 Fuel pump, replace in kind or relocate? |
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| enf2232 |
 Aug 8 2023, 10:51 AM
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#1
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Member  Group: Members Posts: 86 Joined: 13-July 14 From: Toledo, OH Member No.: 17,621 Region Association: None  |
Fuel pump is bad and needs replacement. We can replace with original 3-port in original mounting location or update and relocate to the frunk? What are your opinions?
'72 with non-original engine. 1.7 upgraded with larger displacement cylinders, original fuel injection. |
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Replies(1 - 8)
| brant |
Aug 8 2023, 10:54 AM
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#2
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914 Wizard Group: Members Posts: 11,623 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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3 port pumps are hard to find, expensive to rebuild now a days...
most people will replace with a 2 port pump because they are available and relatively cheap 2 port + 100$ or less 3 port + 400$ or more the relocation to the front (done by the factory in 1975) helps reduce the chance of vapor lock. but were you experiencing vapor lock in the past during hot days? the big bore cylinders mean you might also need 2.0 injectors to move more fuel. or increased fuel pressure.... but you need to use an AFR wide band to tell and to adjust your MPS for the the new displacement. not adjusting means running lean and increased wear or damage to your new motor. |
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| VaccaRabite |
Aug 8 2023, 11:46 AM
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#3
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En Garde! Group: Admin Posts: 13,444 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
Move to the front.
Replace with a 2 port pump. They make the routing of the fuel lines so much easier! Zach |
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| JamesM |
Aug 8 2023, 11:59 AM
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#4
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Senior Member Group: Members Posts: 1,900 Joined: 6-April 06 From: Kearns, UT Member No.: 5,834 Region Association: Intermountain Region |
2 port in the front
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| enf2232 |
Aug 8 2023, 12:29 PM
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#5
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Member Group: Members Posts: 86 Joined: 13-July 14 From: Toledo, OH Member No.: 17,621 Region Association: None |
QUOTE(brant @ Aug 8 2023, 12:54 PM)  3 port pumps are hard to find, expensive to rebuild now a days... most people will replace with a 2 port pump because they are available and relatively cheap 2 port + 100$ or less 3 port + 400$ or more the relocation to the front (done by the factory in 1975) helps reduce the chance of vapor lock. but were you experiencing vapor lock in the past during hot days? the big bore cylinders mean you might also need 2.0 injectors to move more fuel. or increased fuel pressure.... but you need to use an AFR wide band to tell and to adjust your MPS for the the new displacement. not adjusting means running lean and increased wear or damage to your new motor. There was one incident when I might have had the occurrence of vapor lock. Stalled and had trouble restarting but waiting a while and it started. That was before engine work. I can't speak to the injectors right now. Lets assume the mechanic that did the engine work knew what he was doing and changed at that time. I will review parts to verify. |
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| Dustin |
Aug 8 2023, 12:49 PM
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#6
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Member Group: Members Posts: 111 Joined: 19-August 10 From: Woodland Hills, CA Member No.: 12,072 Region Association: None |
QUOTE not adjusting means running lean and increased wear or damage to your new motor. I've heard this before. But, why does running lean lead to increased wear or damage? |
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| brant |
Aug 8 2023, 01:48 PM
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#7
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914 Wizard Group: Members Posts: 11,623 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains
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Air cooled motors are much less heat consistent than a water cooled motor
This is the reason they have to run lower compressions than a water cooled motor Lean will increase heat and also increase pre detonation IE : a hole in your piston and higher operating temperatures The fuel mixture is responsible for a portion of your head cooling Air cooled motors like to run rich and hate to run lean |
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| porschetub |
Aug 8 2023, 02:06 PM
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#8
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Advanced Member Group: Members Posts: 4,699 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
QUOTE(Dustin @ Aug 9 2023, 06:49 AM) QUOTE not adjusting means running lean and increased wear or damage to your new motor. I've heard this before. But, why does running lean lead to increased wear or damage? Lean condition will make the car run poorly ,but the worst problem is overheating and resulting high oil temps ,this also leads to cylinder head failure ,burnt /broken exhaust valves and valve seats that come loose . Engine oil will become too thin and not provide sufficient lubrication to bearing , IMO probably the worst thing to happen to an aircooled engine . |
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| brant |
Aug 8 2023, 02:14 PM
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#9
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914 Wizard Group: Members Posts: 11,623 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains
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Agreed
The worse thing you can do to it |
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