pump and corrosion on the connectors. I checked the old pump and it was dead, and then I supplied 12V to the new pump and it ran. I then jumpered the black pigtail outside the tank to the pump, and it ran again. That sent me after continuity throughout the sending unit. Everything ohmed zero with the exception of the ground prong coming off the side of the yellow plug that's in the tank. I cleaned and polished the connectors and everything was 0.0 ohms solid. I hooked it all up, and after letting it run for a few moments, I then changed the fuel filter. All is good.

Again, thanks to all.

 

That NASTY looking ground terminal had my interest!!!!! Glad that you are back ON THE ROAD!

 

Ok, well, I thought I had this licked, but now I have some other weird problems. I may have a problem with the siphon pump, and/or possibly the new filter. When I first started the car yesterday (before I did the last step to change the filter), I had normal pressure. Now, my pressure is down to 24 psi on the interior gauge, and the fuel indication dropped to zero. I then added some fuel thinking it all siphoned over to the passenger tank. It came up to 1/4 tank and then dropped to zero again within 30 seconds. I cut the key off and then started it again, and it is holding 1/4 tank again. However, my pressure is now showing ~18 psi. I didn't even think the car could run that low, at least I've never heard of that.

I just pulled the cover to get access to the fuel rail, but I need get a fuel gauge, as mine will not work for the fitting (oil gauge I was using for something else). My thoughts are I will confirm I have a low fuel pressure. I guess I'm taking thoughts here, as I think I'm going to wind up draining the passenger side tank and probably pulling that sending unit. However, what is the best path forward for troubleshooting from here. This was really unexpected. I contemplated this being a corrosion issue on the driver's side sending unit, but that would be incredibly quick to have something like that happen.

My hopes are that this is a trash in the tank issue, and my filter is plugging. However, if the filter were plugging, I would assume you could prime it by turning the key on, and the rail should eventually go higher in pressure. Again, this all happened when I changed the filter. So, thanks for the help again guys.

*Edit: I have checked it every half hour, and the pressure keeps dropping on the gauge. I'm beginning to think it's the autometer gauge on the column because the car doesn't seem to run any worse. The gauge is reading 5-6 psi and it's not running rough at all. lol. I'm hoping the rail shows 58 psi when my gauge shows up from Amazon this week, and I need to just clean out the connector for the electrical gauge at the rail. I don't mind replacing parts, I'm just ready to get out of the troubleshooting mode and switch to the driving part.

*2nd Edit: I let it sit overnight, and now the pressure on the gauge is back up to 30 psi. The car runs the same no matter the reading, though.

 

Bill,

Thank you for the referral. We would always be happy to help out.

Thank you,
Gene.

 

Gene, thanks for the response. Once I get to digging into this thing more, I may need to order some parts. Somehow, I'm really hoping I don't for now.

I'm thinking this is a faulty gauge because of how low it read with no issues, but I'll know soon. I'm just too tired from work to dig into it tonight.

 

Good luck on your project and I hope you get it figured out soon. Whenever you need us just let us know and we'll get you taken care of.

 

Ok, my gauge showed up, and this is what I saw...




Looks like my Auto Meter took a dump. So, I'm pretty sure it's the sensor on the gauge. There was no trash in it whatsoever. I think these things can just die. I'll swap it out as soon as I get time. Good news is the fuel gauge is working fine now that I have about 7 gallons in the tank. I also added 7 ounces of Techron to the mix. Feels good to have her running fine again. I appreciate all the help.