blowing fuel pump fuses?
Thread Starter
Racer
Joined: Dec 2006
Posts: 269
Likes: 0
From: Raleigh NC
blowing fuel pump fuses?
i've read all the common electrical issues, but haven't found anything similar to my problem. my 98 c5 vert is eating fuel pump fuses as soon as the car is started. here's how it went:
blew a fuse one day riding down road. replaced it, and all seemed well for about 20-30 miles. blew again getting onto the highway one day. replaced it, and made it about 2 miles before it blew again. now, it lasts all of 5-10 seconds after starting the car before it blows.
i don't think this would be the result of any ground issue, i'm thinking a short in a power wire or the pump has an internal problem. basically i'm just wondering if anyone else has had or heard of a similar problem before i just start randomly ohming the whole fuel pump harness.
the car does have a walbro 255lph pump with only about 5-10k miles, but everything else is still factory.
blew a fuse one day riding down road. replaced it, and all seemed well for about 20-30 miles. blew again getting onto the highway one day. replaced it, and made it about 2 miles before it blew again. now, it lasts all of 5-10 seconds after starting the car before it blows.
i don't think this would be the result of any ground issue, i'm thinking a short in a power wire or the pump has an internal problem. basically i'm just wondering if anyone else has had or heard of a similar problem before i just start randomly ohming the whole fuel pump harness.
the car does have a walbro 255lph pump with only about 5-10k miles, but everything else is still factory.
Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
This is actually pretty simple to troubleshoot, disconnect the connector from the fuel pump, replace the fuse and see if it blows. If the fuse doesn't pop then you know it's a bad pump, if the fuse blows then you know it's a shorted wire.
The only problem with this troubleshooting is, when the key is selected the pump only gets power for 3 seconds if the engine isn't running, so you'll have to jumper across the contacts for the fuel pump relay in order to provide a constant power source when the ignition is turned on.
The only problem with this troubleshooting is, when the key is selected the pump only gets power for 3 seconds if the engine isn't running, so you'll have to jumper across the contacts for the fuel pump relay in order to provide a constant power source when the ignition is turned on.
Thread Starter
Racer
Joined: Dec 2006
Posts: 269
Likes: 0
From: Raleigh NC
okay, i think i've got it narrowed down to a dead short somewhere in the power wire from the relay to the pump. are there any common trouble spots to check before i dive into the whole harness?
also, can anyone tell me what sort of resistance i should be getting through the pump itself?
i'm thinking it's just a wire chaffing somewhere. it started, idled, and revved fine sitting in the driveway. as soon as i started backing up and got to the point where the suspension/chassis flexes going into the street, it blew.
edit: oh, and something is obviously pulling the battery down very fast when the car is off. another finger pointing to a short...
also, can anyone tell me what sort of resistance i should be getting through the pump itself?
i'm thinking it's just a wire chaffing somewhere. it started, idled, and revved fine sitting in the driveway. as soon as i started backing up and got to the point where the suspension/chassis flexes going into the street, it blew.
edit: oh, and something is obviously pulling the battery down very fast when the car is off. another finger pointing to a short...
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
okay, i think i've got it narrowed down to a dead short somewhere in the power wire from the relay to the pump. are there any common trouble spots to check before i dive into the whole harness?
also, can anyone tell me what sort of resistance i should be getting through the pump itself?
i'm thinking it's just a wire chaffing somewhere. it started, idled, and revved fine sitting in the driveway. as soon as i started backing up and got to the point where the suspension/chassis flexes going into the street, it blew.
edit: oh, and something is obviously pulling the battery down very fast when the car is off. another finger pointing to a short...
also, can anyone tell me what sort of resistance i should be getting through the pump itself?
i'm thinking it's just a wire chaffing somewhere. it started, idled, and revved fine sitting in the driveway. as soon as i started backing up and got to the point where the suspension/chassis flexes going into the street, it blew.
edit: oh, and something is obviously pulling the battery down very fast when the car is off. another finger pointing to a short...
As far as the battery getting drawn down, that should be a separate issue since the fuel pump wire isn't hot when the key is off.
Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
The power wire for the fuel pump is protected very well and the only way I can see that it shorted would be if somebody hacked the harness up and maybe ran another wire outside of the original harness.
Did you try to troubleshoot it the way I explained?
Thread Starter
Racer
Joined: Dec 2006
Posts: 269
Likes: 0
From: Raleigh NC
okay, an update... i thought i had the problem found, but it's returned. i found a suspect area in the harness where it goes through the subframe on the driver side. i repaired it, and the car seemed to be fine for the little bit i ran/drove it afterwards. it's started blowing fuses again now, and it's got me stumped. i've ohmed the wires, been back through the harness, run the pumps with the car off, etc. and i'm coming up empty.
the only progress is i've narrowed it down to certain situations where the problem shows. the car will idle just fine as long as you want, and progressive throttle input is fine. however, if i stab the gas with it in park over 5k rpms it blows. same thing in gear... it'll idle and cruise around at part throttle just fine. any load over 1/2-3/4 throttle and it blows.
i'm thinking maybe some sort of issue with the pumps demanding a voltage increase with the increase of fuel flow, but i don't know. anyone have any ideas? the only one i've got right now is gas + matches.
edit: also, i think the battery issue can be disregarded... after a good charge it's okay, pretty sure it was just weak from all of the initial cranking/screwing around with it.
the only progress is i've narrowed it down to certain situations where the problem shows. the car will idle just fine as long as you want, and progressive throttle input is fine. however, if i stab the gas with it in park over 5k rpms it blows. same thing in gear... it'll idle and cruise around at part throttle just fine. any load over 1/2-3/4 throttle and it blows.
i'm thinking maybe some sort of issue with the pumps demanding a voltage increase with the increase of fuel flow, but i don't know. anyone have any ideas? the only one i've got right now is gas + matches.
edit: also, i think the battery issue can be disregarded... after a good charge it's okay, pretty sure it was just weak from all of the initial cranking/screwing around with it.
Last edited by RTR; May 3, 2008 at 11:50 PM.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
okay, an update... i thought i had the problem found, but it's returned. i found a suspect area in the harness where it goes through the subframe on the driver side. i repaired it, and the car seemed to be fine for the little bit i ran/drove it afterwards. it's started blowing fuses again now, and it's got me stumped. i've ohmed the wires, been back through the harness, run the pumps with the car off, etc. and i'm coming up empty.
the only progress is i've narrowed it down to certain situations where the problem shows. the car will idle just fine as long as you want, and progressive throttle input is fine. however, if i stab the gas with it in park over 5k rpms it blows. same thing in gear... it'll idle and cruise around at part throttle just fine. any load over 1/2-3/4 throttle and it blows.
i'm thinking maybe some sort of issue with the pumps demanding a voltage increase with the increase of fuel flow, but i don't know. anyone have any ideas? the only one i've got right now is gas + matches.
edit: also, i think the battery issue can be disregarded... after a good charge it's okay, pretty sure it was just weak from all of the initial cranking/screwing around with it.
the only progress is i've narrowed it down to certain situations where the problem shows. the car will idle just fine as long as you want, and progressive throttle input is fine. however, if i stab the gas with it in park over 5k rpms it blows. same thing in gear... it'll idle and cruise around at part throttle just fine. any load over 1/2-3/4 throttle and it blows.
i'm thinking maybe some sort of issue with the pumps demanding a voltage increase with the increase of fuel flow, but i don't know. anyone have any ideas? the only one i've got right now is gas + matches.
edit: also, i think the battery issue can be disregarded... after a good charge it's okay, pretty sure it was just weak from all of the initial cranking/screwing around with it.
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Thread Starter
Racer
Joined: Dec 2006
Posts: 269
Likes: 0
From: Raleigh NC
okay, i cured my mystery. i found that the upper bellhousing bolt on the passenger side was digging into the main harness that runs to the rear of the car. this happened any time the motor torqued, such as hard revving, acceleration, or going over off camber surfaces. that's why it was so intermentant.
anyway, take a look at that area, especially if you've had your motor out/in before or you have a built motor that moves around a lot. i've put about 600-700 miles on the car (yes, my vette gets DRIVEN, lol) this past week with no issues.
anyway, take a look at that area, especially if you've had your motor out/in before or you have a built motor that moves around a lot. i've put about 600-700 miles on the car (yes, my vette gets DRIVEN, lol) this past week with no issues.
Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
okay, i cured my mystery. i found that the upper bellhousing bolt on the passenger side was digging into the main harness that runs to the rear of the car. this happened any time the motor torqued, such as hard revving, acceleration, or going over off camber surfaces. that's why it was so intermentant.
anyway, take a look at that area, especially if you've had your motor out/in before or you have a built motor that moves around a lot. i've put about 600-700 miles on the car (yes, my vette gets DRIVEN, lol) this past week with no issues.
anyway, take a look at that area, especially if you've had your motor out/in before or you have a built motor that moves around a lot. i've put about 600-700 miles on the car (yes, my vette gets DRIVEN, lol) this past week with no issues.
The harness has a bracket built into it that is supposed to attach to that bolt on the bellhousing, has your motor ot torque tube been removed, if the harness is secured properly it shouldn't rub. I do suspect though that there are a lot of harness's that are unsecured at that point since it's kind of a pain to reattach it.
Thread Starter
Racer
Joined: Dec 2006
Posts: 269
Likes: 0
From: Raleigh NC
yep, it's all been out before. i thought that might be the case about it mounting there, but there's no tab on the harness so i didn't bother. i was able to slide the harness towards the battery box a little then secure it to the other big harness with a ziptie to keep it in place. it's right up against the firewall now and well out of the way.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
Likes: 4,066
From: Cape Coral, Florida
Hi everyone, I am having a similar issue, I hit a bump the other day and lost fuel pressure. I have been testing wires for the past two days. I found that between grey wire exiting the fuse box going to the fuel pump there is a short. It is actually reading as it is grounded somewhere. It just keeps blowing fuses. I ran a wire directly from battery to fuel pump and pump works and starts right up. So I just need to chase the wire from the engine bay back. Does anyone have a wiring diagram for this??
Also @RTR can you specify where you were referring to with the bolt on the bell housing? can you take a picture?
Thanks everyone in advance.
Also @RTR can you specify where you were referring to with the bolt on the bell housing? can you take a picture?
Thanks everyone in advance.
What year is your car ?????
