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Posted by: David_S Jan 20 2008, 01:05 AM

I started tinkering with my project again a few days ago, and am in the process of getting the engine bay back together. Only problem so far is I had to replace the right engine shelf, and I cant remember how the fuel pump mounts ! I attached a pic of the area where the Haynes manual shows it to be, but the pic in the manual isn't the greatest. Also in the pic, what mounts in the slotted J shaped bracked above the motor mount? It has been too long ago since I tore this thing apart and I screwed up and didn't take enough pictures !!!!!! TIA


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Posted by: cwpeden Jan 20 2008, 02:33 AM

I replaced mine and didnt know either, this is what I ened up with

Posted by: cwpeden Jan 20 2008, 02:36 AM

close up


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Posted by: swl Jan 20 2008, 07:51 AM

Here is the 'as installed' position. The pump mounts by way of 2 rubber bushings - noise and vibration isolation. You can just see one at the top of the pump.

Posted by: SirAndy Jan 20 2008, 11:48 AM

Posted by: Cevan Jan 20 2008, 06:29 PM

Why not relocate the pump to the front?

Posted by: ClayPerrine Jan 20 2008, 09:24 PM

You are better off relocating the pump up front. That way you don't get the vapor lock problem. It will vapor lock, because the hot air dump from the heat exchangers points right at it.

Posted by: David_S Jan 20 2008, 11:12 PM

Havent really thought about it that much ......until now. The heat from the heat exchanger really could affect the pump and vapor lock. I guess now would be the time to do it if I was going to do it !!! Now .....where would it mount to in the front trunk ???

Posted by: SirAndy Jan 21 2008, 10:37 AM

huh?

i ran my '70 1.7L for 6 years with the pump in the stock location. never had a single problem with vapor lock. not even on the 110 deg. central valley drives ...
Andy

Posted by: Phoenix914 Jan 21 2008, 12:02 PM

I just replaced the mounts on my '73 because one of them was broken. The mounts stick through the firewall from underneath into the very bottom of the hellhole. It's probably much easier to do it with the engine out! I was practically standing on my head trying to reach down there. It did give me an opportunity to clean out all the gunk that had accumulated, including the mouse carcass.

Posted by: ConeDodger Jan 21 2008, 12:53 PM

In a properly maintained car you should not experience vapor lock. I suspect that Porsche relocated the fuel pump because they couldn't count on people properly maintaining their cars. In the back it is close to a source of heat and possible ignition for those cars that owners maintain poorly.

At the pressure in an EFI system vapor lock shouldn't occur with a properly maintained vehicle. It is easy enough to relocate if you have the proper mount but a pain to replace it and the fuel filter.

That said, mine is up front. But it came that way...

Posted by: SirAndy Jan 21 2008, 12:59 PM

vapor lock happens on the supply side of the pump. they're notoriously bad at pumping vapors ...
Andy

Posted by: swl Jan 22 2008, 11:42 AM

I suspect that the original engineers located the pump close to the engine to minimize the amount of the fuel system that was under pressure. IMHO if you relocate to the front you MUST get rid of the original delivery line and replace it with a hardline.

Posted by: David_S Jan 27 2008, 11:14 AM

So ....going by the pic that SWL posted .....the fuel pump mounts to the frame rail ?? I looked at a 72 here in town and it appears to mount to the engine tin. My 73 tin does not have holes in the tin in the same place as the 72.

Posted by: swl Jan 27 2008, 11:29 AM

definitely not the engine tin. it stays with the car when you drop the engine. There were (I think) only two mounting locations. Originally they were mounted in the rear according to the picture. Then (75?) they moved it to the front and switched to a 2 port. 72 and 73 left the factory with exactly the same mount and plumbing. My pic is of an unmolested 73.

I'm looking at your pic trying to figure out the two holes that are there and can't visualize how they would be used in mounting the fuel pump. There should be two identical holes, one over top the other. Spacing, of course, is the same as the mounting ears on the pump. Fore and aft locations is with the end of the pump almost up to the firewall.

Posted by: David_S Jan 27 2008, 11:39 AM

SWL ......The small hole in my pic is about 1/4" diameter. It is where the clamp is on the brake line in your pic. The other hole in my pic, the one in the corner, is about 1/2" diameter. I assumed it was for a wiring harness grommet. No holes anywhere else, which is why I think I may have welded them up in my repair. From what I can see of your pic, your pump is attached to the frame rail.

Posted by: swl Jan 27 2008, 11:46 AM

My pump is not installed at the moment - would you like me to get a pick of the mount location without the pump in place? It's not too cold out in the garage today. I might even be able to get you a rough distance forward from the firewall and down from the lip.

Posted by: swl Jan 27 2008, 11:50 AM

hmm. on your pic there are a couple of light spots that are pretty close to where I would guess the mounting points to be. Maybe those are remnants of your welding repairs. I don't think you need to be super accurate with the mounting location - just keep it clear of the firewall and as high as possible and you should be good to go. Do you still have the rubber grommets?

Posted by: David_S Jan 27 2008, 11:56 AM

A pic would be wonderful!!!! I did notice the "spots" you are trferring to, and wondered if that is where it went. I don't have the rubber mounts yet, but they are on an order that I am fixing to place.

Posted by: swl Jan 27 2008, 12:20 PM

just had a quicklook. I tried to grab a pic but I was shooting in the dark and they are pretty shitty. I'll have to try again after I break out the trouble light (I'm in hibernation mode up here in the cold cruel north). Looks like Pelican will send you the rubber mounts.
http://www.pelicanparts.com/catalog/shopcart/9144/POR_9144_FULinj_pg3.htm#item11
901-501-864-00-OEM

Posted by: David_S Jan 27 2008, 12:27 PM

SWL ...not a problem. I know what hibernation mode is like!! I will go look at mine later on, and see what I can find for sure! I was mainly curious as to whether it mounted to the engine tin, the engine shelf, or the frame rail. I guess if it comes down to it, I will just have to drill and tap new holes !!! Thanks for your time !!!

Posted by: swl Jan 27 2008, 12:48 PM

Here is the (shitty) pic of the mounts. I'm really curious as to what that piece actually is. If it is part of the boxed in frame then those mounts must be just tapped in.

Posted by: KELTY360 Jan 27 2008, 01:11 PM

My brand new (~1000 miles) '73 1.7 had serious vapor lock problems in 80 degree weather in the mountains of Colorado. When I finally got it back to the dealer they said, "yeah, we know about this, we'll fix it up." Unfortunately, I don't know what the remedy was, but it worked - never had a problem again.

Posted by: stephestrad Jan 8 2014, 10:24 AM

Apologies for reviving an old thread, but this quote about "properly maintained" cars was interesting. I'm experiencing what appears to be classic vapor lock on my '74 2.0. For instance, the other evening after 30 minutes of driving up in the Berkeley hills, I pulled over and spent about 15 minutes watching the sunset. I'm new to the 914 experience, so I'm still learning the sounds, but when I tried to restart the car, it appeared that the starter cranked the engine over, but the engine wouldn't catch. I let the car cool down for an additional 40 minutes, then she fired up. The engine ran a bit roughly for a few minutes -- by this, I mean each time I came to a stop sign, the idle dropped so low that the rpms were barely registering on the tach and the car vibrated enough that I thought she might die out again -- but, by the time I was home, she was purring as normal.

My car has been pretty well maintained (and generally runs well), so I'm curious, if the original fuel pump placement were not the problem, are there specific parts of the car that should I check? Are there maintenance elements that I may have overlooked, but would result in the same symptoms as vapor lock?

Btw, I'm going to try and test the concept of this being vapor lock this weekend. My plan is replicate the problem, then pull the fuel hoses off the injectors and see if I have liquid fuel, or just vapors. Are there any other recommendations for testing vapor lock?

Posted by: JawjaPorsche Jan 8 2014, 10:44 AM

I moved my pump to firewall twenty years ago and have never had vapor lock problems since. The old location was just too hot. This new location makes changing the fuel filter much easier too.


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Posted by: 914_teener Jan 8 2014, 11:14 PM

I moved mine exactly as it appears above and have had my car in the desert and in traffic in 100+ temps...I have never had vapor lock.

I don't think that your problem is vapor lock though. 80 degrees. You might want to start another thread.

Sounds like a different problem to me.

Posted by: stephestrad Jan 9 2014, 12:33 AM

Thanks to you both for the feedback and the location pointer. The firewall sounds easier than moving it all the way up front.

I'll see how the test goes this weekend, then open another thread.

Posted by: Shindog1961 Feb 23 2014, 11:58 PM

I have heard that this pump location requires you to keep your fuel level up. What is your experience?

Posted by: 914_teener Feb 24 2014, 12:13 AM

No problem with the fuel pump mounted on the firewall if that is what you mean.

I have run my fuel level down to the reserve level all the time.

I have cleaned my tank btw.

Posted by: Shindog1961 Feb 24 2014, 12:23 AM

That's exactly what I meant. Glad to know. I agree that sounds preferable to under the fuel tank.

Posted by: Dtjaden Feb 24 2014, 09:47 AM

In 1973 I had a new 914. I was in Minnesota at that time. It would vapor lock frequently whenever the temp went above 85. My solution at the time was to install a second low pressure pump in the front trunk. So it was not just maintenance issues that caused the problem.

Never a problem with my new 1976. I would put the pump in the front as I am going to do when I convert my current 73 back to FI.

Posted by: KELTY360 Feb 24 2014, 10:34 AM

I bought a new '73 1.7 in July of 1973. I drove about 600 miles, took it back for the initial dealer maintenance service and then left from SoCal on a trip to Colorado. Over the course of that amazing trip with my new Porsche I experienced numerous occasions of vapor lock, stranding me in random places for about 30 minutes before it would run again. When I got home and called the dealer, they said, "oh yeah, we know exactly the problem. Bring it in and we'll fix it up." I'm not sure what they did, but I now suspect they relocated the pump under the tank. Never had a vapor lock problem again. My problems had nothing to do with owner maintenance, just a design flaw that the dealer was well aware of and easily corrected.