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Cadillac
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Discussion Starter #1
Hi there.

I have a 69 472. I am taking out an electric fuel pump (previous owners LPG conversion) and returning to use of the mechanical fuel pump.
I bought a new carter mech pump.
I have installed the pump, but I am unsure of what fuel line goes where..

There are 3 ports on the pump. one with an inline filter, and two others, one is smaller than the other. I am guessing the filtered one is the inlet into the pump. the other port is the outlet to the carb, and the smallest one is the return line to the tank.

I have it set up this way but the car will NOT start, it sputters occasionally. I have also tried pouring some gas down the carb and also tried starting ether spray.

Please HELP. the shop manual is not helping me.

Cheers

Jon
 

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1969 Coupe DeVille, 1972 Sedan DeVille
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159 Posts
I believe you got it backwards. The fitting for the metal line (which has the filter behind it) goes to the carb. The larger barb for a rubber hose goes to the tank. The small barb for a rubber hose is the vapor return line to the tank. The line to the carb is furthest forward when the pump is mounted, the inlet line is the next one back and toward the passenger side, the small vapor return line is on the aft side. You've got the filter at the inlet to the carb too.
 

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Discussion Starter #3
Thanks for your reply.

Well, I have now reversed them.
The car will still not start !
there is no fuel flow to the carb at all.

I'm really stumped now.

Could I have broken the new pump by trying to start the car with it hooked up wrong??

I'm totally depressed about this now ! ! I've never been without the car running as long as I've had it. And I have promised to drive the car at my friends wedding in 2 weeks time. He will be very disappointed if they can't have a ride in the caddy

Any ideas or tips on this no fuel prob?

thanks

Jon
 

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'80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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The pump shouldn't kill itself even if hooked up incorrectly. You might try filling the carbonator through the little round vent with gasoline to get the thing running long enough to prime itself. This method will keep the engine lit longer than gas down the throat. You could check for suction at the pump inlet if it won't work after that.
Later GM fuel filters come with a little "rollover valve" installed. If yours didn't originally have this thingy then remove it. Keep the rubber gasket part. Just remove the plastic guts. That one got me once. Could be that the engine has no eccentric for a mechanical pump installed too. Maybe someone left it out during a timing chain job as the car had a mechanical pump anyway. Here's a pic of one. http://cgi.ebay.com/ebaymotors/Cadillac-472-500-Fuel-Pump-Eccentric_W0QQitemZ180058614470QQcmdZViewItem
 

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1970 Eldorado Fleetwood
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I have a 1970 with a 500, but Carter lists the same fuel pump for both. On my car, the nut with the filter behind it goes to the carb. I checked both the shop manual and the Chilton manual for '67 to '89 and neither gave any indication as to which port is suction and which is vapor. They just say, "Hook the line from the gas tank to the suction port". On my car, one port has a larger diameter than the other. That is the fuel suction port. The smaller one is vapor. If yours has different sizes, try hooking the larger one up to the fuel tank.

I also checked Carter's site which was devoid of any technical info on the pump other than they make it (and warranty info). I'm assuming you ended up with Carter part number M6622?

If all else fails, you can call Carter in Southfield, MI at 248.354.7700. "Nice pump...how about some directions?!"

Good luck!
 

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'80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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The smaller fitting is a fuel return. The pump constantly circulates fuel. Extra pressure is routed back to the tank. This helps cut down on vapor lock which is a bigger headache on older high compression cars.
 
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