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Username Post: Fuel Pump Woe        (Topic#356063)
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
04-18-19 10:50 AM - Post#2764479    

my 80 model Chev. Silvarado wasn't starting. Bang -they don't make new carburators so I got a rebuilt.Luckily I have a garage here that know about carbs, so he got it running fine. Now it bogs at any speed @part throttle = timing concern there I've been told (here.) Recently it has not wanted to start again @ no gas in the carb (common - evaporation) but if the check ball in the fuel pump is bad it will push the gas back through the fuel pump and cause a hard start/ no start situation. Ok, get a new overseas $19.95 fuel pump, no problem, that's all that's available here.

I thought I was ok until the mechanic tells me they are all made by the same company and they are cutting corners. My fuel line won't seat because the machining in the pump's inverted flare fitting isn't made correctly, and won't fit the stock fuel line. Something about the bottom of the inverted flare (pump) being too flat.
He said he has seen this in every mechanical (Chevy 350 in this case) pump to date. He even made a new line once for the customer and it still didn't seal. It was then he and another mechanic eyeballed both pumps and discovered the problem. The solution - put an 'O' ring in it.

They just do not want these older vehicles on the road - pollution, they say. Probably correct.

Anyone else discovered this pump fitment problem?

Thanks.
Stan





 
YOUNG57 
Frequent Contributor
Posts: 1141

Loc: Tennessee
Reg: 12-06-10
04-20-19 07:44 AM - Post#2764636    
    In response to 4dr 57

“the machining in the pump's inverted flare fitting isn't made correctly”

The inlet and outlet "fittings" are not inverted flares, they are NPT (National Pipe Thread). No wonder they won’t seat and leak.




 
454cid 
Valued Contributor
Posts: 3121

Age: 46
Loc: West Michigan
Reg: 02-18-12
04-20-19 08:10 PM - Post#2764691    
    In response to YOUNG57

  • YOUNG57 Said:
“the machining in the pump's inverted flare fitting isn't made correctly”

The inlet and outlet "fittings" are not inverted flares, they are NPT (National Pipe Thread). No wonder they won’t seat and leak.




Was GM using hose by 80? My 69 Buick had hard line between the pump and carburetor. It's a different engine, but similar components.


99 K3500 RCLB


 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
04-21-19 09:05 AM - Post#2764723    
    In response to 454cid

MY '80 fuel pump has two hose hook ups. 1 is fuel feed the other is a return line. The only threaded fitting is the pump to carb line (metal.)
I have replaced the pump in the past.

Why is this one different? I looked at the old pump, and it is definitely an inverted flare.
The mechanic said the new pump's flare was not made correctly, blocked off, isn't deep enough...like the machine stopped too soon as it was cutting.Very weird.

Has anyone here replaced their fuel pump lately on a 3 line fuel pump?






 
gchemist 
Senior Chevytalk Moderator
Posts: 24929
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
04-21-19 09:23 AM - Post#2764729    
    In response to 4dr 57

I'll have to check mine. It's a three line pump. What's the part number?

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
454cid 
Valued Contributor
Posts: 3121

Age: 46
Loc: West Michigan
Reg: 02-18-12
04-21-19 10:50 PM - Post#2764793    
    In response to 4dr 57

  • 4dr 57 Said:
MY '80 fuel pump has two hose hook ups. 1 is fuel feed the other is a return line. The only threaded fitting is the pump to carb line (metal.)



Oh, ok. I was thinking of the carb to fuel pump, not the supply line to pump... that would have to involve a short length of hose for vibration.






99 K3500 RCLB


 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
07-14-19 08:21 AM - Post#2770666    
    In response to gchemist

  • gchemist Said:
I'll have to check mine. It's a three line pump. What's the part number?




He didn't put the PN on the receipt.
Summitt Racing has a sweet little 3 port fuel regulator valve. An inline Walbro would finish it off just fine. But I'm getting too old to want to deal with such things.

Now the "Flat Spot" when I push down on the gas at any speed condition is beginning to get worse I guess. A/C on in traffic at a light - press the pedal to take off, the flat spot , and the motor dies (3x's) The timing needs checked - of course everything dirty-the damper area, can barely see it tab, jeeeze..........not to mention its only cool outside in the mornings. And the radio isn't working anymore although I can hear the click thru the speakers. The motor does start well, no gas pedal, just turn the key and wait until it starts. Glad everything else is acceptably in working order.
Stan

It's all good. mostly




 
BoniOni 
Member
Posts: 31

Loc: Austria
Reg: 12-04-05
07-15-19 01:08 AM - Post#2770719    
    In response to 4dr 57

the hard line - pump to carb has double flares on both ends and threads on the inverted flare nuts are NPT. if there's a leak it's up to the line's flares mostly, when they don't match perfectly. If there's a leak, retightening for several times sometimes helps, especially for stainless steel lines this is almost a must in the first time after installation since stainless steel is stiff and gradually needs to adapt to the connected fitting, tin coated steel lines have a "softer" surface on the flare due to the tin and mostly seal instantly. older components usually have a "wear pattern" on the flare that tends to leak when used on a new fitting (fuel pump outlet in this case). I have a flaring tool and did some of these lines on my own already, in some cases I need to redo a flare since it won't seal, even if the double flare "looks good".



 
BoniOni 
Member
Posts: 31

Loc: Austria
Reg: 12-04-05
07-15-19 01:08 AM - Post#2770718    
    In response to 4dr 57





Edited by BoniOni on 07-15-19 01:11 AM. Reason for edit: No reason given.

 
Mad Professor 
Contributor
Posts: 104

Reg: 12-30-08
07-25-19 07:38 AM - Post#2771523    
    In response to 4dr 57

Do you need the return line?

If you can do away with that I'd put on a Carter mechanical pump.

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
89 S10 baja package







 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
07-28-19 05:28 PM - Post#2771839    
    In response to Mad Professor

  • Mad Professor Said:
Do you need the return line?

If you can do away with that I'd put on a Carter mechanical pump.




Good idea - - except I do not want to complicate umm ... things. The truck is 40 years old and it is hard enough finding competent carburator guys, who seem to be the only ones willing to even look at old vehicles. But hey thanks for the energy, I appreciate 9it.
Stan



 
BoniOni 
Member
Posts: 31

Loc: Austria
Reg: 12-04-05
07-29-19 02:26 AM - Post#2771872    
    In response to 4dr 57

without return line you have an increased risk of vapor lock, since vaporized fuel escapes through the return line. Most older mechanical pumps for vehicles built around 1970 have no return line and I had no problem so far having none.



 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
08-03-19 09:07 AM - Post#2772299    
    In response to BoniOni

  • BoniOni Said:
without return line you have an increased risk of vapor lock, since vaporized fuel escapes through the return line. Most older mechanical pumps for vehicles built around 1970 have no return line and I had no problem so far having none.





The canister lines as well as the return line are intact.
I'm going to bring the NPT fittings on the new fuel pump to the mechanics attention.Thanks guys!
Thanks.
Stan

It's all good. mostly




 
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