I finally got my car what I thought was running right. However after a half hour drive the car started to buck at around 3000 rpm. When I came to a stop the car just died. It would restart, but as soon as I gave it some gas it would just die. Acted like it was starved for fuel.

The TPS has been adjusted per the tech articale on pelican. The plugs look good, pump runs and is getting fuel to the cylinders. I thought it could be the fuel filter. This is where it gets strange. My car is a 74 which should have a small inlet and outlet. The filter is in its stock location but has a small inlet and a large outlet like the filters on a 75, 76.

The filter on the right is the replacement, the filter on the left came out of the car.

Click to view attachment

The fuel pump was relocated to the front at some point.

Couple of questions.

#1 Does anyone have pictures of a installation and did you leave the filter in the stock location?

#2 Should the filter be between the tank and the pump,not after the pump?

#3 The fuel filter that I removed was bulged outward. What could cause this?

I'm sure I will come up with more questions. Just a little tired right now.

My filter is after the pump. The filter I have is the small in and big out. If you're getting the right amount of fuel pressure I don't think that is the problem unless the pressure changes once you try to give it fuel. Can you have a pressure gauge on there and have someone watch it while you push on the accel?

Plastic fuel filter should never be on the pressure side of the pump, always on the suction side. Too much chance of the plastic failing from the pressure, they weren't designed to be under pressure. The bulging might be a sign yours is ready to fail. I has seen the plastic filters leak from the pressure of the fuel sitting in the tank. There is a nice BMW metal FI filter that has small in small out fitting for clamped fuel hose that could be used, not sure what else is out there but I am sure there are other.
I would suggest that if you have relocated the fuel pump up front then move the filter up front as well. If you don't has an access panel to get to the pump and filter up front them put a metal filter in the rear.

Jim

One of Babydoll's ('74 2.0) previous owners moved the fuel pump up front, by the steering rack. The filter is a square plastic one like your picture. It sits between the fuel tank and the fuel pump. On the tank end it has a large nipple and on the pump end it has a small nipple. Seems like a convenient way to convert hose sizes between the tank and the pump.

Make sure you have good tunnel fuel lines if you're pumping high pressure fuel through them.

Here's a pic of my 74's front mounted fuel pump. Filter is in-line from tank to pump.

If your car is dying and your filter is clogged (bulged filter), perhaps your tank is full of junk? The tank in my 71 was completely full of rust "crunchies" that clogged the fuel line and car would start but was not drivable as it would stall as soon as I hit the gas and took off.

Yep. Filter goes before the pump.

You want clean fuel going thru your pump.

Also go your FLAPS and find a filter with a metal body. They come in all sizes. Just for a little pice of mind.

The lines coming out of the tunnel are in good shape. Another question is why are there two lines coming out of the tunnel? There is a small line and a bigger line. Is one of them a return line and if so which one is it?

This picture is of the lines coming out of the tunnel.

Click to view attachment

The big line had the filter on it. On the other side of the filter is a small line that goes into the engine compartment and feeds the #3 and 4 cylinders. The other line also goes into the engine compartment and feeds the #1 and 2 cylinders.

I pulled the carpet back in the passenger foot well to see if there was a acsess panel but I got not get the foam block out. I would have to break this into pieces to get it out. Any ideas on this?

Large line was the supply from the fuel tank, gravity feed to the original pump. Small line is the return from the fuel pressure regulator, driver side of engine compartment.

The OE access panel for front pump is in the front trunk. I have seen relocation jobs were there is no access panel, where they mimicked the OE set up and where they strapped the pump and filter to the steering rack or cross beam. So if yours has been relocated, you're just going to have to look around.

Under the passenger floor foam block would not be a good place since a fuel leak could put fuel in the passenger compartment.

Good luck
Jim

If you're moving the fuel pump to the front, that means you are pressurizing the fuel lines between the front of the car to the engine compartment. Those plastic lines were never designed for that kind of pressure.

I think you're nuts to not replace those lines with stainless steel lines. They cost about $85.00 for the pre-bent units, take an hour or so to replace (with the engine left in-place), and provide the ability to correctly handle the pressurized fuel delivery.

Why take a chance???

Let's clear this all up in one post. The filter is BEFORE the pump. ALWAYS. Metal ones, too. Metal filters from your FLAPS are not likely to be FI rated filters, so you want one from a BMW Tii. Dealer item, and readily available. The large line is supply to the pump, and there's a nice little step-down hose from the line to the filter. The 2-size fitting filter is larger on the outlet side (not the inlet), and isn't the same "larger" as the hard line anyway, so it won't work. The feed line goes from the filter to the pump, and from the pump the pressure line goes to the 3/4 injector rail. From there, it goes across the engine to the 1/2 side, ending at the fuel pressure regulator. On a 1.7 or 1.8, it goes through the cold start valve on its way across, right by the distributor. On a 2.0, the CSV is on a line from a tap on the 1/2 injector rail. From the FPR the return line goes across the engine on the rear side, down through the body and back to the tank. It's the smaller diameter hard line. On cars with the 3 fitting pump, the return line is joined by the pump return line in a "Y" fitting near the pump. There is no access panel from the interior to the fuel tank. That's probably a mandated safety rule.

On cars with a 2 fitting pump, the pump is located below the tank, behind a panel on the left side of the trunk firewall.. The tank has a smaller outlet than the earlier tanks, and has a 7.5mm line to the filter. From the filter, a 12mm hose goes to the pump, and a 7.5mm line goes from the pump to a 8mm hard line to the rear. Note that this is smaller than the same line on the earlier cars, so no adapter hose was used. They use a return line directly to the tank, with no "Y" from the pump.

Some people believe there is a vapor lock problem and move the 3 line pump to the front. That's OK, but you need to keep the order of parts intact, and run wires to the front from the existing plug under the car. I don't believe the problem exists, but what do I know.? I've only got 35 years experience on these cars ....

Good luck, The Cap'n

The previous owner is the one who moved the pump up front at some point. I am starting to think I should locate the pump up front and move it back to its original location. The large line feeds the fuel to the injectors. This is the line the filter was on, and on the filter the flow would be backwards hooked up this way.

I believe the filter was put on to make a junction between the large line coming out of the tunnel to the small line going to the motor.



The bmw filter you speak of is available at the beemer dealership?

Yeah, in this one instance, the Cap'n looks to be correct.

A somewhat late reply, but there is, or at lease was, a very real vapor lock problem with the original pump. I am posting this mostly for others referencing this in the future.

My brand new '73 914 left me stranded about 5 times during the first month I had it. I had it back to the dealer each time, and the poor mechanic who did the pre-delivery inspection had to try to find out what was wrong. He exchanged every component on the FI system, one at a time, each time thinking the problem was fixed. Replaced fuel filters, hoses, etc. etc. I would take the car back, and then later after it was suppposedly fixed, usually when I would stop at a stoplight or tool booth, the car would just die in the middle of traffic. I was so pissed, as this was my first new car, and it was turning out to be a POS. Fortunately, I later got it fixed.

Turns out the summer of 73 was a pretty hot one in the eastern US. Somewhere around the end of the summer, the factory had a fix for the problem. This was to basically take off the baffle on the passenger side heat exchanger flapper valve and add a small hose to route the air that blows through the heat exchanger away from the pump. The original bafle (which was a kind of open cap) actually directed the hot air onto the pump, causing the problem. If anyone is interested to see if their car had this modification, the driver side flapper valve should still probably have the cap baffle.

Where can you get the prebent lines? For people that haven't used prebent lines what type of flare did you use on the ends to clamp high pressure lines on?

Check out member vendor Tangerine racing. Link at top of page "CFR". He sells really nice stainless tubes. They now have flares on the end to keep the hoses on.

Not to be argumentative but why would the metal filter have to be FI rated. they are not under pressure in this arrangement. I could see them needing to be FI rated if they are like a GM vehicle mounted on the frame after the in tank pump and under 40 - 60 PSI, but mounted on our 914's they are under gravity feed from the tank. In my thinking you should be able to use any good quality filter, or am I not seeing something?
JIM