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Error401 Error401 is offline
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Join Date: Jul 2010
Posts: 6
'74 2.0 fuel pressure and vaporlock problem

I'm having an issue with my fuel system that has something to do with either the pressure regulator or the check valve in the pump.

I inherited my fathers '74 2.0 914/4 back in 12/08. The last inspection sticker dated from '94. It was garaged during it's hibernation, but it was not prepped for such a long sit.

I had to replace nearly the entire fuel system. Tank, lower lines, strainer sock, pump, filter, (upgraded to metal) tunnel lines, injectors, injector seals and upper lines were all replaced. The only original fuel system parts still in the car are the fuel rails, pressure regulator and the cold start valve. I also replaced the points, plugs, plug wires, dist. cap and rotor, as well as timed it.

It ran great for a couple of months after getting it running again, but it started to get cranky about starting when warm, then it started not starting at all (luckily it was parked at my house when that time came). I put a pressure gauge in line with the CSV to check and set the main pressure regulator. Cycling the key resulted in the pump turning for a second or two, but no pressure. I unhooked the line that goes into the regulator and checked for flow, none.

So, this past weekend I got motivated to get it running again. I decided to try swapping out the FP relay with a new spare and discovered that there is a main engine fuse right next to it (I had replaced all the fuses in the cabin way back when). It was pretty nasty (not blown, just oxidized), so I replaced that too.

Now when it's cold (70f or so) I can hear the pump spin and some gurgling from the tank and it'll start. Pressure gauge reads 28-29psi and life is good. Let it warm up and then shut it off, the pressure bleeds off to 0 in less than a minute and it will not start back up. It takes a couple of hours before it'll start again.

I guess my question is this, what should I look for or test to see why the pressure is dropping so fast, setting up a vapor lock. I read somewhere that he check valve is there to keep pressure on the system to prevent a VL situation. And before anyone asks, the pump was moved up front a long time ago. The replacement pump is a rebuild though. Could the regulator be at fault (it does hold a constant 28-29psi when it running)? If the check valve in the pump is wonky, is there an inline CV that I can use?

Any suggestions or ideas are greatly appreciated.

Old 07-07-2010, 08:31 AM
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