What are the symptoms of a bad Fuel pump VS a bad Fuel Filter? - LS1TECH

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What are the symptoms of a bad Fuel pump VS a bad Fuel Filter?

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Old 06-11-2009, 06:01 PM   #1
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Default What are the symptoms of a bad Fuel pump VS a bad Fuel Filter?

Well as some of you know. My car has had a stumbling problem (probably for over a yr). It stumbles/bogs down when I accelerate. Anyways, I took it to Lethal today, and the tech took it for a ride, came back went inside the office. I went inside, and they told me it was a bad fuel pump. They said my fuel pressure was at 35(Im assuming they used my tach, not sure how accurate it is). Anyways, while I was there. I started thinking that it could be something as easy as a fuel filter? I've always thought that when a fuel pump went out, that it went totally out. I told them my thoughts, and they said it was 100% the fuel pump. I left my car there, and they're supposed to get it swapped out tomorrow. Its $500+, and just want to feel better about the fuel pump being the problem. So I ask, what are the symptoms of both?

I appreciate the help guys.

Patrick.
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Old 06-11-2009, 06:18 PM   #2
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Fuel pump can work half assed for a while. I drove from central Wyoming to Denver on a bad fuel pump. Had to pull over a few times but i made it.
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Old 06-11-2009, 06:48 PM   #3
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have you ever put a filter on it or know if it has had one? should of tried the filter you would be surprised what a dirty filter would cause. I always told customers to try that first if they were unsure of the maintenance history. worst case it does not help but there is not a loss, it is routine maintenance and better to spend $40-60 and it not help then to spend $500 and it not fix the problem.

how does it start in the morning?
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Old 06-11-2009, 06:57 PM   #4
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have you ever put a filter on it or know if it has had one? should of tried the filter you would be surprised what a dirty filter would cause. I always told customers to try that first if they were unsure of the maintenance history. worst case it does not help but there is not a loss, it is routine maintenance and better to spend $40-60 and it not help then to spend $500 and it not fix the problem.

how does it start in the morning?
Thats exactly my mindframe, but they didn't even offer that has an option. I just got off the phone with them and they said that they've seen it so many times and are "99%" sure that its the problem.

It starts in the morning, with no problems at all.
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Old 06-11-2009, 07:40 PM   #5
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If there is a question in your mind about the fuel filter, you simply change it. It costs just a few bucks and is a very simple job.
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Old 06-11-2009, 08:04 PM   #6
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Ya, unfortunately its at lethal right now. They're supposed to start the fuel pump tomorrow morning. Maybe I'll just get a ride out there early in the morning and have them swap the fuel filter first. I'd prefer to be there when they do it.
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Old 06-12-2009, 07:21 AM   #7
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I will just give you an example. Had a customer come in with a little s10 that had like 90k miles on it and ran like complete crap. they said they did not know if anything had been done to the truck but they had never done anything while they owned it. could of been a number of things but with the service history un known take care of cheap maintenance issues first. Needless to say he left and the truck ran great with just a filter.

Are they going to replace the filter when they change the pump?
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Old 06-12-2009, 07:36 AM   #8
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When you replace the fuel pump and it goes out again within 5K miles, your fuel filter is probably the cause.

Learned this the hard way. When I was 20 (I'm 40 now), I had about 60K miles on my 1987 Toyota truck when it started acting up. Replaced the fuel pump, and it ran great for another 4-5K miles, then started doing it again. Asked the parts guy when picking up a second fuel pump what else could be causing it. He asked, "When was the last time you changed the fuel filter?". Uh, duh, never. Replaced the filter and the pump, and it ran beautifully until I sold it at 107K miles. That was the only mechanical failure the truck ever had besides normal wear and tear (battery, brakes, clutch).
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Old 06-12-2009, 07:40 AM   #9
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now-a-days whether you go to autozone or o'reillys they sell you a fuel filter with your pump. A bad filter could cause a pump to go out as well. So even if you replace your filter now...the damage has been done to your pump.
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Old 06-12-2009, 08:38 AM   #10
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Ya, Im about to head to Lethal right now. I'll probably have them do the pump as well. I dont think a stock pump is enough for the car anyways.
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Old 06-12-2009, 08:44 AM   #11
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Ya, Im about to head to Lethal right now. I'll probably have them do the pump as well. I dont think a stock pump is enough for the car anyways.
yah thats a good idea! I dont think its enough either
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Old 06-12-2009, 09:41 AM   #12
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dude it says in your sig you have 433 408. when i did my little 383 the stock pump and injectors were fine at first was good at 433rwhp and 434rwtq. well i had LMR rebuild the top half of the motor(for 500rwhp) it would lean out at 5k with the injectors maxxed (130% duty cycle at 5k) out so i changed to 42 lb. injectors but with 77k on the stock pump they said the pump would probably not keep up with the injectors sure enough car started sputtering intermittantly, so they through a walbro 255 pump and filter and the car has run flawlessly since. so im guessing its wouldn't be a waste of money for you to just do both then youll have a little more comfort not worrying about the motor running out of fuel and burning something up especially on the nitrous.

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Old 06-12-2009, 05:44 PM   #13
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Just got my car back home. The fuel pressure gauge is showing 40, not sure if thats accurate. But its running MF strong right now.
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Old 06-12-2009, 06:00 PM   #14
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So you had the pump replaced?
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Old 06-12-2009, 06:22 PM   #15
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Ya, I had the pump and filter replaced.
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Old 06-12-2009, 10:43 PM   #16
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Quote:
Originally Posted by Donohue96M6Z28 View Post
Just got my car back home. The fuel pressure gauge is showing 40, not sure if thats accurate. But its running MF strong right now.
IF the 40#is correct I do not think that IS sufficint, I would like to see 58-60 # NA and for sure if on spray
just my .02' Johnny
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Old 06-13-2009, 03:50 PM   #17
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yup iy should be at like around 50 psi
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Old 06-13-2009, 03:57 PM   #18
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Hook up a pressure tester on the shrader valve and see what it actually is. Dont really on a gauge that you dont know for sure is saying the right number.
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Old 06-13-2009, 05:45 PM   #19
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It should be 58-60 psi.
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Old 06-14-2009, 07:37 AM   #20
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Quote:
Originally Posted by TWS View Post
If there is a question in your mind about the fuel filter, you simply change it. It costs just a few bucks and is a very simple job.
exactly.... always worth changing out the cheaper part and if the problem is corrected, good.



if nothing improves, change the pump.
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