928 Guys I need help, Fuel pump ? Options

[spare time toys]

When you turn the key on can you hear the fuel pump like you can on say a Suburban? I am thinking my pump may not be coming on and that is my problem.

[rick 918-S]

Just sent you a pm. (I love this garage (IMG:style_emoticons/default/wub.gif) ) But I forgot to mention, check for power to the pumps. (maybe two, use a volt meter. Sent you several other tips and suggestions in the pm.

peace

[jim912928]

nope...pump doesn't come on with just power from the ignition (at least mine doesn't..I've got an 83). Since I've never had fuel delivery problems I've not done much work here...but the 928's run Ljet fuel injection. If that works anything like the Ljet on my 914 (1.8l) the fuel pump doesn't turn on until an air flap in the MAF moves (when you turn the engine over and air get's sucked in). So, you should hear the fuel pump turn on while pumping the engine over..assuming air is moving the air flow flap thingy in the MAF (ie. it's not stuck).

A great source for 928 help is http://forums.rennlist.com .... go to the water cooled forum and click 928's. Very very active board in the 928 world. The other most active board is: http://members3.boardhost.com/928s4vr/

The 928 guru's hang out mostly on these two sites (been a big help to me).

For parts..the best places are Devek, 928 Specialist and 928 International.
http://www.devek.net/
http://www.928gt.com/
http://www.928intl.com/

Jim

[Joe Ricard]

MOre than likely it is the fuel pump relay. pull it out and clean the contacts and put it back in.
Turn the key the pump will go whhrrr and stop.
Then as Jim described the pump won't continue till the circuitry senses that the motor is turnng over. CIS had sensor in distributor. and 2 fuel pumps. later model only have 1. There is a way to jumper the fuel pump. 1st go back there and pull the cover down on the back of the tank disconnect one of the fuel pump wires and do a continuity check of the pump motor.
What year is that beast anyway? tough to tell you what you got to do.

[rick 918-S]

Ya, I don't recall what year you have... The photo Scott posted looks like you have CIS Injection, (two pumps) but I'm no expert.

[spare time toys]

Its a 84 I stopped off at the Porsche shop on the way home and the guy there told me to try cleaning the relay first. I would but we start Special Olympics basket ball tonight and I have to leave like 10 min ago.

[PorscheTom]

I agree with what Jim912928 said.

My '78 928's fuel pump does not run until the car starts. If it happens to stall, I hear it run for a several seconds before it stops. The key to the CIS injection cars is the antibackflow valve in the fuel filter. If it's bad and allows fuel to return to the tank, the car is hard to start until pressure builds back up.

Check out the Rennlist mentioned and chances are you'll find your solution. It's almost as busy as this website.

Good luck!

[Joe Ricard]

Its a 84 I stopped off at the Porsche shop on the way home and the guy there told me to try cleaning the relay first.

Dang glad I though of that 1st. I need to charge more for my 928 wrench
during the 13 yrs of owning my car I believe I turned every nut and bolt on that car.
in the 3 years of owning 914's I already have turned every nut and bolt on all 3 cars.

[spare time toys]

Its a 84 I stopped off at the Porsche shop on the way home and the guy there told me to try cleaning the relay first.

Dang glad I though of that 1st. I need to charge more for my 928 wrench
during the 13 yrs of owning my car I believe I turned every nut and bolt on that car.
in the 3 years of owning 914's I already have turned every nut and bolt on all 3 cars.

Yea I see that but you posted it while I was on my way home from work. I go in front of the place going home so I stopped off

[spare time toys]

I got power to the punp. I turn the key on it shows around 12 volts then drops after a second or so like it is supposed to. with no cranking. When I go back and listen there is no sound. So I figure its a bad pump. Should I get another pump of this style or just get like a holley unit since it will be plumbed into a front mounted fuel cell? This is the relay board. They say the pump relay is number XX nothing on here is labeled XX. So I dont know where the pump relay is. But with power to the pump it must be good.

[jim912928]

Fuel pump relay is the black one....2nd row, 2nd to the last (next to the big double one on the far right). And on an 84 the fuel pump relay is XVII (position 17).

[jim912928]

also...if you want to bypass the relay (don't do this for long)...but you can pull the relay and jumper terminal 30 and 87. Run it for about 30 seconds or so and see if it pumps fuel. This will tell you if the relay is bad or not. If it pumps gas you should get 1350cc's in a 30 second run.

[skline]

That will test the fuel pump and the lines. Watch for leaks

[rick 918-S]

You'll need a high pressure/high volume pump. a Holley won't cut it. I used a pump from a Volvo Turbo with an accumulator to hold the system pressure. You can disconnect the line at the connection over the right cam. Pumper the relay and check for fuel delivery rate as instructed.

[Joe Ricard]

It's an 84 Rich isn't that an L jet car? system pressure should be more like normal american iron. 30 - 40 PSI. You can also use Ford injectors much cheaper. and a wider range of sizes. 19lb, 24lb, 36, ans 42lb for superchargers.

[jim912928]

Unless it has been changed out...84's were ljet. All US bound 928's were either l-jet or lh-jet. All euro spec 928's up through 83's are k-jetronic then those even went l-jet.