Fuel pump lines.... 3 vs 2

[AlexO]

I'm pretty sure my fuel pump is shot. I'd like to swap a know good one in its place to get rolling again... problem is, the only spare pump I have is off my '86 VW with CIS-E. I know it can supply enough fuel, but it only has two fittings, in and out. The 914 fuel pump has 3, so what's the 3rd do and is it really *that* important? Can I just plug it off maybe?

I'm on my way out to get the pump out of the other car, so hopefully I'll be telling you guys how well it worked....
--Alex
-'74 2.0

[Dave at Pelican Parts]

The third fitting is for a return directly from the pump. It connects to a "Y" fitting that goes to the return line in the center tunnel and the fuel pressure regulator.

Replace the "Y" and its hoses with a single piece of hose. Run it from the plastic line coming down through the engine tin, to the center tunnel line.

The important things about a fuel pump are: 1) that it delivers enough pressure, but not too much for the system to deal with; 2) that it delivers enough volume; 3) that the hose fittings are the right sizes; 4) that the electrical connections are correct and the pump doesn't draw too much power for the existing wiring; 5) that it physically fits in place.

I have no idea if your GTI pump meets any of those requirements. Note that too much pressure can cause leaks, and may damage other parts of the fuel system. Also, having the hose fittings the wrong size can cause leaks if you "force" the hoses to fit. Leaks are bad... Keep a fire extinguisher handy!

--DD

[AlexO]

Alright, thanks Dave. I'll have to do some checking up on the pump specs, but at least you straightened out the 3rd hose thing. And about the fire extinguisher.... Gunna have to get a new one, had a small incedent with a MIG welder and a fuel leak....
--Alex

[AlexO]

Well, I checked out the vw pump and its got a banjo fitting on it, screw that. I'm pretty positive that its the pump though. When I turn the key on, it cycles like normal, but pressure only builds to 5psi or so. If I cycle the key quickly, I can get 30ish, but once the pump shuts off, pressure drops completely. Sound like a safe bet?
--Alex

[Dave at Pelican Parts]

Nope. This sounds like normal behavior--except for the part about the pressure dropping quickly. That will make for difficult starting when the engine is warm, but you can overcome that by doing the key on-and-off thing a few times before you try cranking it over.

The pressure drop may be caused by a leaking injector (you weren't pumping the throttle when the pressure dropped, were you?), or a fuel pressure regulator that is leaking, or a leak back through the fuel pump.

The primary suspect (in my eyes) would be the cold start valve. Pull it out of the manifold, build fuel pressure, and see if the CSV leaks or dribbles fuel. If so, replace it.

--DD

[Jim Smolka]

Alex,

Also check to make sure all the lines are not cripped or that the fuel filter is not clogged or that the tank to fuel pump line is not clogged... (3/8" line)

my $0.015 cents worth



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Smoke Daddy