When Fuel Pumps Go Bad

Topic: When Fuel Pumps Go Bad (Read 6397 times) previous topic - next topic

When Fuel Pumps Go Bad

June 02, 2012, 04:07:21 PM

Sounds like a movie title...

Anyway, I just wonder when a fuel pump goes bad, what actually happens? Does it seize up? Do the windings in the motor open up?

I just wonder, because the other day I was driving my 85 XR-7 to work and I stopped for gas. Put in $50 worth, and when I jumped back in to start it, it ran for a second (I assume whatever gas was left in the line) and died. I don't hear the fuel pump prime when I hit the key.

I had my wife bring my tools to the gas station (the attendant and I had pushed it around the side (he must have been eating, I have greasy hand prints all over my trunk and header panel now

)). Anyway, I stuck a fuel pressure gage on it, and it was at 0. I told her to watch it and see if it moved (the traffic noise was too much to be able to hear the pump outside the car). I tried the old trick of beating the tank with a rubber mallet to free a seized pump. When I stood back up, I leaned in and wiggled the wire harness where it goes through the floor groment. My wife comes back and says the gage is up. I don't know which trick worked, but it started and I drove it home. Once home, it is dead again. No wiggling and whacking will revive it. I suppose I am just happy to have not needed a tow truck, heh.

I Tested the inertia switch (good). I grounded the tan wire at the diag connector to trip the fuel pump relay. This makes the relay click (as does turning the key). I have 12v coming out of the relay. I pulled the floor groment out in the trunk and took two small pins and pierced the orange and pink wires. I have 12v between them. However, If I pull the relay and check resistance between orange and pink, it shows completely open.

So wadda ya think? Open windings on the fuel pump, or an open wire between the groment and the pump?

Either way, I bet I will need to drop a tank with $50 gas in it

When Fuel Pumps Go Bad

Reply #1 – June 02, 2012, 04:53:46 PM

I've never opened a "bad" pump so I cant say for sure what happens internally but I would almost bet that the brushes wear to the point that they dont make contact and when you smack the bottom of the tank they move to make contact. you have a few options for pulling the gas out of the tank, you can get a cheap inline electric fuel pump and pull it out or get some clear hose and siphon it out. either way will take some time. have fun :-/

When Fuel Pumps Go Bad

Reply #2 – June 02, 2012, 08:55:10 PM

Quote from: CoogarXR;391332

Sounds like a movie title...

Anyway, I just wonder when a fuel pump goes bad, what actually happens? Does it seize up? Do the windings in the motor open up?

I just wonder, because the other day I was driving my 85 XR-7 to work and I stopped for gas. Put in $50 worth, and when I jumped back in to start it, it ran for a second (I assume whatever gas was left in the line) and died. I don't hear the fuel pump prime when I hit the key.

I had my wife bring my tools to the gas station (the attendant and I had pushed it around the side (he must have been eating, I have greasy hand prints all over my trunk and header panel now )). Anyway, I stuck a fuel pressure gage on it, and it was at 0. I told her to watch it and see if it moved (the traffic noise was too much to be able to hear the pump outside the car). I tried the old trick of beating the tank with a rubber mallet to free a seized pump. When I stood back up, I leaned in and wiggled the wire harness where it goes through the floor groment. My wife comes back and says the gage is up. I don't know which trick worked, but it started and I drove it home. Once home, it is dead again. No wiggling and whacking will revive it. I suppose I am just happy to have not needed a tow truck, heh.

I Tested the inertia switch (good). I grounded the tan wire at the diag connector to trip the fuel pump relay. This makes the relay click (as does turning the key). I have 12v coming out of the relay. I pulled the floor groment out in the trunk and took two small pins and pierced the orange and pink wires. I have 12v between them. However, If I pull the relay and check resistance between orange and pink, it shows completely open.

So wadda ya think? Open windings on the fuel pump, or an open wire between the groment and the pump?

Either way, I bet I will need to drop a tank with $50 gas in it

Well i picked up a 88T-Bird with 54k original miles..And at first i thought there was bad gas in tank..Because it will take forever to start..And after it did start..It would drive..But very boggy and sluggish..Like if my tranny was bad..After several bottles of fuel injector cleaner..and emptyin out bad gas that was sitting for years in tank..I had the same problem..So i knew my fuel pump was bad..After installing Venom fuel pump..WOWWW..She woke up..Instant start...Runs smooth..etc etc..

When Fuel Pumps Go Bad

Reply #3 – June 02, 2012, 09:17:19 PM

I put my money on the wire.

When Fuel Pumps Go Bad

Reply #4 – June 02, 2012, 11:50:04 PM

Quote from: 88turbo;391335

I've never opened a "bad" pump so I cant say for sure what happens internally but I would almost bet that the brushes wear to the point that they dont make contact and when you smack the bottom of the tank they move to make contact. you have a few options for pulling the gas out of the tank, you can get a cheap inline electric fuel pump and pull it out or get some clear hose and siphon it out. either way will take some time. have fun :-/

Spot on as a bored want to know nutty guy i have dissected many pumps. And most times the brushes are worn thin. This is a fact in most cases. Now interesting is what happened to COOGAR is typical and i did a big article about filling up and pump failure. My theory is that when the gas gets low and you pull in to fill up the pump is hot and the gas is very cold. The cold fuel shocks the pump and it fails. I have discussed this with several fuel delivery engineers and they agree with what i say. They also know it is an issue. If you ever pulled out a pump some have a black sleeve over it and the KAZOO is in their to cool the pump when fuel in the tank gets low. Rule of thumb is not to let the fuel go to low. Some modern cars like the camaro are mounting the pumps horizontal with the bottom of the tank. This insures that fuel cools the entire pump. Also modern pumps are surrounded with a captive reservoir now. This keeps fuel surrounding the pump when the tank gets low. The fuel cools the pump. SO I NEVER SHUT DOWN MY ENGINE WHEN FUELING AT THE PUMP. IT ALLOWS THE PUMP TO NOT GET HOT AND GET SHOCKED WITH COLD FUEL FROM THE UNDERGROUND TANK. Just something to think about. Call me nuts but this is something i feel is an issue Thanks

NOTE COOGER never pierce a wire to test it. The hole will allow moisture and crud in to the wire and eventually it will fail. This has happened many many times that i have observed. Always test wiring at a connector and never pierce a wire NEVER EVER. Beating on the tank normally indicates a brush issue. And you just prooved the pump is KAPUT!!!

:burnout::hick:
.

When Fuel Pumps Go Bad

Reply #5 – June 03, 2012, 02:03:15 AM

Quote from: TOM Renzo;391356

Spot on as a bored want to know nutty guy i have dissected many pumps. And most times the brushes are worn thin. This is a fact in most cases. Now interesting is what happened to COOGAR is typical and i did a big article about filling up and pump failure. My theory is that when the gas gets low and you pull in to fill up the pump is hot and the gas is very cold. The cold fuel shocks the pump and it fails. I have discussed this with several fuel delivery engineers and they agree with what i say. They also know it is an issue. If you ever pulled out a pump some have a black sleeve over it and the KAZOO is in their to cool the pump when fuel in the tank gets low. Rule of thumb is not to let the fuel go to low. Some modern cars like the camaro are mounting the pumps horizontal with the bottom of the tank. This insures that fuel cools the entire pump. Also modern pumps are surrounded with a captive reservoir now. This keeps fuel surrounding the pump when the tank gets low. The fuel cools the pump. SO I NEVER SHUT DOWN MY ENGINE WHEN FUELING AT THE PUMP. IT ALLOWS THE PUMP TO NOT GET HOT AND GET SHOCKED WITH COLD FUEL FROM THE UNDERGROUND TANK. Just something to think about. Call me nuts but this is something i feel is an issue Thanks

NOTE COOGER never pierce a wire to test it. The hole will allow moisture and crud in to the wire and eventually it will fail. This has happened many many times that i have observed. Always test wiring at a connector and never pierce a wire NEVER EVER. Beating on the tank normally indicates a brush issue. And you just prooved the pump is KAPUT!!!

:burnout::hick:
.

I agree with this, every time I've had a fuel pump fail was right after filling the tank. what your saying makes perfect sense. I guess I never thought about 'shocking the pump' before

When Fuel Pumps Go Bad

Reply #6 – June 03, 2012, 08:46:03 AM

I typically don't pierce wires, but it was the only way I could test that end without a tank drop. I have some good 3M waterproof electrical tape I plan on sealing the wire with after I am done.

I think I am gonna have to drop that tank anyway. I just need to find something to put 13 or so gallons of gas in. I could just put it in my van, but that'd be a waste putting 93 octane in a van with 300k miles on it, lol.

When Fuel Pumps Go Bad

Reply #7 – June 03, 2012, 09:53:00 AM

Quote from: TOM Renzo;391356

Spot on as a bored want to know nutty guy i have dissected many pumps. And most times the brushes are worn thin. This is a fact in most cases. Now interesting is what happened to COOGAR is typical and i did a big article about filling up and pump failure. My theory is that when the gas gets low and you pull in to fill up the pump is hot and the gas is very cold. The cold fuel shocks the pump and it fails. I have discussed this with several fuel delivery engineers and they agree with what i say. They also know it is an issue. If you ever pulled out a pump some have a black sleeve over it and the KAZOO is in their to cool the pump when fuel in the tank gets low. Rule of thumb is not to let the fuel go to low. Some modern cars like the camaro are mounting the pumps horizontal with the bottom of the tank. This insures that fuel cools the entire pump. Also modern pumps are surrounded with a captive reservoir now. This keeps fuel surrounding the pump when the tank gets low. The fuel cools the pump. SO I NEVER SHUT DOWN MY ENGINE WHEN FUELING AT THE PUMP. IT ALLOWS THE PUMP TO NOT GET HOT AND GET SHOCKED WITH COLD FUEL FROM THE UNDERGROUND TANK. Just something to think about. Call me nuts but this is something i feel is an issue Thanks

NOTE COOGER never pierce a wire to test it. The hole will allow moisture and crud in to the wire and eventually it will fail. This has happened many many times that i have observed. Always test wiring at a connector and never pierce a wire NEVER EVER. Beating on the tank normally indicates a brush issue. And you just prooved the pump is KAPUT!!!

:burnout::hick:
.

I agree Tom, you are not crazy and that make perfect sense.

When Fuel Pumps Go Bad

Reply #8 – June 10, 2012, 12:32:40 PM

brass bushings for the stator wear and allow the pump stator to go off center, crashes the brushes.,,locks up the pump.
two out of two failed pumps had plent of brush remaining but under a magnefying glass i could see the wabble in the stator shaft towards the brush end of the pump.

pretty much the same for power door locks, they are motors as well.

cooling theory is good , like it but i run a 12v fuel pump for my parts washer and its an old bosch not submerged.

When Fuel Pumps Go Bad

Reply #9 – June 10, 2012, 12:42:18 PM

Quote from: CoogarXR;391332

I Tested the inertia switch (good). I grounded the tan wire at the diag connector to trip the fuel pump relay. This makes the relay click (as does turning the key). I have 12v coming out of the relay. I pulled the floor groment out in the trunk and took two small pins and pierced the orange and pink wires. I have 12v between them. However, If I pull the relay and check resistance between orange and pink, it shows completely open.

So wadda ya think? Open windings on the fuel pump, or an open wire between the groment and the pump?

with relay disconnected, power the fuel pump from battery source , and do it 10 out of 10 tries. wiggle test wiring with power applied.

if pump fails, then your wiring or pump is bad.

BTW, probing wiring with a stick pin is in shop manuals but agree with whats said although im guilty of doing it myself.

When Fuel Pumps Go Bad

Reply #10 – June 10, 2012, 01:15:33 PM

I haven't done anything else to it yet. I had to work on my Astro van... It's old and rusty, and has 300k miles on it. I debated junking it. I called the s yard, and they offered me $450 if it drives in. So I found a better Astro van on CL for $450 that needs some minor work (but looks much better and has half the miles) for $450. So I bought it. When I junk my old van, I will essentially break even. I got the new van 90% roadworthy. Once it's finished, the cougar will get my full attention, heh.

When Fuel Pumps Go Bad

Reply #11 – June 12, 2012, 02:04:33 AM

At least you made it home, avoiding a tow bill! Mine went out a few years ago in my Cougar in the middle of the woods in Indiana, 130 miles away from home with a trunk full of camping gear and a cooler full of food.

It was shortly after doing the complete HO swap, old pump had enough. Was parked at the entrance of an old cemetary to make a phone call (hard to find cellphone reception in the sticks!) Put it in gear to take off, she died...I knew exactly what it was, imediately popped the trunk to check the inertia switch and had my sidekick turn the key to see if I could hear the pump..no dice. $80 tow bill to a shop in Crawfordsville, $80 hotel room, $120 to rent a vehicle to go back home and $300 to track a pump down and replace it, 3 days later she was running again. Relaxing camping trip turned to expensive fiasco.

What ticked me off the worst was that I had a brand new BBK 110lph sitting in the package in my garage! Also, you know you have a bond with a car when you feel anxiety over leaving it back at a strange shop 130 miles away from home for 2 days!

When Fuel Pumps Go Bad

Reply #12 – June 12, 2012, 08:11:48 AM

Actually their are other reasons for pump failures. A lot of times it is LOW VOLTAGE. I often thought about this and looked in to it in great DETAIL. As i know bushings wear out Brush failure is in my view very critical as well. So with this i have a rule in my shop. SOLDER EVERY CONNECTION INCLUDING THE PUMP LEADS.

Below is a common problem in GM cars. Here is a unit that failed . I am very familiar with this unit as being an S10. Owning a TYPHOON and working on many GM products one gets to know things out of the ordinary. This unit was replaced a year ago by a competitor that priced the job much less then us. But as you can see we wound up with the job any way. Here is a typical unit that had a brand new sender assembly and pump. The garage that changed it contacted me for the FIX. So here is the issue. The contacts are to small to handle the PUMPS CURRENT. So the pump ran at low voltage. I have a fix for this as usual. Look at the photos. So Jcassidy you cant generalize a fix all the time. When pumps fail i look in to other reasons. GM uses this pump assembly in many cars so why did this one FAIL?? LOW VOLTAGE DIFFERENT CONNECTORS NOT SOLDERED. I solder and modify all these units including the pump connections as well. Nothing better than a soldered connection in my book!!!

Here is where i ground the pump and fuel sensor. This allows me to use a pair of extra wires to feed the pump with 12 VOLTS with no voltage drop across the connector'

Here is what i do i remove the grounds and relocate them to the pickup tubes and bridge the pump feed wires. Now the pump has 3 wires feeding it. I ground the tank sender as well so i gain the wiring i need through the assembly.

Here is where i bridge the 3 wires to complete my FIX. The blazer fired up and has a pump that is getting ample amounts of voltage and current and all is good in the WORLD. Always try and figure out why things happen. If you get in to this habit it can save you a lot og GRIEF AND A TOW TRUCK. Thanks Tom

Now the pump has 3 wires feeding it. !!!!!

And naturally i provide a hefty ground wire to return the CURRENT. The tank unit is now provided with a heavy wire to complete my MODIFICATION TO THIS PUMP

Here is the new ground for the fuel sender. Internal instead of external. This is how i am able to get extra connections through the electrical connector in the tank assembly

When Fuel Pumps Go Bad

Reply #13 – June 13, 2012, 01:01:35 AM

good mods,

if you clip on to the conductor with needle nose vise grips up at the point where you skinned the wire and then add your heat to make the connection, your insulation on your conductor wont sneak backwards shrinking up on you, the vise grips will absorb the heat trying to move up the conductor and stop the heat at that point. im surprised you dont slip on some heat string way up the conductor prior to torching. Thats a lot of heat to make those connections, looks good man.

When Fuel Pumps Go Bad

Reply #14 – June 13, 2012, 01:24:18 AM

Quote

SO I NEVER SHUT DOWN MY ENGINE WHEN FUELING AT THE PUMP. IT ALLOWS THE PUMP TO NOT GET HOT AND GET SHOCKED WITH COLD FUEL FROM THE UNDERGROUND TANK.

Depending on where one lives, this can actually be highly illegal. Also I don't care what supposed safety measures are in place on newer gas station pumps and vehicle fuel systems, as someone who has bee inside a jet fuel tank and witnessed a static electricity arc over 1/2" long while in said tank I would never do it.