924Board.org

[Rhubie]

So. FML
I bought a 1980 porsche 924 in june that didnt start due to a bad fuel pump I had to replace. Once done with that I replaced the injector line to cylinder 4 from the dizzy due to a leak. After that I thought I was all ready to go but she only sputtered for me. Didn't fully start, but would crank make some noise and quite.

After that I thought I had a vacuum leak. I did. The intake boot but the next rubber piece next to that had a hose that lead out of it with a massive crack. Fixed that.

Started her again. I got her to idle at 400 rpm and then die. Great. Some progress.

Thought Id try new plugs. Did that, tested and got blue sparks.

Now just cranks. And cranks. No start

I thought my car wasn't getting fuel due to the fact that it didn't smell like gas after several times cranking. But heres where it gets really weird.

When I was fiddling around with the fused, specifically the fuel pump one just to make sure it worked, I took it out to inspect it and forgot about it.

Well.. While cranking(without the fuel pump fuse) it started. Idled great at 1200 and died. Obviously because there was no more fuel to burn.

Placing the fuel pump fuse back in she refuses to start.

I need help.

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ALL THE THINGS THAT I HAVE NOTICED

She will not stay running after the starter is engaged, and dies completely after I take the key out of the 3rd position.

Air pressure when she starts without the fuse is at 4 bar.

My idle control thingy right next to the carburetor was disconnected(I can get a picture because I don't know for sure what it is, just a guess)

My ground from the battery to the block gets hot after I crank it several times.

There are 4 wires leading outside of my firewall from where all the fuses and ignition starter is.

2 are grounds. 1 is blue. and 1 red with black stripes that is much thicker.

Bad ground maybe?
Or missing that wire? Im lost.

[Rhubie]

It wasn't the ground.. but the negative. Corroded cable?

[Sunset924]

You need fuel, air, compression, and proper engine / ignition timing to have a running engine. As you had it running, we will assume you have compression and both aspects of timing are in order. You also observed good spark. I am leaning to a fuel issue.

To confirm this, you can take off your air tube to the throttle body and spray in some wd40 or other flammable liquid and attempt to start the vehicle. If it starts and you can continue short bursts of your chosen spray into the intake and have the engine remain running,you have a fuel related issue. Please take caution.

Cis has a few parts but it is not overly complicated (good information on cis troubleshooting can be found on this board). I would say first check for fuel pressure but the proper gauge setup isent common in everyone's tool box.

What I would try next: get access to a digital volt ohm meter, and give this a shot... set your meter to volts Dc and probe the + and negative terminals on your fuel pump. Key on engine off, Have an assistant remove your air filter and lift the fuel plate, note your voltage reading. Now have assistant crank over vehicle and note voltage reading. We want to verify the pump is receiving power.

With the plate lifted you should be within 0.5v of battery static voltage (take a reading directly at your battery) if your pump voltage is lower, you have a voltage drop issue that we can hunt down. While cranking, your reading will be lower (no lower than 9.6v) as the starter will have the potential to draw 200 some amps. In both instances you should hear the pump hum.
If this is not the case, we have a few things we can try next.

If your readings look good and the pump hums, check for fuel off the outlet of the fuel filter mounted in the engine compartment... if you have a good flow of fuel, ideally we need a pressure reading but we can go further into diagnosis of cis without for basic checks.

If no fuel or very little, check for a clogged fuel filter, then to make sure the tank is not plugging the inlet to the pump, and finally for fuel output directly after the check valve on the fuel pump, and we can go from there. Keep us posted and good luck

[KDJones2000]

Sounds like your ignition switch may be bad.

The coil is energized when the key is cranking the starter. It goes through a different path when you release the key.

These switches are a known weak point.

Good luck.
_________________
1987 924S SPEC car
Team Toofah Racing
1988 944 Turbo S

[Eric P]

Let me start off by saying that I have a fairly limited knowledge of these things so take everything I say with a grain of salt.

I bought a 924 a little over a month ago and had a similar issue with the starting then stalling and dying and this is based off my experiences over the past few weeks.

The first step that I would take is to eliminate all air leaks in your intake. The "idle control thingy right next to your carburetor" needs to be hooked up. I believe that you're talking about your AAV (Auxiliary Air Valve) which adds more air to the fuel/air mix to help start your engine. It serves a similar function to a choke on a carburetor. Another thing to note is that unless somebody has really messed with your engine, you have fuel injection and not a carburetor. Check for cracks in your intake and disconnected hoses. Your car will run poorly if at all if you have any air leaks.

Step 2 is to go out and get a toggle switch, a couple short lengths of wire, and a couple blade connectors. Pull the fuel pump relay and wire in the toggle switch between pins 30 and 87 (far left and far right pins on the relay). Note that with this setup the ignition key does not need to be on for the fuel pump to run.

Step 3 pull off the air box and filter so you can reach the air flow plate next to your fuel distributor. You should be able to lift the plate from the bottom side. Pull out your fuel injectors from the head (they just pull out) and point them into bottles. I used plastic water bottles with an x shape cut in the lid but any clear fuel resistant bottle will do.

Step 4 **IMPORTANT** grab a fire extinguisher and keep it next to the car. This is a must any time you're messing with gas. It isn't worth burning your car or garage down and it isn't worth getting hurt. Been there. Done that. bought the t-shirt. If you don't have one, go out and buy one. You should always have a fire extinguisher in the garage anyway.

Step 5 test it. Turn your fuel pump toggle switch to on and listen for the pump running (correct answer is yes). Go up front and look to see if your injectors are spraying (correct answer is no) if they are, shut it down. If they aren't, lift the flow plate next to the fuel distributor and see if you have fuel flow out of the injectors (the answer should be yes). Check all injectors to make sure they appear to be flowing properly. They should all spray an even cone with a fine mist and make a high pitch squeaking noise. Don't forget to turn the toggle switch off and put the injectors back in when you're done.

Give that a shot then report back here. My assumption is that it's a problem with the CIS system as you were just messing with that. Good luck and let us know what you find!
_________________
1980 924 NA, US model
1987 924S, US model

[Rhubie]

Thank you for all the replies!
Ill check the voltage with the fuel pump and the relation to the air flow plate for sure. The pump does hum though, I can confirm that. I have also tested to see if the pump works by removing the hose going to the distributor and placing into a water bottle and allowing the engine to crank. Fuel did come out. I also removed the lines to the injectors to check if the distributor is clogged and got the same amount of fuel as my previous results.

Now to check if the pump has a voltage relation to the air plate.
I will also check the fuel filter to see if it is clogged but will order a new for safe measure.

I do have an ignition switch on hand, although I don't think that is the problem ill probably replace it just to eliminate it.

Ill pull the injectors last because it has idled, which makes me believe it does have that cone of fine mist coming out. But I will pull them in the next few days as well has get new O rings for them too. Any tips to removing the injectors?

[Eric P]

The reason I said to pull the injectors isn't so much to check the flow pattern as much as to make sure an injector isn't stuck open. You'll never know if you don't pull them. If you want to check the correct operation of your CIS system, you really need to see what's happening on the business end of the injectors.

I just pulled mine out by hand but I've heard of people having to use pliers. Just don't pull on the line. Pull on the injector itself.
_________________
1980 924 NA, US model
1987 924S, US model

[Rhubie]

Alright

New Fuel Filter is in. Old one had visible clog on both ends. No beauno.

After replacing I tried starting the car for shits and giggles. Voila she ran. For a couple seconds and died. She repeated this for two more times and then just cranked.

I go to check under the car for leaks and what not and find my internal fuel pump is leaking. A drip every 45 ish seconds. I don't know if its bad or what but i've heard the 924 is able to run without it.. So anyone know a good sealant to put around the leak or do I need to replace it?

Also I apologize for the lack of updates... had a small procedure done and have been doped up for the past couple of days lol

[Rhubie]

OR could i just replace it with a fuel strainer?

[Paul]

Sounds like its starting on the fuel supplied by the electrically operated cold start injector which only operates while the starter is cranking and even then for only a few seconds.

PULL the CIS injectors and test as already suggested.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[RC]

Yes, as Paul suggested.

Remove all injectors, spray lube (WD40 etc) around injector O rings, pull up on the bolt head using vice grip pliers, place injectors in empty beer bottles or whatever. Remove the large upper rubber from the AFM so you can lift plate. Jump the FPR or otherwise supply power to pump. Only earlier cars have the (blue connector) switch on AFM, later ones use a special FPRelay.

What happens?
When you lift AFM plate?
Do all bottles contain same amount of fuel?
_________________
World`s quickest 924 2L slushbox

[Rhubie]

So I pulled all the injectors and also got some new O rings for them too.

I didn't buy a switch but some rubber gloves and and wire and just touched the negative to the battery. Worked just fine.

The injectors came to life with out the MAF, or the plate that moves up and supposed to trigger the injectors. All sprayed fine mist with a high pitched noise except one.

I also found, that even though they are constant and mechanical that one of them was leaking and probably not giving the best spray pattern and will be buying a new one here soon.

[Paul]

Injectors should not spray until the plate is moved.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Rhubie]

Oh I know.. I just don't know what to do now

[Paul]

Adjust the metering screw until the injectors stop spraying when the plate is at rest.

Then check the system and control pressures with a CIS gauge set.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.