C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Drain tank to replace fuel pump?

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Old Nov 7, 2005 | 11:16 AM
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Default Drain tank to replace fuel pump?

A buddy's fuel pump just died on his '96, and I offered to help him swap it out this week. I see my FSM (which is for a '94) lists draining the fuel tank as one of the steps. I can't, for the life of me, figure out why this should be necessary, and I've never heard of anyone doing it. Am I missing something here?

Also, any tips that go beyond the obvious, and beyond what's listed in the FSM?

TIA.

Be well,

SJW
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Old Nov 7, 2005 | 11:28 AM
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no need... that's a waste of good gas. The pump is 100% reachable from the top.
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Old Nov 7, 2005 | 11:29 AM
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Gas is heavy....something along the lines of 8lbs per gallon. Draining the tank will relieve some weight when you have to lower/drop it.
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Old Nov 7, 2005 | 11:32 AM
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there is no need to remove the tank for this service. The pump, as I said, is 100% servicable from the top...
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Old Nov 7, 2005 | 11:47 AM
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Originally Posted by bogus
there is no need to remove the tank for this service. The pump, as I said, is 100% servicable from the top...
Thanks for the sanity check, Bogus. I'm baffled as to why the FSM recommends draining the tank. Odd...

Be well,

SJW
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Old Nov 7, 2005 | 11:48 AM
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I just replaced my pump took about 30 minutes from the top. Had a full tank of gas did not drain a drop. Easy process.
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Old Nov 7, 2005 | 11:52 AM
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Originally Posted by cajun86
I just replaced my pump took about 30 minutes from the top. Had a full tank of gas did not drain a drop. Easy process.
This is exactly what I've heard from everyone else who's ever changed out a pump on a C4, and it really puzzled me why draining was recommended. I wasn't about to drain the thing unless somebody on the Forum pointed out a really good reason why I should.

Thanks guys, for the reassurance. Gotta love this Forum.



Be well,

SJW
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Old Nov 7, 2005 | 02:40 PM
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My manual says nothing about draining the tank. I can think of a good reason not to drain it. It isn't the liquid gasoline that is so dangerous, it is the vapors, the air and fuel above the liquid that is so explosive. The more fuel in the tank, the less vapors to explode.

RACE ON!!!
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Old Nov 7, 2005 | 02:51 PM
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Originally Posted by CFI-EFI
My manual says nothing about draining the tank. I can think of a good reason not to drain it. It isn't the liquid gasoline that is so dangerous, it is the vapors, the air and fuel above the liquid that is so explosive. The more fuel in the tank, the less vapors to explode.

RACE ON!!!

i agree!
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Old Nov 7, 2005 | 03:08 PM
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I know that the repair labor/cost book Chevy provides to the dealerships calls for dropping the tank and something like 2 hrs of labor. I forget exactly how much labor.
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Old Nov 7, 2005 | 03:41 PM
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Originally Posted by CentralCoaster
I know that the repair labor/cost book Chevy provides to the dealerships calls for dropping the tank and something like 2 hrs of labor. I forget exactly how much labor.
That lesson cost me about $200. The book is wrong. Mine was not done at a dealer it was from a private shop. The POS told me the book said 2 1/2 hours of labor to drop the tank and replace the pump. My car was dead at the shop so he had me by the hairs. When I went to pick it up I complained and he admitted he didn't drop the tank but the policy was to charge the book rate.

Wait, it gets better, the car still wouldn't start. Then he replaced the coil and it started and ran just fine. If it wasn't for the fact that the car has over 100k on it and it probably needed a filter and pump soon anyway, I'd really be pizzed.

No, I am not going back.
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Old Nov 7, 2005 | 03:48 PM
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Originally Posted by Yellow95
When I went to pick it up I complained and he admitted he didn't drop the tank but the policy was to charge the book rate.
Wow, what an azzhat. I can understand that they win/lose time with every job they do, and it supposedly evens out in the end, or rewards proficient shops, but in this case it's not that he's doing it quicker, it's that the book is plain wrong.

Had he dropped the tank and done it in 2 hrs, then I guess yeah, he should charge for 2 hrs labor UNLESS the customer calls him out on it.

Because you know if the shop took 3 hrs to do a 2.5 hr job, and charged you for 3, a customer "in the know" would be pissed.

These book times go out the window though on mutiple/overlapping repairs. Timing chain and water pump for example.. combined labor is way less than doing seperate. What would this shop charge you for on that?
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Old Nov 7, 2005 | 03:52 PM
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I got hosed by a honda dealer on that once... I had paid to have the rotors cut, yet they charged me again for labour to replace the pads!!! Even tho the calipers come off either way.
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Old Nov 7, 2005 | 04:26 PM
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Originally Posted by CFI-EFI
My manual says nothing about draining the tank. I can think of a good reason not to drain it. It isn't the liquid gasoline that is so dangerous, it is the vapors, the air and fuel above the liquid that is so explosive. The more fuel in the tank, the less vapors to explode.

RACE ON!!!
I couldn't agree more. Makes absolutely no sense to me, but the FSM (red) for my '94 lists as follows:

Fuel Sender Assembly Replacement

Remove or Disconnect:

1. Negative battery cable.

2. Relieve fuel system pressure.

3. Fuel filler cap.

4. Drain fuel tank.

...etc.

Beats me.

One thing's for sure -- I will be skipping Step 4.

Thanks again, all.

Be well,

SJW
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Old Nov 7, 2005 | 04:33 PM
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Originally Posted by CentralCoaster
I know that the repair labor/cost book Chevy provides to the dealerships calls for dropping the tank and something like 2 hrs of labor.
That is interesting. The service manual says not to pull the tank, but the flat rate book "pays" them to.


Originally Posted by Yellow95
Wait, it gets better, the car still wouldn't start. Then he replaced the coil and it started and ran just fine.
You're lucky they didn't charge you to R&R the engine to change the coil... or did they? BTW, whose idea was it to replace the fuel pump?

RACE ON!!!
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Old Nov 7, 2005 | 04:33 PM
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hell... I skipped 1 and 4.
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Old Nov 7, 2005 | 04:46 PM
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I think the book may just be using the C.Y.A. policy. You know Cover Your A$$. They are covering theirs in case some shade tree hillbilly decides to have a Marlboro hanging out his mouth during the process of removing the fuel pump without draining the tank. Or uses his ligther to look in the tank.

Now as far as dropping the tank!! Well thats just retarded. Must just be one of those "help shops score easy charges" things.

I did mine from the top in about 40 minutes without draining or dropping and I wasn't in a hurry.
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Old Nov 7, 2005 | 04:53 PM
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Originally Posted by skateparkdave
I think the book may just be using the C.Y.A. policy. You know Cover Your A$$. They are covering theirs in case some shade tree hillbilly decides to have a Marlboro hanging out his mouth during the process of removing the fuel pump without draining the tank. Or uses his ligther to look in the tank.
Re-read post number 8. Draining the tank makes for a bigger explosion. A full tank explodes with a lot less violence, but the fire lasts longer.

RACE ON!!!
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Old Nov 7, 2005 | 04:55 PM
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Originally Posted by skateparkdave
I think the book may just be using the C.Y.A. policy. You know Cover Your A$$. They are covering theirs in case some shade tree hillbilly decides to have a Marlboro hanging out his mouth during the process of removing the fuel pump without draining the tank. Or uses his ligther to look in the tank.

Now as far as dropping the tank!! Well thats just retarded. Must just be one of those "help shops score easy charges" things.

I did mine from the top in about 40 minutes without draining or dropping and I wasn't in a hurry.
As CFI-EFI noted, the chance of explosion/fire might well increase, rather than decrease, with the tank drained than with it full, so I don't see this as a likely explanation.

I can only guess that some mechanics who didn't bother to look it up would just presume that the tank must be dropped, as this is the case on many vehicles. I dunno...

Be well,

SJW
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Old Nov 7, 2005 | 05:02 PM
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So maybe they should add some billable hours to that job for purging the tank with nitrogen and steam cleaning it first?
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