newbie need electrical/fuel pump help

jim912928 · 10-11-2003, 03:34 PM

Hi, just got a 75 914 project car (haven't owned a 914 since 1976!)...it is rust free, but hasn't run 6 years. I took out the plugs, squirted some oil, changed the oil, put in a battery and turned it over. Lights come on, engine turns over freely, heater blower works, spark at plugs...but fuel pump doesn't buzz. I tested for voltage at the pump and nothing. I put in new fuses at the relay board..nothing..i switched around relays that work into the fuel pump relay slot...nothing. Any suggestions?

Thanks...Jim

p.s. i'm also working without manuals until they come..so bare with me alittle...but I've got the bug to get this one running!

Dave at Pelican Parts · Dave at Pelican Parts's Garage

What kind of fuel system does it have? Carbs or injection? If injection, is it D-jetronic (silver grenade-like thing over on the right wall of the engine bay with one vacuum hose and one wire bundle going to it) or L-jetronic (air cleaner over on left side is bolted to a small box with a quarter-circle 'bump out" in the side of it)?

All of those control the fuel pump differently. With carbs, you're at the mercy of whomever converted it over. The power comes from whatever they wanted to hook it up to.

D-jet has the ECU switch on the fuel pump relay which lives on the relay board. Happens when the starter is engaged, when the engine is running over ~100 RPM, and also for ~1.5 seconds when the key goes from "off" to "on".

L-jet hooks the pump up to the "double relay" that hangs off the battery tray. A switch inside the air flow meter runs the pump when the vane in the meter gets moved by incoming air. The starter circuit is also hooked up to trigger the fuel pump section of the dual relay.

The particular system you have will determine which direction you start troubleshooting in.

--DD

jim912928 · 10-11-2003, 06:04 PM

Thanks Dave for your quick response, stupid me should have said what type of fuel system was installed. It is the L-jetronic...has a square aircleaner on the drivers side..and the double relay that hands off the battery tray. For more info, this car sat outside in the southern california desert area for 6 years...so very dry...and alot of fine dirt over everything.

MontyQ · 10-13-2003, 08:53 AM

I had a similar problem with an AZ car that had sat in someone's driveway for a couple of years. Turned out to be a bad connection in the bypass that someone had wired for the seatbelt warning relay that sits under the passenger seat.

Monty

Tidybuoy · 10-13-2003, 03:13 PM

Since you have an "L-Jet" 1.8 motor, the only way that the fuel pump will run is when the engine is cranking. The air flow meter controls the fuel pump. To test the fuel pump when the engine is not running, you remove the square black cover over the air flow meter (about a 3 x 4) cover that is kinda glued on & will need to be pryed off. Then, with the ignition on, if you manually turn the air flap, you should hear the fuel pump.

Since you car is a 1976, the fuel pump is located in the front trunk under the gas tank. It may be hard to hear the fuel pump so you might need to use something to hold the air flap open well listening up front.

Another thing, the fuel pump relay is a duel relay bolted to the side of the battery & get corroded very easily. Unplug & clean up with a wire brush & this may help.

Vern

D7N7MASTER · D7N7MASTER's Garage

If you just need to know if the fuel pump is functional, hit it with a remote 12V source. No noise. No pump.

jim912928 · 10-13-2003, 07:46 PM

I checked the fuel pump by hooking it up directly to a 12v source..no noise. However, I also get no voltage to the wires at the pump...so i need to clean those double relays by the battery, check the passenger seat (seems like two heavy yellow wires were cut...and taped together as if they were looped.

Tidybuoy · 10-14-2003, 07:29 AM

The thing under the passenger seat is the seat belt device that prevents the car from starting if the belts are not fastened.

There was a Porsche fix on this which included connecting the large yellow wire to another one (I'm not sure which) but someone on this board knows about this.

Vern

MontyQ · 10-14-2003, 08:32 AM

The large yellow wires were the problem on my 1975 with the same symptons...

Monty

robphelan · 10-14-2003, 09:27 AM

I had a similar prob w/my carb'd 2.0 - turns out the wire to the coil was popped off - no power to the pump

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Definitely a different fuel pump setup than the injected cars!!

I agree with the advice on here about checking the double relay.

You can unbolt the air flow meter from the air cleaner, then turn the key on and stick a pencil or a chopstick or something into the end of the meter to move the vane. That should get the pump to run.

Dig into the wiring diagrams for the L-jet system and have at the car with your voltmeter.
http://www.pelicanparts.com/914/parts/Electrical/914_electric_74_AFC-B.jpg
http://www.pelicanparts.com/914/parts/Electrical/914_electric_74_AFC-A.jpg

--DD

jim912928 · 10-18-2003, 04:00 PM

Thanks all for the advice....i was checking electrics at the pump by just turning on the ignition and getting nothing. With the advice here letting me know with L-jet that the air flowing through the meter triggers the pump....i then had someone crank while i put a volt meter on the + and - at the pump.......I get voltage!!!! Since the pump doesn't make a sound it looks like I have a bad pump.

Thanks again to all, and I'll be asking more stuff as i slowly but surely fix things (need to get some manuals soon!).