I have done some troubleshooting of my 98 due to a lack of fuel pressure. I have a fuel pressure gauge on the interior pillar, and it reads zero when I try to start the car. The starter engages, but nothing happens. The fuel pressure gauge usually jumps up over 50 psi immediately, but today, it is actually moving to zero. When off, it sits at the bottom of the gauge, but when you turn the ignition on, it bumps slightly to zero. This is what I have checked so far:

-- Check 20A fuel pump fuse. It is good.
-- Pulled relay 35; have 12V on 86 and 87 with the ignition on; ground reads ~0 ohms on 85; installed jumper from 30 to 87 and it would not start.
-- Cannot hear fuel pump running with the ignition on.
-- No current codes; there were some historical codes, but nothing related to the fuel pump
-- Pulled the connector at the pump. It has 4 pins. I tested for voltage, and there was 5.04V on the second to last pin. I'm not sure of the numbers, and I don't know which is ground. I just saw an odd voltage on the plug.
-- When I pulled the plug of the connector, my cluster read low fuel as it should. Goes away when plugged back in. Not sure if that helps, though.
-- Tried multiple keys to see if it is the security hardware on the key. Both did the same thing.
-- The tank has fuel (~half tank).

I'm thinking the fuel pump is gone. It's a LPE pump that was installed with the supercharger. It has very low miles on it (less than 5k), but I have been cranking the car periodically with gas that is surely older than I'd like in the tank.

I'd be glad to try any other troubleshooting steps others suggest.

 

A few other questions I'm wondering about as I sit here at work:

-- Are there any other fuses I will need to check? I checked the 20A in the fuse box with the relay, but are there any others?
-- On the 4 pins on the pigtail to the pump, I am assuming the pins are power, ground, fuel level, and ???.
-- Could there be another cable that I'm missing that feeds power to the pump? The pigtail cable seems rather thin to supply power to the fuel pump, but that is just me eyeballing it.
-- Anything that could be related to the jet pump on the passenger side? I really don't see how, but I'm wondering if that failing could somehow cause the main pump not to function.
-- Is there a recommended way to test the pump? I am wondering if be safe to hook up a 12v source to the pump to get it to run for just a second. The thing that is throwing me off is the reading of 5V on the second to last pin. I reallly thought this was a 12V input pump.

Thanks, everyone

 

First of all, the pump only gets power for a few seconds for priming the system when you turn the key on.

Pump don't run until it sees x amount of engine rpm

You need to jump the pump for testing

The low volt signal your seeing is most likely fuel level sensor

 

Thanks for the reply. Actually, that's exactly what I was thinking a few seconds ago (it's all slowly coming back). I did jump the pump out, and it didn't start. Now, I need to just jump it out or have the wife cut the key on to test if I see the 2 second spike of 12V. I do have 12V in the box, so it should be good. It sounds more and more like the pump is toast, but I'll run through the last few checks.

BTW, any recommendation for a new pump? I had the LPE, and I can go back with it. I think it was mostly my fault for letting it run for too long with fuel just sitting. Where is a reasonable place to buy a suitable replacement?

 

Have you used the actual SCHEMATIC to do all the necessary meter troubleshooting??

 

I think that is a 2001 + fuel electrical system;


Bill

 

Thanks, Bill. It looks like the 5V reading is from the rheostat on my level. So, I'll try to jump out the pins again and measure across the pump (gray to black wires). That is straight line voltage, so I won't worry unless it's something other than ~12V.

I need to also go back and check voltages, but I thought both the PCM and Hot In were giving me constant 12V. I really need to look again. If that is the case, then the PCM isn't providing the cutout that it should. Maybe it was late, but I thought that was really what was happening. That certainly would be a different issue, but I need to sort it out. I think it's all fine, and I just lost the pump. We'll soon see.

I also need to make sure the wire that I'm using to test will actually fit down in the blade slots. I had to used a stranded wire to make sure I could touch the voltages. I'll firmly test the jumper, and I'll verify the voltage on the plug. After that, I can't think of anything to look for. It's looks like that's it from the schematic. Thanks again.

 

Ok, so I checked it again. Getting 12V for ~2 seconds on pin "A" as shown above, when the ignition is switched on. It gets constant 12V when I installed the jumper (did that first). The relay and circuit are good.

Sounds like I need a new pump.

 

yep

 

Just ordered a pump. Thanks, guys!

 

On a side note, does anyone know why all instructions say not to take off the metal shield below the tank? They say just to take the front bolts out and loosen it, but specifically say not to remove it. I actually removed it completely when I was troubleshooting the other day. I'm guessing because it may be hard to line it up to put it back in, but it's pretty straightforward.

Trivial moreless at this point, but I was curious.

 

Gravity

 

Alright, so I should finally have time to start digging into it tomorrow. So, tonight, I started trying to figure out a way to drain the tank with a dead pump. I first took my Pella siphon pump tube and tried to feed it down the gas tank opening. It actually went into the tank because it's very stiff, and it went in the full 36" length of the tube. It never hit bottom. The issue is it also never hit any drop of gas.

So, I'm assuming it somehow goes across the top of the driver's side tank and actually toward the passenger side. So, it never hit gas. I'm really hoping that's what happened. I got under the car and put my hand on the pump while the wife turned the key forward...nothing. The pump doesn't make a sound or vibration. I view this as a good thing, as I was wondering if it somehow was the siphon jet pump, and all of my gas is actually stuck in the passenger side tank. BTW, when this first started, I added about a gallon to the tank to see it was just low. It didn't do anything.

So, my gauge is reading just under a half tank, and I'm assuming I have close to 9 gallons of gas sitting in the tank ready to come out when I start to crack the pump or disconnect the lines. I'm trying to come up with a plan to catch all of it in any case. However, could this actually be something else? I guess I'll know either way soon.

*Edit: I think I'm overthinking this one. I checked the voltage to the connector, but nothing happens at the pump. No buzz, no vibration, nothing. So, now, I think I just need to come up with a way to get the fuel out as easy as possible. While I'm in there, I'm going to reach in and clean out the tank, as well as change the filter. If anyone thinks I have something else going on, just let me know. Otherwise, I'm planning to get on this by tomorrow or Friday at the latest.

 

Have you checked the pump ground? It's on the OE stud right there close-by on the frame rail unless you have some sort of custom wiring setup.

You wouldn't be the first to have :
1. broken wire
2. corroded/poor connection on stud

 

Ground stud:

http://img.photobucket.com/albums/v4...tudpics017.jpg

Btw, disregard the EBTCM/ABS unit seen in this pic. It's a '97 or '98 and they were all in the rear of the car.

 

I'll check. I believe I checked continuity from the ground on the plug to a good ground point on the vehicle and it showed no resistance, but I'll verify.

 

I just slowly cracked open the bolts and drained the gas into a container then topped off the mower, Whatever spills evaporates so no biggie just smells.

Also u MUST replace the gasket & BOLTS when you do the pump swap. A lot of places offer a package/kit with the pump or at least state u need to replace the bolts & gasket.

 

Thanks for the tip. I actually just cracked the flange and let it drain to a pan. It only had about 2 gallons in the tank. I have the new gasket and bolt kit, too. Here's the problem. the two wires connecting to the rheostat board for the sending unit broke flush with the board right as I was maneuvering it back in the hole. There is no way to solder them back either. So, I'm now paused waiting for a new float kit to come in. $78 on Amazon, which seemed to be a good price. I'm not sure if it's necessary, but I'm definitely going to bump the pump with the connector connected before I install it back in. The hardest part of the job is getting it in and out of the tank. I think that's what did the damage to the old wires anyway. It was my fault, I should have realized they were taking some stress in the process.

 

I ordered my pump from lingenfelter and it came with awesome instructions, colored pictures on how to maneuver the pump in and out. I'll see if I can print/post them up for ya.

 

I just checked and they have all their instructions on the website. Hope that helps ya out.