'79 924 n/a wont turn over.

[rrya4281]

So i recently acquired a 1979 924 n/a that was not running. The guy I got it from had been starting it a couple times a year just to keep everything in check, but this summer couldn't get it started, so it ended up in my garage. I thought i could just replace the battery and have it going in no time, but that wasn't the case. So i took the logical steps and replaced the starter, and the power wire from the battery to the starter, and battery cable ends. I have checked grounds, and they all seem ok. So here is the problem I am having, when I turn the key all the electronics come on fine, power to everything every time, however when i turn the key to start i can hear the starter engage the flywheel, but doesn't seem to have enough power to turn the engine over, so i don't think it has anything to do with the relay because there is obviously power getting to the starter. That being said i have manually turned the engine over with no problem, so i know the engine isn't seized or anything. Anybody have any ideas of where to go from here?

[rrya4281]

Brand new battery, new starter, Positive cable replaced, negative cable replaced, cable ends replaced, grounds checked...

[jeffrsmith]

I would double check the grounds. Try running a jumper cable from the negative post of the battery directly to the starter case, if it works you know you have a ground issue that needs to be dealt with. If this is the case you can work back from there.

[rrya4281]

Done, thank you jeffrsmith, that was exactly the problem. Now on to the next problem...I think its a fuel pump issue, I'm not hearing the fuel pump at all, and its turning, but not starting.

[jeffrsmith]

Sorry, can't help with that issue, I am not familiar with early 924's.

[jeffrsmith]

I did a search, check these links out, they seem to have some good info related to the problem you describe

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/634418-fuel-pump-test-engine-will-not-start.html

Fuel

924.ORG FAQ

[rrya4281]

Thank you, that is great info. And I appreciate the help, even though I have worked on cars for over 15 years, this is my first Porsche and am finding it quite challenging, in a good way.

[ditch68]

Fuel pump relays frequently fail on these. You can jump out the relay (I don't recall which terminals off the top of my head) to test the fuel pump with no relay. BUT, the relay is a safety feature, these cars have about 75psi of fuel pressure when running, and if you crash, and the engine stops, the fuel gets cut off. Imagine fuel being pumped at that rate after a crash, very dangerous. With the relay jumped, the fuel will just keep pumping!

Also, the system likely lost it's prime from sitting, so it will take a bit of fuel pump running to get it pressurized.

Tap the ignition and bump the engine over, then let go of the key and let the pump run for the couple seconds it will. It will shut off, repeat this procedure until it is primed and tries to start. Start it with the gas pedal floored.

Go over to the 924 board and search, all the answers are there!

924Board.org :: Index

Jeff

[jeffrsmith]

Originally Posted by rrya4281

Thank you, that is great info. And I appreciate the help, even though I have worked on cars for over 15 years, this is my first Porsche and am finding it quite challenging, in a good way.

I too am on my first Porsche, definitely different from wrenching on domestic makes.

[rrya4281]

So, I replaced the fuel pump relay and still no dice. I read the shop manual and still can't figure out why the fuel pump isn't getting power, I can hear the relay clicking when I turn the ignition to "on". But its obviously not sending power to the pump...

[tamathumper]

Does the pump run when you jumper the relay?

[rrya4281]

I have searched how to jumper it and can't find anything specific enough that helps, the shop manual says L14 and L15 but nothing on the relay or the board have markings like this. So I tried searching what color the wires are to jump, and can't seem to find that info. So any help would be appreciated.

[mytrplseven]

Originally Posted by rrya4281

I have searched how to jumper it and can't find anything specific enough that helps, the shop manual says L14 and L15 but nothing on the relay or the board have markings like this. So I tried searching what color the wires are to jump, and can't seem to find that info. So any help would be appreciated.

If your starter isn't turning over to start with, is there some reason we can't rule out the ignition switch? I'm not familiar with 924's but if the switch is defective or the connector has fallen off the back, wouldn't this be a possibility?

[rrya4281]

The starter is now turning over just fine, in fact the car starts perfectly if i spray starter fluid in the intake manifold. I am not getting power to the fuel pump, so i replaced the fuel pump relay, that did not solve the probelm, and i am unable to find any info on exactly which two wires i need to jump together to get power to the fuel pump to test it. The shop manual i have says to jump L14 and L15, but i have no idea which wires those are, there are no markings on the relay, or on the relay board that even remotely resemble those numbers, and all of the articles i have found online are for 944's which is no help because the relay panel is competley different than mine.

[jeffrsmith]

Take a look at this, it talks about what wires to jumper to test the fuel pump - doesn't mention L14 and L15.

Acknowledgements

[rrya4281]

Thanks for the link, that is very helpful! I will be making a jumper this weekend and see if I can get this car fired up!

[Slam]

Why not drag a battery to the rear of the car, disconnect the pump electrics and then put 12V through it to see if the pump kicks. It may be slugged up after sitting. Then check and clean the pump ground. Run a long wire from the batt positive in the car and see if the pump kicks again. That'll tell you a lot. Also, have a look at the fuel dizzy. There should be a switch on the DS of it that engages when the air plate moves. It's a cutoff switch activated by airflow. Another simple fix, that should be done anyway, is to replace the ignition switch electric portion. If that's bad you can crank all day and get nowhere.

[rrya4281]

*UPDATE* So I finnaly got some time to mess around with this car. I replaced the fuel pump and fuel filter, and was able to get the fuel pump to work perfectly while i used a jump to bypass the relay. So the car started and ran perfectly. My issue now is that after getting the fuel pump mounted to the chassis i am no longer getting power to it even with the jumper in place. The fuse seems to be just fine, and i changed nothing other than using the factory mount to strap the pump to the chassis. I checked both the constant 12v wire and the ignition 12v that are going to the relay and they are both getting power just fine. So I am out of ideas other than the power wire going to the fuel pump being cut or something, but it worked fine for short time, and only gave me problems once the fuel pump was straped down, so i doubt that its an issue. Are there any other factors that im not taking into account that anyone can think of? Im going to take another look at it this weekend, hopefully i can get this car up and running well.

[fiat22turbo]

The pump grounds to a ground point between the rear taillights. Check that to make sure it is clean and tight.

[rrya4281]

I will check that, sounds like it might me the likly culprit because when i ran the test on the puel pump it was working great, but it was hanging by the leads witch might have put enough pressure on the ground lead that it was able to make a good connection.